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Import //base/debugging:stacktrace from abseil. 

This code is all Apache 2 licensed, and all headers were maintained when
concatinated, so we should be completely fine from a legal standpoint.

I've scriptified the steps that I took so that if we need to update this code
in the future, it hopefully shouldn't be too much of a hassle.
This commit is contained in:
Alex Miller 2017-10-13 14:13:47 -07:00
parent f997cb9038
commit 1a91aab1d7
9 changed files with 4165 additions and 0 deletions
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3023
flow/stacktrace.amalgamation.cpp Normal file
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//
// 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
//
// http://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.
//
// Routines to extract the current stack trace. These functions are
// thread-safe and async-signal-safe.
// Note that stack trace functionality is platform dependent and requires
// additional support from the compiler/build system in many cases. (That is,
// this generally only works on platforms/builds that have been specifically
// configured to support it.)
#ifndef ABSL_DEBUGGING_STACKTRACE_H_
#define ABSL_DEBUGGING_STACKTRACE_H_
namespace absl {
// Skips the most recent "skip_count" stack frames (also skips the
// frame generated for the "absl::GetStackFrames" routine itself), and then
// records the pc values for up to the next "max_depth" frames in
// "result", and the corresponding stack frame sizes in "sizes".
// Returns the number of values recorded in "result"/"sizes".
//
// Example:
// main() { foo(); }
// foo() { bar(); }
// bar() {
// void* result[10];
// int sizes[10];
// int depth = absl::GetStackFrames(result, sizes, 10, 1);
// }
//
// The absl::GetStackFrames call will skip the frame for "bar". It will
// return 2 and will produce pc values that map to the following
// procedures:
// result[0] foo
// result[1] main
// (Actually, there may be a few more entries after "main" to account for
// startup procedures.)
// And corresponding stack frame sizes will also be recorded:
// sizes[0] 16
// sizes[1] 16
// (Stack frame sizes of 16 above are just for illustration purposes.)
// Stack frame sizes of 0 or less indicate that those frame sizes couldn't
// be identified.
//
// This routine may return fewer stack frame entries than are
// available. Also note that "result" and "sizes" must both be non-null.
extern int GetStackFrames(void** result, int* sizes, int max_depth,
int skip_count);
// Same as above, but to be used from a signal handler. The "uc" parameter
// should be the pointer to ucontext_t which was passed as the 3rd parameter
// to sa_sigaction signal handler. It may help the unwinder to get a
// better stack trace under certain conditions. The "uc" may safely be null.
//
// If min_dropped_frames is not null, stores in *min_dropped_frames a
// lower bound on the number of dropped stack frames. The stored value is
// guaranteed to be >= 0. The number of real stack frames is guaranteed to
// be >= skip_count + max_depth + *min_dropped_frames.
extern int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
int skip_count, const void* uc,
int* min_dropped_frames);
// This is similar to the absl::GetStackFrames routine, except that it returns
// the stack trace only, and not the stack frame sizes as well.
// Example:
// main() { foo(); }
// foo() { bar(); }
// bar() {
// void* result[10];
// int depth = absl::GetStackTrace(result, 10, 1);
// }
//
// This produces:
// result[0] foo
// result[1] main
// .... ...
//
// "result" must not be null.
extern int GetStackTrace(void** result, int max_depth, int skip_count);
// Same as above, but to be used from a signal handler. The "uc" parameter
// should be the pointer to ucontext_t which was passed as the 3rd parameter
// to sa_sigaction signal handler. It may help the unwinder to get a
// better stack trace under certain conditions. The "uc" may safely be null.
//
// If min_dropped_frames is not null, stores in *min_dropped_frames a
// lower bound on the number of dropped stack frames. The stored value is
// guaranteed to be >= 0. The number of real stack frames is guaranteed to
// be >= skip_count + max_depth + *min_dropped_frames.
extern int GetStackTraceWithContext(void** result, int max_depth,
int skip_count, const void* uc,
int* min_dropped_frames);
// Call this to provide a custom function for unwinding stack frames
// that will be used every time someone invokes one of the static
// GetStack{Frames,Trace}{,WithContext}() functions above.
//
// The arguments passed to the unwinder function will match the
// arguments passed to absl::GetStackFramesWithContext() except that sizes
// will be non-null iff the caller is interested in frame sizes.
//
// If unwinder is null, we revert to the default stack-tracing behavior.
//
// ****************************************************************
// WARNINGS
//
// absl::SetStackUnwinder is not suitable for general purpose use. It is
// provided for custom runtimes.
