8293325: Minor improvements to macos catch_mach_exception_raise() error handling

Reviewed-by: amenkov, dcubed, sspitsyn

Author: plummercj

src/jdk.hotspot.agent/macosx/native/libsaproc/MacosxDebuggerLocal.m

@@ -869,19 +869,25 @@ kern_return_t catch_mach_exception_raise(
   }
 
   // This message should denote a Unix soft signal, with
-  // 1. the exception type = EXC_SOFTWARE
-  // 2. codes[0] (which is the code) = EXC_SOFT_SIGNAL
-  // 3. codes[1] (which is the sub-code) = SIGSTOP
-  if (!(exception_type == EXC_SOFTWARE &&
-        codes[0] == EXC_SOFT_SIGNAL    &&
-        codes[num_codes -1] == SIGSTOP)) {
+  // 1. the exception type = EXC_SOFTWARE (5)
+  // 2. codes[0] (which is the code) = EXC_SOFT_SIGNAL (0x10003 / 65539)
+  // 3. codes[1] (which is the sub-code) = SIGSTOP (17)
+  if (exception_type != EXC_SOFTWARE || codes[0] != EXC_SOFT_SIGNAL) {
     print_error("catch_mach_exception_raise: Message doesn't denote a Unix "
                 "soft signal. exception_type = %d, codes[0] = %d, "
                 "codes[num_codes -1] = 0x%llx, num_codes = %d\n",
                 exception_type, codes[0], codes[num_codes - 1], num_codes);
     return GOT_UNKNOWN_EXC;
   }
-  return KERN_SUCCESS;
+  int sig = codes[num_codes -1];
+  if (sig == SIGSTOP) {
+    return KERN_SUCCESS;
+  } else {
+    // Sometimes we get SIGTRAP(4) or SIGILL(5) instead of SIGSTOP (17) on aarch64.
+    // We currently can't deal with them. See JDK-8288429.
+    print_error("catch_mach_exception_raise: signal is not SIGSTOP (%d)\n", sig);
+    return GOT_UNKNOWN_EXC;
+  }
 }
 
 kern_return_t catch_mach_exception_raise_state(