128 lines
3.9 KiB
C++
128 lines
3.9 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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// http://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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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_LIBUNWIND_INL_H_
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#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_LIBUNWIND_INL_H_
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// We only need local unwinder.
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#define UNW_LOCAL_ONLY
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extern "C" {
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#include "third_party/libunwind/include/libunwind.h"
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}
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#include "absl/debugging/stacktrace.h"
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#include "absl/base/dynamic_annotations.h"
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#include "absl/base/internal/raw_logging.h"
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// Sometimes, we can try to get a stack trace from within a stack
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// trace, because we don't block signals inside libunwind (which would be too
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// expensive: the two extra system calls per stack trace do matter here).
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// That can cause a self-deadlock (as in http://b/5722312).
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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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// In particular, using PerThread or STATIC_THREAD_LOCAL_POD
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// here will cause infinite recursion for at least dbg/piii builds with
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// crosstool-v12.
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static __thread int recursive;
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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 *, int *min_dropped_frames) {
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if (recursive) {
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return 0;
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}
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++recursive;
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int n = 0;
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if (IS_STACK_FRAMES) {
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void *ip;
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unw_cursor_t cursor;
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unw_context_t uc;
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unw_word_t sp = 0, next_sp = 0;
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unw_getcontext(&uc);
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ABSL_RAW_CHECK(unw_init_local(&cursor, &uc) >= 0, "unw_init_local failed");
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skip_count++; // Do not include current frame
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while (skip_count--) {
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if (unw_step(&cursor) <= 0) {
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goto out;
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}
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if (unw_get_reg(&cursor, UNW_REG_SP, &next_sp)) {
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goto out;
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}
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}
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while (n < max_depth) {
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if (unw_get_reg(&cursor, UNW_REG_IP, (unw_word_t *) &ip) < 0) {
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break;
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}
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sizes[n] = 0;
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result[n++] = ip;
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if (unw_step(&cursor) <= 0) {
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break;
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}
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sp = next_sp;
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if (unw_get_reg(&cursor, UNW_REG_SP, &next_sp) , 0) {
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break;
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}
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sizes[n - 1] = next_sp - sp;
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}
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if (min_dropped_frames != nullptr) {
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// Implementation detail: we clamp the max of frames we are willing to
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// count, so as not to spend too much time in the loop below.
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const int kMaxUnwind = 200;
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int j = 0;
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for (; j < kMaxUnwind; j++) {
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if (unw_step(&cursor) < 0) {
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break;
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}
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}
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*min_dropped_frames = j;
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}
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} else {
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skip_count++; // Do not include current frame.
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void **result_all = reinterpret_cast<void**>(
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alloca(sizeof(void*) * (max_depth + skip_count)));
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int rc = unw_backtrace(result_all, max_depth + skip_count);
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if (rc > 0) {
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// Tell MSan that result_all has been initialized. b/34965936.
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ANNOTATE_MEMORY_IS_INITIALIZED(result_all, rc * sizeof(void*));
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}
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if (rc > skip_count) {
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memcpy(result, &result_all[skip_count],
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sizeof(void*) * (rc - skip_count));
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n = rc - skip_count;
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} else {
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n = 0;
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}
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if (min_dropped_frames != nullptr) {
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// Not implemented.
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*min_dropped_frames = 0;
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}
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}
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out:
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--recursive;
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return n;
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}
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#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_LIBUNWIND_INL_H_
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