1 files changed, 129 insertions, 0 deletions
diff --git a/chromium/v8/src/heap/base/stack.cc b/chromium/v8/src/heap/base/stack.cc
new file mode 100644
index 00000000000..cd284444747
--- /dev/null
+++ b/chromium/v8/src/heap/base/stack.cc
@@ -0,0 +1,129 @@
+// 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.
+
+#include "src/heap/base/stack.h"
+
+#include <limits>
+
+#include "src/base/platform/platform.h"
+#include "src/heap/cppgc/globals.h"
+#include "src/heap/cppgc/sanitizers.h"
+
+namespace heap {
+namespace base {
+
+using IterateStackCallback = void (*)(const Stack*, StackVisitor*, intptr_t*);
+extern "C" void PushAllRegistersAndIterateStack(const Stack*, StackVisitor*,
+                                                IterateStackCallback);
+
+Stack::Stack(const void* stack_start) : stack_start_(stack_start) {}
+
+bool Stack::IsOnStack(void* slot) const {
+  void* raw_slot = v8::base::Stack::GetStackSlot(slot);
+  return v8::base::Stack::GetCurrentStackPosition() <= raw_slot &&
+         raw_slot <= stack_start_;
+}
+
+namespace {
+
+#ifdef V8_USE_ADDRESS_SANITIZER
+
+// No ASAN support as accessing fake frames otherwise results in
+// "stack-use-after-scope" warnings.
+NO_SANITIZE_ADDRESS
+void IterateAsanFakeFrameIfNecessary(StackVisitor* visitor,
+                                     void* asan_fake_stack,
+                                     const void* stack_start,
+                                     const void* stack_end, void* address) {
+  // When using ASAN fake stack a pointer to the fake frame is kept on the
+  // native frame. In case |addr| points to a fake frame of the current stack
+  // iterate the fake frame. Frame layout see
+  // https://github.com/google/sanitizers/wiki/AddressSanitizerUseAfterReturn
+  if (asan_fake_stack) {
+    void* fake_frame_begin;
+    void* fake_frame_end;
+    void* real_stack_frame = __asan_addr_is_in_fake_stack(
+        asan_fake_stack, address, &fake_frame_begin, &fake_frame_end);
+    if (real_stack_frame) {
+      // |address| points to a fake frame. Check that the fake frame is part
+      // of this stack.
+      if (stack_start >= real_stack_frame && real_stack_frame >= stack_end) {
+        // Iterate the fake frame.
+        for (void** current = reinterpret_cast<void**>(fake_frame_begin);
+             current < fake_frame_end; ++current) {
+          void* addr = *current;
+          if (addr == nullptr) continue;
+          visitor->VisitPointer(addr);
+        }
+      }
+    }
+  }
+}
+
+#endif  // V8_USE_ADDRESS_SANITIZER
+
+void IterateSafeStackIfNecessary(StackVisitor* visitor) {
+#if defined(__has_feature)
+#if __has_feature(safe_stack)
+  // Source:
+  // https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/safestack/safestack.cpp
+  constexpr size_t kSafeStackAlignmentBytes = 16;
+  void* stack_end = __builtin___get_unsafe_stack_ptr();
+  void* stack_start = __builtin___get_unsafe_stack_top();
+  CHECK_GT(stack_start, stack_end);
+  CHECK_EQ(0u, reinterpret_cast<uintptr_t>(stack_end) &
+                   (kSafeStackAlignmentBytes - 1));
+  CHECK_EQ(0u, reinterpret_cast<uintptr_t>(stack_start) &
+                   (kSafeStackAlignmentBytes - 1));
+  void** current = reinterpret_cast<void**>(stack_end);
+  for (; current < stack_start; ++current) {
+    void* address = *current;
+    if (address == nullptr) continue;
+    visitor->VisitPointer(address);
+  }
+#endif  // __has_feature(safe_stack)
+#endif  // defined(__has_feature)
+}
+
+// Called by the trampoline that pushes registers on the stack. This method
+// should never be inlined to ensure that a possible redzone cannot contain
+// any data that needs to be scanned.
+V8_NOINLINE
+// No ASAN support as method accesses redzones while walking the stack.
+NO_SANITIZE_ADDRESS
+void IteratePointersImpl(const Stack* stack, StackVisitor* visitor,
+                         intptr_t* stack_end) {
+#ifdef V8_USE_ADDRESS_SANITIZER
+  void* asan_fake_stack = __asan_get_current_fake_stack();
+#endif  // V8_USE_ADDRESS_SANITIZER
+  // All supported platforms should have their stack aligned to at least
+  // sizeof(void*).
+  constexpr size_t kMinStackAlignment = sizeof(void*);
+  void** current = reinterpret_cast<void**>(stack_end);
+  CHECK_EQ(0u, reinterpret_cast<uintptr_t>(current) & (kMinStackAlignment - 1));
+  for (; current < stack->stack_start(); ++current) {
+    // MSAN: Instead of unpoisoning the whole stack, the slot's value is copied
+    // into a local which is unpoisoned.
+    void* address = *current;
+    MSAN_UNPOISON(&address, sizeof(address));
+    if (address == nullptr) continue;
+    visitor->VisitPointer(address);
+#ifdef V8_USE_ADDRESS_SANITIZER
+    IterateAsanFakeFrameIfNecessary(visitor, asan_fake_stack,
+                                    stack->stack_start(), stack_end, address);
+#endif  // V8_USE_ADDRESS_SANITIZER
+  }
+}
+
+}  // namespace
+
+void Stack::IteratePointers(StackVisitor* visitor) const {
+  PushAllRegistersAndIterateStack(this, visitor, &IteratePointersImpl);
+  // No need to deal with callee-saved registers as they will be kept alive by
+  // the regular conservative stack iteration.
+  IterateSafeStackIfNecessary(visitor);
+}
+
+}  // namespace base
+}  // namespace heap