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* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-12-04 8:14 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-12-04 8:14 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=98c163157aa7ee8759b5b4b149c747822dd2889b
commit 98c163157aa7ee8759b5b4b149c747822dd2889b
Author: Florian Weimer <fweimer@redhat.com>
Date: Fri Dec 4 09:13:43 2020 +0100
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag in cache entries,
and picks the supported cache entry with the highest priority.
The elf/tst-glibc-hwcaps-prepend-cache test documents a non-desired
aspect of the current cache implementation: If the cache selects a DSO
that does not exist on disk, _dl_map_object falls back to open_path,
which may or may not find an alternative implementation. This is an
existing limitation that also applies to the legacy hwcaps processing
for ld.so.cache.
Diff:
---
elf/Makefile | 18 ++
elf/dl-cache.c | 194 ++++++++++++++++++++-
elf/dl-hwcaps.c | 78 +++++++++
elf/dl-hwcaps.h | 19 ++
elf/tst-glibc-hwcaps-cache.c | 45 +++++
elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf | 2 +
elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
elf/tst-glibc-hwcaps-cache.script | 6 +
elf/tst-glibc-hwcaps-prepend-cache.c | 149 ++++++++++++++++
.../postclean.req | 0
10 files changed, 508 insertions(+), 3 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index b28930432d..95cbf66c25 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -173,6 +173,12 @@ tests-container := \
tst-ldconfig-bad-aux-cache \
tst-ldconfig-ld_so_conf-update
+ifeq (no,$(build-hardcoded-path-in-tests))
+# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
+# interferes with its test objectives.
+tests-container += tst-glibc-hwcaps-prepend-cache
+endif
+
tests := tst-tls9 tst-leaks1 \
tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
tst-auxv tst-stringtable
@@ -1865,6 +1871,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
$< > $@; \
$(evaluate-test)
+# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
+# library via ld.so.cache. Test setup is contained in the test
+# itself.
+$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
+$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
+ $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
+ $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
+
# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
# suppress all auto-detected subdirectories.
$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
@@ -1876,3 +1890,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
--glibc-hwcaps-mask does-not-exist \
$< > $@; \
$(evaluate-test)
+
+# Generic dependency for sysdeps implementation of
+# tst-glibc-hwcaps-cache.
+$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..e32688c0c9 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,144 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Ordered comparision of a hwcaps string from the cache on the left
+ (identified by its string table index) and a _dl_hwcaps_priorities
+ element on the right. */
+static int
+glibc_hwcaps_compare (uint32_t left_index, struct dl_hwcaps_priority *right)
+{
+ const char *left_name = (const char *) cache + left_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp != 0)
+ return cmp;
+ if (left_name_length < right->name_length)
+ return -1;
+ else if (left_name_length > right->name_length)
+ return 1;
+ else
+ return 0;
+}
+
+/* Initialize the glibc_hwcaps_priorities array and its length,
+ glibc_hwcaps_priorities_length. */
+static void
+glibc_hwcaps_priorities_init (void)
+{
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return;
+
+ uint32_t length = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ uint32_t *new_allocation = malloc (length * sizeof (uint32_t));
+ if (new_allocation == NULL)
+ /* This effectively disables hwcaps on memory allocation
+ errors. */
+ return;
+
+ glibc_hwcaps_priorities = new_allocation;
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ if (*left < cachesize)
+ {
+ int cmp = glibc_hwcaps_compare (*left, right);
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* This does not need to repeated initialization attempts because
+ this function is only called if there is glibc-hwcaps data in the
+ cache, so the first call initializes the glibc_hwcaps_priorities
+ array. */
+ if (glibc_hwcaps_priorities_length == 0)
+ glibc_hwcaps_priorities_init ();
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +212,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +270,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +282,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +303,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +530,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index f611f3a1a6..5a71f80154 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ uint32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index ab39d8a46d..ddfdde278e 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c
new file mode 100644
index 0000000000..4bad56afc0
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.c
@@ -0,0 +1,45 @@
+/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This program is just a wrapper that runs ldconfig followed by
+ tst-glibc-hwcaps. The actual test is provided via an
+ implementation in a sysdeps subdirectory. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/support.h>
+#include <unistd.h>
+
+int
+main (int argc, char **argv)
+{
+ /* Run ldconfig to populate the cache. */
+ {
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ if (system (command) != 0)
