Backported PR nodejs#35986

common.gypi

@@ -34,7 +34,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.45',
+    'v8_embedder_string': '-node.49 ',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/BUILD.gn

@@ -2907,6 +2907,7 @@ v8_source_set("v8_base_without_compiler") {
     "src/wasm/baseline/liftoff-compiler.cc",
     "src/wasm/baseline/liftoff-compiler.h",
     "src/wasm/baseline/liftoff-register.h",
+    "src/wasm/code-space-access.h",
     "src/wasm/compilation-environment.h",
     "src/wasm/decoder.h",
     "src/wasm/function-body-decoder-impl.h",

deps/v8/include/v8-platform.h

@@ -240,7 +240,13 @@ class PageAllocator {
     kReadWrite,
     // TODO(hpayer): Remove this flag. Memory should never be rwx.
     kReadWriteExecute,
-    kReadExecute
+    kReadExecute,
+    // Set this when reserving memory that will later require kReadWriteExecute
+    // permissions. The resulting behavior is platform-specific, currently
+    // this is used to set the MAP_JIT flag on Apple Silicon.
+    // TODO(jkummerow): Remove this when Wasm has a platform-independent
+    // w^x implementation.
+    kNoAccessWillJitLater
   };
 
   /**

deps/v8/src/base/page-allocator.cc

@@ -6,6 +6,10 @@
 
 #include "src/base/platform/platform.h"
 
+#if V8_OS_MACOSX
+#include <sys/mman.h>  // For MAP_JIT.
+#endif
+
 namespace v8 {
 namespace base {
 
@@ -21,6 +25,8 @@ STATIC_ASSERT_ENUM(PageAllocator::kReadWriteExecute,
                    base::OS::MemoryPermission::kReadWriteExecute);
 STATIC_ASSERT_ENUM(PageAllocator::kReadExecute,
                    base::OS::MemoryPermission::kReadExecute);
+STATIC_ASSERT_ENUM(PageAllocator::kNoAccessWillJitLater,
+                   base::OS::MemoryPermission::kNoAccessWillJitLater);
 
 #undef STATIC_ASSERT_ENUM
 
@@ -38,6 +44,14 @@ 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))
+   // 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.
+   if (access == PageAllocator::kNoAccessWillJitLater) {
+     access = PageAllocator::kNoAccess;
+   }
+  #endif
   return base::OS::Allocate(hint, size, alignment,
                             static_cast<base::OS::MemoryPermission>(access));
 }

deps/v8/src/base/platform/platform-cygwin.cc

@@ -33,6 +33,7 @@ namespace {
 DWORD GetProtectionFromMemoryPermission(OS::MemoryPermission access) {
   switch (access) {
     case OS::MemoryPermission::kNoAccess:
+    case OS::MemoryPermission::kNoAccessWillJitLater:
       return PAGE_NOACCESS;
     case OS::MemoryPermission::kRead:
       return PAGE_READONLY;

deps/v8/src/base/platform/platform-fuchsia.cc

@@ -18,6 +18,7 @@ namespace {
 uint32_t GetProtectionFromMemoryPermission(OS::MemoryPermission access) {
   switch (access) {
     case OS::MemoryPermission::kNoAccess:
+    case OS::MemoryPermission::kNoAccessWillJitLater:
       return 0;  // no permissions
     case OS::MemoryPermission::kRead:
       return ZX_VM_PERM_READ;

deps/v8/src/base/platform/platform-posix.cc

@@ -111,6 +111,7 @@ const int kMmapFdOffset = 0;
 int GetProtectionFromMemoryPermission(OS::MemoryPermission access) {
   switch (access) {
     case OS::MemoryPermission::kNoAccess:
+    case OS::MemoryPermission::kNoAccessWillJitLater:
       return PROT_NONE;
     case OS::MemoryPermission::kRead:
       return PROT_READ;
@@ -134,6 +135,11 @@ int GetFlagsForMemoryPermission(OS::MemoryPermission access) {
     flags |= MAP_LAZY;
 #endif  // V8_OS_QNX
   }
+  #if V8_OS_MACOSX && V8_HOST_ARCH_ARM64 && defined(MAP_JIT)
+    if (access == OS::MemoryPermission::kNoAccessWillJitLater) {
+      flags |= MAP_JIT;
+    }
+  #endif
   return flags;
 }
 

