tsan: strip __libc_start_main frame

[dvyukov]

Summary

We strip all frames below main but in some cases it may be not enough.
Namely, when main is instrumented but does not call any other instrumented code.
In this case tsan_func_entry in main obtains PC pointing to libc_start_main
(as we pass caller PC to tsan_func_entry), but nothing obtains PC pointing
to main itself (as main does not call any instrumented code).
In such case we will not have main in the stack, and stripping everything
below main won't work.
So strip libc_start_main explicitly as well.
But keep stripping of main because __libc_start_main is glibc/linux-specific,
so looking for main is more reliable (and usually main is present in stacks).

Depends on D106957.

[vitalybuka]

compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp

72

To my taste this stripping adds no value.
Stripping of top internal frames makes sense, as usually users walk from the top to the frame relevant to the error.
As a user myself I am sometimes annoyed by top irrelevant frames. But I don't care about spam in the bottom.

[dvyukov]

compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp

72

Acknowledged

compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp

#if !SANITIZER_GO
   // Strip frame above 'main'
   if (last2 && 0 == internal_strcmp(last2, "main")) {
     last_frame->ClearAll();
     last_frame2->next = nullptr;
   // Strip our internal thread start routine.
   } else if (last && 0 == internal_strcmp(last, "__tsan_thread_start_func")) {
     last_frame->ClearAll();
     last_frame2->next = nullptr;
-  // Strip global ctors init.
-  } else if (last && 0 == internal_strcmp(last, "__do_global_ctors_aux")) {
+    // Strip global ctors init, .preinit_array and main caller.
+  } else if (last && (0 == internal_strcmp(last, "__do_global_ctors_aux") ||
+                      0 == internal_strcmp(last, "__libc_csu_init") ||
+                      0 == internal_strcmp(last, "__libc_start_main"))) {
     last_frame->ClearAll();
     last_frame2->next = nullptr;
   // If both are 0, then we probably just failed to symbolize.
   } else if (last || last2) {
     // Ensure that we recovered stack completely. Trimmed stack
     // can actually happen if we do not instrument some code,
     // so it's only a debug print. However we must try hard to not miss it
     // due to our fault.

compiler-rt/test/tsan/java_symbolization.cpp

 // CHECK:     #2 Caller1 CallerFile.java:111:22
 // CHECK:     #3 Caller2 CallerFile.java:333:44
 // CHECK-NOT: #4
 // CHECK:   Previous write
 // CHECK:     #0 MyInnerFunc MyInnerFile.java:1234:56
 // CHECK:     #1 MyOuterFunc MyOuterFile.java:4321:65
 // CHECK:     #2 Caller1 CallerFile.java:111:22
 // CHECK:     #3 Caller2 CallerFile.java:333:44
-// On Linux/glibc #4 is __libc_start_main, but can be something else elsewhere.
-// CHECK:     #4
+// CHECK-NOT: #4
 // CHECK:   Location is heap block of size 32 at {{.*}} allocated by main thread:
 // CHECK:     #0 Allocer1 Alloc.java:11:222
 // CHECK:     #1 Allocer2 Alloc.java:33:444
-// On Linux/glibc #2 is __libc_start_main, but can be something else elsewhere.
-// CHECK:     #2
+// CHECK-NOT: #2
 // CHECK: DONE