[traphandler] Fix ProbeMemory on Mac release builds

For some reason, the "ret" instruction goes missing on Mac release
builds, probably because the compiler decides to split the inline
assembly block and move the "v8_probe_memory_continuation" block
somewhere else. This CL fixes that by adding another explicit "ret" at
the end of "ProbeMemory".

Also, we remove the "v8_probe_memory_address" symbol (which is identical
to just "ProbeMemory"), to prevent the compiler from splitting
"ProbeMemory" and "v8_probe_memory_address".

R=ahaas@chromium.org

Bug: v8:11955
Change-Id: I2e63b2db94206e329be214ab7b553ab502d6ecc2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3071202Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76091}

src/trap-handler/handler-inside-posix.cc

@@ -39,6 +39,10 @@
 #include "src/trap-handler/trap-handler-internal.h"
 #include "src/trap-handler/trap-handler.h"
 
+#ifdef V8_TRAP_HANDLER_VIA_SIMULATOR
+#include "src/trap-handler/trap-handler-simulator.h"
+#endif
+
 namespace v8 {
 namespace internal {
 namespace trap_handler {
@@ -83,9 +87,8 @@ class UnmaskOobSignalScope {
 };
 
 #ifdef V8_TRAP_HANDLER_VIA_SIMULATOR
-// These are addresses inside the "ProbeMemory" function, defined in
-// "handler-outside-simulators.cc".
-extern "C" char v8_probe_memory_address[];
+// This is the address where we continue on a failed "ProbeMemory". It's defined
+// in "handler-outside-simulators.cc".
 extern "C" char v8_probe_memory_continuation[];
 #endif  // V8_TRAP_HANDLER_VIA_SIMULATOR
 
@@ -132,7 +135,7 @@ bool TryHandleSignal(int signum, siginfo_t* info, void* context) {
 
 #ifdef V8_TRAP_HANDLER_VIA_SIMULATOR
     // Only handle signals triggered by the load in {ProbeMemory}.
-    if (fault_addr != reinterpret_cast<uintptr_t>(&v8_probe_memory_address)) {
+    if (fault_addr != reinterpret_cast<uintptr_t>(&ProbeMemory)) {
       return false;
     }
 

src/trap-handler/handler-outside-simulator.cc

@@ -14,16 +14,15 @@
 // Define the ProbeMemory function declared in trap-handler-simulators.h.
 asm(
     ".globl " SYMBOL(ProbeMemory) "                 \n"
-    ".globl " SYMBOL(v8_probe_memory_address) "     \n"
-    ".globl " SYMBOL(v8_probe_memory_continuation) "\n"
     SYMBOL(ProbeMemory) ":                          \n"
     // First parameter (address) passed in %rdi.
     // The second parameter (pc) is unused here. It is read by the trap handler
     // instead.
-    SYMBOL(v8_probe_memory_address) ":              \n"
     "  movb (%rdi), %al                             \n"
     // Return 0 on success.
     "  xorl %eax, %eax                              \n"
+    "  ret                                          \n"
+    ".globl " SYMBOL(v8_probe_memory_continuation) "\n"
     SYMBOL(v8_probe_memory_continuation) ":         \n"
     // If the trap handler continues here, it wrote the landing pad in %rax.
     "  ret                                          \n");