111 lines
3.8 KiB
C++
111 lines
3.8 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Portable implementation - just use glibc
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//
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// Note: The glibc implementation may cause a call to malloc.
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// This can cause a deadlock in HeapProfiler.
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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
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#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
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#include <emscripten.h>
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#include <atomic>
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#include <cstring>
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#include "absl/base/attributes.h"
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#include "absl/debugging/stacktrace.h"
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extern "C" {
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uintptr_t emscripten_stack_snapshot();
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uint32_t emscripten_stack_unwind_buffer(uintptr_t pc, void *buffer,
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uint32_t depth);
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}
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// Sometimes, we can try to get a stack trace from within a stack
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// trace, which can cause a self-deadlock.
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// Protect against such reentrant call by failing to get a stack trace.
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//
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// We use __thread here because the code here is extremely low level -- it is
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// called while collecting stack traces from within malloc and mmap, and thus
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// can not call anything which might call malloc or mmap itself.
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static __thread int recursive = 0;
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// The stack trace function might be invoked very early in the program's
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// execution (e.g. from the very first malloc).
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// As such, we suppress usage of backtrace during this early stage of execution.
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static std::atomic<bool> disable_stacktraces(true); // Disabled until healthy.
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// Waiting until static initializers run seems to be late enough.
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// This file is included into stacktrace.cc so this will only run once.
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ABSL_ATTRIBUTE_UNUSED static int stacktraces_enabler = []() {
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// Check if we can even create stacktraces. If not, bail early and leave
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// disable_stacktraces set as-is.
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// clang-format off
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if (!EM_ASM_INT({ return (typeof wasmOffsetConverter !== 'undefined'); })) {
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return 0;
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}
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// clang-format on
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disable_stacktraces.store(false, std::memory_order_relaxed);
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return 0;
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}();
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template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
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static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
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const void *ucp, int *min_dropped_frames) {
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if (recursive || disable_stacktraces.load(std::memory_order_relaxed)) {
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return 0;
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}
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++recursive;
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static_cast<void>(ucp); // Unused.
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constexpr int kStackLength = 64;
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void *stack[kStackLength];
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int size;
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uintptr_t pc = emscripten_stack_snapshot();
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size = emscripten_stack_unwind_buffer(pc, stack, kStackLength);
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int result_count = size - skip_count;
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if (result_count < 0) result_count = 0;
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if (result_count > max_depth) result_count = max_depth;
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for (int i = 0; i < result_count; i++) result[i] = stack[i + skip_count];
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if (IS_STACK_FRAMES) {
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// No implementation for finding out the stack frame sizes yet.
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memset(sizes, 0, sizeof(*sizes) * result_count);
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}
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if (min_dropped_frames != nullptr) {
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if (size - skip_count - max_depth > 0) {
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*min_dropped_frames = size - skip_count - max_depth;
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} else {
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*min_dropped_frames = 0;
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}
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}
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--recursive;
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return result_count;
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}
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace debugging_internal {
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bool StackTraceWorksForTest() { return true; }
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} // namespace debugging_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
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