From: Florian Weimer <fweimer@redhat.com>
To: libc-alpha@sourceware.org
Subject: [PATCH 22/28] elf: Add extension mechanism to ld.so.cache
Date: Thu, 01 Oct 2020 18:33:57 +0200 [thread overview]
Message-ID: <f4f7adb2d40bdf268d06e3bfb68dbd12ce44d304.1601569371.git.fweimer@redhat.com> (raw)
In-Reply-To: <cover.1601569371.git.fweimer@redhat.com>
A previously unused new-format header field is used to record
the address of an extension directory.
This change adds a demo extension which records the version of
ldconfig which builds a file.
---
elf/cache.c | 89 +++++++++++++++++++++++++++
sysdeps/generic/dl-cache.h | 123 ++++++++++++++++++++++++++++++++++++-
2 files changed, 211 insertions(+), 1 deletion(-)
diff --git a/elf/cache.c b/elf/cache.c
index e0aa616352..3a02a4070a 100644
--- a/elf/cache.c
+++ b/elf/cache.c
@@ -15,6 +15,7 @@
You should have received a copy of the GNU General Public License
along with this program; if not, see <https://www.gnu.org/licenses/>. */
+#include <assert.h>
#include <errno.h>
#include <error.h>
#include <dirent.h>
@@ -33,6 +34,7 @@
#include <ldconfig.h>
#include <dl-cache.h>
+#include <version.h>
struct cache_entry
{
@@ -161,6 +163,21 @@ check_new_cache (struct cache_file_new *cache)
error (EXIT_FAILURE, 0, _("Cache file has wrong endianness.\n"));
}
+/* Print the extension information at the cache at start address
+ FILE_BASE, of ltength FILE_SIZE bytes. The new-format cache header
+ is at CACHE, and the file name for diagnostics is CACHE_NAME. */
+static void
+print_extensions (struct cache_extension_all_loaded *ext)
+{
+ if (ext->sections[cache_extension_tag_generator].base != NULL)
+ {
+ fputs (_("Cache generated by: "), stdout);
+ fwrite (ext->sections[cache_extension_tag_generator].base, 1,
+ ext->sections[cache_extension_tag_generator].size, stdout);
+ putchar ('\n');
+ }
+}
+
/* Print the whole cache file, if a file contains the new cache format
hidden in the old one, print the contents of the new format. */
void
@@ -250,6 +267,11 @@ print_cache (const char *cache_name)
}
else if (format == 1)
{
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cache_size, &ext))
+ error (EXIT_FAILURE, 0,
+ _("Malformed extension data in cache file %s\n"), cache_name);
+
printf (_("%d libs found in cache `%s'\n"),
cache_new->nlibs, cache_name);
@@ -260,6 +282,7 @@ print_cache (const char *cache_name)
cache_new->libs[i].osversion,
cache_new->libs[i].hwcap,
cache_data + cache_new->libs[i].value);
+ print_extensions (&ext);
}
/* Cleanup. */
munmap (cache, cache_size);
@@ -301,6 +324,45 @@ compare (const struct cache_entry *e1, const struct cache_entry *e2)
return res;
}
+/* Size of the cache extension directory. All tags are assumed to be
+ present. */
+enum
+ {
+ cache_extension_size = (offsetof (struct cache_extension, sections)
+ + (cache_extension_count
+ * sizeof (struct cache_extension_section)))
+ };
+
+/* Write the cache extensions to FD. The extension directory is
+ assumed to be located at CACHE_EXTENSION_OFFSET. */
+static void
+write_extensions (int fd, uint32_t cache_extension_offset)
+{
+ assert ((cache_extension_offset % 4) == 0);
+
+ struct cache_extension *ext = xmalloc (cache_extension_size);
