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* [glibc] elf: Fix DTV gap reuse logic (BZ #27135)
@ 2021-07-14 18:10 Adhemerval Zanella
0 siblings, 0 replies; 2+ messages in thread
From: Adhemerval Zanella @ 2021-07-14 18:10 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=ba33937be210da5d07f7f01709323743f66011ce
commit ba33937be210da5d07f7f01709323743f66011ce
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri Jun 25 10:54:12 2021 -0300
elf: Fix DTV gap reuse logic (BZ #27135)
This is updated version of the 572bd547d57a (reverted by 40ebfd016ad2)
that fixes the _dl_next_tls_modid issues.
This issue with 572bd547d57a patch is the DTV entry will be only
update on dl_open_worker() with the update_tls_slotinfo() call after
all dependencies are being processed by _dl_map_object_deps(). However
_dl_map_object_deps() itself might call _dl_next_tls_modid(), and since
the _dl_tls_dtv_slotinfo_list::map is not yet set the entry will be
wrongly reused.
This patch fixes by renaming the _dl_next_tls_modid() function to
_dl_assign_tls_modid() and by passing the link_map so it can set
the slotinfo value so a subsequente _dl_next_tls_modid() call will
see the entry as allocated.
The intermediary value is cleared up on remove_slotinfo() for the case
a library fails to load with RTLD_NOW.
This patch fixes BZ #27135.
Checked on x86_64-linux-gnu.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Diff:
---
elf/Makefile | 64 ++++++++++-
elf/dl-close.c | 8 +-
elf/dl-load.c | 2 +-
elf/dl-open.c | 10 --
elf/dl-tls.c | 17 +--
elf/rtld.c | 2 +-
elf/tst-tls20.c | 275 +++++++++++++++++++++++++++++++++++++++++++--
sysdeps/generic/ldsodefs.h | 4 +-
8 files changed, 349 insertions(+), 33 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index 4b320e8b3a..bdd5cc9e1a 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -253,6 +253,13 @@ one-hundred = $(foreach x,0 1 2 3 4 5 6 7 8 9, \
0$x 1$x 2$x 3$x 4$x 5$x 6$x 7$x 8$x 9$x)
tst-tls-many-dynamic-modules := \
$(foreach n,$(one-hundred),tst-tls-manydynamic$(n)mod)
+tst-tls-many-dynamic-modules-dep-suffixes = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 \
+ 14 15 16 17 18 19
+tst-tls-many-dynamic-modules-dep = \
+ $(foreach n,$(tst-tls-many-dynamic-modules-dep-suffixes),tst-tls-manydynamic$(n)mod-dep)
+tst-tls-many-dynamic-modules-dep-bad-suffixes = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
+tst-tls-many-dynamic-modules-dep-bad = \
+ $(foreach n,$(tst-tls-many-dynamic-modules-dep-bad-suffixes),tst-tls-manydynamic$(n)mod-dep-bad)
extra-test-objs += $(tlsmod17a-modules:=.os) $(tlsmod18a-modules:=.os) \
tst-tlsalign-vars.o
test-extras += tst-tlsmod17a tst-tlsmod18a tst-tlsalign-vars
@@ -325,6 +332,8 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
tst-audit11mod1 tst-audit11mod2 tst-auditmod11 \
tst-audit12mod1 tst-audit12mod2 tst-audit12mod3 tst-auditmod12 \
tst-latepthreadmod $(tst-tls-many-dynamic-modules) \
+ $(tst-tls-many-dynamic-modules-dep) \
+ $(tst-tls-many-dynamic-modules-dep-bad) \
tst-nodelete-dlclose-dso tst-nodelete-dlclose-plugin \
tst-main1mod tst-absolute-sym-lib \
tst-absolute-zero-lib tst-big-note-lib tst-unwind-ctor-lib \
@@ -1812,10 +1821,63 @@ $(objpfx)tst-rtld-help.out: $(objpfx)ld.so
$(evaluate-test)
# Reuses tst-tls-many-dynamic-modules
+$(patsubst %,$(objpfx)%.os,$(tst-tls-many-dynamic-modules-dep)): \
+ $(objpfx)tst-tls-manydynamic%mod-dep.os : tst-tls-manydynamicmod.c
+ $(compile-command.c) \
+ -DNAME=tls_global_$* -DSETTER=set_value_$* -DGETTER=get_value_$*
+$(patsubst %,$(objpfx)%.os,$(tst-tls-many-dynamic-modules-dep-bad)): \
+ $(objpfx)tst-tls-manydynamic%mod-dep-bad.os : tst-tls-manydynamicmod.c
+ $(compile-command.c) \
+ -DNAME=tls_global_$* -DSETTER=set_value_$* -DGETTER=get_value_$*
tst-tls20mod-bad.so-no-z-defs = yes
+# Single dependency.
