[sancov] Handle fork.

Reset coverage data on fork().
For memory-mapped mode (coverage_direct=1) this helps avoid loss of data
(before this change two processes would write to the same file simultaneously).
For normal mode, this reduces coverage dump size, because PCs from the parent
process are no longer inherited by the child.

llvm-svn: 210180

7 files changed, 155 insertions, 8 deletions

diff --git a/compiler-rt/lib/asan/asan_interceptors.cc b/compiler-rt/lib/asan/asan_interceptors.cc
index 9dccddfa7e5..4ae03ece25d 100644
--- a/compiler-rt/lib/asan/asan_interceptors.cc
+++ b/compiler-rt/lib/asan/asan_interceptors.cc
@@ -697,6 +697,16 @@ INTERCEPTOR(int, __cxa_atexit, void (*func)(void *), void *arg,
 }
 #endif  // ASAN_INTERCEPT___CXA_ATEXIT
 
+#if ASAN_INTERCEPT_FORK
+INTERCEPTOR(int, fork, void) {
+  ENSURE_ASAN_INITED();
+  if (common_flags()->coverage) CovBeforeFork();
+  int pid = REAL(fork)();
+  if (common_flags()->coverage) CovAfterFork(pid);
+  return pid;
+}
+#endif  // ASAN_INTERCEPT_FORK
+
 #if SANITIZER_WINDOWS
 INTERCEPTOR_WINAPI(DWORD, CreateThread,
                    void* security, uptr stack_size,
@@ -808,6 +818,10 @@ void InitializeAsanInterceptors() {
   ASAN_INTERCEPT_FUNC(__cxa_atexit);
 #endif
 
+#if ASAN_INTERCEPT_FORK
+  ASAN_INTERCEPT_FUNC(fork);
+#endif
+
   // Some Windows-specific interceptors.
 #if SANITIZER_WINDOWS
   InitializeWindowsInterceptors();
diff --git a/compiler-rt/lib/asan/asan_interceptors.h b/compiler-rt/lib/asan/asan_interceptors.h
index 3b7b2653b3f..9ba4cd7bfb2 100644
--- a/compiler-rt/lib/asan/asan_interceptors.h
+++ b/compiler-rt/lib/asan/asan_interceptors.h
@@ -27,6 +27,7 @@
 # define ASAN_INTERCEPT_INDEX 1
 # define ASAN_INTERCEPT_PTHREAD_CREATE 1
 # define ASAN_INTERCEPT_MLOCKX 1
+# define ASAN_INTERCEPT_FORK 1
 #else
 # define ASAN_INTERCEPT_ATOLL_AND_STRTOLL 0
 # define ASAN_INTERCEPT__LONGJMP 0
@@ -34,6 +35,7 @@
 # define ASAN_INTERCEPT_INDEX 0
 # define ASAN_INTERCEPT_PTHREAD_CREATE 0
 # define ASAN_INTERCEPT_MLOCKX 0
+# define ASAN_INTERCEPT_FORK 0
 #endif
 
 #if SANITIZER_FREEBSD || SANITIZER_LINUX
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common.h b/compiler-rt/lib/sanitizer_common/sanitizer_common.h
index 7411b8dd9f8..435e1fafb8e 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common.h
@@ -193,6 +193,8 @@ void CovPrepareForSandboxing(__sanitizer_sandbox_arguments *args);
 void SetSandboxingCallback(void (*f)());
 
 void CovUpdateMapping();
+void CovBeforeFork();
+void CovAfterFork(int child_pid);
 
 void InitTlsSize();
 uptr GetTlsSize();
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep.cc b/compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
index e0f021f89b1..206d07ccd59 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
@@ -59,6 +59,8 @@ namespace __sanitizer {
 class CoverageData {
  public:
   void Init();
+  void BeforeFork();
+  void AfterFork(int child_pid);
   void Extend(uptr npcs);
   void Add(uptr pc);
 