+ ext->magic = cache_extension_magic;
+ ext->count = cache_extension_count;
+
+ for (int i = 0; i < cache_extension_count; ++i)
+ {
+ ext->sections[i].tag = i;
+ ext->sections[i].flags = 0;
+ }
+
+ const char *generator
+ = "ldconfig " PKGVERSION RELEASE " release version " VERSION;
+ ext->sections[cache_extension_tag_generator].offset
+ = cache_extension_offset + cache_extension_size;
+ ext->sections[cache_extension_tag_generator].size = strlen (generator);
+
+ if (write (fd, ext, cache_extension_size) != cache_extension_size
+ || write (fd, generator, strlen (generator)) != strlen (generator))
+ error (EXIT_FAILURE, errno, _("Writing of cache extension data failed"));
+
+ free (ext);
+}
+
/* Save the contents of the cache. */
void
save_cache (const char *cache_name)
@@ -435,6 +497,25 @@ save_cache (const char *cache_name)
&& idx_old < cache_entry_old_count)
file_entries->libs[idx_old] = file_entries->libs[idx_old - 1];
+ /* Compute the location of the extension directory. This
+ implementation puts the directory after the string table. The
+ size computation matches the write calls below. The extension
+ directory does not exist with format 0, so the value does not
+ matter. */
+ uint32_t extension_offset = 0;
+ if (opt_format != 2)
+ extension_offset += file_entries_size;
+ if (opt_format != 0)
+ {
+ if (opt_format != 2)
+ extension_offset += pad;
+ extension_offset += file_entries_new_size;
+ }
+ extension_offset += total_strlen;
+ extension_offset = roundup (extension_offset, 4); /* Provide alignment. */
+ if (opt_format != 0)
+ file_entries_new->extension_offset = extension_offset;
+
/* Write out the cache. */
/* Write cache first to a temporary file and rename it later. */
@@ -473,6 +554,14 @@ save_cache (const char *cache_name)
if (write (fd, strings, total_strlen) != (ssize_t) total_strlen)
error (EXIT_FAILURE, errno, _("Writing of cache data failed"));
+ if (opt_format != 0)
+ {
+ /* Align file position to 4. */
+ off64_t old_offset = lseek64 (fd, extension_offset, SEEK_SET);
+ assert ((unsigned long long int) (extension_offset - old_offset) < 4);
+ write_extensions (fd, extension_offset);
+ }
+
/* Make sure user can always read cache file */
if (chmod (temp_name, S_IROTH|S_IRGRP|S_IRUSR|S_IWUSR))
error (EXIT_FAILURE, errno,
diff --git a/sysdeps/generic/dl-cache.h b/sysdeps/generic/dl-cache.h
index 1b04211f6b..b154740da9 100644
--- a/sysdeps/generic/dl-cache.h
+++ b/sysdeps/generic/dl-cache.h
@@ -21,7 +21,9 @@
#include <endian.h>
#include <stdbool.h>
+#include <stddef.h>
#include <stdint.h>
+#include <string.h>
#ifndef _DL_CACHE_DEFAULT_ID
# define _DL_CACHE_DEFAULT_ID 3
@@ -115,7 +117,11 @@ struct cache_file_new
uint8_t padding_unsed[3]; /* Not used, for future extensions. */
- uint32_t unused[4]; /* Leave space for future extensions
+ /* File offset of the extension directory. See struct
+ cache_extension below. Must be a multiple of four. */
+ uint32_t extension_offset;
+
+ uint32_t unused[3]; /* Leave space for future extensions
and align to 8 byte boundary. */
struct file_entry_new libs[0]; /* Entries describing libraries. */
/* After this the string table of size len_strings is found. */