+ return 1;
+ free (command);
+ }
+
+ /* Reuse tst-glibc-hwcaps. Since this code is running in a
+ container, we can launch it directly. */
+ char *path = xasprintf ("%s/elf/tst-glibc-hwcaps", support_objdir_root);
+ execv (path, argv);
+ printf ("error: execv of %s failed: %m\n", path);
+ return 1;
+}
diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
new file mode 100644
index 0000000000..e1e74dbda2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
@@ -0,0 +1,2 @@
+# This file was created to suppress a warning from ldconfig:
+# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
diff --git a/elf/tst-glibc-hwcaps-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
new file mode 100644
index 0000000000..6356d15208
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.script
@@ -0,0 +1,6 @@
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
+
+cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so
+cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so
+cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
new file mode 100644
index 0000000000..40509cebe2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-prepend-cache.c
@@ -0,0 +1,149 @@
+/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xunistd.h>
+
+/* Invoke /sbin/ldconfig with some error checking. */
+static void
+run_ldconfig (void)
+{
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ TEST_COMPARE (system (command), 0);
+ free (command);
+}
+
+/* The library under test. */
+#define SONAME "libmarkermod1.so"
+
+static int
+do_test (void)
+{
+ if (dlopen (SONAME, RTLD_NOW) != NULL)
+ FAIL_EXIT1 (SONAME " is already on the search path");
+
+ /* Install the default implementation of libmarkermod1.so. */
+ xmkdirp ("/etc", 0777);
+ support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/" SONAME);
+ free (src);
+ }
+ run_ldconfig ();
+ {
+ /* The default implementation can now be loaded. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+
+ /* Add the first override to the directory that is searched last. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the first implementation. The cache has not been
+ updated. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ /* Add the second override to the directory that is searched first. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the third implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 3);
+ xdlclose (handle);
+ }
+
+ /* Remove the second override again, without running ldconfig.
+ Ideally, this would revert to implementation 2. However, in the
+ current implementation, the cache returns exactly one file name
+ which does not exist after unlinking, so the dlopen fails. */
+ xunlink ("/glibc-test/lib/glibc-hwcaps/prepend3/" SONAME);
+ TEST_VERIFY (dlopen (SONAME, RTLD_NOW) == NULL);
+ run_ldconfig ();
+ {
+ /* After running ldconfig, the second implementation is available
+ once more. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ return 0;
+}
+
+static void
+prepare (int argc, char **argv)
+{
+ const char *no_restart = "no-restart";
+ if (argc == 2 && strcmp (argv[1], no_restart) == 0)
+ return;
+ /* Re-execute the test with an explicit loader invocation. */
+ execl (support_objdir_elf_ldso,
+ support_objdir_elf_ldso,
+ "--glibc-hwcaps-prepend", "prepend3:prepend2",
+ argv[0], no_restart,
+ NULL);
+ printf ("error: execv of %s failed: %m\n", argv[0]);
+ _exit (1);
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
^ permalink raw reply [flat|nested] 7+ messages in thread
* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-12-01 20:55 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-12-01 20:55 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b80f24fa4a291d646438d85fa11c1e6937be7a70
commit b80f24fa4a291d646438d85fa11c1e6937be7a70
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Dec 1 10:58:51 2020 +0100
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag in cache entries,
and picks the supported cache entry with the highest priority.
The elf/tst-glibc-hwcaps-prepend-cache test documents a non-desired
aspect of the current cache implementation: If the cache selects a DSO
that does not exist on disk, _dl_map_object falls back to open_path,
which may or may not find an alternative implementation. This is an
existing limitation that also applies to the legacy hwcaps processing
for ld.so.cache.
Diff:
---
elf/Makefile | 18 ++
elf/dl-cache.c | 194 ++++++++++++++++++++-
elf/dl-hwcaps.c | 78 +++++++++
elf/dl-hwcaps.h | 19 ++
elf/tst-glibc-hwcaps-cache.c | 45 +++++
elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf | 2 +
elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
elf/tst-glibc-hwcaps-cache.script | 6 +
elf/tst-glibc-hwcaps-prepend-cache.c | 150 ++++++++++++++++
.../postclean.req | 0
10 files changed, 509 insertions(+), 3 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index b28930432d..95cbf66c25 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -173,6 +173,12 @@ tests-container := \
tst-ldconfig-bad-aux-cache \
tst-ldconfig-ld_so_conf-update
+ifeq (no,$(build-hardcoded-path-in-tests))
+# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
+# interferes with its test objectives.
+tests-container += tst-glibc-hwcaps-prepend-cache
+endif
+
tests := tst-tls9 tst-leaks1 \
tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
tst-auxv tst-stringtable
@@ -1865,6 +1871,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
$< > $@; \
$(evaluate-test)
+# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
+# library via ld.so.cache. Test setup is contained in the test
+# itself.