@@ -86,6 +88,7 @@ class CoverageData {
   StaticSpinMutex mu;
 
   void DirectOpen();
+  void ReInit();
 };
 
 static CoverageData coverage_data;
@@ -107,23 +110,47 @@ void CoverageData::DirectOpen() {
 void CoverageData::Init() {
   pc_array = reinterpret_cast<uptr *>(
       MmapNoReserveOrDie(sizeof(uptr) * kPcArrayMaxSize, "CovInit"));
+  pc_fd = kInvalidFd;
   if (common_flags()->coverage_direct) {
     atomic_store(&pc_array_size, 0, memory_order_relaxed);
     atomic_store(&pc_array_index, 0, memory_order_relaxed);
   } else {
-    pc_fd = 0;
     atomic_store(&pc_array_size, kPcArrayMaxSize, memory_order_relaxed);
     atomic_store(&pc_array_index, 0, memory_order_relaxed);
   }
 }
 
+void CoverageData::ReInit() {
+  internal_munmap(pc_array, sizeof(uptr) * kPcArrayMaxSize);
+  if (pc_fd != kInvalidFd) internal_close(pc_fd);
+  if (common_flags()->coverage_direct) {
+    // In memory-mapped mode we must extend the new file to the known array
+    // size.
+    uptr size = atomic_load(&pc_array_size, memory_order_relaxed);
+    Init();
+    if (size) Extend(size);
+  } else {
+    Init();
+  }
+}
+
+void CoverageData::BeforeFork() {
+  mu.Lock();
+}
+
+void CoverageData::AfterFork(int child_pid) {
+  // We are single-threaded so it's OK to release the lock early.
+  mu.Unlock();
+  if (child_pid == 0) ReInit();
+}
+
 // Extend coverage PC array to fit additional npcs elements.
 void CoverageData::Extend(uptr npcs) {
   if (!common_flags()->coverage_direct) return;
   SpinMutexLock l(&mu);
 
-  if (!pc_fd) DirectOpen();
-  CHECK(pc_fd);
+  if (pc_fd == kInvalidFd) DirectOpen();
+  CHECK_NE(pc_fd, kInvalidFd);
 
   uptr size = atomic_load(&pc_array_size, memory_order_relaxed);
   size += npcs * sizeof(uptr);
@@ -324,6 +351,15 @@ int MaybeOpenCovFile(const char *name) {
   if (!common_flags()->coverage) return -1;
   return CovOpenFile(true /* packed */, name);
 }
+
+void CovBeforeFork() {
+  coverage_data.BeforeFork();
+}
+
+void CovAfterFork(int child_pid) {
+  coverage_data.AfterFork(child_pid);
+}
+
 }  // namespace __sanitizer
 
 extern "C" {
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc b/compiler-rt/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
index b3c8dc8916a..bfeb3210758 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
@@ -36,8 +36,27 @@
 namespace __sanitizer {
 
 static const uptr kMaxNumberOfModules = 1 << 14;
+static const uptr kMaxTextSize = 64 * 1024;
 
-static char *last_mapping;
+struct CachedMapping {
+ public:
+  bool TestAndUpdate(const char *new_mapping) {
+    int new_pid = internal_getpid();
+    if (last_mapping && last_pid == new_pid &&
+        internal_strcmp(last_mapping, new_mapping) == 0)
+      return false;
+    if (!last_mapping) last_mapping = (char *)InternalAlloc(kMaxTextSize);
+    last_pid = new_pid;
+    internal_strncpy(last_mapping, new_mapping, kMaxTextSize);
+    return true;
+  }
+
+ private:
+  char *last_mapping;
+  int last_pid;
+};
+
+static CachedMapping cached_mapping;
 static StaticSpinMutex mapping_mu;
 
 void CovUpdateMapping() {
@@ -45,7 +64,6 @@ void CovUpdateMapping() {
 
   SpinMutexLock l(&mapping_mu);
 
-  const uptr kMaxTextSize = 64 * 1024;
   InternalScopedString text(kMaxTextSize);
   InternalScopedBuffer<char> modules_data(kMaxNumberOfModules *
                                           sizeof(LoadedModule));
@@ -66,9 +84,8 @@ void CovUpdateMapping() {
   }
 
