MSVSphere Packaging Team
4 months ago
parent
cb1cb291eb
commit
d04fce7775
@ -0,0 +1,43 @@
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commit afe42e935b3ee97bac9a7064157587777259c60e
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Mon Jun 3 10:49:40 2024 +0200
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elf: Avoid some free (NULL) calls in _dl_update_slotinfo
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This has been confirmed to work around some interposed mallocs. Here
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is a discussion of the impact test ust/libc-wrapper/test_libc-wrapper
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in lttng-tools:
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New TLS usage in libgcc_s.so.1, compatibility impact
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<https://inbox.sourceware.org/libc-alpha/8734v1ieke.fsf@oldenburg.str.redhat.com/>
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Reportedly, this patch also papers over a similar issue when tcmalloc
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2.9.1 is not compiled with -ftls-model=initial-exec. Of course the
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goal really should be to compile mallocs with the initial-exec TLS
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model, but this commit appears to be a useful interim workaround.
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Fixes commit d2123d68275acc0f061e73d5f86ca504e0d5a344 ("elf: Fix slow
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tls access after dlopen [BZ #19924]").
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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diff --git a/elf/dl-tls.c b/elf/dl-tls.c
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index 7b3dd9ab60..670dbc42fc 100644
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--- a/elf/dl-tls.c
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+++ b/elf/dl-tls.c
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@@ -819,7 +819,14 @@ _dl_update_slotinfo (unsigned long int req_modid, size_t new_gen)
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dtv entry free it. Note: this is not AS-safe. */
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/* XXX Ideally we will at some point create a memory
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pool. */
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- free (dtv[modid].pointer.to_free);
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+ /* Avoid calling free on a null pointer. Some mallocs
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+ incorrectly use dynamic TLS, and depending on how the
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+ free function was compiled, it could call
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+ __tls_get_addr before the null pointer check in the
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+ free implementation. Checking here papers over at
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+ least some dynamic TLS usage by interposed mallocs. */
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+ if (dtv[modid].pointer.to_free != NULL)
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+ free (dtv[modid].pointer.to_free);
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dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
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dtv[modid].pointer.to_free = NULL;
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@ -0,0 +1,500 @@
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commit 018f0fc3b818d4d1460a4e2384c24802504b1d20
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Mon Jul 1 17:42:04 2024 +0200
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elf: Support recursive use of dynamic TLS in interposed malloc
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It turns out that quite a few applications use bundled mallocs that
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have been built to use global-dynamic TLS (instead of the recommended
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initial-exec TLS). The previous workaround from
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commit afe42e935b3ee97bac9a7064157587777259c60e ("elf: Avoid some
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free (NULL) calls in _dl_update_slotinfo") does not fix all
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encountered cases unfortunatelly.
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This change avoids the TLS generation update for recursive use
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of TLS from a malloc that was called during a TLS update. This
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is possible because an interposed malloc has a fixed module ID and
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TLS slot. (It cannot be unloaded.) If an initially-loaded module ID
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is encountered in __tls_get_addr and the dynamic linker is already
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in the middle of a TLS update, use the outdated DTV, thus avoiding
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another call into malloc. It's still necessary to update the
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DTV to the most recent generation, to get out of the slow path,
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which is why the check for recursion is needed.
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The bookkeeping is done using a global counter instead of per-thread
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flag because TLS access in the dynamic linker is tricky.
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All this will go away once the dynamic linker stops using malloc
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for TLS, likely as part of a change that pre-allocates all TLS
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during pthread_create/dlopen.
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Fixes commit d2123d68275acc0f061e73d5f86ca504e0d5a344 ("elf: Fix slow
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tls access after dlopen [BZ #19924]").
