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| author | Jakub Jelinek <jakub@redhat.com> | 2020-12-03 13:33:44 +0100 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2020-12-03 13:48:55 +0100 |
| commit | 1d9cbb96082e646de7515a1667efa041ffb79958 (patch) | |
| tree | b52e641f97c37dfed401538a038a4ae058ea87ce /sysdeps/x86_64 | |
| parent | 7c331116971d38e57703af4097ed13ab6bef91d0 (diff) | |
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x86: Fix THREAD_SELF definition to avoid ld.so crash (bug 27004)
The previous definition of THREAD_SELF did not tell the compiler
that %fs (or %gs) usage is invalid for the !DL_LOOKUP_GSCOPE_LOCK
case in _dl_lookup_symbol_x. As a result, ld.so could try to use the
TCB before it was initialized.
As the comment in tls.h explains, asm volatile is undesirable here.
Using the __seg_fs (or __seg_gs) namespace does not interfere with
optimization, and expresses that THREAD_SELF is potentially trapping.
Diffstat (limited to 'sysdeps/x86_64')
| -rw-r--r-- | sysdeps/x86_64/nptl/tls.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h index a08bf972de..ccb5f24d92 100644 --- a/sysdeps/x86_64/nptl/tls.h +++ b/sysdeps/x86_64/nptl/tls.h @@ -180,11 +180,16 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80, assignments like pthread_descr self = thread_self(); do not get optimized away. */ -# define THREAD_SELF \ +# if __GNUC_PREREQ (6, 0) +# define THREAD_SELF \ + (*(struct pthread *__seg_fs *) offsetof (struct pthread, header.self)) +# else +# define THREAD_SELF \ ({ struct pthread *__self; \ asm ("mov %%fs:%c1,%0" : "=r" (__self) \ : "i" (offsetof (struct pthread, header.self))); \ __self;}) +# endif /* Magic for libthread_db to know how to do THREAD_SELF. */ # define DB_THREAD_SELF_INCLUDE <sys/reg.h> /* For the FS constant. */ |