// Some things to watch out for when calling absl::SetStackUnwinder:
//
// (a) The unwinder may be called from within signal handlers and
// therefore must be async-signal-safe.
//
// (b) Even after a custom stack unwinder has been unregistered, other
// threads may still be in the process of using that unwinder.
// Therefore do not clean up any state that may be needed by an old
// unwinder.
// ****************************************************************
extern void SetStackUnwinder(int (*unwinder)(void** pcs, int* sizes,
int max_depth, int skip_count,
const void* uc,
int* min_dropped_frames));
// Function that exposes built-in stack-unwinding behavior, ignoring
// any calls to absl::SetStackUnwinder().
//
// pcs must NOT be null.
//
// sizes may be null.
// uc may be null.
// min_dropped_frames may be null.
//
// The semantics are the same as the corresponding GetStack*() function in the
// case where absl::SetStackUnwinder() was never called. Equivalents are:
//
// null sizes | non-nullptr sizes
// |==========================================================|
// null uc | GetStackTrace() | GetStackFrames() |
// non-null uc | GetStackTraceWithContext() | GetStackFramesWithContext() |
// |==========================================================|
extern int DefaultStackUnwinder(void** pcs, int* sizes, int max_depth,
int skip_count, const void* uc,
int* min_dropped_frames);
} // namespace absl
#endif // ABSL_DEBUGGING_STACKTRACE_H_

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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
// Generate stack tracer for aarch64
#if defined(__linux__)
#include <sys/mman.h>
#include <ucontext.h>
#include <unistd.h>
#endif
#include <atomic>
#include <cassert>
#include <cstdint>
#include <iostream>
static const uintptr_t kUnknownFrameSize = 0;
#if defined(__linux__)
// Returns the address of the VDSO __kernel_rt_sigreturn function, if present.
static const unsigned char* GetKernelRtSigreturnAddress() {
constexpr uintptr_t kImpossibleAddress = 1;
static std::atomic<uintptr_t> memoized{kImpossibleAddress};
uintptr_t address = memoized.load(std::memory_order_relaxed);
if (address != kImpossibleAddress) {
return reinterpret_cast<const unsigned char*>(address);
}
address = reinterpret_cast<uintptr_t>(nullptr);
#ifdef ABSL_HAVE_VDSO_SUPPORT
absl::debug_internal::VDSOSupport vdso;
if (vdso.IsPresent()) {
absl::debug_internal::VDSOSupport::SymbolInfo symbol_info;
if (!vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.6.39", STT_FUNC,
&symbol_info) ||
symbol_info.address == nullptr) {
// Unexpected: VDSO is present, yet the expected symbol is missing
// or null.
assert(false && "VDSO is present, but doesn't have expected symbol");
} else {
if (reinterpret_cast<uintptr_t>(symbol_info.address) !=
kImpossibleAddress) {
address = reinterpret_cast<uintptr_t>(symbol_info.address);
} else {
assert(false && "VDSO returned invalid address");
}
}
}
#endif
memoized.store(address, std::memory_order_relaxed);
return reinterpret_cast<const unsigned char*>(address);
}
#endif // __linux__
// Compute the size of a stack frame in [low..high). We assume that
// low < high. Return size of kUnknownFrameSize.
template<typename T>
static inline uintptr_t ComputeStackFrameSize(const T* low,
const T* high) {
const char* low_char_ptr = reinterpret_cast<const char *>(low);
const char* high_char_ptr = reinterpret_cast<const char *>(high);
return low < high ? high_char_ptr - low_char_ptr : kUnknownFrameSize;
}
// Given a pointer to a stack frame, locate and return the calling
// stackframe, or return null if no stackframe can be found. Perform sanity
// checks (the strictness of which is controlled by the boolean parameter
// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
template<bool STRICT_UNWINDING, bool WITH_CONTEXT>
static void **NextStackFrame(void **old_frame_pointer, const void *uc) {
void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);
bool check_frame_size = true;
#if defined(__linux__)
if (WITH_CONTEXT && uc != nullptr) {
// Check to see if next frame's return address is __kernel_rt_sigreturn.
if (old_frame_pointer[1] == GetKernelRtSigreturnAddress()) {
const ucontext_t *ucv = static_cast<const ucontext_t *>(uc);
// old_frame_pointer[0] is not suitable for unwinding, look at
// ucontext to discover frame pointer before signal.
void **const pre_signal_frame_pointer =
reinterpret_cast<void **>(ucv->uc_mcontext.regs[29]);
// Check that alleged frame pointer is actually readable. This is to
// prevent "double fault" in case we hit the first fault due to e.g.