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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Conflicts:
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elf/Makefile - tests and module-names differences
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diff -Nrup a/elf/Makefile b/elf/Makefile
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--- a/elf/Makefile 2024-07-09 22:06:30.237752048 -0400
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+++ b/elf/Makefile 2024-07-10 14:09:02.996759220 -0400
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@@ -423,6 +423,7 @@ tests += \
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tst-nodeps2 \
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tst-noload \
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tst-null-argv \
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+ tst-recursive-tls \
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tst-relsort1 \
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tst-ro-dynamic \
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tst-rtld-run-static \
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@@ -783,6 +784,23 @@ modules-names = \
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tst-nodeps1-mod \
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tst-nodeps2-mod \
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tst-null-argv-lib \
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+ tst-recursive-tlsmallocmod \
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+ tst-recursive-tlsmod0 \
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+ tst-recursive-tlsmod1 \
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+ tst-recursive-tlsmod2 \
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+ tst-recursive-tlsmod3 \
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+ tst-recursive-tlsmod4 \
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+ tst-recursive-tlsmod5 \
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+ tst-recursive-tlsmod6 \
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+ tst-recursive-tlsmod7 \
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+ tst-recursive-tlsmod8 \
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+ tst-recursive-tlsmod9 \
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+ tst-recursive-tlsmod10 \
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+ tst-recursive-tlsmod11 \
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+ tst-recursive-tlsmod12 \
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+ tst-recursive-tlsmod13 \
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+ tst-recursive-tlsmod14 \
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+ tst-recursive-tlsmod15 \
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tst-relsort1mod1 \
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tst-relsort1mod2 \
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tst-ro-dynamic-mod \
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@@ -2725,3 +2743,11 @@ CFLAGS-tst-tlsgap-mod0.c += -mtls-dialec
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CFLAGS-tst-tlsgap-mod1.c += -mtls-dialect=gnu2
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CFLAGS-tst-tlsgap-mod2.c += -mtls-dialect=gnu2
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endif
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+
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+$(objpfx)tst-recursive-tls: $(objpfx)tst-recursive-tlsmallocmod.so
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+# More objects than DTV_SURPLUS, to trigger DTV reallocation.
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+$(objpfx)tst-recursive-tls.out: \
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+ $(patsubst %,$(objpfx)tst-recursive-tlsmod%.so, \
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+ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)
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+$(objpfx)tst-recursive-tlsmod%.os: tst-recursive-tlsmodN.c
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+ $(compile-command.c) -DVAR=thread_$* -DFUNC=get_threadvar_$*
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diff --git a/elf/dl-tls.c b/elf/dl-tls.c
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index 670dbc42fc..3d221273f1 100644
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--- a/elf/dl-tls.c
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+++ b/elf/dl-tls.c
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@@ -75,6 +75,31 @@
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/* Default for dl_tls_static_optional. */
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#define OPTIONAL_TLS 512
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+/* Used to count the number of threads currently executing dynamic TLS
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+ updates. Used to avoid recursive malloc calls in __tls_get_addr
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+ for an interposed malloc that uses global-dynamic TLS (which is not
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+ recommended); see _dl_tls_allocate_active checks. This could be a
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+ per-thread flag, but would need TLS access in the dynamic linker. */
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+unsigned int _dl_tls_threads_in_update;
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+
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+static inline void
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+_dl_tls_allocate_begin (void)
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+{
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+ atomic_fetch_add_relaxed (&_dl_tls_threads_in_update, 1);
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+}
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+
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+static inline void
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+_dl_tls_allocate_end (void)
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+{
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+ atomic_fetch_add_relaxed (&_dl_tls_threads_in_update, -1);
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+}
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+
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+static inline bool
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+_dl_tls_allocate_active (void)
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+{
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+ return atomic_load_relaxed (&_dl_tls_threads_in_update) > 0;
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+}
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+
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/* Compute the static TLS surplus based on the namespace count and the
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TLS space that can be used for optimizations. */
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static inline int
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@@ -425,12 +450,18 @@ _dl_allocate_tls_storage (void)
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size += TLS_PRE_TCB_SIZE;
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#endif
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- /* Perform the allocation. Reserve space for the required alignment
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- and the pointer to the original allocation. */
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+ /* Reserve space for the required alignment and the pointer to the
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+ original allocation. */
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size_t alignment = GLRO (dl_tls_static_align);
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+
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+ /* Perform the allocation. */
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+ _dl_tls_allocate_begin ();
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void *allocated = malloc (size + alignment + sizeof (void *));
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if (__glibc_unlikely (allocated == NULL))
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- return NULL;
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+ {
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+ _dl_tls_allocate_end ();
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+ return NULL;
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+ }
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/* Perform alignment and allocate the DTV. */
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#if TLS_TCB_AT_TP
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@@ -466,6 +497,8 @@ _dl_allocate_tls_storage (void)
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result = allocate_dtv (result);
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if (result == NULL)
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free (allocated);
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+
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+ _dl_tls_allocate_end ();
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return result;
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}
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@@ -483,6 +516,7 @@ _dl_resize_dtv (dtv_t *dtv, size_t max_modid)
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size_t newsize = max_modid + DTV_SURPLUS;
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size_t oldsize = dtv[-1].counter;
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+ _dl_tls_allocate_begin ();
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if (dtv == GL(dl_initial_dtv))
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{
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/* This is the initial dtv that was either statically allocated in
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@@ -502,6 +536,7 @@ _dl_resize_dtv (dtv_t *dtv, size_t max_modid)
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if (newp == NULL)
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oom ();
