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- // Copyright 2021 The Chromium 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 "base/profiler/frame_pointer_unwinder.h"
- #include "base/check_op.h"
- #include "base/notreached.h"
- #include "base/numerics/clamped_math.h"
- #include "base/profiler/module_cache.h"
- #include "build/build_config.h"
- #if BUILDFLAG(IS_APPLE)
- #include <pthread/stack_np.h>
- #endif
- namespace {
- // Given a frame pointer, returns the frame pointer of the calling stack
- // frame and places the return address of the calling stack frame into
- // `return_address`. Shim around `pthread_stack_frame_decode_np` where
- // available since it handles pointer authentication on supported platforms.
- // NB: The caller *must* ensure that there are 2+ uintptr_t's worth of memory at
- // `frame_pointer`.
- uintptr_t DecodeFrame(uintptr_t frame_pointer, uintptr_t* return_address) {
- #if BUILDFLAG(IS_APPLE)
- if (__builtin_available(macOS 10.14, iOS 12, *))
- return pthread_stack_frame_decode_np(frame_pointer, return_address);
- #endif
- const uintptr_t* fp = reinterpret_cast<uintptr_t*>(frame_pointer);
- uintptr_t next_frame = *fp;
- *return_address = *(fp + 1);
- return next_frame;
- }
- } // namespace
- namespace base {
- FramePointerUnwinder::FramePointerUnwinder() = default;
- bool FramePointerUnwinder::CanUnwindFrom(const Frame& current_frame) const {
- return current_frame.module && current_frame.module->IsNative();
- }
- UnwindResult FramePointerUnwinder::TryUnwind(RegisterContext* thread_context,
- uintptr_t stack_top,
- std::vector<Frame>* stack) const {
- // We expect the frame corresponding to the |thread_context| register state to
- // exist within |stack|.
- DCHECK_GT(stack->size(), 0u);
- #if defined(ARCH_CPU_ARM64)
- constexpr uintptr_t align_mask = 0x1;
- #elif defined(ARCH_CPU_X86_64)
- constexpr uintptr_t align_mask = 0xf;
- #endif
- uintptr_t next_frame = RegisterContextFramePointer(thread_context);
- uintptr_t frame_lower_bound = RegisterContextStackPointer(thread_context);
- const auto is_fp_valid = [&](uintptr_t fp) {
- // Ensure there's space on the stack to read two values: the caller's
- // frame pointer and the return address.
- return next_frame >= frame_lower_bound &&
- ClampAdd(next_frame, sizeof(uintptr_t) * 2) <= stack_top &&
- (next_frame & align_mask) == 0;
- };
- if (!is_fp_valid(next_frame))
- return UnwindResult::kAborted;
- for (;;) {
- if (!stack->back().module) {
- return UnwindResult::kAborted;
- }
- if (!stack->back().module->IsNative()) {
- // This is a non-native module associated with the auxiliary unwinder
- // (e.g. corresponding to a frame in V8 generated code). Report as
- // UNRECOGNIZED_FRAME to allow that unwinder to unwind the frame.
- return UnwindResult::kUnrecognizedFrame;
- }
- uintptr_t retaddr;
- uintptr_t frame = next_frame;
- next_frame = DecodeFrame(frame, &retaddr);
- frame_lower_bound = frame + 1;
- // If `next_frame` is 0, we've hit the root and `retaddr` isn't useful.
- // Bail without recording the frame.
- if (next_frame == 0)
- return UnwindResult::kCompleted;
- const ModuleCache::Module* module =
- module_cache()->GetModuleForAddress(retaddr);
- // V8 doesn't conform to the x86_64 ABI re: stack alignment. For V8 frames,
- // let the V8 unwinder determine whether the FP is valid or not.
- bool is_non_native_module = module && !module->IsNative();
- // If the FP doesn't look correct, don't record this frame.
- if (!is_non_native_module && !is_fp_valid(next_frame))
- return UnwindResult::kAborted;
- RegisterContextFramePointer(thread_context) = next_frame;
- RegisterContextInstructionPointer(thread_context) = retaddr;
- RegisterContextStackPointer(thread_context) = frame + sizeof(uintptr_t) * 2;
- stack->emplace_back(retaddr, module);
- }
- NOTREACHED();
- return UnwindResult::kCompleted;
- }
- } // namespace base
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