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