blob: 798503ed863b25b632091b2eca8f2c67c8b341bc [file] [log] [blame]
// Copyright (c) 2012 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/debug/stack_trace.h"
#include <string.h>
#include <algorithm>
#include <sstream>
#include "base/logging.h"
#include "base/macros.h"
#if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
#if defined(OS_LINUX) || defined(OS_ANDROID)
#include <pthread.h>
#include "base/process/process_handle.h"
#include "base/threading/platform_thread.h"
#endif
#if defined(OS_MACOSX)
#include <pthread.h>
#endif
#if defined(OS_LINUX) && defined(__GLIBC__)
extern "C" void* __libc_stack_end;
#endif
#endif // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
namespace base {
namespace debug {
namespace {
#if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
#if defined(__arm__) && defined(__GNUC__) && !defined(__clang__)
// GCC and LLVM generate slightly different frames on ARM, see
// https://llvm.org/bugs/show_bug.cgi?id=18505 - LLVM generates
// x86-compatible frame, while GCC needs adjustment.
constexpr size_t kStackFrameAdjustment = sizeof(uintptr_t);
#else
constexpr size_t kStackFrameAdjustment = 0;
#endif
uintptr_t GetNextStackFrame(uintptr_t fp) {
return reinterpret_cast<const uintptr_t*>(fp)[0] - kStackFrameAdjustment;
}
uintptr_t GetStackFramePC(uintptr_t fp) {
return reinterpret_cast<const uintptr_t*>(fp)[1];
}
bool IsStackFrameValid(uintptr_t fp, uintptr_t prev_fp, uintptr_t stack_end) {
// With the stack growing downwards, older stack frame must be
// at a greater address that the current one.
if (fp <= prev_fp) return false;
// Assume huge stack frames are bogus.
if (fp - prev_fp > 100000) return false;
// Check alignment.
if (fp & (sizeof(uintptr_t) - 1)) return false;
if (stack_end) {
// Both fp[0] and fp[1] must be within the stack.
if (fp > stack_end - 2 * sizeof(uintptr_t)) return false;
// Additional check to filter out false positives.
if (GetStackFramePC(fp) < 32768) return false;
}
return true;
};
// ScanStackForNextFrame() scans the stack for a valid frame to allow unwinding
// past system libraries. Only supported on Linux where system libraries are
// usually in the middle of the trace:
//
// TraceStackFramePointers
// <more frames from Chrome>
// base::WorkSourceDispatch <-- unwinding stops (next frame is invalid),
// g_main_context_dispatch ScanStackForNextFrame() is called
// <more frames from glib>
// g_main_context_iteration
// base::MessagePumpGlib::Run <-- ScanStackForNextFrame() finds valid frame,
// base::RunLoop::Run unwinding resumes
// <more frames from Chrome>
// __libc_start_main
//
// For stack scanning to be efficient it's very important for the thread to
// be started by Chrome. In that case we naturally terminate unwinding once
// we reach the origin of the stack (i.e. GetStackEnd()). If the thread is
// not started by Chrome (e.g. Android's main thread), then we end up always
// scanning area at the origin of the stack, wasting time and not finding any
// frames (since Android libraries don't have frame pointers).
//
// ScanStackForNextFrame() returns 0 if it couldn't find a valid frame
// (or if stack scanning is not supported on the current platform).
uintptr_t ScanStackForNextFrame(uintptr_t fp, uintptr_t stack_end) {
#if defined(OS_LINUX)
// Enough to resume almost all prematurely terminated traces.
constexpr size_t kMaxStackScanArea = 8192;
if (!stack_end) {
// Too dangerous to scan without knowing where the stack ends.
return 0;
}
fp += sizeof(uintptr_t); // current frame is known to be invalid
uintptr_t last_fp_to_scan = std::min(fp + kMaxStackScanArea, stack_end) -
sizeof(uintptr_t);
for (;fp <= last_fp_to_scan; fp += sizeof(uintptr_t)) {
uintptr_t next_fp = GetNextStackFrame(fp);
if (IsStackFrameValid(next_fp, fp, stack_end)) {
// Check two frames deep. Since stack frame is just a pointer to
// a higher address on the stack, it's relatively easy to find
// something that looks like one. However two linked frames are
// far less likely to be bogus.
uintptr_t next2_fp = GetNextStackFrame(next_fp);
if (IsStackFrameValid(next2_fp, next_fp, stack_end)) {
return fp;
}
}
}
#endif // defined(OS_LINUX)
return 0;
}
// Links stack frame |fp| to |parent_fp|, so that during stack unwinding
// TraceStackFramePointers() visits |parent_fp| after visiting |fp|.