deps/v8/src/base/platform/platform-win32.cc

@@ -753,6 +753,7 @@ namespace {
 DWORD GetProtectionFromMemoryPermission(OS::MemoryPermission access) {
   switch (access) {
     case OS::MemoryPermission::kNoAccess:
+    case OS::MemoryPermission::kNoAccessWillJitLater:
       return PAGE_NOACCESS;
     case OS::MemoryPermission::kRead:
       return PAGE_READONLY;

deps/v8/src/base/platform/platform.h

@@ -163,7 +163,10 @@ class V8_BASE_EXPORT OS {
     kReadWrite,
     // TODO(hpayer): Remove this flag. Memory should never be rwx.
     kReadWriteExecute,
-    kReadExecute
+    kReadExecute,
+    // TODO(jkummerow): Remove this when Wasm has a platform-independent
+    // w^x implementation.
+    kNoAccessWillJitLater
   };
 
   static bool HasLazyCommits();

deps/v8/src/utils/allocation.cc

@@ -207,15 +207,17 @@ bool OnCriticalMemoryPressure(size_t length) {
 }
 
 VirtualMemory::VirtualMemory(v8::PageAllocator* page_allocator, size_t size,
-                             void* hint, size_t alignment)
+                             void* hint, size_t alignment, JitPermission jit)
     : page_allocator_(page_allocator) {
   DCHECK_NOT_NULL(page_allocator);
   DCHECK(IsAligned(size, page_allocator_->CommitPageSize()));
   size_t page_size = page_allocator_->AllocatePageSize();
   alignment = RoundUp(alignment, page_size);
-  Address address = reinterpret_cast<Address>(
-      AllocatePages(page_allocator_, hint, RoundUp(size, page_size), alignment,
-                    PageAllocator::kNoAccess));
+  PageAllocator::Permission permissions =
+      jit == kMapAsJittable ? PageAllocator::kNoAccessWillJitLater
+                            : PageAllocator::kNoAccess;
+  Address address = reinterpret_cast<Address>(AllocatePages(
+      page_allocator_, hint, RoundUp(size, page_size), alignment, permissions));
   if (address != kNullAddress) {
     DCHECK(IsAligned(address, alignment));
     region_ = base::AddressRegion(address, size);

deps/v8/src/utils/allocation.h

@@ -150,15 +150,18 @@ V8_EXPORT_PRIVATE bool OnCriticalMemoryPressure(size_t length);
 // Represents and controls an area of reserved memory.
 class V8_EXPORT_PRIVATE VirtualMemory final {
  public:
+  enum JitPermission { kNoJit, kMapAsJittable };
+
   // Empty VirtualMemory object, controlling no reserved memory.
   VirtualMemory() = default;
 
   // Reserves virtual memory containing an area of the given size that is
   // aligned per |alignment| rounded up to the |page_allocator|'s allocate page
   // size. The |size| must be aligned with |page_allocator|'s commit page size.
   // This may not be at the position returned by address().
-  VirtualMemory(v8::PageAllocator* page_allocator, size_t size, void* hint,
-                size_t alignment = 1);
+  VirtualMemory(v8::PageAllocator* page_allocator,
+                size_t size, void* hint, size_t alignment = 1,
+                JitPermission jit = kNoJit);
 
   // Construct a virtual memory by assigning it some already mapped address
   // and size.