+$(objpfx)tst-tls-manydynamic0mod-dep.so: $(objpfx)tst-tls-manydynamic1mod-dep.so
+# Double dependencies.
+$(objpfx)tst-tls-manydynamic2mod-dep.so: $(objpfx)tst-tls-manydynamic3mod-dep.so \
+ $(objpfx)tst-tls-manydynamic4mod-dep.so
+# Double dependencies with each dependency depent of another module.
+$(objpfx)tst-tls-manydynamic5mod-dep.so: $(objpfx)tst-tls-manydynamic6mod-dep.so \
+ $(objpfx)tst-tls-manydynamic7mod-dep.so
+$(objpfx)tst-tls-manydynamic6mod-dep.so: $(objpfx)tst-tls-manydynamic8mod-dep.so
+$(objpfx)tst-tls-manydynamic7mod-dep.so: $(objpfx)tst-tls-manydynamic8mod-dep.so
+# Long chain with one double dependency in the middle
+$(objpfx)tst-tls-manydynamic9mod-dep.so: $(objpfx)tst-tls-manydynamic10mod-dep.so \
+ $(objpfx)tst-tls-manydynamic11mod-dep.so
+$(objpfx)tst-tls-manydynamic10mod-dep.so: $(objpfx)tst-tls-manydynamic12mod-dep.so
+$(objpfx)tst-tls-manydynamic12mod-dep.so: $(objpfx)tst-tls-manydynamic13mod-dep.so
+# Long chain with two double depedencies in the middle
+$(objpfx)tst-tls-manydynamic14mod-dep.so: $(objpfx)tst-tls-manydynamic15mod-dep.so
+$(objpfx)tst-tls-manydynamic15mod-dep.so: $(objpfx)tst-tls-manydynamic16mod-dep.so \
+ $(objpfx)tst-tls-manydynamic17mod-dep.so
+$(objpfx)tst-tls-manydynamic16mod-dep.so: $(objpfx)tst-tls-manydynamic18mod-dep.so \
+ $(objpfx)tst-tls-manydynamic19mod-dep.so
+# Same but with an invalid module.
+# Single dependency.
+$(objpfx)tst-tls-manydynamic0mod-dep-bad.so: $(objpfx)tst-tls20mod-bad.so
+# Double dependencies.
+$(objpfx)tst-tls-manydynamic1mod-dep-bad.so: $(objpfx)tst-tls-manydynamic2mod-dep-bad.so \
+ $(objpfx)tst-tls20mod-bad.so
+# Double dependencies with each dependency depent of another module.
