CPU/Recompiler: Use MAP_JIT for code space on Apple Silicon

src/common/jit_code_buffer.cpp

@@ -13,6 +13,11 @@ Log_SetChannel(JitCodeBuffer);
 #include <sys/mman.h>
 #endif
 
+#if defined(__APPLE__) && defined(__aarch64__)
+// pthread_jit_write_protect_np()
+#include <pthread.h>
+#endif
+
 JitCodeBuffer::JitCodeBuffer() = default;
 
 JitCodeBuffer::JitCodeBuffer(u32 size, u32 far_code_size)
@@ -46,8 +51,13 @@ bool JitCodeBuffer::Allocate(u32 size /* = 64 * 1024 * 1024 */, u32 far_code_siz
     return false;
   }
 #elif defined(__linux__) || defined(__ANDROID__) || defined(__APPLE__) || defined(__HAIKU__) || defined(__FreeBSD__)
-  m_code_ptr = static_cast<u8*>(
-    mmap(nullptr, m_total_size, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
+  int flags = MAP_PRIVATE | MAP_ANONYMOUS;
+#if defined(__APPLE__) && defined(__aarch64__)
+  // MAP_JIT and toggleable write protection is required on Apple Silicon.
+  flags |= MAP_JIT;
+#endif
+
+  m_code_ptr = static_cast<u8*>(mmap(nullptr, m_total_size, PROT_READ | PROT_WRITE | PROT_EXEC, flags, -1, 0));
   if (!m_code_ptr)
   {
     Log_ErrorPrintf("mmap(RWX, %u) for internal buffer failed: %d", m_total_size, errno);
@@ -195,6 +205,8 @@ void JitCodeBuffer::CommitFarCode(u32 length)
 
 void JitCodeBuffer::Reset()
 {
+  WriteProtect(false);
+
   m_free_code_ptr = m_code_ptr + m_guard_size;
   m_code_used = 0;
   std::memset(m_free_code_ptr, 0, m_code_size);
@@ -207,6 +219,8 @@ void JitCodeBuffer::Reset()
     std::memset(m_free_far_code_ptr, 0, m_far_code_size);
     FlushInstructionCache(m_free_far_code_ptr, m_far_code_size);
   }
+
+  WriteProtect(true);
 }
 
 void JitCodeBuffer::Align(u32 alignment, u8 padding_value)
@@ -231,3 +245,26 @@ void JitCodeBuffer::FlushInstructionCache(void* address, u32 size)
 #error Unknown platform.
 #endif
 }
+
+#if defined(__APPLE__) && defined(__aarch64__)
+
+void JitCodeBuffer::WriteProtect(bool enabled)
+{
+  static bool initialized = false;
+  static bool needs_write_protect = false;
+
+  if (!initialized)
+  {
+    initialized = true;
+    needs_write_protect = (pthread_jit_write_protect_supported_np() != 0);
+    if (needs_write_protect)
+      Log_InfoPrint("pthread_jit_write_protect_np() will be used before writing to JIT space.");
+  }
+
+  if (!needs_write_protect)
+    return;
+
+  pthread_jit_write_protect_np(enabled ? 1 : 0);
+}
+
+#endif

src/common/jit_code_buffer.h

@@ -29,6 +29,13 @@ public:
   /// Flushes the instruction cache on the host for the specified range.
   static void FlushInstructionCache(void* address, u32 size);
 
+  /// For Apple Silicon - Toggles write protection on the JIT space.
+#if defined(__APPLE__) && defined(__aarch64__)
+  static void WriteProtect(bool enabled);
+#else
+  ALWAYS_INLINE static void WriteProtect(bool enabled) {}
+#endif
+
 private:
   u8* m_code_ptr = nullptr;
   u8* m_free_code_ptr = nullptr;
@@ -45,4 +52,3 @@ private:
   u32 m_old_protection = 0;
   bool m_owns_buffer = false;
 };
-

src/core/cpu_code_cache.cpp

@@ -286,6 +286,8 @@ void Execute()
 
 void CompileDispatcher()
 {
+  s_code_buffer.WriteProtect(false);
+
   {
     Recompiler::CodeGenerator cg(&s_code_buffer);
     s_asm_dispatcher = cg.CompileDispatcher();
@@ -294,6 +296,8 @@ void CompileDispatcher()
     Recompiler::CodeGenerator cg(&s_code_buffer);
     s_single_block_asm_dispatcher = cg.CompileSingleBlockDispatcher();
   }
+
+  s_code_buffer.WriteProtect(true);
 }
 
 CodeBlock::HostCodePointer* GetFastMapPointer()
@@ -613,8 +617,12 @@ bool CompileBlock(CodeBlock* block)
       Flush();
     }
 
+    s_code_buffer.WriteProtect(false);
     Recompiler::CodeGenerator codegen(&s_code_buffer);
-    if (!codegen.CompileBlock(block, &block->host_code, &block->host_code_size))
+    const bool compile_result = codegen.CompileBlock(block, &block->host_code, &block->host_code_size);
+    s_code_buffer.WriteProtect(true);
+
+    if (!compile_result)
     {
       Log_ErrorPrintf("Failed to compile host code for block at 0x%08X", block->key.GetPC());
       return false;
@@ -839,7 +847,10 @@ Common::PageFaultHandler::HandlerResult MMapPageFaultHandler(void* exception_pc,
       }
 
       // found it, do fixup
-      if (Recompiler::CodeGenerator::BackpatchLoadStore(lbi))
+      s_code_buffer.WriteProtect(false);
+      const bool backpatch_result = Recompiler::CodeGenerator::BackpatchLoadStore(lbi);
+      s_code_buffer.WriteProtect(true);
+      if (backpatch_result)
       {
         // remove the backpatch entry since we won't be coming back to this one
         block->loadstore_backpatch_info.erase(bpi_iter);
@@ -880,7 +891,10 @@ Common::PageFaultHandler::HandlerResult LUTPageFaultHandler(void* exception_pc,
     if (lbi.host_pc == exception_pc)
     {
       // found it, do fixup
-      if (Recompiler::CodeGenerator::BackpatchLoadStore(lbi))
+      s_code_buffer.WriteProtect(false);
+      const bool backpatch_result = Recompiler::CodeGenerator::BackpatchLoadStore(lbi);
+      s_code_buffer.WriteProtect(true);
+      if (backpatch_result)
       {
         // remove the backpatch entry since we won't be coming back to this one
         block->loadstore_backpatch_info.erase(bpi_iter);