[asan] Change default of allow_user_segv_handler to true

[vitalybuka]

Rebase

lib/asan/scripts/asan_device_setup

 ASAN_OPTIONS=$ASAN_OPTIONS \\
 ASAN_ACTIVATION_OPTIONS=include_if_exists=/data/local/tmp/asan.options.%b \\
 LD_PRELOAD=$_ld_preload \\
 exec $_to \$@
 
 EOF
 }
 
-# On Android-L not allowing user segv handler breaks some applications.
-if [[ PRE_L -eq 0 ]]; then
-    ASAN_OPTIONS="$ASAN_OPTIONS,allow_user_segv_handler=1"
-fi
-
 if [[ x$extra_options != x ]] ; then
     ASAN_OPTIONS="$ASAN_OPTIONS,$extra_options"
 fi
 
 # Zygote wrapper.
 if [[ -f "$TMPDIR/app_process64" ]]; then
   # A 64-bit device.
   if [[ ! -f "$TMPDIR/app_process64.real" ]]; then

lib/asan/tests/asan_test.cc

TEST(AddressSanitizer, BitFieldNegativeTest) {
   x->b = 0;
   delete Ident(x);
 }
 
 #if ASAN_NEEDS_SEGV
 namespace {
 
 const char kSEGVCrash[] = "AddressSanitizer: SEGV on unknown address";
-const char kOverriddenHandler[] = "ASan signal handler has been overridden\n";
+const char kOverriddenSigactionHandler[] = "Test sigaction handler\n";
+const char kOverriddenSignalHandler[] = "Test signal handler\n";
 
 TEST(AddressSanitizer, WildAddressTest) {
   char *c = (char*)0x123;
   EXPECT_DEATH(*c = 0, kSEGVCrash);
 }
 
 void my_sigaction_sighandler(int, siginfo_t*, void*) {
-  fprintf(stderr, kOverriddenHandler);
+  fprintf(stderr, kOverriddenSigactionHandler);
   exit(1);
 }
 
 void my_signal_sighandler(int signum) {
-  fprintf(stderr, kOverriddenHandler);
+  fprintf(stderr, kOverriddenSignalHandler);
   exit(1);
 }
 
 TEST(AddressSanitizer, SignalTest) {
   struct sigaction sigact;
   memset(&sigact, 0, sizeof(sigact));
   sigact.sa_sigaction = my_sigaction_sighandler;
   sigact.sa_flags = SA_SIGINFO;
-  // ASan should silently ignore sigaction()...
+  char *c = (char *)0x123;
+
+  EXPECT_DEATH(*c = 0, kSEGVCrash);
+
+  // ASan should allow to set sigaction()...
   EXPECT_EQ(0, sigaction(SIGSEGV, &sigact, 0));
 #ifdef __APPLE__
   EXPECT_EQ(0, sigaction(SIGBUS, &sigact, 0));
 #endif
-  char *c = (char*)0x123;
-  EXPECT_DEATH(*c = 0, kSEGVCrash);
+  EXPECT_DEATH(*c = 0, kOverriddenSigactionHandler);
+
   // ... and signal().
-  EXPECT_EQ(0, signal(SIGSEGV, my_signal_sighandler));
-  EXPECT_DEATH(*c = 0, kSEGVCrash);
+  EXPECT_NE(SIG_ERR, signal(SIGSEGV, my_signal_sighandler));
+  EXPECT_DEATH(*c = 0, kOverriddenSignalHandler);
 }
 }  // namespace
 #endif
 
 static void TestLargeMalloc(size_t size) {
   char buff[1024];
   sprintf(buff, "is located 1 bytes to the left of %lu-byte", (long)size);
   EXPECT_DEATH(Ident((char*)malloc(size))[-1] = 0, buff);

lib/sanitizer_common/sanitizer_flags.inc

COMMON_FLAG(HandleSignalMode, handle_sigbus, kHandleSignalYes,
             COMMON_FLAG_HANDLE_SIGNAL_HELP(SIGBUS))
 COMMON_FLAG(HandleSignalMode, handle_abort, kHandleSignalNo,
             COMMON_FLAG_HANDLE_SIGNAL_HELP(SIGABRT))
 COMMON_FLAG(HandleSignalMode, handle_sigill, kHandleSignalNo,
             COMMON_FLAG_HANDLE_SIGNAL_HELP(SIGILL))
 COMMON_FLAG(HandleSignalMode, handle_sigfpe, kHandleSignalYes,
             COMMON_FLAG_HANDLE_SIGNAL_HELP(SIGFPE))
 #undef COMMON_FLAG_HANDLE_SIGNAL_HELP
-COMMON_FLAG(bool, allow_user_segv_handler, false,
+COMMON_FLAG(bool, allow_user_segv_handler, true,
             "If set, allows user to register a SEGV handler even if the tool "
             "registers one.")
 COMMON_FLAG(bool, use_sigaltstack, true,
             "If set, uses alternate stack for signal handling.")
 COMMON_FLAG(bool, detect_deadlocks, false,
             "If set, deadlock detection is enabled.")
 COMMON_FLAG(
     uptr, clear_shadow_mmap_threshold, 64 * 1024,