[msan] Disable mlock/mlockall to work around a linux kernel bug.

The same logic is present in ASan and TSan.

llvm-svn: 193755

compiler-rt/lib/msan/msan_interceptors.cc

@@ -1172,6 +1172,35 @@ INTERCEPTOR(void *, shmat, int shmid, const void *shmaddr, int shmflg) {
   return p;
 }
 
+// Linux kernel has a bug that leads to kernel deadlock if a process
+// maps TBs of memory and then calls mlock().
+static void MlockIsUnsupported() {
+  static atomic_uint8_t printed;
+  if (atomic_exchange(&printed, 1, memory_order_relaxed))
+    return;
+  if (common_flags()->verbosity > 0)
+    Printf("INFO: MemorySanitizer ignores mlock/mlockall/munlock/munlockall\n");
+}
+
+INTERCEPTOR(int, mlock, const void *addr, uptr len) {
+  MlockIsUnsupported();
+  return 0;
+}
+
+INTERCEPTOR(int, munlock, const void *addr, uptr len) {
+  MlockIsUnsupported();
+  return 0;
+}
+
+INTERCEPTOR(int, mlockall, int flags) {
+  MlockIsUnsupported();
+  return 0;
+}
+
+INTERCEPTOR(int, munlockall, void) {
+  MlockIsUnsupported();
+  return 0;
+}
 
 struct MSanInterceptorContext {
   bool in_interceptor_scope;

compiler-rt/lib/msan/tests/msan_test.cc

@@ -3496,3 +3496,10 @@ TEST(MemorySanitizerAllocator, get_allocated_size_and_ownership) {
 
   delete int_ptr;
 }
+
+TEST(MemorySanitizer, MlockTest) {
+  EXPECT_EQ(0, mlockall(MCL_CURRENT));
+  EXPECT_EQ(0, mlock((void*)0x12345, 0x5678));
+  EXPECT_EQ(0, munlockall());
+  EXPECT_EQ(0, munlock((void*)0x987, 0x654));
+}