// Both frame pointers must come from __builtin_frame_address().
// Returns previous stack frame |fp| was linked to.
void* LinkStackFrames(void* fpp, void* parent_fp) {
uintptr_t fp = reinterpret_cast<uintptr_t>(fpp) - kStackFrameAdjustment;
void* prev_parent_fp = reinterpret_cast<void**>(fp)[0];
reinterpret_cast<void**>(fp)[0] = parent_fp;
return prev_parent_fp;
}
#endif // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
} // namespace
#if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
uintptr_t GetStackEnd() {
#if defined(OS_ANDROID)
// Bionic reads proc/maps on every call to pthread_getattr_np() when called
// from the main thread. So we need to cache end of stack in that case to get
// acceptable performance.
// For all other threads pthread_getattr_np() is fast enough as it just reads
// values from its pthread_t argument.
static uintptr_t main_stack_end = 0;
bool is_main_thread = GetCurrentProcId() == PlatformThread::CurrentId();
if (is_main_thread && main_stack_end) {
return main_stack_end;
}
uintptr_t stack_begin = 0;
size_t stack_size = 0;
pthread_attr_t attributes;
int error = pthread_getattr_np(pthread_self(), &attributes);
if (!error) {
error = pthread_attr_getstack(
&attributes, reinterpret_cast<void**>(&stack_begin), &stack_size);
pthread_attr_destroy(&attributes);
}
DCHECK(!error);
uintptr_t stack_end = stack_begin + stack_size;
if (is_main_thread) {
main_stack_end = stack_end;
}
return stack_end; // 0 in case of error
#elif defined(OS_LINUX) && defined(__GLIBC__)
if (GetCurrentProcId() == PlatformThread::CurrentId()) {
// For the main thread we have a shortcut.
return reinterpret_cast<uintptr_t>(__libc_stack_end);
}
// No easy way to get end of the stack for non-main threads,
// see crbug.com/617730.
#elif defined(OS_MACOSX)
return reinterpret_cast<uintptr_t>(pthread_get_stackaddr_np(pthread_self()));
#endif
// Don't know how to get end of the stack.
return 0;
}
#endif // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
StackTrace::StackTrace() : StackTrace(arraysize(trace_)) {}
StackTrace::StackTrace(const void* const* trace, size_t count) {
count = std::min(count, arraysize(trace_));
if (count)
memcpy(trace_, trace, count * sizeof(trace_[0]));
count_ = count;
}
const void *const *StackTrace::Addresses(size_t* count) const {
*count = count_;
if (count_)
return trace_;
return NULL;
}
std::string StackTrace::ToString() const {
std::stringstream stream;
#if !defined(__UCLIBC__) && !defined(_AIX)
OutputToStream(&stream);
#endif
return stream.str();
}
#if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
size_t TraceStackFramePointers(const void** out_trace,
size_t max_depth,
size_t skip_initial) {
// Usage of __builtin_frame_address() enables frame pointers in this
// function even if they are not enabled globally. So 'fp' will always
// be valid.
uintptr_t fp = reinterpret_cast<uintptr_t>(__builtin_frame_address(0)) -
kStackFrameAdjustment;
uintptr_t stack_end = GetStackEnd();
size_t depth = 0;
while (depth < max_depth) {
if (skip_initial != 0) {
skip_initial--;
} else {
out_trace[depth++] = reinterpret_cast<const void*>(GetStackFramePC(fp));
}
uintptr_t next_fp = GetNextStackFrame(fp);
if (IsStackFrameValid(next_fp, fp, stack_end)) {
fp = next_fp;
continue;
}
next_fp = ScanStackForNextFrame(fp, stack_end);
if (next_fp) {
fp = next_fp;
continue;
}
// Failed to find next frame.
break;
}
return depth;
}
ScopedStackFrameLinker::ScopedStackFrameLinker(void* fp, void* parent_fp)
: fp_(fp),
parent_fp_(parent_fp),
original_parent_fp_(LinkStackFrames(fp, parent_fp)) {}
ScopedStackFrameLinker::~ScopedStackFrameLinker() {
void* previous_parent_fp = LinkStackFrames(fp_, original_parent_fp_);
CHECK_EQ(parent_fp_, previous_parent_fp)
<< "Stack frame's parent pointer has changed!";
}
#endif // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
} // namespace debug
} // namespace base