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}
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+ _dl_tls_allocate_end ();
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newp[0].counter = newsize;
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@@ -676,7 +711,9 @@ allocate_dtv_entry (size_t alignment, size_t size)
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if (powerof2 (alignment) && alignment <= _Alignof (max_align_t))
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{
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/* The alignment is supported by malloc. */
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+ _dl_tls_allocate_begin ();
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void *ptr = malloc (size);
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+ _dl_tls_allocate_end ();
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return (struct dtv_pointer) { ptr, ptr };
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}
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@@ -688,7 +725,10 @@ allocate_dtv_entry (size_t alignment, size_t size)
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/* Perform the allocation. This is the pointer we need to free
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later. */
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+ _dl_tls_allocate_begin ();
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void *start = malloc (alloc_size);
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+ _dl_tls_allocate_end ();
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+
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if (start == NULL)
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return (struct dtv_pointer) {};
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@@ -826,7 +866,11 @@ _dl_update_slotinfo (unsigned long int req_modid, size_t new_gen)
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free implementation. Checking here papers over at
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least some dynamic TLS usage by interposed mallocs. */
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if (dtv[modid].pointer.to_free != NULL)
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- free (dtv[modid].pointer.to_free);
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+ {
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+ _dl_tls_allocate_begin ();
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+ free (dtv[modid].pointer.to_free);
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+ _dl_tls_allocate_end ();
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+ }
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dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
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dtv[modid].pointer.to_free = NULL;
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@@ -956,10 +1000,22 @@ __tls_get_addr (GET_ADDR_ARGS)
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size_t gen = atomic_load_relaxed (&GL(dl_tls_generation));
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if (__glibc_unlikely (dtv[0].counter != gen))
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{
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- /* Update DTV up to the global generation, see CONCURRENCY NOTES
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- in _dl_update_slotinfo. */
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- gen = atomic_load_acquire (&GL(dl_tls_generation));
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- return update_get_addr (GET_ADDR_PARAM, gen);
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+ if (_dl_tls_allocate_active ()
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+ && GET_ADDR_MODULE < _dl_tls_initial_modid_limit)
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+ /* This is a reentrant __tls_get_addr call, but we can
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+ satisfy it because it's an initially-loaded module ID.
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+ These TLS slotinfo slots do not change, so the
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+ out-of-date generation counter does not matter. However,
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+ if not in a TLS update, still update_get_addr below, to
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+ get off the slow path eventually. */
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+ ;
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+ else
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+ {
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+ /* Update DTV up to the global generation, see CONCURRENCY NOTES
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+ in _dl_update_slotinfo. */
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+ gen = atomic_load_acquire (&GL(dl_tls_generation));
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+ return update_get_addr (GET_ADDR_PARAM, gen);
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+ }
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}
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void *p = dtv[GET_ADDR_MODULE].pointer.val;
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@@ -969,7 +1025,7 @@ __tls_get_addr (GET_ADDR_ARGS)
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return (char *) p + GET_ADDR_OFFSET;
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}
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-#endif
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+#endif /* SHARED */
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/* Look up the module's TLS block as for __tls_get_addr,
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@@ -1018,6 +1074,25 @@ _dl_tls_get_addr_soft (struct link_map *l)
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return data;
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}
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+size_t _dl_tls_initial_modid_limit;
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+
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+void
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+_dl_tls_initial_modid_limit_setup (void)
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+{
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+ struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
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+ size_t idx;
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+ for (idx = 0; idx < listp->len; ++idx)
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+ {
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+ struct link_map *l = listp->slotinfo[idx].map;
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+ if (l == NULL
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+ /* The object can be unloaded, so its modid can be
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+ reassociated. */
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+ || !(l->l_type == lt_executable || l->l_type == lt_library))
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+ break;
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+ }
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+ _dl_tls_initial_modid_limit = idx;
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+}
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+
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void
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_dl_add_to_slotinfo (struct link_map *l, bool do_add)
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@@ -1050,9 +1125,11 @@ _dl_add_to_slotinfo (struct link_map *l, bool do_add)
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the first slot. */
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assert (idx == 0);
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+ _dl_tls_allocate_begin ();
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listp = (struct dtv_slotinfo_list *)
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malloc (sizeof (struct dtv_slotinfo_list)
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+ TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
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+ _dl_tls_allocate_end ();
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if (listp == NULL)
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{
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/* We ran out of memory while resizing the dtv slotinfo list. */
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diff --git a/elf/rtld.c b/elf/rtld.c
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index e9525ea987..6352ba76c5 100644
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--- a/elf/rtld.c
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+++ b/elf/rtld.c
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@@ -788,6 +788,8 @@ init_tls (size_t naudit)
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_dl_fatal_printf ("\
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cannot allocate TLS data structures for initial thread\n");
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+ _dl_tls_initial_modid_limit_setup ();
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+
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/* Store for detection of the special case by __tls_get_addr
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so it knows not to pass this dtv to the normal realloc. */
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GL(dl_initial_dtv) = GET_DTV (tcbp);
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diff --git a/elf/tst-recursive-tls.c b/elf/tst-recursive-tls.c
|
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new file mode 100644
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index 0000000000..716d1f783a
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--- /dev/null
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+++ b/elf/tst-recursive-tls.c
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@@ -0,0 +1,60 @@
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+/* Test with interposed malloc with dynamic TLS.
