tsan: remove real func check from interceptors

[dvyukov]

Summary

If the real function is not intercepted,
we are going to crash one way or another.
The question is just in the failure mode:
error message vs NULL deref. But the message
costs us a check in every interceptor and
they are not observed to be failing in real life
for a long time, also other sanitizers don't
have this check as well (also crash on
NULL deref if that happens).
Remove the check from non-debug mode.

[amyk]

Hello,

It looks like this patch is causing the following LIT test failure (https://lab.llvm.org/buildbot/#/builders/105/builds/16777/steps/7/logs/FAIL__SanitizerCommon-tsan-powerpc64le-Linux__ptra):

SanitizerCommon-tsan-powerpc64le-Linux :: Linux/ptrace.cpp

On the following PPC LE buildbots:

https://lab.llvm.org/buildbot/#/builders/105
https://lab.llvm.org/buildbot/#/builders/121
https://lab.llvm.org/buildbot/#/builders/57

Would you be able to take a look at this failure and resolve it, or pull this patch accordingly?
Thank you in advance.

[dvyukov]

Hi Amy,

I am completely puzzled how this change can cause such failure mode...
It looks like some latent bugs (stack corruption) on powerpc. I don't have access to powerpc machines, so I can only offer this:
https://reviews.llvm.org/D112703

compiler-rt/lib/tsan/rtl/tsan_interceptors.h

#define SCOPED_INTERCEPTOR_RAW(func, ...)      \
   ThreadState *thr = cur_thread_init();        \
   const uptr caller_pc = GET_CALLER_PC();      \
   ScopedInterceptor si(thr, #func, caller_pc); \
   const uptr pc = GET_CURRENT_PC();            \
   (void)pc;
 
 #define SCOPED_TSAN_INTERCEPTOR(func, ...)                                \
   SCOPED_INTERCEPTOR_RAW(func, __VA_ARGS__);                              \
-  if (REAL(func) == 0) {                                                  \
-    Report("FATAL: ThreadSanitizer: failed to intercept %s\n", #func);    \
-    Die();                                                                \
-  }                                                                       \
+  DCHECK(REAL(func));                                                     \
   if (!thr->is_inited || thr->ignore_interceptors || thr->in_ignored_lib) \
     return REAL(func)(__VA_ARGS__);
 
 #define SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_START() \
     si.DisableIgnores();
 
 #define SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_END() \
     si.EnableIgnores();