deps/v8/src/wasm/code-space-access.h

@@ -0,0 +1,69 @@
+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_WASM_CODE_SPACE_ACCESS_H_
+#define V8_WASM_CODE_SPACE_ACCESS_H_
+
+#include "src/base/build_config.h"
+#include "src/base/macros.h"
+#include "src/common/globals.h"
+
+namespace v8 {
+namespace internal {
+
+#if defined(V8_OS_MACOSX) && defined(V8_HOST_ARCH_ARM64)
+
+// Ignoring this warning is considered better than relying on
+// __builtin_available.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
+inline void SwitchMemoryPermissionsToWritable() {
+  pthread_jit_write_protect_np(0);
+}
+inline void SwitchMemoryPermissionsToExecutable() {
+  pthread_jit_write_protect_np(1);
+}
+#pragma clang diagnostic pop
+
+namespace wasm {
+
+class CodeSpaceWriteScope {
+ public:
+  // TODO(jkummerow): Background threads could permanently stay in
+  // writable mode; only the main thread has to switch back and forth.
+  CodeSpaceWriteScope() {
+    if (code_space_write_nesting_level_ == 0) {
+      SwitchMemoryPermissionsToWritable();
+    }
+    code_space_write_nesting_level_++;
+  }
+  ~CodeSpaceWriteScope() {
+    code_space_write_nesting_level_--;
+    if (code_space_write_nesting_level_ == 0) {
+      SwitchMemoryPermissionsToExecutable();
+    }
+  }
+
+ private:
+  static thread_local int code_space_write_nesting_level_;
+};
+
+#define CODE_SPACE_WRITE_SCOPE CodeSpaceWriteScope _write_access_;
+
+}  // namespace wasm
+
+#else  // Not Mac-on-arm64.
+
+// Nothing to do, we map code memory with rwx permissions.
+inline void SwitchMemoryPermissionsToWritable() {}
+inline void SwitchMemoryPermissionsToExecutable() {}
+
+#define CODE_SPACE_WRITE_SCOPE
+
+#endif  // V8_OS_MACOSX && V8_HOST_ARCH_ARM64
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_WASM_CODE_SPACE_ACCESS_H_

deps/v8/src/wasm/wasm-code-manager.cc

@@ -6,6 +6,7 @@
 
 #include <iomanip>
 
+#include "src/base/build_config.h"
 #include "src/base/adapters.h"
 #include "src/base/macros.h"
 #include "src/base/platform/platform.h"
@@ -21,6 +22,7 @@
 #include "src/snapshot/embedded/embedded-data.h"
 #include "src/utils/ostreams.h"
 #include "src/utils/vector.h"
+#include "src/wasm/code-space-access.h"
 #include "src/wasm/compilation-environment.h"
 #include "src/wasm/function-compiler.h"
 #include "src/wasm/jump-table-assembler.h"
@@ -45,6 +47,10 @@ namespace wasm {
 
 using trap_handler::ProtectedInstructionData;
 
+#if defined(V8_OS_MACOSX) && defined(V8_HOST_ARCH_ARM64)
+thread_local int CodeSpaceWriteScope::code_space_write_nesting_level_ = 0;
+#endif
+
 base::AddressRegion DisjointAllocationPool::Merge(base::AddressRegion region) {
   auto dest_it = regions_.begin();
   auto dest_end = regions_.end();
@@ -626,6 +632,7 @@ void WasmCodeAllocator::FreeCode(Vector<WasmCode* const> codes) {
   // Zap code area and collect freed code regions.
   DisjointAllocationPool freed_regions;
   size_t code_size = 0;
+  CODE_SPACE_WRITE_SCOPE
   for (WasmCode* code : codes) {
     ZapCode(code->instruction_start(), code->instructions().size());
     FlushInstructionCache(code->instruction_start(),
@@ -731,6 +738,7 @@ CompilationEnv NativeModule::CreateCompilationEnv() const {
 }
 
 WasmCode* NativeModule::AddCodeForTesting(Handle<Code> code) {
+  CODE_SPACE_WRITE_SCOPE
   return AddAndPublishAnonymousCode(code, WasmCode::kFunction);
 }
 