+$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
+$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
+ $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
+ $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
+
# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
# suppress all auto-detected subdirectories.
$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
@@ -1876,3 +1890,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
--glibc-hwcaps-mask does-not-exist \
$< > $@; \
$(evaluate-test)
+
+# Generic dependency for sysdeps implementation of
+# tst-glibc-hwcaps-cache.
+$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..e32688c0c9 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,144 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Ordered comparision of a hwcaps string from the cache on the left
+ (identified by its string table index) and a _dl_hwcaps_priorities
+ element on the right. */
+static int
+glibc_hwcaps_compare (uint32_t left_index, struct dl_hwcaps_priority *right)
+{
+ const char *left_name = (const char *) cache + left_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp != 0)
+ return cmp;
+ if (left_name_length < right->name_length)
+ return -1;
+ else if (left_name_length > right->name_length)
+ return 1;
+ else
+ return 0;
+}
+
+/* Initialize the glibc_hwcaps_priorities array and its length,
+ glibc_hwcaps_priorities_length. */
+static void
+glibc_hwcaps_priorities_init (void)
+{
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return;
+
+ uint32_t length = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ uint32_t *new_allocation = malloc (length * sizeof (uint32_t));
+ if (new_allocation == NULL)
+ /* This effectively disables hwcaps on memory allocation
+ errors. */
+ return;
+
+ glibc_hwcaps_priorities = new_allocation;
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ if (*left < cachesize)
+ {
+ int cmp = glibc_hwcaps_compare (*left, right);
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* This does not need to repeated initialization attempts because
+ this function is only called if there is glibc-hwcaps data in the
+ cache, so the first call initializes the glibc_hwcaps_priorities
+ array. */
+ if (glibc_hwcaps_priorities_length == 0)
+ glibc_hwcaps_priorities_init ();
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +212,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +270,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +282,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +303,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +530,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index f611f3a1a6..5a71f80154 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ uint32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index ab39d8a46d..ddfdde278e 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c
new file mode 100644
index 0000000000..4bad56afc0
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.c
@@ -0,0 +1,45 @@
+/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This program is just a wrapper that runs ldconfig followed by
+ tst-glibc-hwcaps. The actual test is provided via an
+ implementation in a sysdeps subdirectory. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/support.h>
+#include <unistd.h>
+
+int
+main (int argc, char **argv)
+{
+ /* Run ldconfig to populate the cache. */
+ {
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ if (system (command) != 0)
+ return 1;
+ free (command);
+ }
+
+ /* Reuse tst-glibc-hwcaps. Since this code is running in a
+ container, we can launch it directly. */
+ char *path = xasprintf ("%s/elf/tst-glibc-hwcaps", support_objdir_root);
+ execv (path, argv);
+ printf ("error: execv of %s failed: %m\n", path);
+ return 1;
+}
diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
new file mode 100644
index 0000000000..e1e74dbda2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
@@ -0,0 +1,2 @@
+# This file was created to suppress a warning from ldconfig:
+# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
diff --git a/elf/tst-glibc-hwcaps-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
new file mode 100644
index 0000000000..6356d15208
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.script
@@ -0,0 +1,6 @@
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
+
+cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so
+cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so
+cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
new file mode 100644
index 0000000000..0c1b99b14f
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-prepend-cache.c
@@ -0,0 +1,150 @@
+/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xunistd.h>
+
+/* Invoke /sbin/ldconfig with some error checking. */
+static void
+run_ldconfig (void)
+{
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ TEST_COMPARE (system (command), 0);
+ free (command);
+}
+
+/* The library under test. */
+#define SONAME "libmarkermod1.so"
+
+static int
+do_test (void)
+{
+ if (dlopen (SONAME, RTLD_NOW) != NULL)
+ FAIL_EXIT1 (SONAME " is already on the search path");
+
+ /* Install the default implementation of libmarkermod1.so. */
+ xmkdirp ("/etc", 0777);
+ support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/" SONAME);
+ free (src);
+ }
+ run_ldconfig ();
+ {
+ /* The default implementation can now be loaded. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+
+ /* Add the first override to the directory that is searched last. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the first implementation. The cache has not been
+ updated. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ /* Add the second override to the directory that is searched first. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the third implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 3);
+ xdlclose (handle);
+ }
+
+ /* Remove the second override again, without running ldconfig.