@@ -134,6 +140,121 @@ cache_file_new_matches_endian (const struct cache_file_new *cache)
}
+/* Randomly chosen magic value, which allows for additional
+ consistency verification. */
+enum { cache_extension_magic = (uint32_t) -358342284 };
+
+/* Tag values for different kinds of extension sections. Similar to
+ SHT_* constants. */
+enum cache_extension_tag
+ {
+ /* Array of bytes containing the glibc version that generated this
+ cache file. */
+ cache_extension_tag_generator,
+
+ /* Total number of known cache extension tags. */
+ cache_extension_count
+ };
+
+/* Element in the array following struct cache_extension. Similar to
+ an ELF section header. */
+struct cache_extension_section
+{
+ /* Type of the extension section. A enum cache_extension_tag value. */
+ uint32_t tag;
+
+ /* Extension-specific flags. Currently generated as zero. */
+ uint32_t flags;
+
+ /* Offset from the start of the file for the data in this extension
+ section. Specific extensions can have alignment constraints. */
+ uint32_t offset;
+
+ /* Length in bytes of the extension data. Specific extensions may
+ have size requirements. */
+ uint32_t size;
+};
+
+/* The extension directory in the cache. An array of struct
+ cache_extension_section entries. */
+struct cache_extension
+{
+ uint32_t magic; /* Always cache_extension_magic. */
+ uint32_t count; /* Number of following entries. */
+
+ /* count section descriptors of type struct cache_extension_section
+ follow. */
+ struct cache_extension_section sections[];
+};
+
+/* A relocated version of struct cache_extension_section. */
+struct cache_extension_loaded
+{
+ /* Address and size of this extension section. base is NULL if the
+ section is missing from the file. */
+ const void *base;
+ size_t size;
+
+ /* Flags from struct cache_extension_section. */
+ uint32_t flags;
+};
+
+/* All supported extension sections, relocated. Filled in by
+ cache_extension_load below. */
+struct cache_extension_all_loaded
+{
+ struct cache_extension_loaded sections[cache_extension_count];
+};
+
+static bool __attribute__ ((unused))
+cache_extension_load (const struct cache_file_new *cache,
+ const void *file_base, size_t file_size,
+ struct cache_extension_all_loaded *loaded)
+{
+ memset (loaded, 0, sizeof (*loaded));
+ if (cache->extension_offset == 0)
+ /* No extensions present. This is not a format error. */
+ return true;
+ if ((cache->extension_offset % 4) != 0)
+ /* Extension offset is misaligned. */
+ return false;
+ size_t size_tmp;
+ if (__builtin_add_overflow (cache->extension_offset,
+ sizeof (struct cache_extension), &size_tmp)
+ || size_tmp > file_size)
+ /* Extension extends beyond the end of the file. */
+ return false;
+ const struct cache_extension *ext = file_base + cache->extension_offset;
+ if (ext->magic != cache_extension_magic)
+ return false;
+ if (__builtin_mul_overflow (ext->count,
+ sizeof (struct cache_extension_section),
+ &size_tmp)
+ || __builtin_add_overflow (cache->extension_offset
+ + sizeof (struct cache_extension), size_tmp,
+ &size_tmp)
+ || size_tmp > file_size)
+ /* Extension array extends beyond the end of the file. */
+ return false;