   // Do not write mapping if it is the same as the one we've wrote last time.
-  if (last_mapping && (internal_strcmp(last_mapping, text.data()) == 0)) return;
-  if (!last_mapping) last_mapping = (char *)InternalAlloc(kMaxTextSize);
-  internal_strncpy(last_mapping, text.data(), kMaxTextSize);
+  if (!cached_mapping.TestAndUpdate(text.data()))
+    return;
 
   int err;
   InternalScopedString tmp_path(64 +
diff --git a/compiler-rt/test/asan/TestCases/Linux/coverage-fork-direct.cc b/compiler-rt/test/asan/TestCases/Linux/coverage-fork-direct.cc
new file mode 100644
index 00000000000..7489b72505a
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Linux/coverage-fork-direct.cc
@@ -0,0 +1,38 @@
+// RUN: %clangxx_asan -mllvm -asan-coverage=1 %s -o %t
+// RUN: rm -rf %T/coverage-fork-direct
+// RUN: mkdir -p %T/coverage-fork-direct && cd %T/coverage-fork-direct
+// RUN: (ASAN_OPTIONS=coverage=1:coverage_direct=1:verbosity=1 %run %t; \
+// RUN:  %sancov rawunpack *.sancov.raw; %sancov print *.sancov) 2>&1
+//
+// XFAIL: android
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+__attribute__((noinline))
+void foo() { printf("foo\n"); }
+
+__attribute__((noinline))
+void bar() { printf("bar\n"); }
+
+__attribute__((noinline))
+void baz() { printf("baz\n"); }
+
+int main(int argc, char **argv) {
+  pid_t child_pid = fork();
+  if (child_pid == 0) {
+    fprintf(stderr, "Child PID: %d\n", getpid());
+    baz();
+  } else {
+    fprintf(stderr, "Parent PID: %d\n", getpid());
+    foo();
+    bar();
+  }
+  return 0;
+}
+
+// CHECK-DAG: Child PID: [[ChildPID:[0-9]+]]
+// CHECK-DAG: Parent PID: [[ParentPID:[0-9]+]]
+// CHECK-DAG: read 3 PCs from {{.*}}.[[ParentPID]].sancov
+// CHECK-DAG: read 1 PCs from {{.*}}.[[ChildPID]].sancov
diff --git a/compiler-rt/test/asan/TestCases/Linux/coverage-fork.cc b/compiler-rt/test/asan/TestCases/Linux/coverage-fork.cc
new file mode 100644
index 00000000000..28b2a49840b
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Linux/coverage-fork.cc
@@ -0,0 +1,38 @@
+// RUN: %clangxx_asan -mllvm -asan-coverage=1 %s -o %t
+// RUN: export ASAN_OPTIONS=coverage=1:coverage_direct=0:verbosity=1
+// RUN: rm -rf %T/coverage-fork
+// RUN: mkdir -p %T/coverage-fork && cd %T/coverage-fork
+// RUN: %run %t 2>&1 | FileCheck %s
+//
+// XFAIL: android
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+__attribute__((noinline))
+void foo() { printf("foo\n"); }
+
+__attribute__((noinline))
+void bar() { printf("bar\n"); }
+
+__attribute__((noinline))
+void baz() { printf("baz\n"); }
+
+int main(int argc, char **argv) {
+  pid_t child_pid = fork();
+  if (child_pid == 0) {
+    fprintf(stderr, "Child PID: %d\n", getpid());
+    baz();
+  } else {
+    fprintf(stderr, "Parent PID: %d\n", getpid());
+    foo();
+    bar();
+  }
+  return 0;
+}
+
+// CHECK-DAG: Child PID: [[ChildPID:[0-9]+]]
+// CHECK-DAG: [[ChildPID]].sancov: 1 PCs written
+// CHECK-DAG: Parent PID: [[ParentPID:[0-9]+]]
+// CHECK-DAG: [[ParentPID]].sancov: 3 PCs written