+ Ideally, this would revert to implementation 2. However, in the
+ current implementation, the cache returns exactly one file name
+ which does not exist after unlinking, so the dlopen fails. */
+ xunlink ("/glibc-test/lib/glibc-hwcaps/prepend3/" SONAME);
+ TEST_VERIFY (dlopen (SONAME, RTLD_NOW) == NULL);
+ run_ldconfig ();
+ system("/sbin/ldconfig -p");
+ {
+ /* After running ldconfig, the second implementation is available
+ once more. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ return 0;
+}
+
+static void
+prepare (int argc, char **argv)
+{
+ const char *no_restart = "no-restart";
+ if (argc == 2 && strcmp (argv[1], no_restart) == 0)
+ return;
+ /* Re-execute the test with an explicit loader invocation. */
+ execl (support_objdir_elf_ldso,
+ support_objdir_elf_ldso,
+ "--glibc-hwcaps-prepend", "prepend3:prepend2",
+ argv[0], no_restart,
+ NULL);
+ printf ("error: execv of %s failed: %m\n", argv[0]);
+ _exit (1);
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
^ permalink raw reply [flat|nested] 7+ messages in thread
* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-12-01 11:35 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-12-01 11:35 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d9a2c34c93dcb6db9ee0de4a0fd43ddec1d1086d
commit d9a2c34c93dcb6db9ee0de4a0fd43ddec1d1086d
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Dec 1 10:58:51 2020 +0100
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
the supported cache entry with the highest priority.
Diff:
---
elf/Makefile | 18 ++
elf/dl-cache.c | 182 ++++++++++++++++++++-
elf/dl-hwcaps.c | 78 +++++++++
elf/dl-hwcaps.h | 19 +++
elf/tst-glibc-hwcaps-cache.c | 45 +++++
elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf | 2 +
elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
elf/tst-glibc-hwcaps-cache.script | 6 +
elf/tst-glibc-hwcaps-prepend-cache.c | 133 +++++++++++++++
.../postclean.req | 0
10 files changed, 480 insertions(+), 3 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index b28930432d..95cbf66c25 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -173,6 +173,12 @@ tests-container := \
tst-ldconfig-bad-aux-cache \
tst-ldconfig-ld_so_conf-update
+ifeq (no,$(build-hardcoded-path-in-tests))
+# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
+# interferes with its test objectives.
+tests-container += tst-glibc-hwcaps-prepend-cache
+endif
+
tests := tst-tls9 tst-leaks1 \
tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
tst-auxv tst-stringtable
@@ -1865,6 +1871,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
$< > $@; \
$(evaluate-test)
+# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
+# library via ld.so.cache. Test setup is contained in the test
+# itself.
+$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
+$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
+ $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
+ $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
+
# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
# suppress all auto-detected subdirectories.
$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
@@ -1876,3 +1890,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
--glibc-hwcaps-mask does-not-exist \
$< > $@; \
$(evaluate-test)
+
+# Generic dependency for sysdeps implementation of
+# tst-glibc-hwcaps-cache.
+$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..13efc6f95f 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,132 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t __attribute__ ((noinline, noclone))
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* Using a zero-length array as an indicator that nothing has been
+ loaded is not a problem: It does not lead to repeated
+ initialization attempts because caches without an extension
+ section are processed without calling this function (unless the
+ file is corrupted). */
+ if (glibc_hwcaps_priorities_length == 0)
+ {
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return 0;
+
+ uint32_t length
+ = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
+ if (glibc_hwcaps_priorities == NULL)
+ /* Disable hwcaps on memory allocation error. */
+ return 0;
+
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left
+ = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end
+ = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ uint32_t string_table_index = *left;
+ if (string_table_index < cachesize)
+ {
+ const char *left_name
+ = (const char *) cache + string_table_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp == 0)
+ {
+ if (left_name_length < right->name_length)
+ cmp = -1;
+ else if (left_name_length > right->name_length)
+ cmp = 1;
+ }
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+ }
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +518,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index f611f3a1a6..51cc787b54 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ int32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index ab39d8a46d..ddfdde278e 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c
new file mode 100644
index 0000000000..4bad56afc0
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.c
@@ -0,0 +1,45 @@
+/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This program is just a wrapper that runs ldconfig followed by
+ tst-glibc-hwcaps. The actual test is provided via an
+ implementation in a sysdeps subdirectory. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/support.h>
