[tsan] Allow unloading of ignored libraries

Allows unloading and reloading of ignored libraries.
We don't attempt to reuse or free memory of unloaded library.
So TSan will assert if an ignored library is reloaded 128 times.

Author: goussepi

compiler-rt/lib/sanitizer_common/sanitizer_libignore.cpp

@@ -33,6 +33,7 @@ void LibIgnore::AddIgnoredLibrary(const char *name_templ) {
   lib->name = nullptr;
   lib->real_name = nullptr;
   lib->loaded = false;
+  lib->ignored_code_range_id = kInvalidCodeRangeId;
 }
 
 void LibIgnore::OnLibraryLoaded(const char *name) {
@@ -81,17 +82,24 @@ void LibIgnore::OnLibraryLoaded(const char *name) {
         const uptr idx =
             atomic_load(&ignored_ranges_count_, memory_order_relaxed);
         CHECK_LT(idx, ARRAY_SIZE(ignored_code_ranges_));
-        ignored_code_ranges_[idx].begin = range.beg;
+        ignored_code_ranges_[idx].begin(range.beg);
         ignored_code_ranges_[idx].end = range.end;
+        ignored_code_ranges_[idx].loaded = 1;
+        // Record the index of the ignored range.
+        lib->ignored_code_range_id = idx;
         atomic_store(&ignored_ranges_count_, idx + 1, memory_order_release);
         break;
       }
     }
     if (lib->loaded && !loaded) {
-      Report("%s: library '%s' that was matched against called_from_lib"
+      VReport(1, "%s: library '%s' that was matched against called_from_lib"
              " suppression '%s' is unloaded\n",
              SanitizerToolName, lib->name, lib->templ);
-      Die();
+      // The library is unloaded so mark the ignored code range as unloaded.
+      CHECK_NE(lib->ignored_code_range_id, kInvalidCodeRangeId);
+      ignored_code_ranges_[lib->ignored_code_range_id].loaded = 0;
+      lib->ignored_code_range_id = kInvalidCodeRangeId;
+      lib->loaded = false;
     }
   }
 

compiler-rt/lib/sanitizer_common/sanitizer_libignore.h

@@ -54,24 +54,51 @@ class LibIgnore {
     char *name;
     char *real_name;  // target of symlink
     bool loaded;
+    uptr ignored_code_range_id;
   };
 
   struct LibCodeRange {
     uptr begin;
     uptr end;
   };
 
+  // Marks a range as loaded by utilizing the least significant bit of the code
+  // range. Assumes the start of the code range is 2-byte aligned.
+  struct LibLoadedCodeRange {
+    uptr begin() const { return begin_ << 1; }
+    void begin(uptr begin) {
+      CHECK_EQ(begin & 0x1, 0);
+      begin_ = begin >> 1;
+    }
+
+  private:
+    uptr begin_ : 63;
+
+  public:
+    uptr loaded : 1;
+    uptr end;
+  };
+
+  static_assert(sizeof(LibLoadedCodeRange) == 16,
+                "LibLoadedCodeRange size expected to be 16-bytes for "
+                "performance reasons.");
+
+  inline bool IsInRange(uptr pc, const LibLoadedCodeRange &range) const {
+    return (pc >= range.begin() && pc < range.end);
+  }
+
   inline bool IsInRange(uptr pc, const LibCodeRange &range) const {
     return (pc >= range.begin && pc < range.end);
   }
 
   static const uptr kMaxIgnoredRanges = 128;
   static const uptr kMaxInstrumentedRanges = 1024;
   static const uptr kMaxLibs = 1024;
+  static const uptr kInvalidCodeRangeId = ~0x0ULL;
 
   // Hot part:
   atomic_uintptr_t ignored_ranges_count_;
-  LibCodeRange ignored_code_ranges_[kMaxIgnoredRanges];
+  LibLoadedCodeRange ignored_code_ranges_[kMaxIgnoredRanges];
 
   atomic_uintptr_t instrumented_ranges_count_;
   LibCodeRange instrumented_code_ranges_[kMaxInstrumentedRanges];
@@ -90,7 +117,8 @@ class LibIgnore {
 inline bool LibIgnore::IsIgnored(uptr pc, bool *pc_in_ignored_lib) const {
   const uptr n = atomic_load(&ignored_ranges_count_, memory_order_acquire);
   for (uptr i = 0; i < n; i++) {
-    if (IsInRange(pc, ignored_code_ranges_[i])) {
+    if (ignored_code_ranges_[i].loaded &&
+        IsInRange(pc, ignored_code_ranges_[i])) {
       *pc_in_ignored_lib = true;
       return true;
     }

compiler-rt/test/tsan/ignore_lib3.cpp

@@ -3,10 +3,10 @@
 
 // RUN: %clangxx_tsan -O1 %s -DLIB -fPIC -fno-sanitize=thread -shared -o %t-dir/libignore_lib3.so
 // RUN: %clangxx_tsan -O1 %s %link_libcxx_tsan -o %t-dir/executable
-// RUN: %env_tsan_opts=suppressions='%s.supp' %deflake %run %t-dir/executable | FileCheck %s
+// RUN: %env_tsan_opts=suppressions='%s.supp':verbosity=1 %run %t-dir/executable 2>&1 | FileCheck %s
 
 // Tests that unloading of a library matched against called_from_lib suppression
-// causes program crash (this is not supported).
+// is supported.
 
 // Some aarch64 kernels do not support non executable write pages
 // REQUIRES: stable-runtime
@@ -22,18 +22,31 @@
 
 int main(int argc, char **argv) {
   std::string lib = std::string(dirname(argv[0])) + "/libignore_lib3.so";
-  void *h = dlopen(lib.c_str(), RTLD_GLOBAL | RTLD_NOW);
-  dlclose(h);
+  void *h;
+  void (*f)();
+  // Try opening, closing and reopening the ignored lib.
+  for (unsigned int k = 0; k < 2; k++) {
+    h = dlopen(lib.c_str(), RTLD_GLOBAL | RTLD_NOW);
+    if (h == 0)
+      exit(printf("failed to load the library (%d)\n", errno));
+    f = (void (*)())dlsym(h, "libfunc");
+    if (f == 0)
+      exit(printf("failed to find the func (%d)\n", errno));
+    f();
+    dlclose(h);
+  }
   fprintf(stderr, "OK\n");
 }
 
 #else  // #ifdef LIB
 
-extern "C" void libfunc() {
-}
+#include "ignore_lib_lib.h"
 
 #endif  // #ifdef LIB
 
-// CHECK: ThreadSanitizer: library {{.*}} that was matched against called_from_lib suppression 'ignore_lib3.so' is unloaded
-// CHECK-NOT: OK
+// CHECK: Matched called_from_lib suppression 'ignore_lib3.so'
+// CHECK: library '{{.*}}ignore_lib3.so' that was matched against called_from_lib suppression 'ignore_lib3.so' is unloaded
+// CHECK: Matched called_from_lib suppression 'ignore_lib3.so'
+// CHECK: library '{{.*}}ignore_lib3.so' that was matched against called_from_lib suppression 'ignore_lib3.so' is unloaded
+// CHECK: OK