+$(objpfx)tst-tls-manydynamic3mod-dep-bad.so: $(objpfx)tst-tls-manydynamic4mod-dep-bad.so \
+ $(objpfx)tst-tls-manydynamic5mod-dep-bad.so
+$(objpfx)tst-tls-manydynamic4mod-dep-bad.so: $(objpfx)tst-tls20mod-bad.so
+$(objpfx)tst-tls-manydynamic5mod-dep-bad.so: $(objpfx)tst-tls20mod-bad.so
+# Long chain with one double dependency in the middle
+$(objpfx)tst-tls-manydynamic6mod-dep-bad.so: $(objpfx)tst-tls-manydynamic7mod-dep-bad.so \
+ $(objpfx)tst-tls-manydynamic8mod-dep-bad.so
+$(objpfx)tst-tls-manydynamic7mod-dep-bad.so: $(objpfx)tst-tls-manydynamic9mod-dep-bad.so
+$(objpfx)tst-tls-manydynamic9mod-dep-bad.so: $(objpfx)tst-tls20mod-bad.so
+# Long chain with two double depedencies in the middle
+$(objpfx)tst-tls-manydynamic10mod-dep-bad.so: $(objpfx)tst-tls-manydynamic11mod-dep-bad.so
+$(objpfx)tst-tls-manydynamic11mod-dep-bad.so: $(objpfx)tst-tls-manydynamic12mod-dep-bad.so \
+ $(objpfx)tst-tls-manydynamic13mod-dep-bad.so
+$(objpfx)tst-tls-manydynamic12mod-dep-bad.so: $(objpfx)tst-tls-manydynamic14mod-dep-bad.so \
+ $(objpfx)tst-tls20mod-bad.so
$(objpfx)tst-tls20: $(shared-thread-library)
$(objpfx)tst-tls20.out: $(objpfx)tst-tls20mod-bad.so \
- $(tst-tls-many-dynamic-modules:%=$(objpfx)%.so)
+ $(tst-tls-many-dynamic-modules:%=$(objpfx)%.so) \
+ $(tst-tls-many-dynamic-modules-dep:%=$(objpfx)%.so) \
+ $(tst-tls-many-dynamic-modules-dep-bad:%=$(objpfx)%.so) \
# Reuses tst-tls-many-dynamic-modules
$(objpfx)tst-tls21: $(shared-thread-library)
diff --git a/elf/dl-close.c b/elf/dl-close.c
index 3720e47dd1..f39001cab9 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -77,8 +77,6 @@ remove_slotinfo (size_t idx, struct dtv_slotinfo_list *listp, size_t disp,
object that wasn't fully set up. */
if (__glibc_likely (old_map != NULL))
{
- assert (old_map->l_tls_modid == idx);
-
/* Mark the entry as unused. These can be read concurrently. */
atomic_store_relaxed (&listp->slotinfo[idx - disp].gen,
GL(dl_tls_generation) + 1);
@@ -88,7 +86,11 @@ remove_slotinfo (size_t idx, struct dtv_slotinfo_list *listp, size_t disp,
/* If this is not the last currently used entry no need to look
further. */
if (idx != GL(dl_tls_max_dtv_idx))
- return true;
+ {
+ /* There is an unused dtv entry in the middle. */
+ GL(dl_tls_dtv_gaps) = true;
+ return true;
+ }
}
while (idx - disp > (disp == 0 ? 1 + GL(dl_tls_static_nelem) : 0))
diff --git a/elf/dl-load.c b/elf/dl-load.c
index a08df001af..650e4edc35 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1498,7 +1498,7 @@ cannot enable executable stack as shared object requires");
not set up TLS data structures, so don't use them now. */
|| __glibc_likely (GL(dl_tls_dtv_slotinfo_list) != NULL)))
/* Assign the next available module ID. */
- l->l_tls_modid = _dl_next_tls_modid ();
+ _dl_assign_tls_modid (l);
#ifdef DL_AFTER_LOAD
DL_AFTER_LOAD (l);
diff --git a/elf/dl-open.c b/elf/dl-open.c
index a066f39bd0..d2240d8747 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -899,16 +899,6 @@ no more namespaces available for dlmopen()"));
state if relocation failed, for example. */
if (args.map)
{
- /* Maybe some of the modules which were loaded use TLS.