+#include <unistd.h>
+
+int
+main (int argc, char **argv)
+{
+ /* Run ldconfig to populate the cache. */
+ {
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ if (system (command) != 0)
+ return 1;
+ free (command);
+ }
+
+ /* Reuse tst-glibc-hwcaps. Since this code is running in a
+ container, we can launch it directly. */
+ char *path = xasprintf ("%s/elf/tst-glibc-hwcaps", support_objdir_root);
+ execv (path, argv);
+ printf ("error: execv of %s failed: %m\n", path);
+ return 1;
+}
diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
new file mode 100644
index 0000000000..e1e74dbda2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
@@ -0,0 +1,2 @@
+# This file was created to suppress a warning from ldconfig:
+# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
diff --git a/elf/tst-glibc-hwcaps-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
new file mode 100644
index 0000000000..6356d15208
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.script
@@ -0,0 +1,6 @@
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
+
+cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so
+cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so
+cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
new file mode 100644
index 0000000000..eedbf5f6df
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-prepend-cache.c
@@ -0,0 +1,133 @@
+/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xunistd.h>
+
+/* Invoke /sbin/ldconfig with some error checking. */
+static void
+run_ldconfig (void)
+{
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ TEST_COMPARE (system (command), 0);
+ free (command);
+}
+
+/* The library under test. */
+#define SONAME "libmarkermod1.so"
+
+static int
+do_test (void)
+{
+ if (dlopen (SONAME, RTLD_NOW) != NULL)
+ FAIL_EXIT1 (SONAME " is already on the search path");
+
+ /* Install the default implementation of libmarkermod1.so. */
+ xmkdirp ("/etc", 0777);
+ support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/" SONAME);
+ free (src);
+ }
+ run_ldconfig ();
+ {
+ /* The default implementation can now be loaded. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+
+ /* Add the first override to the directory that is searched last. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the first implementation. The cache has not been
+ updated. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ /* Add the second override to the directory that is searched first. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the third implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 3);
+ xdlclose (handle);
+ }
+
+ return 0;
+}
+
+static void
+prepare (int argc, char **argv)
+{
+ const char *no_restart = "no-restart";
+ if (argc == 2 && strcmp (argv[1], no_restart) == 0)
+ return;
+ /* Re-execute the test with an explicit loader invocation. */
+ execl (support_objdir_elf_ldso,
+ support_objdir_elf_ldso,
+ "--glibc-hwcaps-prepend", "prepend3:prepend2",
+ argv[0], no_restart,
+ NULL);
+ printf ("error: execv of %s failed: %m\n", argv[0]);
+ _exit (1);
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
^ permalink raw reply [flat|nested] 7+ messages in thread
* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-11-26 18:44 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-11-26 18:44 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0b82dce6f85dac0907c4ceeaa6e7b463f7235a24
commit 0b82dce6f85dac0907c4ceeaa6e7b463f7235a24
Author: Florian Weimer <fweimer@redhat.com>
Date: Thu Nov 26 16:59:44 2020 +0100
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
the supported cache entry with the highest priority.
Diff:
---
elf/Makefile | 18 ++
elf/dl-cache.c | 182 ++++++++++++++++++++-
elf/dl-hwcaps.c | 78 +++++++++
elf/dl-hwcaps.h | 19 +++
elf/tst-glibc-hwcaps-cache.c | 45 +++++
elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf | 2 +
elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
elf/tst-glibc-hwcaps-cache.script | 6 +
elf/tst-glibc-hwcaps-prepend-cache.c | 133 +++++++++++++++
.../postclean.req | 0
10 files changed, 480 insertions(+), 3 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index ce07ac63ef..7e5c249a36 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -173,6 +173,12 @@ tests-container := \
tst-ldconfig-bad-aux-cache \
tst-ldconfig-ld_so_conf-update
+ifeq (no,$(build-hardcoded-path-in-tests))
+# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
+# interferes with its test objectives.
+tests-container += tst-glibc-hwcaps-prepend-cache
+endif
+
tests := tst-tls9 tst-leaks1 \
tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
tst-auxv tst-stringtable
@@ -1861,6 +1867,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
$< > $@; \
$(evaluate-test)
+# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
+# library via ld.so.cache. Test setup is contained in the test
+# itself.
+$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
+$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
+ $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
+ $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
+
# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
# suppress all auto-detected subdirectories.
$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
@@ -1872,3 +1886,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
--glibc-hwcaps-mask does-not-exist \
$< > $@; \
$(evaluate-test)
+
+# Generic dependency for sysdeps implementation of
+# tst-glibc-hwcaps-cache.