+ for (uint32_t i = 0; i < ext->count; ++i)
+ {
+ if (__builtin_add_overflow (ext->sections[i].offset,
+ ext->sections[i].size, &size_tmp)
+ || size_tmp > file_size)
+ /* Extension data extends beyond the end of the file. */
+ return false;
+
+ uint32_t tag = ext->sections[i].tag;
+ if (tag >= cache_extension_count)
+ /* Tag is out of range and unrecognized. */
+ continue;
+ loaded->sections[tag].base = file_base + ext->sections[i].offset;
+ loaded->sections[tag].size = ext->sections[i].size;
+ loaded->sections[tag].flags = ext->sections[i].flags;
+ }
+ return true;
+}
+
/* Used to align cache_file_new. */
#define ALIGN_CACHE(addr) \
(((addr) + __alignof__ (struct cache_file_new) -1) \
--
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next prev parent reply other threads:[~2020-10-01 16:34 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 16:31 [PATCH 00/28] glibc-hwcaps support Florian Weimer
2020-10-01 16:31 ` [PATCH 01/28] elf: Do not search HWCAP subdirectories in statically linked binaries Florian Weimer
2020-10-01 18:22 ` Adhemerval Zanella
2020-10-01 18:24 ` Carlos O'Donell
2020-10-01 18:29 ` Adhemerval Zanella
2020-10-01 20:24 ` Carlos O'Donell
2020-10-01 16:31 ` [PATCH 02/28] elf: Implement __rtld_malloc_is_full Florian Weimer
2020-10-01 18:23 ` Adhemerval Zanella
2020-10-08 9:44 ` Florian Weimer
2020-10-01 16:31 ` [PATCH 03/28] elf: Implement _dl_write Florian Weimer
2020-10-05 19:46 ` Adhemerval Zanella
2020-10-01 16:31 ` [PATCH 04/28] elf: Extract command-line/environment variables state from rtld.c Florian Weimer
2020-10-06 20:45 ` Adhemerval Zanella
2020-10-08 11:32 ` Florian Weimer
2020-10-01 16:32 ` [PATCH 05/28] elf: Move ld.so error/help output to _dl_usage Florian Weimer
2020-10-06 21:06 ` Adhemerval Zanella
2020-10-08 12:19 ` Florian Weimer
2020-10-01 16:32 ` [PATCH 06/28] elf: Record whether paths come from LD_LIBRARY_PATH or --library-path Florian Weimer
2020-10-07 16:39 ` Adhemerval Zanella
2020-10-07 16:49 ` Florian Weimer
2020-10-01 16:32 ` [PATCH 07/28] elf: Implement ld.so --help Florian Weimer
2020-10-07 17:16 ` Adhemerval Zanella
2020-10-08 13:13 ` Florian Weimer
2020-10-01 16:32 ` [PATCH 08/28] elf: Implement ld.so --version Florian Weimer
2020-10-07 18:36 ` Adhemerval Zanella
2020-10-07 18:38 ` Adhemerval Zanella
2020-10-08 13:37 ` Florian Weimer
2020-10-01 16:32 ` [PATCH 09/28] scripts/update-copyrights: Update csu/version.c, elf/dl-usage.c Florian Weimer
2020-10-07 18:41 ` Adhemerval Zanella
2020-10-01 16:32 ` [PATCH 10/28] elf: Use the term "program interpreter" in the ld.so help message Florian Weimer
2020-10-07 21:08 ` Adhemerval Zanella
2020-10-08 14:08 ` Florian Weimer
2020-10-01 16:32 ` [PATCH 11/28] elf: Print the full name of the dynamic loader " Florian Weimer
2020-10-08 12:38 ` Adhemerval Zanella
2020-10-01 16:32 ` [PATCH 12/28] elf: Make __rtld_env_path_list and __rtld_search_dirs global variables Florian Weimer
2020-10-08 13:27 ` Adhemerval Zanella
2020-10-01 16:32 ` [PATCH 13/28] elf: Add library search path information to ld.so --help Florian Weimer
2020-10-08 16:22 ` Adhemerval Zanella
2020-10-01 16:33 ` [PATCH 14/28] elf: Enhance ld.so --help to print HWCAP subdirectories Florian Weimer