- Since it will be removed in the following _dl_close call
- we have to mark the dtv array as having gaps to fill the
- holes. This is a pessimistic assumption which won't hurt
- if not true. There is no need to do this when we are
- loading the auditing DSOs since TLS has not yet been set
- up. */
- if ((mode & __RTLD_AUDIT) == 0)
- GL(dl_tls_dtv_gaps) = true;
-
_dl_close_worker (args.map, true);
/* All l_nodelete_pending objects should have been deleted
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index 2b5161d10a..423e380f7c 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -126,8 +126,8 @@ oom (void)
}
-size_t
-_dl_next_tls_modid (void)
+void
+_dl_assign_tls_modid (struct link_map *l)
{
size_t result;
@@ -157,7 +157,11 @@ _dl_next_tls_modid (void)
}
if (result - disp < runp->len)
- break;
+ {
+ /* Mark the entry as used, so any dependency see it. */
+ atomic_store_relaxed (&runp->slotinfo[result - disp].map, l);
+ break;
+ }
disp += runp->len;
}
@@ -184,17 +188,14 @@ _dl_next_tls_modid (void)
atomic_store_relaxed (&GL(dl_tls_max_dtv_idx), result);
}
- return result;
+ l->l_tls_modid = result;
}
size_t
_dl_count_modids (void)
{
- /* It is rare that we have gaps; see elf/dl-open.c (_dl_open) where
- we fail to load a module and unload it leaving a gap. If we don't
- have gaps then the number of modids is the current maximum so
- return that. */
+ /* The count is the max unless dlclose or failed dlopen created gaps. */
if (__glibc_likely (!GL(dl_tls_dtv_gaps)))
return GL(dl_tls_max_dtv_idx);
diff --git a/elf/rtld.c b/elf/rtld.c
index e3fb2a5b2a..d733359eaf 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1721,7 +1721,7 @@ dl_main (const ElfW(Phdr) *phdr,
/* Add the dynamic linker to the TLS list if it also uses TLS. */
if (GL(dl_rtld_map).l_tls_blocksize != 0)
/* Assign a module ID. Do this before loading any audit modules. */
- GL(dl_rtld_map).l_tls_modid = _dl_next_tls_modid ();
+ _dl_assign_tls_modid (&GL(dl_rtld_map));
audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_AUDIT);
audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_DEPAUDIT);
diff --git a/elf/tst-tls20.c b/elf/tst-tls20.c
index 9977ec8032..d8d04fe574 100644
--- a/elf/tst-tls20.c
+++ b/elf/tst-tls20.c
@@ -16,12 +16,14 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <array_length.h>
#include <dlfcn.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <support/check.h>
#include <support/support.h>
+#include <support/test-driver.h>
#include <support/xdlfcn.h>
#include <support/xthread.h>
@@ -59,28 +61,75 @@ access (int i)
char *buf = xasprintf ("tls_global_%02d", i);
dlerror ();
int *p = dlsym (mod[i], buf);
- printf ("mod[%d]: &tls = %p\n", i, p);
+ if (test_verbose)
+ printf ("mod[%d]: &tls = %p\n", i, p);
if (p == NULL)
FAIL_EXIT1 ("dlsym failed: %s\n", dlerror ());
+ TEST_COMPARE (*p, 0);
++*p;
free (buf);
}
+static void
+access_mod (const char *modname, void *mod, int i)
+{
+ char *modsym = xasprintf ("tls_global_%d", i);
+ dlerror ();
+ int *p = dlsym (mod, modsym);
+ if (test_verbose)
+ printf ("%s: &tls = %p\n", modname, p);
+ if (p == NULL)
+ FAIL_EXIT1 ("dlsym failed: %s\n", dlerror ());
+ TEST_COMPARE (*p, 0);
+ ++*p;
+ free (modsym);
+}
+
+static void
+access_dep (int i)
+{
+ char *modname = xasprintf ("tst-tls-manydynamic%dmod-dep.so", i);
+ void *moddep = xdlopen (modname, RTLD_LAZY);
+ access_mod (modname, moddep, i);
+ free (modname);
+ xdlclose (moddep);
+}
+
+struct start_args
+{
+ const char *modname;
+ void *mod;
+ int modi;
+ int ndeps;
+ const int *deps;
+};
+
static void *
start (void *a)
{
+ struct start_args *args = a;
+
for (int i = 0; i < NMOD; i++)
if (mod[i] != NULL)