+$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..13efc6f95f 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,132 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t __attribute__ ((noinline, noclone))
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* Using a zero-length array as an indicator that nothing has been
+ loaded is not a problem: It does not lead to repeated
+ initialization attempts because caches without an extension
+ section are processed without calling this function (unless the
+ file is corrupted). */
+ if (glibc_hwcaps_priorities_length == 0)
+ {
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return 0;
+
+ uint32_t length
+ = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
+ if (glibc_hwcaps_priorities == NULL)
+ /* Disable hwcaps on memory allocation error. */
+ return 0;
+
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left
+ = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end
+ = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ uint32_t string_table_index = *left;
+ if (string_table_index < cachesize)
+ {
+ const char *left_name
+ = (const char *) cache + string_table_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp == 0)
+ {
+ if (left_name_length < right->name_length)
+ cmp = -1;
+ else if (left_name_length > right->name_length)
+ cmp = 1;
+ }
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+ }
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +518,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index f611f3a1a6..51cc787b54 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ int32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index ab39d8a46d..ddfdde278e 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c
new file mode 100644
index 0000000000..4bad56afc0
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.c
@@ -0,0 +1,45 @@
+/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This program is just a wrapper that runs ldconfig followed by
+ tst-glibc-hwcaps. The actual test is provided via an
+ implementation in a sysdeps subdirectory. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/support.h>
+#include <unistd.h>
+
+int
+main (int argc, char **argv)
+{
+ /* Run ldconfig to populate the cache. */
+ {
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ if (system (command) != 0)
+ return 1;
+ free (command);
+ }
+
+ /* Reuse tst-glibc-hwcaps. Since this code is running in a
+ container, we can launch it directly. */
+ char *path = xasprintf ("%s/elf/tst-glibc-hwcaps", support_objdir_root);
+ execv (path, argv);
+ printf ("error: execv of %s failed: %m\n", path);
+ return 1;
+}
diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
new file mode 100644
index 0000000000..e1e74dbda2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
@@ -0,0 +1,2 @@
+# This file was created to suppress a warning from ldconfig:
+# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
diff --git a/elf/tst-glibc-hwcaps-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
new file mode 100644
index 0000000000..6356d15208
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.script
@@ -0,0 +1,6 @@
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
+
+cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so
+cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so
+cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
new file mode 100644
index 0000000000..eedbf5f6df
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-prepend-cache.c
@@ -0,0 +1,133 @@
+/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xunistd.h>
+
+/* Invoke /sbin/ldconfig with some error checking. */
+static void
+run_ldconfig (void)
+{
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ TEST_COMPARE (system (command), 0);
+ free (command);
+}
+
+/* The library under test. */
+#define SONAME "libmarkermod1.so"
+
+static int
+do_test (void)
+{
+ if (dlopen (SONAME, RTLD_NOW) != NULL)
+ FAIL_EXIT1 (SONAME " is already on the search path");
+
+ /* Install the default implementation of libmarkermod1.so. */
+ xmkdirp ("/etc", 0777);
+ support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/" SONAME);
+ free (src);
+ }
+ run_ldconfig ();
+ {
+ /* The default implementation can now be loaded. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+
+ /* Add the first override to the directory that is searched last. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the first implementation. The cache has not been
+ updated. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ /* Add the second override to the directory that is searched first. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the third implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 3);
+ xdlclose (handle);
+ }
+
+ return 0;
+}
+
+static void
+prepare (int argc, char **argv)
+{
+ const char *no_restart = "no-restart";
+ if (argc == 2 && strcmp (argv[1], no_restart) == 0)
+ return;
+ /* Re-execute the test with an explicit loader invocation. */
+ execl (support_objdir_elf_ldso,
+ support_objdir_elf_ldso,
+ "--glibc-hwcaps-prepend", "prepend3:prepend2",
+ argv[0], no_restart,
+ NULL);
+ printf ("error: execv of %s failed: %m\n", argv[0]);
+ _exit (1);
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
^ permalink raw reply [flat|nested] 7+ messages in thread
* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-11-26 18:11 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-11-26 18:11 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0b82dce6f85dac0907c4ceeaa6e7b463f7235a24
commit 0b82dce6f85dac0907c4ceeaa6e7b463f7235a24
Author: Florian Weimer <fweimer@redhat.com>
Date: Thu Nov 26 16:59:44 2020 +0100
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
the supported cache entry with the highest priority.
Diff:
---
elf/Makefile | 18 ++
elf/dl-cache.c | 182 ++++++++++++++++++++-
elf/dl-hwcaps.c | 78 +++++++++
elf/dl-hwcaps.h | 19 +++
elf/tst-glibc-hwcaps-cache.c | 45 +++++
elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf | 2 +
elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
elf/tst-glibc-hwcaps-cache.script | 6 +
elf/tst-glibc-hwcaps-prepend-cache.c | 133 +++++++++++++++
.../postclean.req | 0
10 files changed, 480 insertions(+), 3 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index ce07ac63ef..7e5c249a36 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -173,6 +173,12 @@ tests-container := \
tst-ldconfig-bad-aux-cache \
tst-ldconfig-ld_so_conf-update
+ifeq (no,$(build-hardcoded-path-in-tests))
+# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
+# interferes with its test objectives.
