Revert "[ptr-cage] Turn on shared pointer cage by default for arm64 and x64"

This reverts commit 6c65e858.

Reason for revert: V8 Linux64 fyi bots are red https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20-%20fyi/21963/overview

Original change's description:
> [ptr-cage] Turn on shared pointer cage by default for arm64 and x64
>
> Bug: v8:11460
> Change-Id: I9ab419b5e90fbe677e1d63b41699d90552839e98
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2873226
> Commit-Queue: Shu-yu Guo <syg@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74422}

Bug: v8:11460
Change-Id: Ia97838cdce5073cbdb8eaa3aa819aa92c2a081dd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2878854
Auto-Submit: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#74425}

BUILD.gn

@@ -360,7 +360,7 @@ if (v8_enable_pointer_compression == "") {
       v8_current_cpu == "arm64" || v8_current_cpu == "x64"
 }
 if (v8_enable_pointer_compression_shared_cage == "") {
-  v8_enable_pointer_compression_shared_cage = v8_enable_pointer_compression
+  v8_enable_pointer_compression_shared_cage = false
 }
 if (v8_enable_fast_torque == "") {
   v8_enable_fast_torque = v8_enable_fast_mksnapshot
@@ -432,8 +432,7 @@ assert(v8_current_cpu != "x86" || !v8_untrusted_code_mitigations,
 assert(v8_current_cpu == "arm64" || !v8_control_flow_integrity,
        "Control-flow integrity is only supported on arm64")
 
-if (v8_enable_shared_ro_heap && v8_enable_pointer_compression &&
-    !v8_enable_pointer_compression_shared_cage) {
+if (v8_enable_shared_ro_heap && v8_enable_pointer_compression) {
   assert(
       is_linux || is_chromeos || is_android,
       "Sharing read-only heap with pointer compression is only supported on Linux or Android")

src/builtins/x64/builtins-x64.cc

@@ -384,6 +384,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
 
 #ifdef V8_COMPRESS_POINTERS_IN_SHARED_CAGE
     // Initialize the pointer cage base register.
+    // TODO(syg): Actually make a cage.
     __ LoadRootRelative(kPtrComprCageBaseRegister,
                         IsolateData::cage_base_offset());
 #endif

src/diagnostics/unwinding-info-win64.cc

@@ -577,11 +577,6 @@ void UnregisterNonABICompliantCodeRange(void* start) {
       ExceptionHandlerRecord* record =
           reinterpret_cast<ExceptionHandlerRecord*>(start);
       CHECK(::RtlDeleteFunctionTable(record->runtime_function));
-
-      // Unprotect reserved page.
-      DWORD old_protect;
-      CHECK(VirtualProtect(start, sizeof(ExceptionHandlerRecord),
-                           PAGE_READWRITE, &old_protect));
     }
 #endif  // V8_OS_WIN_X64
   } else {
@@ -590,11 +585,6 @@ void UnregisterNonABICompliantCodeRange(void* start) {
     if (record->dynamic_table) {
       DeleteGrowableFunctionTable(record->dynamic_table);
     }
-
-    // Unprotect reserved page.
-    DWORD old_protect;
-    CHECK(VirtualProtect(start, sizeof(CodeRangeUnwindingRecord),
-                         PAGE_READWRITE, &old_protect));
   }
 }
 

src/execution/isolate.cc

@@ -3053,8 +3053,7 @@ void Isolate::Deinit() {
 
 #if defined(V8_OS_WIN64)
   if (win64_unwindinfo::CanRegisterUnwindInfoForNonABICompliantCodeRange() &&
-      heap()->memory_allocator() && RequiresCodeRange() &&
-      heap()->code_range()->AtomicDecrementUnwindInfoUseCount() == 1) {
+      heap()->memory_allocator() && RequiresCodeRange()) {
     const base::AddressRegion& code_region = heap()->code_region();
     void* start = reinterpret_cast<void*>(code_region.begin());
     win64_unwindinfo::UnregisterNonABICompliantCodeRange(start);
@@ -3785,8 +3784,7 @@ bool Isolate::Init(SnapshotData* startup_snapshot_data,
   }
 
 #if defined(V8_OS_WIN64)
-  if (win64_unwindinfo::CanRegisterUnwindInfoForNonABICompliantCodeRange() &&
-      heap()->code_range()->AtomicIncrementUnwindInfoUseCount() == 0) {
+  if (win64_unwindinfo::CanRegisterUnwindInfoForNonABICompliantCodeRange()) {
     const base::AddressRegion& code_region = heap()->code_region();
     void* start = reinterpret_cast<void*>(code_region.begin());
     size_t size_in_bytes = code_region.size();

src/heap/code-range.h

@@ -84,21 +84,8 @@ class CodeRange final : public VirtualMemoryCage {
                                  const uint8_t* embedded_blob_code,
                                  size_t embedded_blob_code_size);
 
-#ifdef V8_OS_WIN64
-  // 64-bit Windows needs to track how many Isolates are using the CodeRange for
-  // registering and unregistering of unwind info. Note that even though
-  // CodeRanges are used with std::shared_ptr, std::shared_ptr::use_count should
-  // not be used for synchronization as it's usually implemented with a relaxed
-  // read.
-  uint32_t AtomicIncrementUnwindInfoUseCount() {
-    return unwindinfo_use_count_.fetch_add(1, std::memory_order_acq_rel);
-  }
-
-  uint32_t AtomicDecrementUnwindInfoUseCount() {
-    return unwindinfo_use_count_.fetch_sub(1, std::memory_order_acq_rel);
-  }
-#endif  // V8_OS_WIN64
-
+  // Initializes the process-wide code range if RequiresProcessWideCodeRange()
+  // is true.
   static void InitializeProcessWideCodeRangeOnce(
       v8::PageAllocator* page_allocator, size_t requested_size);
 
@@ -110,10 +97,6 @@ class CodeRange final : public VirtualMemoryCage {
   // Used when short builtin calls are enabled, where embedded builtins are
   // copied into the CodeRange so calls can be nearer.
   uint8_t* embedded_blob_code_copy_ = nullptr;
-
-#ifdef V8_OS_WIN64
-  std::atomic<uint32_t> unwindinfo_use_count_{0};
-#endif
 };
 
 }  // namespace internal

src/heap/heap.h

@@ -892,8 +892,6 @@ class Heap {
 
   const base::AddressRegion& code_region();
 
-  CodeRange* code_range() { return code_range_.get(); }
-
   LocalHeap* main_thread_local_heap() { return main_thread_local_heap_; }
 
   // ===========================================================================

tools/v8heapconst.py

@@ -500,9 +500,9 @@ KNOWN_OBJECTS = {
 
 # Lower 32 bits of first page addresses for various heap spaces.
 HEAP_FIRST_PAGES = {
-  0x080c0000: "old_space",
-  0x08100000: "map_space",
-  0x08000000: "read_only_space",
+  0x08100000: "old_space",
+  0x08140000: "map_space",
+  0x08040000: "read_only_space",
 }
 
 # List of known V8 Frame Markers.