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// 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/sanitizer/asan.h"
#include "src/base/sanitizer/msan.h"
#include "src/heap/base/memory-tagging.h"
#include "src/base/sanitizer/tsan.h"
namespace heap::base {
// Function with architecture-specific implementation:
// Pushes all callee-saved registers to the stack and invokes the callback,
// passing the supplied pointers (stack and argument) and the intended stack
// marker.
extern "C" void PushAllRegistersAndIterateStack(
Stack* stack, void* argument, Stack::IterateStackCallback callback);
bool Stack::IsOnStack(const void* slot) const {
DCHECK_NOT_NULL(stack_start_);
#ifdef V8_USE_ADDRESS_SANITIZER
// If the slot is part of a fake frame, then it is definitely on the stack.
if (__asan_addr_is_in_fake_stack(__asan_get_current_fake_stack(),
const_cast<void*>(slot), nullptr, nullptr)) {
return true;
}
// Fall through as there is still a regular stack present even when running
// with ASAN fake stacks.
#endif // V8_USE_ADDRESS_SANITIZER
#if defined(__has_feature)
#if __has_feature(safe_stack)
if (__builtin___get_unsafe_stack_top() >= slot &&
slot >= __builtin___get_unsafe_stack_ptr()) {
return true;
}
#endif // __has_feature(safe_stack)
#endif // defined(__has_feature)
return v8::base::Stack::GetCurrentStackPosition() <= slot &&
slot <= stack_start_;
}
namespace {
#ifdef V8_USE_ADDRESS_SANITIZER
// No ASAN support as accessing fake frames otherwise results in
// "stack-use-after-scope" warnings.
DISABLE_ASAN
// No TSAN support as the stack may not be exclusively owned by the current
// thread, e.g., for interrupt handling. Atomic reads are not enough as the
// other thread may use a lock to synchronize the access.
DISABLE_TSAN
void IterateAsanFakeFrameIfNecessary(StackVisitor* visitor,
const void* asan_fake_stack,
const void* stack_start,
const void* stack_end,
const 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) return;
void* fake_frame_begin;
void* fake_frame_end;
void* real_stack_frame = __asan_addr_is_in_fake_stack(
const_cast<void*>(asan_fake_stack), const_cast<void*>(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 (const void* const* current =
reinterpret_cast<const void* const*>(fake_frame_begin);
current < fake_frame_end; ++current) {
const void* address = *current;
if (address == nullptr) continue;
visitor->VisitPointer(address);
}
}
}
}
#else
void IterateAsanFakeFrameIfNecessary(StackVisitor* visitor,
const void* asan_fake_stack,
const void* stack_start,
const void* stack_end,
const void* address) {}
#endif // V8_USE_ADDRESS_SANITIZER
void IterateUnsafeStackIfNecessary(StackVisitor* visitor) {
#if defined(__has_feature)
#if __has_feature(safe_stack)
// Source:
// https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/safestack/safestack.cpp
constexpr size_t kSafeStackAlignmentBytes = 16;
const void* stack_end = __builtin___get_unsafe_stack_ptr();
const 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));
for (const void* const* current =
reinterpret_cast<const void* const*>(stack_end);
current < stack_start; ++current) {
const void* address = *current;
if (address == nullptr) continue;
visitor->VisitPointer(address);
}
#endif // __has_feature(safe_stack)
#endif // defined(__has_feature)
}
// 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.
DISABLE_ASAN
// No TSAN support as the stack may not be exclusively owned by the current
// thread, e.g., for interrupt handling. Atomic reads are not enough as the
// other thread may use a lock to synchronize the access.
DISABLE_TSAN
void IteratePointersInStack(StackVisitor* visitor, const void* top,
const void* start, const void* asan_fake_stack) {
for (const void* const* current = reinterpret_cast<const void* const*>(top);
current < start; ++current) {
// MSAN: Instead of unpoisoning the whole stack, the slot's value is copied
// into a local which is unpoisoned.
const void* address = *current;
MSAN_MEMORY_IS_INITIALIZED(&address, sizeof(address));
if (address == nullptr) continue;
visitor->VisitPointer(address);
IterateAsanFakeFrameIfNecessary(visitor, asan_fake_stack, start, top,
address);
}
}
} // namespace
// static
void Stack::IteratePointersImpl(const Stack* stack, void* argument,
const void* stack_end) {
StackVisitor* visitor = static_cast<StackVisitor*>(argument);
#ifdef V8_USE_ADDRESS_SANITIZER
const void* asan_fake_stack = __asan_get_current_fake_stack();
#else
const void* asan_fake_stack = nullptr;
#endif // V8_USE_ADDRESS_SANITIZER
// Iterate through the stack.
// All supported platforms should have their stack aligned to at least
// sizeof(void*).
constexpr size_t kMinStackAlignment = sizeof(void*);
CHECK_EQ(0u,
reinterpret_cast<uintptr_t>(stack_end) & (kMinStackAlignment - 1));
{
// Temporarily stop checking MTE tags whilst scanning the stack (whilst V8
// may not be tagging its portion of the stack, higher frames from the OS or
// libc could be using stack tagging.)
SuspendTagCheckingScope s;
IteratePointersInStack(visitor,
reinterpret_cast<const void* const*>(stack_end),
stack->stack_start_, asan_fake_stack);
for (const auto& segment : stack->inactive_stacks_) {
IteratePointersInStack(visitor, segment.top, segment.start,
asan_fake_stack);
}
IterateUnsafeStackIfNecessary(visitor);
}
}
void Stack::IteratePointersForTesting(StackVisitor* visitor) {
SetMarkerAndCallback(
[this, visitor]() { IteratePointersUntilMarker(visitor); });
}
void Stack::IteratePointersUntilMarker(StackVisitor* visitor) const {
DCHECK_NOT_NULL(stack_start_);
DCHECK_NOT_NULL(stack_marker_);
DCHECK_GE(stack_start_, stack_marker_);
IteratePointersImpl(this, visitor, stack_marker_);
}
#ifdef DEBUG
// static
bool Stack::IsOnCurrentStack(const void* ptr) {
DCHECK_NOT_NULL(ptr);
const void* current_stack_start = v8::base::Stack::GetStackStart();
const void* current_stack_top = v8::base::Stack::GetCurrentStackPosition();
return ptr <= current_stack_start && ptr >= current_stack_top;
}
#endif // DEBUG
void Stack::AddStackSegment(const void* start, const void* top) {
DCHECK_LE(top, start);
inactive_stacks_.push_back({start, top});
}
void Stack::ClearStackSegments() { inactive_stacks_.clear(); }
void Stack::SetMarkerAndCallbackHelper(void* argument,
IterateStackCallback callback) {
PushAllRegistersAndIterateStack(this, argument, callback);
// TODO(chromium:1056170): Add support for SIMD and/or filtering.
}
} // namespace heap::base
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