+tests-container += tst-glibc-hwcaps-prepend-cache
+endif
+
tests := tst-tls9 tst-leaks1 \
tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
tst-auxv tst-stringtable
@@ -1861,6 +1867,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
$< > $@; \
$(evaluate-test)
+# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
+# library via ld.so.cache. Test setup is contained in the test
+# itself.
+$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
+$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
+ $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
+ $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
+
# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
# suppress all auto-detected subdirectories.
$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
@@ -1872,3 +1886,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
--glibc-hwcaps-mask does-not-exist \
$< > $@; \
$(evaluate-test)
+
+# Generic dependency for sysdeps implementation of
+# tst-glibc-hwcaps-cache.
+$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..13efc6f95f 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,132 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t __attribute__ ((noinline, noclone))
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* Using a zero-length array as an indicator that nothing has been
+ loaded is not a problem: It does not lead to repeated
+ initialization attempts because caches without an extension
+ section are processed without calling this function (unless the
+ file is corrupted). */
+ if (glibc_hwcaps_priorities_length == 0)
+ {
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return 0;
+
+ uint32_t length
+ = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
+ if (glibc_hwcaps_priorities == NULL)
+ /* Disable hwcaps on memory allocation error. */
+ return 0;
+
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left
+ = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end
+ = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ uint32_t string_table_index = *left;
+ if (string_table_index < cachesize)
+ {
+ const char *left_name
+ = (const char *) cache + string_table_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp == 0)
+ {
+ if (left_name_length < right->name_length)
+ cmp = -1;
+ else if (left_name_length > right->name_length)
+ cmp = 1;
+ }
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+ }
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +518,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index f611f3a1a6..51cc787b54 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ int32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index ab39d8a46d..ddfdde278e 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c
new file mode 100644
index 0000000000..4bad56afc0
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.c
@@ -0,0 +1,45 @@
+/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This program is just a wrapper that runs ldconfig followed by
+ tst-glibc-hwcaps. The actual test is provided via an
+ implementation in a sysdeps subdirectory. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/support.h>
+#include <unistd.h>
+
+int
+main (int argc, char **argv)
+{
+ /* Run ldconfig to populate the cache. */
+ {
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ if (system (command) != 0)
+ return 1;
+ free (command);
+ }
+
+ /* Reuse tst-glibc-hwcaps. Since this code is running in a
+ container, we can launch it directly. */
+ char *path = xasprintf ("%s/elf/tst-glibc-hwcaps", support_objdir_root);
+ execv (path, argv);
+ printf ("error: execv of %s failed: %m\n", path);
+ return 1;
+}
diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
new file mode 100644
index 0000000000..e1e74dbda2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
@@ -0,0 +1,2 @@
+# This file was created to suppress a warning from ldconfig:
+# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
diff --git a/elf/tst-glibc-hwcaps-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
new file mode 100644
index 0000000000..6356d15208
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-cache.script
@@ -0,0 +1,6 @@
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
+
+cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so
+cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so
+cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
new file mode 100644
index 0000000000..eedbf5f6df
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-prepend-cache.c
@@ -0,0 +1,133 @@
+/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xunistd.h>
+
+/* Invoke /sbin/ldconfig with some error checking. */
+static void
+run_ldconfig (void)
+{
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ TEST_COMPARE (system (command), 0);
+ free (command);
+}
+
+/* The library under test. */
+#define SONAME "libmarkermod1.so"
+
+static int
+do_test (void)
+{
+ if (dlopen (SONAME, RTLD_NOW) != NULL)
+ FAIL_EXIT1 (SONAME " is already on the search path");
+
+ /* Install the default implementation of libmarkermod1.so. */
+ xmkdirp ("/etc", 0777);
+ support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/" SONAME);
+ free (src);
+ }
+ run_ldconfig ();
+ {
+ /* The default implementation can now be loaded. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+
+ /* Add the first override to the directory that is searched last. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the first implementation. The cache has not been
+ updated. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ /* Add the second override to the directory that is searched first. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the third implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 3);
+ xdlclose (handle);
+ }
+
+ return 0;
+}
+
+static void
+prepare (int argc, char **argv)
+{
+ const char *no_restart = "no-restart";
+ if (argc == 2 && strcmp (argv[1], no_restart) == 0)
+ return;
+ /* Re-execute the test with an explicit loader invocation. */
+ execl (support_objdir_elf_ldso,
+ support_objdir_elf_ldso,
+ "--glibc-hwcaps-prepend", "prepend3:prepend2",
+ argv[0], no_restart,
+ NULL);
+ printf ("error: execv of %s failed: %m\n", argv[0]);
+ _exit (1);
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
^ permalink raw reply [flat|nested] 7+ messages in thread
* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-10-14 15:12 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-10-14 15:12 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=587fc3e8e3ef420e6d2303f937d25aed327c2bce
commit 587fc3e8e3ef420e6d2303f937d25aed327c2bce
Author: Florian Weimer <fweimer@redhat.com>
Date: Mon Oct 12 16:53:20 2020 +0200
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
the supported cache entry with the highest priority.