// stack corruption.
if (!absl::debug_internal::AddressIsReadable(
pre_signal_frame_pointer))
return nullptr;
// Alleged frame pointer is readable, use it for further unwinding.
new_frame_pointer = pre_signal_frame_pointer;
// Skip frame size check if we return from a signal. We may be using a
// an alternate stack for signals.
check_frame_size = false;
}
}
#endif
// aarch64 ABI requires stack pointer to be 16-byte-aligned.
if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 15) != 0)
return nullptr;
// Check frame size. In strict mode, we assume frames to be under
// 100,000 bytes. In non-strict mode, we relax the limit to 1MB.
if (check_frame_size) {
const uintptr_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
const uintptr_t frame_size =
ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
if (frame_size == kUnknownFrameSize || frame_size > max_size)
return nullptr;
}
return new_frame_pointer;
}
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) {
#ifdef __GNUC__
void **frame_pointer = reinterpret_cast<void**>(__builtin_frame_address(0));
#else
# error reading stack point not yet supported on this platform.
#endif
skip_count++; // Skip the frame for this function.
int n = 0;
// The frame pointer points to low address of a frame. The first 64-bit
// word of a frame points to the next frame up the call chain, which normally
// is just after the high address of the current frame. The second word of
// a frame contains return adress of to the caller. To find a pc value
// associated with the current frame, we need to go down a level in the call
// chain. So we remember return the address of the last frame seen. This
// does not work for the first stack frame, which belongs to UnwindImp() but
// we skip the frame for UnwindImp() anyway.
void* prev_return_address = nullptr;
while (frame_pointer && n < max_depth) {
// The absl::GetStackFrames routine is called when we are in some
// informational context (the failure signal handler for example).
// Use the non-strict unwinding rules to produce a stack trace
// that is as complete as possible (even if it contains a few bogus
// entries in some rare cases).
void **next_frame_pointer =
NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
if (skip_count > 0) {
skip_count--;
} else {
result[n] = prev_return_address;
if (IS_STACK_FRAMES) {
sizes[n] = ComputeStackFrameSize(frame_pointer, next_frame_pointer);
}
n++;
}
prev_return_address = frame_pointer[1];
frame_pointer = next_frame_pointer;
}
if (min_dropped_frames != nullptr) {
// Implementation detail: we clamp the max of frames we are willing to
// count, so as not to spend too much time in the loop below.
const int kMaxUnwind = 200;
int j = 0;
for (; frame_pointer != nullptr && j < kMaxUnwind; j++) {
frame_pointer =
NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp);
}
*min_dropped_frames = j;
}
return n;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_

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// Copyright 2011 and onwards Google Inc.
// All rights reserved.
//
// Author: Doug Kwan
// This is inspired by Craig Silverstein's PowerPC stacktrace code.
//
#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
#include <cstdint>
// WARNING:
// This only works if all your code is in either ARM or THUMB mode. With
// interworking, the frame pointer of the caller can either be in r11 (ARM
// mode) or r7 (THUMB mode). A callee only saves the frame pointer of its
// mode in a fixed location on its stack frame. If the caller is a different
// mode, there is no easy way to find the frame pointer. It can either be
// still in the designated register or saved on stack along with other callee
// saved registers.
// Given a pointer to a stack frame, locate and return the calling
// stackframe, or return nullptr if no stackframe can be found. Perform sanity
// checks (the strictness of which is controlled by the boolean parameter
// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
template<bool STRICT_UNWINDING>
static void **NextStackFrame(void **old_sp) {
void **new_sp = (void**) old_sp[-1];
// Check that the transition from frame pointer old_sp to frame
// pointer new_sp isn't clearly bogus
if (STRICT_UNWINDING) {
// With the stack growing downwards, older stack frame must be
// at a greater address that the current one.
if (new_sp <= old_sp) return nullptr;
// Assume stack frames larger than 100,000 bytes are bogus.
if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
} else {
// In the non-strict mode, allow discontiguous stack frames.
// (alternate-signal-stacks for example).
if (new_sp == old_sp) return nullptr;
// And allow frames upto about 1MB.
if ((new_sp > old_sp)
&& ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
}
if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return nullptr;
return new_sp;
}
// This ensures that absl::GetStackTrace sets up the Link Register properly.
