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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.
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@ -1,3 +1,9 @@
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2016-03-23 Nick Alcock <nick.alcock@oracle.com>
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* sysdeps/unix/sysv/linux/i386/pthread_cond_timedwait.S: Reload
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call-clobbered %eax on retry path.
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* sysdeps/unix/sysv/linux/i386/pthread_cond_wait.S: Likewise.
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2016-03-22 H.J. Lu <hongjiu.lu@intel.com>
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* sysdeps/x86_64/multiarch/memcpy-avx-unaligned.S (MEMCPY):
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@ -297,6 +297,7 @@ __pthread_cond_timedwait:
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correctly. */
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movl dep_mutex(%ebx), %eax
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call __pthread_mutex_cond_lock_adjust
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movl dep_mutex(%ebx), %eax
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xorl %edx, %edx
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call __pthread_mutex_unlock_usercnt
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jmp 8b
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@ -309,6 +309,7 @@ __pthread_cond_wait:
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correctly. */
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movl dep_mutex(%ebx), %eax
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call __pthread_mutex_cond_lock_adjust
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movl dep_mutex(%ebx), %eax
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xorl %edx, %edx
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call __pthread_mutex_unlock_usercnt
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jmp 8b
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