access (i);
+
+ if (args != NULL)
+ {
+ access_mod (args->modname, args->mod, args->modi);
+ for (int n = 0; n < args->ndeps; n++)
+ access_dep (args->deps[n]);
+ }
+
return 0;
}
-static int
-do_test (void)
+/* This test gaps with shared libraries with dynamic TLS that has no
+ dependencies. The DTV gap is set with by trying to load an invalid
+ module, the entry should be used on the dlopen. */
+static void
+do_test_no_depedency (void)
{
- int i;
-
- for (i = 0; i < NMOD; i++)
+ for (int i = 0; i < NMOD; i++)
{
load_mod (i);
/* Bump the generation of mod[0] without using new dtv slot. */
@@ -91,8 +140,220 @@ do_test (void)
pthread_t t = xpthread_create (0, start, 0);
xpthread_join (t);
}
- for (i = 0; i < NMOD; i++)
+ for (int i = 0; i < NMOD; i++)
unload_mod (i);
+}
+
+/* The following test check DTV gaps handling with shared libraries that has
+ dependencies. It defines 5 different sets:
+
+ 1. Single dependency:
+ mod0 -> mod1
+ 2. Double dependency:
+ mod2 -> [mod3,mod4]
+ 3. Double dependency with each dependency depent of another module:
+ mod5 -> [mod6,mod7] -> mod8
+ 4. Long chain with one double dependency in the middle:
+ mod9 -> [mod10, mod11] -> mod12 -> mod13
+ 5. Long chain with two double depedencies in the middle:
+ mod14 -> mod15 -> [mod16, mod17]
+ mod15 -> [mod18, mod19]
+
+ This does not cover all the possible gaps and configuration, but it
+ should check if different dynamic shared sets are placed correctly in
+ different gaps configurations. */
+
+static int
+nmodules (uint32_t v)
+{
+ unsigned int r = 0;
+ while (v >>= 1)
+ r++;
+ return r + 1;
+}
+
+static inline bool
+is_mod_set (uint32_t g, uint32_t n)
+{
+ return (1U << (n - 1)) & g;
+}
+
+static void
+print_gap (uint32_t g)
+{
+ if (!test_verbose)
+ return;
+ printf ("gap: ");
+ int nmods = nmodules (g);
+ for (int n = 1; n <= nmods; n++)
+ printf ("%c", ((1 << (n - 1)) & g) == 0 ? 'G' : 'M');
+ printf ("\n");
+}
+
+static void
+do_test_dependency (void)
+{
+ /* Maps the module and its dependencies, use thread to access the TLS on
+ each loaded module. */
+ static const int tlsmanydeps0[] = { 1 };
+ static const int tlsmanydeps1[] = { 3, 4 };
+ static const int tlsmanydeps2[] = { 6, 7, 8 };
+ static const int tlsmanydeps3[] = { 10, 11, 12 };
+ static const int tlsmanydeps4[] = { 15, 16, 17, 18, 19 };
+ static const struct tlsmanydeps_t
+ {
+ int modi;
+ int ndeps;
+ const int *deps;
+ } tlsmanydeps[] =
+ {
+ { 0, array_length (tlsmanydeps0), tlsmanydeps0 },
+ { 2, array_length (tlsmanydeps1), tlsmanydeps1 },
+ { 5, array_length (tlsmanydeps2), tlsmanydeps2 },
+ { 9, array_length (tlsmanydeps3), tlsmanydeps3 },
+ { 14, array_length (tlsmanydeps4), tlsmanydeps4 },
+ };
+
+ /* The gap configuration is defined as a bitmap: the bit set represents a
+ loaded module prior the tests execution, while a bit unsed is a module
+ unloaded. Not all permtation will show gaps, but it is simpler than
+ define each one independently. */
+ for (uint32_t g = 0; g < 64; g++)
+ {
+ print_gap (g);
+ int nmods = nmodules (g);
+
+ int mods[nmods];
+ /* We use '0' as indication for a gap, to avoid the dlclose on iteration
+ cleanup. */
+ for (int n = 1; n <= nmods; n++)
+ {
+ load_mod (n);
+ mods[n] = n;
+ }
+ for (int n = 1; n <= nmods; n++)
+ {
+ if (!is_mod_set (g, n))
+ {
+ unload_mod (n);
+ mods[n] = 0;
+ }
+ }
+
+ for (int t = 0; t < array_length (tlsmanydeps); t++)
+ {
+ char *moddepname = xasprintf ("tst-tls-manydynamic%dmod-dep.so",
+ tlsmanydeps[t].modi);
+ void *moddep = xdlopen (moddepname, RTLD_LAZY);
+
+ /* Access TLS in all loaded modules. */
+ struct start_args args =
+ {
+ moddepname,
+ moddep,
+ tlsmanydeps[t].modi,
