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| author | Nick Alcock <nick.alcock@oracle.com> | 2016-03-23 13:40:14 +0100 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2016-03-23 13:40:14 +0100 |
| commit | 7a25d6a84df9fea56963569ceccaaf7c2a88f161 (patch) | |
| tree | e701185129f1018d96af4555c440e12d0189d33b /sysdeps/unix/sysv/linux | |
| parent | 3c9a4cd16cbc7b79094fec68add2df66061ab5d7 (diff) | |
| download | glibc-7a25d6a84df9fea56963569ceccaaf7c2a88f161.tar.gz glibc-7a25d6a84df9fea56963569ceccaaf7c2a88f161.tar.xz glibc-7a25d6a84df9fea56963569ceccaaf7c2a88f161.zip | |
x86, pthread_cond_*wait: Do not depend on %eax not being clobbered
The x86-specific versions of both pthread_cond_wait and pthread_cond_timedwait have (in their fall-back-to-futex-wait slow paths) calls to __pthread_mutex_cond_lock_adjust followed by __pthread_mutex_unlock_usercnt, which load the parameters before the first call but then assume that the first parameter, in %eax, will survive unaffected. This happens to have been true before now, but %eax is a call-clobbered register, and this assumption is not safe: it could change at any time, at GCC's whim, and indeed the stack-protector canary checking code clobbers %eax while checking that the canary is uncorrupted. So reload %eax before calling __pthread_mutex_unlock_usercnt. (Do this unconditionally, even when stack-protection is not in use, because it's the right thing to do, it's a slow path, and anything else is dicing with death.) * sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S: Reload call-clobbered %eax on retry path. * sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S: Likewise.
Diffstat (limited to 'sysdeps/unix/sysv/linux')
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S | 1 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S | 1 |
2 files changed, 2 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S b/sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S index 96f8a8dc73..6256376923 100644 --- a/sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S +++ b/sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S @@ -297,6 +297,7 @@ __pthread_cond_timedwait: correctly. */ movl dep_mutex(%ebx), %eax call __pthread_mutex_cond_lock_adjust + movl dep_mutex(%ebx), %eax xorl %edx, %edx call __pthread_mutex_unlock_usercnt jmp 8b diff --git a/sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S b/sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S index 94302b0641..5016718801 100644 --- a/sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S +++ b/sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S @@ -309,6 +309,7 @@ __pthread_cond_wait: correctly. */ movl dep_mutex(%ebx), %eax call __pthread_mutex_cond_lock_adjust + movl dep_mutex(%ebx), %eax xorl %edx, %edx call __pthread_mutex_unlock_usercnt jmp 8b |