[compiler-rt] r287632 - tsan: switch libignore from /proc/self/maps to dl_iterate_phdr

[Dmitry Vyukov via llvm-commits]

Author: dvyukov
Date: Tue Nov 22 03:49:11 2016
New Revision: 287632

URL: http://llvm.org/viewvc/llvm-project?rev=287632&view=rev
Log:
tsan: switch libignore from /proc/self/maps to dl_iterate_phdr

/proc/self/maps can't be read atomically, this leads to episodic
crashes in libignore as it thinks that a module is loaded twice.
See the new test for an example.
dl_iterate_phdr does not have this problem.
Switch libignore to dl_iterate_phdr.


Added:
    compiler-rt/trunk/test/tsan/ignore_lib5.cc
    compiler-rt/trunk/test/tsan/ignore_lib5.cc.supp
Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_libignore.cc

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_libignore.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_libignore.cc?rev=287632&r1=287631&r2=287632&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_libignore.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_libignore.cc Tue Nov 22 03:49:11 2016
@@ -50,23 +50,23 @@ void LibIgnore::OnLibraryLoaded(const ch
   }
 
   // Scan suppressions list and find newly loaded and unloaded libraries.
-  MemoryMappingLayout proc_maps(/*cache_enabled*/false);
-  InternalScopedString module(kMaxPathLength);
+  ListOfModules modules;
+  modules.init();
   for (uptr i = 0; i < count_; i++) {
     Lib *lib = &libs_[i];
     bool loaded = false;
-    proc_maps.Reset();
-    uptr b, e, off, prot;
-    while (proc_maps.Next(&b, &e, &off, module.data(), module.size(), &prot)) {
-      if ((prot & MemoryMappingLayout::kProtectionExecute) == 0)
-        continue;
-      if (TemplateMatch(lib->templ, module.data()) ||
-          (lib->real_name &&
-          internal_strcmp(lib->real_name, module.data()) == 0)) {
+    for (const auto &mod : modules) {
+      for (const auto &range : mod.ranges()) {
+        if (!range.executable)
+          continue;
+        if (!TemplateMatch(lib->templ, mod.full_name()) &&
+            !(lib->real_name &&
+            internal_strcmp(lib->real_name, mod.full_name()) == 0))
+          continue;
         if (loaded) {
           Report("%s: called_from_lib suppression '%s' is matched against"
                  " 2 libraries: '%s' and '%s'\n",
-                 SanitizerToolName, lib->templ, lib->name, module.data());
+                 SanitizerToolName, lib->templ, lib->name, mod.full_name());
           Die();
         }
         loaded = true;
@@ -75,13 +75,14 @@ void LibIgnore::OnLibraryLoaded(const ch
         VReport(1,
                 "Matched called_from_lib suppression '%s' against library"
                 " '%s'\n",
-                lib->templ, module.data());
+                lib->templ, mod.full_name());
         lib->loaded = true;
-        lib->name = internal_strdup(module.data());
+        lib->name = internal_strdup(mod.full_name());
         const uptr idx = atomic_load(&loaded_count_, memory_order_relaxed);
-        code_ranges_[idx].begin = b;
-        code_ranges_[idx].end = e;
+        code_ranges_[idx].begin = range.beg;
+        code_ranges_[idx].end = range.end;
         atomic_store(&loaded_count_, idx + 1, memory_order_release);
+        break;
       }
     }
     if (lib->loaded && !loaded) {

Added: compiler-rt/trunk/test/tsan/ignore_lib5.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/tsan/ignore_lib5.cc?rev=287632&view=auto
==============================================================================
--- compiler-rt/trunk/test/tsan/ignore_lib5.cc (added)
+++ compiler-rt/trunk/test/tsan/ignore_lib5.cc Tue Nov 22 03:49:11 2016
@@ -0,0 +1,65 @@
+// RUN: %clangxx_tsan -O1 %s -DLIB -fPIC -fno-sanitize=thread -shared -o %T/libignore_lib1.so
+// RUN: %clangxx_tsan -O1 %s -o %t
+// RUN: echo running w/o suppressions:
+// RUN: %deflake %run %t | FileCheck %s --check-prefix=CHECK-NOSUPP
+// RUN: echo running with suppressions:
+// RUN: %env_tsan_opts=suppressions='%s.supp' %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-WITHSUPP
+
+// REQUIRES: stable-runtime
+
+// Previously the test episodically failed with:
+//   ThreadSanitizer: called_from_lib suppression '/libignore_lib1.so$' is
+//   matched against 2 libraries: '/libignore_lib1.so' and '/libignore_lib1.so'
+// This was caused by non-atomicity of reading of /proc/self/maps.
+
+#ifndef LIB
+
+#include <dlfcn.h>
+#include <sys/mman.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <libgen.h>
+#include <string>
+#include "test.h"
+
+void *thr(void *arg) {
+  // This thread creates lots of separate mappings in /proc/self/maps before
+  // the ignored library.
+  for (int i = 0; i < 10000; i++) {
+    if (i == 5000)
+      barrier_wait(&barrier);
+    mmap(0, 4096, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1 , 0);
+    mmap(0, 4096, PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1 , 0);
+  }
+  return 0;
+}
+
+int main(int argc, char **argv) {
+  barrier_init(&barrier, 2);
+  pthread_t th;
+  pthread_create(&th, 0, thr, 0);
+  barrier_wait(&barrier);
+  std::string lib = std::string(dirname(argv[0])) + "/libignore_lib1.so";
+  void *h = dlopen(lib.c_str(), RTLD_GLOBAL | RTLD_NOW);
+  if (h == 0)
+    exit(printf("failed to load the library (%d)\n", errno));
+  void (*f)() = (void(*)())dlsym(h, "libfunc");
+  if (f == 0)
+    exit(printf("failed to find the func (%d)\n", errno));
+  pthread_join(th, 0);
+  f();
+}
+
+#else  // #ifdef LIB
+
+#include "ignore_lib_lib.h"
+
+#endif  // #ifdef LIB
+
+// CHECK-NOSUPP: WARNING: ThreadSanitizer: data race
+// CHECK-NOSUPP: OK
+
+// CHECK-WITHSUPP-NOT: WARNING: ThreadSanitizer: data race
+// CHECK-WITHSUPP: OK
+

Added: compiler-rt/trunk/test/tsan/ignore_lib5.cc.supp
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/tsan/ignore_lib5.cc.supp?rev=287632&view=auto
==============================================================================
--- compiler-rt/trunk/test/tsan/ignore_lib5.cc.supp (added)
+++ compiler-rt/trunk/test/tsan/ignore_lib5.cc.supp Tue Nov 22 03:49:11 2016
@@ -0,0 +1,2 @@
+called_from_lib:/libignore_lib1.so$
+