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+ Copyright (C) 2024 Free Software Foundation, Inc.
|
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+ This file is part of the GNU C Library.
|
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+
|
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+ The GNU C Library is free software; you can redistribute it and/or
|
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+ modify it under the terms of the GNU Lesser General Public
|
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+ License as published by the Free Software Foundation; either
|
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+ version 2.1 of the License, or (at your option) any later version.
|
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+
|
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+ The GNU C Library is distributed in the hope that it will be useful,
|
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
|
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||||
+ Lesser General Public License for more details.
|
||||
+
|
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+ You should have received a copy of the GNU Lesser General Public
|
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+ License along with the GNU C Library; if not, see
|
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+ <https://www.gnu.org/licenses/>. */
|
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+
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+#include <array_length.h>
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+#include <stdio.h>
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+#include <support/check.h>
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+#include <support/xdlfcn.h>
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+
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+/* Defined in tst-recursive-tlsmallocmod.so. */
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+extern __thread unsigned int malloc_subsytem_counter;
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+
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+static int
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+do_test (void)
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+{
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+ /* 16 is large enough to exercise the DTV resizing case. */
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+ void *handles[16];
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+
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+ for (unsigned int i = 0; i < array_length (handles); ++i)
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+ {
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+ /* Re-use the TLS slot for module 0. */
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+ if (i > 0)
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+ xdlclose (handles[0]);
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+
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+ char soname[30];
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+ snprintf (soname, sizeof (soname), "tst-recursive-tlsmod%u.so", i);
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+ handles[i] = xdlopen (soname, RTLD_NOW);
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+
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+ if (i > 0)
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+ {
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+ handles[0] = xdlopen ("tst-recursive-tlsmod0.so", RTLD_NOW);
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+ int (*fptr) (void) = xdlsym (handles[0], "get_threadvar_0");
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+ /* May trigger TLS storage allocation using malloc. */
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+ TEST_COMPARE (fptr (), 0);
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+ }
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+ }
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+
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+ for (unsigned int i = 0; i < array_length (handles); ++i)
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+ xdlclose (handles[i]);
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+
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+ printf ("info: malloc subsystem calls: %u\n", malloc_subsytem_counter);
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+ TEST_VERIFY (malloc_subsytem_counter > 0);
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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diff --git a/elf/tst-recursive-tlsmallocmod.c b/elf/tst-recursive-tlsmallocmod.c
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new file mode 100644
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index 0000000000..c24e9945d1
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--- /dev/null
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+++ b/elf/tst-recursive-tlsmallocmod.c
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@@ -0,0 +1,64 @@
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+/* Interposed malloc with dynamic TLS.
|
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+ Copyright (C) 2024 Free Software Foundation, Inc.
|
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+ This file is part of the GNU C Library.
