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| author |   Jakub Jelinek <jakub@redhat.com> | 2020-12-03 13:33:44 +0100 |
|---|---|---|
| committer |   Sergei Trofimovich <slyfox@gentoo.org> | 2020-12-08 07:34:24 +0000 |
| commit | e88935d964f9a4f8274d30369de4a427be1caef2 (patch) | |
| tree | 915cae9ccc197c697baa65351aa0a197de6ce911 | |
| parent | __vfscanf_internal: fix aliasing violation (bug 26690) (diff) | |
| download | glibc-e88935d964f9a4f8274d30369de4a427be1caef2.tar.gz glibc-e88935d964f9a4f8274d30369de4a427be1caef2.tar.bz2 glibc-e88935d964f9a4f8274d30369de4a427be1caef2.zip | |
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.
(cherry picked from commit 1d9cbb96082e646de7515a1667efa041ffb79958)
Added to Gentoo for gcc-11 compatibility.
| -rw-r--r-- | sysdeps/i386/nptl/tls.h | 7 | ||||
| -rw-r--r-- | sysdeps/x86_64/nptl/tls.h | 7 |
2 files changed, 12 insertions, 2 deletions
diff --git a/sysdeps/i386/nptl/tls.h b/sysdeps/i386/nptl/tls.h index ec03fc189c..01945220cb 100644 --- a/sysdeps/i386/nptl/tls.h +++ b/sysdeps/i386/nptl/tls.h @@ -240,11 +240,16 @@ tls_fill_user_desc (union user_desc_init *desc, 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_gs *) offsetof (struct pthread, header.self)) +# else +# define THREAD_SELF \ ({ struct pthread *__self; \ asm ("movl %%gs:%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 \ diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h index 7ba9c4e69b..8f32a669ca 100644 --- a/sysdeps/x86_64/nptl/tls.h +++ b/sysdeps/x86_64/nptl/tls.h @@ -186,11 +186,16 @@ _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. */ |