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//===-- backtrace_sanitizer_common.cpp --------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include "gwp_asan/optional/backtrace.h"
#include "gwp_asan/options.h"
#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_flag_parser.h"
#include "sanitizer_common/sanitizer_flags.h"
#include "sanitizer_common/sanitizer_stacktrace.h"
void __sanitizer::BufferedStackTrace::UnwindImpl(uptr pc, uptr bp,
void *context,
bool request_fast,
u32 max_depth) {
if (!StackTrace::WillUseFastUnwind(request_fast))
return Unwind(max_depth, pc, 0, context, 0, 0, false);
uptr top = 0;
uptr bottom = 0;
GetThreadStackTopAndBottom(/*at_initialization*/ false, &top, &bottom);
return Unwind(max_depth, pc, bp, context, top, bottom, request_fast);
namespace {
size_t BacktraceCommon(uintptr_t *TraceBuffer, size_t Size, void *Context) {
// Use the slow sanitizer unwinder in the segv handler. Fast frame pointer
// unwinders can end up dropping frames because the kernel sigreturn() frame's
// return address is the return address at time of fault. This has the result
// of never actually capturing the PC where the signal was raised.
bool UseFastUnwind = (Context == nullptr);
__sanitizer::BufferedStackTrace Trace;
if (Size > __sanitizer::kStackTraceMax)
Size = __sanitizer::kStackTraceMax;
(__sanitizer::uptr)__builtin_frame_address(0), Context,
UseFastUnwind, Size - 1);
memcpy(TraceBuffer, Trace.trace, Trace.size * sizeof(uintptr_t));
return Trace.size;
size_t Backtrace(uintptr_t *TraceBuffer, size_t Size) {
return BacktraceCommon(TraceBuffer, Size, nullptr);
size_t SegvBacktrace(uintptr_t *TraceBuffer, size_t Size, void *Context) {
return BacktraceCommon(TraceBuffer, Size, Context);
static void PrintBacktrace(uintptr_t *Trace, size_t TraceLength,
gwp_asan::Printf_t Printf) {
__sanitizer::StackTrace StackTrace;
StackTrace.trace = reinterpret_cast<__sanitizer::uptr *>(Trace);
StackTrace.size = TraceLength;
if (StackTrace.size == 0) {
Printf(" <unknown (does your allocator support backtracing?)>\n\n");
} // anonymous namespace
namespace gwp_asan {
namespace backtrace {
// This function is thread-compatible. It must be synchronised in respect to any
// other calls to getBacktraceFunction(), calls to getPrintBacktraceFunction(),
// and calls to either of the functions that they return. Furthermore, this may
// require synchronisation with any calls to sanitizer_common that use flags.
// Generally, this function will be called during the initialisation of the
// allocator, which is done in a thread-compatible manner.
options::Backtrace_t getBacktraceFunction() {
// The unwinder requires the default flags to be set.
return Backtrace;
PrintBacktrace_t getPrintBacktraceFunction() { return PrintBacktrace; }
SegvBacktrace_t getSegvBacktraceFunction() { return SegvBacktrace; }
} // namespace backtrace
} // namespace gwp_asan