|
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+
|
||||
+ 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 <stdlib.h>
|
||||
+#include <dlfcn.h>
|
||||
+
|
||||
+__thread unsigned int malloc_subsytem_counter;
|
||||
+
|
||||
+static __typeof (malloc) *malloc_fptr;
|
||||
+static __typeof (free) *free_fptr;
|
||||
+static __typeof (calloc) *calloc_fptr;
|
||||
+static __typeof (realloc) *realloc_fptr;
|
||||
+
|
||||
+static void __attribute__ ((constructor))
|
||||
+init (void)
|
||||
+{
|
||||
+ malloc_fptr = dlsym (RTLD_NEXT, "malloc");
|
||||
+ free_fptr = dlsym (RTLD_NEXT, "free");
|
||||
+ calloc_fptr = dlsym (RTLD_NEXT, "calloc");
|
||||
+ realloc_fptr = dlsym (RTLD_NEXT, "realloc");
|
||||
+}
|
||||
+
|
||||
+void *
|
||||
+malloc (size_t size)
|
||||
+{
|
||||
+ ++malloc_subsytem_counter;
|
||||
+ return malloc_fptr (size);
|
||||
+}
|
||||
+
|
||||
+void
|
||||
+free (void *ptr)
|
||||
+{
|
||||
+ ++malloc_subsytem_counter;
|
||||
+ return free_fptr (ptr);
|
||||
+}
|
||||
+
|
||||
+void *
|
||||
+calloc (size_t a, size_t b)
|
||||
+{
|
||||
+ ++malloc_subsytem_counter;
|
||||
+ return calloc_fptr (a, b);
|
||||
+}
|
||||
+
|
||||
+void *
|
||||
+realloc (void *ptr, size_t size)
|
||||
+{
|
||||
+ ++malloc_subsytem_counter;
|
||||
+ return realloc_fptr (ptr, size);
|
||||
+}
|
||||
diff --git a/elf/tst-recursive-tlsmodN.c b/elf/tst-recursive-tlsmodN.c
|
||||
new file mode 100644
|
||||
index 0000000000..bb7592aee6
|
||||
--- /dev/null
|
||||
+++ b/elf/tst-recursive-tlsmodN.c
|
||||
@@ -0,0 +1,28 @@
|
||||
+/* Test module with global-dynamic TLS. Used to trigger DTV reallocation.
|
||||
+ Copyright (C) 2024 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/>. */
|
||||
+
|
||||
+/* Compiled with VAR and FUNC set via -D. FUNC requires some
|
||||
+ relocation against TLS variable VAR. */
|
||||
+
|
||||
+__thread int VAR;
|
||||
+
|
||||
+int
|
||||
+FUNC (void)
|
||||
+{
|
||||
+ return VAR;
|
||||
+}
|
||||
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
|
||||
index 50f58a60e3..656e8a3fa0 100644
|
||||
--- a/sysdeps/generic/ldsodefs.h
|
||||
+++ b/sysdeps/generic/ldsodefs.h
|
||||
@@ -1256,6 +1256,20 @@ extern struct link_map *_dl_update_slotinfo (unsigned long int req_modid,
|
||||
size_t gen)
|
||||
attribute_hidden;
|
||||
|
||||
+/* The last TLS module ID that is initially loaded, plus 1. TLS
|
||||
+ addresses for modules with IDs lower than that can be obtained from
|
||||
+ the DTV even if its generation is outdated. */
|
||||
+extern size_t _dl_tls_initial_modid_limit attribute_hidden attribute_relro;
|
||||
+
|
||||
+/* Compute _dl_tls_initial_modid_limit. To be called after initial
|
||||
+ relocation. */
|
||||
+void _dl_tls_initial_modid_limit_setup (void) attribute_hidden;
|
||||
+
|
||||
+/* Number of threads currently in a TLS update. This is used to
|
||||
+ detect reentrant __tls_get_addr calls without a per-thread
|
||||
+ flag. */
|
||||
+extern unsigned int _dl_tls_threads_in_update attribute_hidden;
|
||||
+
|
||||
/* Look up the module's TLS block as for __tls_get_addr,
|
||||
but never touch anything. Return null if it's not allocated yet. */
|
||||
extern void *_dl_tls_get_addr_soft (struct link_map *l) attribute_hidden;
|
||||
diff --git a/sysdeps/x86_64/dl-tls.c b/sysdeps/x86_64/dl-tls.c
|
||||
index 869023bbba..b3c1e4fcd7 100644
|
||||
--- a/sysdeps/x86_64/dl-tls.c
|
||||
+++ b/sysdeps/x86_64/dl-tls.c
|
||||
@@ -41,7 +41,10 @@ __tls_get_addr_slow (GET_ADDR_ARGS)
|
||||
dtv_t *dtv = THREAD_DTV ();
|
||||
|
||||
size_t gen = atomic_load_acquire (&GL(dl_tls_generation));
|
||||
- if (__glibc_unlikely (dtv[0].counter != gen))
|
||||
+ if (__glibc_unlikely (dtv[0].counter != gen)
|
||||
+ /* See comment in __tls_get_addr in elf/dl-tls.c. */
|
||||
+ && !(_dl_tls_allocate_active ()
|
||||
+ && GET_ADDR_MODULE < _dl_tls_initial_modid_limit))
|
||||
return update_get_addr (GET_ADDR_PARAM, gen);
|
||||
|
||||
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, NULL);
|
||||
Loading…
Reference in new issue