2020-10-08 16:27 ` Adhemerval Zanella
2020-10-09 8:18 ` Florian Weimer
2020-10-09 13:49 ` Matheus Castanho
2020-10-09 17:08 ` Florian Weimer
2020-10-09 17:12 ` Florian Weimer
2020-10-09 18:54 ` Matheus Castanho
2020-10-12 9:47 ` Florian Weimer
2020-10-01 16:33 ` [PATCH 15/28] elf: Do not pass GLRO(dl_platform), GLRO(dl_platformlen) to _dl_important_hwcaps Florian Weimer
2020-10-08 18:04 ` Adhemerval Zanella
2020-10-01 16:33 ` [PATCH 16/28] elf: Add glibc-hwcaps support for LD_LIBRARY_PATH Florian Weimer
2020-10-08 10:13 ` Szabolcs Nagy
2020-10-09 9:08 ` Florian Weimer
2020-10-09 10:50 ` Szabolcs Nagy
2020-10-09 10:55 ` Florian Weimer
2020-10-09 11:03 ` Szabolcs Nagy
2020-10-08 23:16 ` Paul A. Clarke
2020-10-09 8:56 ` Florian Weimer
2020-10-09 13:19 ` Adhemerval Zanella
2020-10-12 11:54 ` Florian Weimer
2020-10-01 16:33 ` [PATCH 17/28] x86_64: Add glibc-hwcaps support Florian Weimer
2020-10-01 16:33 ` [PATCH 18/28] powerpc64le: " Florian Weimer
2020-10-01 18:56 ` Paul A. Clarke
2020-10-05 9:47 ` Florian Weimer
2020-10-05 19:15 ` Paul A. Clarke
2020-10-06 12:20 ` Florian Weimer
2020-10-06 17:45 ` Paul A. Clarke
2020-10-09 9:06 ` Florian Weimer
2020-10-01 16:33 ` [PATCH 19/28] s390x: Add " Florian Weimer
2020-10-01 16:33 ` [PATCH 20/28] aarch64: " Florian Weimer
2020-10-14 13:46 ` Adhemerval Zanella
2020-10-14 14:08 ` Florian Weimer
2020-10-14 14:15 ` Adhemerval Zanella
2020-10-14 14:37 ` Szabolcs Nagy
2020-10-14 14:43 ` Adhemerval Zanella
2020-10-14 15:13 ` Florian Weimer
2020-10-14 14:44 ` Florian Weimer
2020-10-14 15:09 ` Szabolcs Nagy
2020-10-01 16:33 ` [PATCH 21/28] elf: Add endianness markup to ld.so.cache Florian Weimer
2020-10-14 14:07 ` Adhemerval Zanella
2020-10-01 16:33 ` Florian Weimer [this message]
2020-10-15 17:52 ` [PATCH 22/28] elf: Add extension mechanism " Adhemerval Zanella
2020-10-30 12:22 ` Florian Weimer
2020-11-03 12:45 ` Adhemerval Zanella
2020-11-03 15:30 ` Florian Weimer
2020-10-01 16:34 ` [PATCH 23/28] elf: Unify old and new format cache handling code in ld.so Florian Weimer
2020-10-16 14:37 ` Adhemerval Zanella
2020-10-30 13:22 ` Florian Weimer
2020-11-03 13:02 ` Adhemerval Zanella
2020-10-01 16:34 ` [PATCH 24/28] elf: Implement a string table for ldconfig, with tail merging Florian Weimer
2020-10-20 14:25 ` Adhemerval Zanella
2020-10-30 17:08 ` Florian Weimer
2020-11-03 13:05 ` Adhemerval Zanella
2020-11-03 15:29 ` Florian Weimer
2020-10-01 16:34 ` [PATCH 25/28] elf: Implement tail merging of strings in ldconfig Florian Weimer
2020-10-22 21:08 ` Adhemerval Zanella
2020-10-30 17:36 ` Florian Weimer
2020-10-01 16:34 ` [PATCH 26/28] elf: In ldconfig, extract the new_sub_entry function from search_dir Florian Weimer
2020-10-27 13:15 ` Adhemerval Zanella
2020-10-01 16:34 ` [PATCH 27/28] elf: Process glibc-hwcaps subdirectories in ldconfig Florian Weimer
2020-10-27 17:28 ` Adhemerval Zanella
2020-11-04 11:57 ` Florian Weimer
2020-10-01 16:34 ` [PATCH 28/28] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing Florian Weimer
2020-10-01 16:50 ` [PATCH 00/28] glibc-hwcaps support H.J. Lu
2020-10-01 16:54 ` Florian Weimer
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