@@ -742,6 +750,7 @@ void NativeModule::UseLazyStub(uint32_t func_index) {
   if (!lazy_compile_table_) {
     uint32_t num_slots = module_->num_declared_functions;
     WasmCodeRefScope code_ref_scope;
+    CODE_SPACE_WRITE_SCOPE
     DCHECK_EQ(1, code_space_data_.size());
     lazy_compile_table_ = CreateEmptyJumpTableInRegion(
         JumpTableAssembler::SizeForNumberOfLazyFunctions(num_slots),
@@ -924,6 +933,7 @@ std::unique_ptr<WasmCode> NativeModule::AddCodeWithCodeSpace(
   OwnedVector<byte> reloc_info;
   if (desc.reloc_size > 0) {
     reloc_info = OwnedVector<byte>::New(desc.reloc_size);
+    CODE_SPACE_WRITE_SCOPE
     memcpy(reloc_info.start(), desc.buffer + desc.buffer_size - desc.reloc_size,
            desc.reloc_size);
   }
@@ -1070,6 +1080,7 @@ WasmCode* NativeModule::AddDeserializedCode(
     OwnedVector<const byte> reloc_info,
     OwnedVector<const byte> source_position_table, WasmCode::Kind kind,
     ExecutionTier tier) {
+  // CodeSpaceWriteScope is provided by the caller.
   Vector<uint8_t> dst_code_bytes =
       code_allocator_.AllocateForCode(this, instructions.size());
   memcpy(dst_code_bytes.begin(), instructions.begin(), instructions.size());
@@ -1126,6 +1137,7 @@ WasmCode* NativeModule::CreateEmptyJumpTableInRegion(
   Vector<uint8_t> code_space =
       code_allocator_.AllocateForCodeInRegion(this, jump_table_size, region);
   DCHECK(!code_space.empty());
+  CODE_SPACE_WRITE_SCOPE
   ZapCode(reinterpret_cast<Address>(code_space.begin()), code_space.size());
   std::unique_ptr<WasmCode> code{new WasmCode{
       this,                                     // native_module
@@ -1171,6 +1183,7 @@ void NativeModule::AddCodeSpace(base::AddressRegion region) {
 #endif  // V8_OS_WIN64
 
   WasmCodeRefScope code_ref_scope;
+  CODE_SPACE_WRITE_SCOPE
   WasmCode* jump_table = nullptr;
   const uint32_t num_wasm_functions = module_->num_declared_functions;
   const bool has_functions = num_wasm_functions > 0;
@@ -1353,7 +1366,11 @@ VirtualMemory WasmCodeManager::TryAllocate(size_t size, void* hint) {
   if (!memory_tracker_->ReserveAddressSpace(size)) return {};
   if (hint == nullptr) hint = page_allocator->GetRandomMmapAddr();
 
-  VirtualMemory mem(page_allocator, size, hint, allocate_page_size);
+  // When we start exposing Wasm in jitless mode, then the jitless flag
+  // will have to determine whether we set kMapAsJittable or not.
+  DCHECK(!FLAG_jitless);
+  VirtualMemory mem(page_allocator, size, hint, allocate_page_size,
+                    VirtualMemory::kMapAsJittable);
   if (!mem.IsReserved()) {
     memory_tracker_->ReleaseReservation(size);
     return {};
@@ -1513,6 +1530,7 @@ std::vector<WasmCode*> NativeModule::AddCompiledCode(
   DCHECK(!results.empty());
   // First, allocate code space for all the results.
   size_t total_code_space = 0;
+  CODE_SPACE_WRITE_SCOPE
   for (auto& result : results) {
     DCHECK(result.succeeded());
     total_code_space += RoundUp<kCodeAlignment>(result.code_desc.instr_size);

deps/v8/src/wasm/wasm-serialization.cc

@@ -14,6 +14,7 @@
 #include "src/utils/ostreams.h"
 #include "src/utils/utils.h"
 #include "src/utils/version.h"
+#include "src/wasm/code-space-access.h"
 #include "src/wasm/function-compiler.h"
 #include "src/wasm/module-compiler.h"
 #include "src/wasm/module-decoder.h"
@@ -537,6 +538,7 @@ bool NativeModuleDeserializer::ReadCode(uint32_t fn_index, Reader* reader) {
           protected_instructions_size);
   reader->ReadVector(Vector<byte>::cast(protected_instructions.as_vector()));
 
+  CODE_SPACE_WRITE_SCOPE
   WasmCode* code = native_module_->AddDeserializedCode(
       fn_index, code_buffer, stack_slot_count, tagged_parameter_slots,
       safepoint_table_offset, handler_table_offset, constant_pool_offset,