#ifdef __GNUC__
void StacktraceArmDummyFunction() __attribute__((noinline));
void StacktraceArmDummyFunction() { __asm__ volatile(""); }
#else
# error StacktraceArmDummyFunction() needs to be ported to this platform.
#endif
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) {
#ifdef __GNUC__
void **sp = reinterpret_cast<void**>(__builtin_frame_address(0));
#else
# error reading stack point not yet supported on this platform.
#endif
// On ARM, the return address is stored in the link register (r14).
// This is not saved on the stack frame of a leaf function. To
// simplify code that reads return addresses, we call a dummy
// function so that the return address of this function is also
// stored in the stack frame. This works at least for gcc.
StacktraceArmDummyFunction();
int n = 0;
while (sp && n < max_depth) {
// The absl::GetStackFrames routine is called when we are in some
// informational context (the failure signal handler for example).
// Use the non-strict unwinding rules to produce a stack trace
// that is as complete as possible (even if it contains a few bogus
// entries in some rare cases).
void **next_sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
if (skip_count > 0) {
skip_count--;
} else {
result[n] = *sp;
if (IS_STACK_FRAMES) {
if (next_sp > sp) {
sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
} else {
// A frame-size of 0 is used to indicate unknown frame size.
sizes[n] = 0;
}
}
n++;
}
sp = next_sp;
}
if (min_dropped_frames != nullptr) {
// Implementation detail: we clamp the max of frames we are willing to
// count, so as not to spend too much time in the loop below.
const int kMaxUnwind = 200;
int j = 0;
for (; sp != nullptr && j < kMaxUnwind; j++) {
sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
}
*min_dropped_frames = j;
}
return n;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_

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// Copyright 2000 - 2007 Google Inc.
// All rights reserved.
//
// Author: Sanjay Ghemawat
//
// 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_GENERIC_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
#include <execinfo.h>
#include <cstring>
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) {
static const int kStackLength = 64;
void * stack[kStackLength];
int size;
size = backtrace(stack, kStackLength);
skip_count++; // we want to skip the current frame as well
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;
}
}
return result_count;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_

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// 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
//
// http://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.
//
// Produce stack trace. I'm guessing (hoping!) the code is much like
// for x86. For apple machines, at least, it seems to be; see
// http://developer.apple.com/documentation/mac/runtimehtml/RTArch-59.html
// http://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
// Linux has similar code: http://patchwork.ozlabs.org/linuxppc/patch?id=8882
#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
#if defined(__linux__)
#include <asm/ptrace.h> // for PT_NIP.
#include <ucontext.h> // for ucontext_t
#endif
#include <unistd.h>
#include <cassert>
#include <cstdint>
#include <cstdio>
// Given a stack pointer, return the saved link register value.
// Note that this is the link register for a callee.
static inline void *StacktracePowerPCGetLR(void **sp) {
// PowerPC has 3 main ABIs, which say where in the stack the
// Link Register is. For DARWIN and AIX (used by apple and
// linux ppc64), it's in sp[2]. For SYSV (used by linux ppc),
// it's in sp[1].
#if defined(_CALL_AIX) || defined(_CALL_DARWIN)
return *(sp+2);
#elif defined(_CALL_SYSV)
return *(sp+1);
#elif defined(__APPLE__) || (defined(__linux__) && defined(__PPC64__))
// This check is in case the compiler doesn't define _CALL_AIX/etc.
return *(sp+2);
#elif defined(__linux)
// This check is in case the compiler doesn't define _CALL_SYSV.
return *(sp+1);
#else
#error Need to specify the PPC ABI for your archiecture.
#endif
}
// Given a pointer to a stack frame, locate and return the calling
// stackframe, or return null if no stackframe can be found. Perform sanity
// checks (the strictness of which is controlled by the boolean parameter
// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
template<bool STRICT_UNWINDING, bool IS_WITH_CONTEXT>
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack.
ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack.
static void **NextStackFrame(void **old_sp, const void *uc) {
void **new_sp = (void **) *old_sp;
enum { kStackAlignment = 16 };
// Check that the transition from frame pointer old_sp to frame
// pointer new_sp isn't clearly bogus
if (STRICT_UNWINDING) {
// With the stack growing downwards, older stack frame must be
// at a greater address that the current one.
if (new_sp <= old_sp) return nullptr;
// Assume stack frames larger than 100,000 bytes are bogus.
if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
} else {
// In the non-strict mode, allow discontiguous stack frames.
// (alternate-signal-stacks for example).
if (new_sp == old_sp) return nullptr;
// And allow frames upto about 1MB.
if ((new_sp > old_sp)
&& ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
}
if ((uintptr_t)new_sp % kStackAlignment != 0) return nullptr;
#if defined(__linux__)
enum StackTraceKernelSymbolStatus {
kNotInitialized = 0, kAddressValid, kAddressInvalid };
if (IS_WITH_CONTEXT && uc != nullptr) {
static StackTraceKernelSymbolStatus kernel_symbol_status =
kNotInitialized; // Sentinel: not computed yet.