+ tlsmanydeps[t].ndeps,
+ tlsmanydeps[t].deps
+ };
+ pthread_t t = xpthread_create (0, start, &args);
+ xpthread_join (t);
+
+ free (moddepname);
+ xdlclose (moddep);
+ }
+
+ for (int n = 1; n <= nmods; n++)
+ if (mods[n] != 0)
+ unload_mod (n);
+ }
+}
+
+/* The following test check DTV gaps handling with shared libraries that has
+ invalid dependencies. It defines 5 different sets:
+
+ 1. Single dependency:
+ mod0 -> invalid
+ 2. Double dependency:
+ mod1 -> [mod2,invalid]
+ 3. Double dependency with each dependency depent of another module:
+ mod3 -> [mod4,mod5] -> invalid
+ 4. Long chain with one double dependency in the middle:
+ mod6 -> [mod7, mod8] -> mod12 -> invalid
+ 5. Long chain with two double depedencies in the middle:
+ mod10 -> mod11 -> [mod12, mod13]
+ mod12 -> [mod14, invalid]
+
+ This does not cover all the possible gaps and configuration, but it
+ should check if different dynamic shared sets are placed correctly in
+ different gaps configurations. */
+
+static void
+do_test_invalid_dependency (bool bind_now)
+{
+ static const int tlsmanydeps[] = { 0, 1, 3, 6, 10 };
+
+ /* The gap configuration is defined as a bitmap: the bit set represents a
+ loaded module prior the tests execution, while a bit unsed is a module
+ unloaded. Not all permtation will show gaps, but it is simpler than
+ define each one independently. */
+ for (uint32_t g = 0; g < 64; g++)
+ {
+ print_gap (g);
+ int nmods = nmodules (g);
+
+ int mods[nmods];
+ /* We use '0' as indication for a gap, to avoid the dlclose on iteration
+ cleanup. */
+ for (int n = 1; n <= nmods; n++)
+ {
+ load_mod (n);
+ mods[n] = n;
+ }
+ for (int n = 1; n <= nmods; n++)
+ {
+ if (!is_mod_set (g, n))
+ {
+ unload_mod (n);
+ mods[n] = 0;
+ }
+ }
+
+ for (int t = 0; t < array_length (tlsmanydeps); t++)
+ {
+ char *moddepname = xasprintf ("tst-tls-manydynamic%dmod-dep-bad.so",
+ tlsmanydeps[t]);
+ void *moddep;
+ if (bind_now)
+ {
+ moddep = dlopen (moddepname, RTLD_NOW);
+ TEST_VERIFY (moddep == 0);
+ }
+ else
+ moddep = dlopen (moddepname, RTLD_LAZY);
+
+ /* Access TLS in all loaded modules. */
+ pthread_t t = xpthread_create (0, start, NULL);
+ xpthread_join (t);
+
+ free (moddepname);
+ if (!bind_now)
+ xdlclose (moddep);
+ }
+
+ for (int n = 1; n <= nmods; n++)
+ if (mods[n] != 0)
+ unload_mod (n);
+ }
+}
+
+static int
+do_test (void)
+{
+ do_test_no_depedency ();
+ do_test_dependency ();
+ do_test_invalid_dependency (true);
+ do_test_invalid_dependency (false);
+
return 0;
}
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 176394de4d..9c15259236 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -1171,8 +1171,8 @@ extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
extern void _dl_sysdep_start_cleanup (void) attribute_hidden;
-/* Determine next available module ID. */
-extern size_t _dl_next_tls_modid (void) attribute_hidden;
+/* Determine next available module ID and set the L l_tls_modid. */
+extern void _dl_assign_tls_modid (struct link_map *l) attribute_hidden;
/* Count the modules with TLS segments. */
extern size_t _dl_count_modids (void) attribute_hidden;
^ permalink raw reply [flat|nested] 2+ messages in thread
* [glibc] elf: Fix DTV gap reuse logic [BZ #27135]
@ 2021-05-11 16:17 Szabolcs Nagy
0 siblings, 0 replies; 2+ messages in thread
From: Szabolcs Nagy @ 2021-05-11 16:17 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=572bd547d57a39b6cf0ea072545dc4048921f4c3
commit 572bd547d57a39b6cf0ea072545dc4048921f4c3
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Thu Dec 31 13:59:38 2020 +0000
elf: Fix DTV gap reuse logic [BZ #27135]
For some reason only dlopen failure caused dtv gaps to be reused.
