[wasm] Disable MAP_JIT functionality on iOS

pthread_jit_write_protect* functions are only available on arm64 Mac,
not on iOS (which also sets V8_{TARGET_,}OS_MACOSX).
This CL refactors the logic to detect whether pthread_jit_write_protect
and MAP_JIT are available and defines a global preprocessor macro which
can subsequently be used instead of the existing complex condition.

R=jkummerow@chromium.org, mlippautz@chromium.org

Change-Id: I63894f42df35406d6eee90a4ce5070c2fde7b566
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3077154Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Auto-Submit: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76143}

include/v8config.h

@@ -553,6 +553,13 @@ V8 shared library set USING_V8_SHARED.
 
 #endif  // V8_OS_WIN
 
+// pthread_jit_write_protect is only available on arm64 Mac.
+#if defined(V8_OS_MACOSX) && !defined(V8_OS_IOS) && defined(V8_HOST_ARCH_ARM64)
+# define V8_HAS_PTHREAD_JIT_WRITE_PROTECT 1
+#else
+# define V8_HAS_PTHREAD_JIT_WRITE_PROTECT 0
+#endif
+
 // clang-format on
 
 #undef V8_HAS_CPP_ATTRIBUTE

src/base/page-allocator.cc

@@ -45,7 +45,7 @@ void* PageAllocator::GetRandomMmapAddr() {
 
 void* PageAllocator::AllocatePages(void* hint, size_t size, size_t alignment,
                                    PageAllocator::Permission access) {
-#if !(V8_OS_MACOSX && V8_HOST_ARCH_ARM64 && defined(MAP_JIT))
+#if !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
   // kNoAccessWillJitLater is only used on Apple Silicon. Map it to regular
   // kNoAccess on other platforms, so code doesn't have to handle both enum
   // values.

src/base/platform/platform-posix.cc

@@ -153,7 +153,7 @@ int GetFlagsForMemoryPermission(OS::MemoryPermission access,
     flags |= MAP_LAZY;
 #endif  // V8_OS_QNX
   }
-#if V8_OS_MACOSX && V8_HOST_ARCH_ARM64 && defined(MAP_JIT)
+#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
   if (access == OS::MemoryPermission::kNoAccessWillJitLater) {
     flags |= MAP_JIT;
   }

src/wasm/code-space-access.cc

@@ -14,16 +14,16 @@ namespace wasm {
 thread_local int CodeSpaceWriteScope::code_space_write_nesting_level_ = 0;
 // The thread-local counter (above) is only valid if a single thread only works
 // on one module at a time. This second thread-local checks that.
-#if defined(DEBUG) && (!defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64))
+#if defined(DEBUG) && !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
 thread_local NativeModule* CodeSpaceWriteScope::current_native_module_ =
     nullptr;
 #endif
 
 // TODO(jkummerow): Background threads could permanently stay in
 // writable mode; only the main thread has to switch back and forth.
-#if defined(V8_OS_MACOSX) && defined(V8_HOST_ARCH_ARM64)
+#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
 CodeSpaceWriteScope::CodeSpaceWriteScope(NativeModule*) {
-#else  // !defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64)
+#else  // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
 CodeSpaceWriteScope::CodeSpaceWriteScope(NativeModule* native_module)
     : native_module_(native_module) {
 #ifdef DEBUG
@@ -32,7 +32,7 @@ CodeSpaceWriteScope::CodeSpaceWriteScope(NativeModule* native_module)
   }
   DCHECK_EQ(native_module, current_native_module_);
 #endif  // DEBUG
-#endif  // !defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64)
+#endif  // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
   if (code_space_write_nesting_level_ == 0) {
     SetWritable();
   }
@@ -44,7 +44,7 @@ CodeSpaceWriteScope::~CodeSpaceWriteScope() {
   if (code_space_write_nesting_level_ == 0) SetExecutable();
 }
 
-#if defined(V8_OS_MACOSX) && defined(V8_HOST_ARCH_ARM64)
+#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
 
 // Ignoring this warning is considered better than relying on
 // __builtin_available.
@@ -59,7 +59,7 @@ void CodeSpaceWriteScope::SetExecutable() const {
 }
 #pragma clang diagnostic pop
 
-#else  // !defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64)
+#else  // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
 
 void CodeSpaceWriteScope::SetWritable() const {
   DCHECK_NOT_NULL(native_module_);
@@ -82,7 +82,7 @@ void CodeSpaceWriteScope::SetExecutable() const {
   }
 }
 
-#endif  // !defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64)
+#endif  // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
 
 }  // namespace wasm
 }  // namespace internal

src/wasm/code-space-access.h

@@ -55,7 +55,7 @@ class V8_NODISCARD CodeSpaceWriteScope final {
 
  private:
   static thread_local int code_space_write_nesting_level_;
-#if defined(DEBUG) && (!defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64))
+#if defined(DEBUG) && !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
   static thread_local NativeModule* current_native_module_;
 #endif
 
@@ -66,7 +66,7 @@ class V8_NODISCARD CodeSpaceWriteScope final {
   // allocation which region to switch permissions for. On non-M1 hardware
   // without memory protection key support, we need the code space from the
   // {native_module_}.
-#if !defined(V8_OS_MACOSX) || !defined(V8_HOST_ARCH_ARM64)
+#if !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
   NativeModule* const native_module_;
 #endif
 };