[PATCH] [TSan][MIPS] Adding support for MIPS64

[Sagar Thakur]

================
Comment at: lib/tsan/rtl/tsan_interceptors.cc:661
@@ +660,3 @@
+#ifdef __mips__
+  // For mips memset gets called before a call to __cxa_guard_aquire
+  // which causes a crash in REAL(pthread_create) during initialization
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samsonov wrote:
> sagar wrote:
> > samsonov wrote:
> > > I don't understand this comment. Why does REAL(pthread_create) crash?
> > As per my observation, in x86_64 first __cxa_guard_aquired() is called and its interceptor calls Initialize().
> > Initialize() creates background thread.
> > But in mips64 __interceptor_memset gets called before __cxa_guard_aquire() interceptor. So Initialize() is called from within __intercerptor_memset and REAL(pthread_create) emits a SIGIOT.
> > 
> > @dvyukov I don't know why such behaviour in mips, can you help us with this?
> Why does the call to REAL(pthread_create) succeeds if it is issued from `__cxa_guard_acquired` interceptor and fails if it is issued from `memset` interceptor? I think you'd have to figure it out.
> 
> I don't see the immediate problem from your description: memset interceptor calls Initialize(), which calls InitializeIntercepotrs() (that is supposed to initialize all REAL(foo) function pointers), and only then calls internal_start_thread.
While debugging the code, I observed that __interceptor_memset and __cxa_guard_acquire are being called even before __start. So its reference is probably in LLVM/clang. I have no knowledge from where they are being called.

Through strace in x86_64, the sequence of calls observed:
  rt_sigaction() -> rt_sigprocmask() -> __cxa_guard_acquired() -> Initialize()

In case of mips64, the sequence is:
  __interceptor_memset() -> Initialize()

So for mips64 there is no signal handler registered during Initialize() because rt_sigaction syscall is not yet issued.

I will be very thankful if someone could advice me on how to solve this issue.

http://reviews.llvm.org/D6291