It is possible that the intent was to never reuse modids for a
different module, but after dlopen failure all gaps are reused
not just the ones caused by the unfinished dlopened.
So the code has to handle reused modids already which seems to
work, however the data races at thread creation and tls access
(see bug 19329 and bug 27111) may be more severe if slots are
reused so this is scheduled after those fixes. I think fixing
the races are not simpler if reuse is disallowed and reuse has
other benefits, so set GL(dl_tls_dtv_gaps) whenever entries are
removed from the middle of the slotinfo list. The value does
not have to be correct: incorrect true value causes the next
modid query to do a slotinfo walk, incorrect false will leave
gaps and new entries are added at the end.
Fixes bug 27135.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Diff:
---
elf/dl-close.c | 6 +++++-
elf/dl-open.c | 10 ----------
elf/dl-tls.c | 5 +----
3 files changed, 6 insertions(+), 15 deletions(-)
diff --git a/elf/dl-close.c b/elf/dl-close.c
index 3720e47dd1..9f31532f41 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -88,7 +88,11 @@ remove_slotinfo (size_t idx, struct dtv_slotinfo_list *listp, size_t disp,
/* If this is not the last currently used entry no need to look
further. */
if (idx != GL(dl_tls_max_dtv_idx))
- return true;
+ {
+ /* There is an unused dtv entry in the middle. */
+ GL(dl_tls_dtv_gaps) = true;
+ return true;
+ }
}
while (idx - disp > (disp == 0 ? 1 + GL(dl_tls_static_nelem) : 0))
diff --git a/elf/dl-open.c b/elf/dl-open.c
index bb79ef00f1..0887fc5cc5 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -890,16 +890,6 @@ no more namespaces available for dlmopen()"));
state if relocation failed, for example. */
if (args.map)
{
- /* Maybe some of the modules which were loaded use TLS.
- Since it will be removed in the following _dl_close call
- we have to mark the dtv array as having gaps to fill the
- holes. This is a pessimistic assumption which won't hurt
- if not true. There is no need to do this when we are
- loading the auditing DSOs since TLS has not yet been set
- up. */
- if ((mode & __RTLD_AUDIT) == 0)
- GL(dl_tls_dtv_gaps) = true;
-
_dl_close_worker (args.map, true);
/* All l_nodelete_pending objects should have been deleted
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index dc69cd984e..67781bc108 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -191,10 +191,7 @@ _dl_next_tls_modid (void)
size_t
_dl_count_modids (void)
{
- /* It is rare that we have gaps; see elf/dl-open.c (_dl_open) where
- we fail to load a module and unload it leaving a gap. If we don't
- have gaps then the number of modids is the current maximum so
- return that. */
+ /* The count is the max unless dlclose or failed dlopen created gaps. */
if (__glibc_likely (!GL(dl_tls_dtv_gaps)))
return GL(dl_tls_max_dtv_idx);
^ permalink raw reply [flat|nested] 2+ messages in thread
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