[compiler-rt] d31b2dc - tsan: add debugging code for ptrace test failures

[Dmitry Vyukov via llvm-commits]

Author: Dmitry Vyukov
Date: 2021-10-29T17:37:02+02:00
New Revision: d31b2dc235f1b1eff27c553012520792b7a0eb47

URL: https://github.com/llvm/llvm-project/commit/d31b2dc235f1b1eff27c553012520792b7a0eb47
DIFF: https://github.com/llvm/llvm-project/commit/d31b2dc235f1b1eff27c553012520792b7a0eb47.diff

LOG: tsan: add debugging code for ptrace test failures

Debugging of crashes on powerpc after commit:
c80604f7a3 ("tsan: remove real func check from interceptors")
Somehow replacing if with DCHECK leads to strange failures in:
SanitizerCommon-tsan-powerpc64le-Linux :: Linux/ptrace.cpp
https://lab.llvm.org/buildbot/#/builders/105
https://lab.llvm.org/buildbot/#/builders/121
https://lab.llvm.org/buildbot/#/builders/57

The hypothesis is that something writes out-of-bounds
into pt_regs on stack and that corrupts internal tsan state.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D112703

Added: 
    

Modified: 
    compiler-rt/lib/tsan/rtl/tsan_interceptors.h
    compiler-rt/test/sanitizer_common/TestCases/Linux/ptrace.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors.h b/compiler-rt/lib/tsan/rtl/tsan_interceptors.h
index 3886a30cd88d1..61dbb81ffec43 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors.h
@@ -43,9 +43,26 @@ inline bool in_symbolizer() {
   ScopedInterceptor si(thr, #func, GET_CALLER_PC()); \
   UNUSED const uptr pc = GET_CURRENT_PC();
 
+#ifdef __powerpc64__
+// Debugging of crashes on powerpc after commit:
+// c80604f7a3 ("tsan: remove real func check from interceptors")
+// Somehow replacing if with DCHECK leads to strange failures in:
+// SanitizerCommon-tsan-powerpc64le-Linux :: Linux/ptrace.cpp
+// https://lab.llvm.org/buildbot/#/builders/105
+// https://lab.llvm.org/buildbot/#/builders/121
+// https://lab.llvm.org/buildbot/#/builders/57
+#  define CHECK_REAL_FUNC(func)                                          \
+    if (REAL(func) == 0) {                                               \
+      Report("FATAL: ThreadSanitizer: failed to intercept %s\n", #func); \
+      Die();                                                             \
+    }
+#else
+#  define CHECK_REAL_FUNC(func) DCHECK(REAL(func))
+#endif
+
 #define SCOPED_TSAN_INTERCEPTOR(func, ...)                                \
   SCOPED_INTERCEPTOR_RAW(func, __VA_ARGS__);                              \
-  DCHECK(REAL(func));                                                     \
+  CHECK_REAL_FUNC(func);                                                  \
   if (!thr->is_inited || thr->ignore_interceptors || thr->in_ignored_lib) \
     return REAL(func)(__VA_ARGS__);
 

diff  --git a/compiler-rt/test/sanitizer_common/TestCases/Linux/ptrace.cpp b/compiler-rt/test/sanitizer_common/TestCases/Linux/ptrace.cpp
index 82532c35fab5e..a2d32439e5003 100644
--- a/compiler-rt/test/sanitizer_common/TestCases/Linux/ptrace.cpp
+++ b/compiler-rt/test/sanitizer_common/TestCases/Linux/ptrace.cpp
@@ -3,15 +3,16 @@
 // UNSUPPORTED: android
 
 #include <assert.h>
+#include <elf.h>
 #include <signal.h>
 #include <stdio.h>
+#include <string.h>
 #include <sys/ptrace.h>
 #include <sys/types.h>
+#include <sys/uio.h>
 #include <sys/user.h>
 #include <sys/wait.h>
-#include <sys/uio.h>
 #include <unistd.h>
-#include <elf.h>
 #if __mips64 || __arm__
  #include <asm/ptrace.h>
  #include <sys/procfs.h>
@@ -46,9 +47,14 @@ int main(void) {
 #endif // __x86_64__
 
 #if (__powerpc64__ || __mips64 || __arm__)
-    struct pt_regs regs;
+    // Check that nothing writes out-of-bounds.
+    struct pt_regs regs_buf[4];
+    memset(&regs_buf, 0xcd, sizeof(regs_buf));
+    struct pt_regs &regs = regs_buf[1];
     res = ptrace((enum __ptrace_request)PTRACE_GETREGS, pid, NULL, &regs);
     assert(!res);
+    assert(memcmp(&regs_buf[0], &regs_buf[3], sizeof(regs_buf[3])) == 0);
+    assert(memcmp(&regs_buf[2], &regs_buf[3], sizeof(regs_buf[3])) == 0);
 #if (__powerpc64__)
     if (regs.nip)
       printf("%lx\n", regs.nip);