Diff:
---
elf/dl-cache.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
elf/dl-hwcaps.c | 78 ++++++++++++++++++++++++
elf/dl-hwcaps.h | 19 ++++++
3 files changed, 276 insertions(+), 3 deletions(-)
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..13efc6f95f 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,132 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t __attribute__ ((noinline, noclone))
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* Using a zero-length array as an indicator that nothing has been
+ loaded is not a problem: It does not lead to repeated
+ initialization attempts because caches without an extension
+ section are processed without calling this function (unless the
+ file is corrupted). */
+ if (glibc_hwcaps_priorities_length == 0)
+ {
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return 0;
+
+ uint32_t length
+ = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
+ if (glibc_hwcaps_priorities == NULL)
+ /* Disable hwcaps on memory allocation error. */
+ return 0;
+
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left
+ = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end
+ = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ uint32_t string_table_index = *left;
+ if (string_table_index < cachesize)
+ {
+ const char *left_name
+ = (const char *) cache + string_table_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp == 0)
+ {
+ if (left_name_length < right->name_length)
+ cmp = -1;
+ else if (left_name_length > right->name_length)
+ cmp = 1;
+ }
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+ }
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +518,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index f611f3a1a6..51cc787b54 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ int32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index 8a42926ac2..8a4b6fd9eb 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -131,4 +131,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
^ permalink raw reply [flat|nested] 7+ messages in thread
* [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
@ 2020-10-01 16:55 Florian Weimer
0 siblings, 0 replies; 7+ messages in thread
From: Florian Weimer @ 2020-10-01 16:55 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=704c48fd058d2eb3b4925f4f5b883ec40a2ca421
commit 704c48fd058d2eb3b4925f4f5b883ec40a2ca421
Author: Florian Weimer <fweimer@redhat.com>
Date: Fri Jun 19 15:17:48 2020 +0200
elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
the supported cache entry with the highest priority.
Diff:
---
elf/dl-cache.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
elf/dl-hwcaps.c | 78 ++++++++++++++++++++++++
elf/dl-hwcaps.h | 19 ++++++
3 files changed, 276 insertions(+), 3 deletions(-)
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 02c46ffb0c..4714119974 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -35,6 +35,132 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t __attribute__ ((noinline, noclone))
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* Using a zero-length array as an indicator that nothing has been
+ loaded is not a problem: It does not lead to repeated
+ initialization attempts because caches without an extension
+ section are processed without calling this function (unless the
+ file is corrupted). */
+ if (glibc_hwcaps_priorities_length == 0)
+ {
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return 0;
+
+ uint32_t length
+ = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
+ if (glibc_hwcaps_priorities == NULL)
+ /* Disable hwcaps on memory allocation error. */
+ return 0;
+
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_full ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left
+ = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end
+ = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ uint32_t string_table_index = *left;
+ if (string_table_index < cachesize)
+ {
+ const char *left_name
+ = (const char *) cache + string_table_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp == 0)
+ {
+ if (left_name_length < right->name_length)
+ cmp = -1;
+ else if (left_name_length > right->name_length)
+ cmp = 1;
+ }
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+ }
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +518,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index 4de94759a2..cb53337025 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ int32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
count_hwcaps (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
count_hwcaps (&hwcaps_counts, _dl_hwcaps_subdirs, hwcaps_subdirs_active,
glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index a6453f15f3..4b4c143854 100644
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -110,4 +110,23 @@ extern const char _dl_hwcaps_subdirs[] attribute_hidden;
bitmask. */
int32_t _dl_hwcaps_subdirs_active (void) attribute_hidden;
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-12-04 8:14 UTC | newest]
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2020-12-04 8:14 [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing Florian Weimer
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2020-12-01 20:55 Florian Weimer
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