// Initialize with sentinel value: __kernel_rt_sigtramp_rt64 can not
// possibly be there.
static const unsigned char *kernel_sigtramp_rt64_address = nullptr;
if (kernel_symbol_status == kNotInitialized) {
absl::debug_internal::VDSOSupport vdso;
if (vdso.IsPresent()) {
absl::debug_internal::VDSOSupport::SymbolInfo
sigtramp_rt64_symbol_info;
if (!vdso.LookupSymbol(
"__kernel_sigtramp_rt64", "LINUX_2.6.15",
absl::debug_internal::VDSOSupport::kVDSOSymbolType,
&sigtramp_rt64_symbol_info) ||
sigtramp_rt64_symbol_info.address == nullptr) {
// Unexpected: VDSO is present, yet the expected symbol is missing
// or null.
assert(false && "VDSO is present, but doesn't have expected symbol");
kernel_symbol_status = kAddressInvalid;
} else {
kernel_sigtramp_rt64_address =
reinterpret_cast<const unsigned char *>(
sigtramp_rt64_symbol_info.address);
kernel_symbol_status = kAddressValid;
}
} else {
kernel_symbol_status = kAddressInvalid;
}
}
if (new_sp != nullptr &&
kernel_symbol_status == kAddressValid &&
StacktracePowerPCGetLR(new_sp) == kernel_sigtramp_rt64_address) {
const ucontext_t* signal_context =
reinterpret_cast<const ucontext_t*>(uc);
void **const sp_before_signal =
reinterpret_cast<void**>(signal_context->uc_mcontext.gp_regs[PT_R1]);
// Check that alleged sp before signal is nonnull and is reasonably
// aligned.
if (sp_before_signal != nullptr &&
((uintptr_t)sp_before_signal % kStackAlignment) == 0) {
// Check that alleged stack pointer is actually readable. This is to
// prevent a "double fault" in case we hit the first fault due to e.g.
// a stack corruption.
if (absl::debug_internal::AddressIsReadable(sp_before_signal)) {
// Alleged stack pointer is readable, use it for further unwinding.
new_sp = sp_before_signal;
}
}
}
}
#endif
return new_sp;
}
// This ensures that absl::GetStackTrace sets up the Link Register properly.
void StacktracePowerPCDummyFunction() __attribute__((noinline));
void StacktracePowerPCDummyFunction() { __asm__ volatile(""); }
template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack.
ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack.
static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
const void *ucp, int *min_dropped_frames) {
void **sp;
// Apple OS X uses an old version of gnu as -- both Darwin 7.9.0 (Panther)
// and Darwin 8.8.1 (Tiger) use as 1.38. This means we have to use a
// different asm syntax. I don't know quite the best way to discriminate
// systems using the old as from the new one; I've gone with __APPLE__.
#ifdef __APPLE__
__asm__ volatile ("mr %0,r1" : "=r" (sp));
#else
__asm__ volatile ("mr %0,1" : "=r" (sp));
#endif
// On PowerPC, the "Link Register" or "Link Record" (LR), is a stack
// entry that holds the return address of the subroutine call (what
// instruction we run after our function finishes). This is the
// same as the stack-pointer of our parent routine, which is what we
// want here. While the compiler will always(?) set up LR for
// subroutine calls, it may not for leaf functions (such as this one).
// This routine forces the compiler (at least gcc) to push it anyway.
StacktracePowerPCDummyFunction();
// The LR save area is used by the callee, so the top entry is bogus.
skip_count++;
int n = 0;
// Unlike ABIs of X86 and ARM, PowerPC ABIs say that return address (in
// the link register) of a function call is stored in the caller's stack
// frame instead of the callee's. When we look for the return address
// associated with a stack frame, we need to make sure that there is a
// caller frame before it. So we call NextStackFrame before entering the
// loop below and check next_sp instead of sp for loop termination.
// The outermost frame is set up by runtimes and it does not have a
// caller frame, so it is skipped.
// The absl::GetStackFrames routine is called when we are in some
// informational context (the failure signal handler for example).
// Use the non-strict unwinding rules to produce a stack trace
// that is as complete as possible (even if it contains a few
// bogus entries in some rare cases).
void **next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
while (next_sp && n < max_depth) {
if (skip_count > 0) {
skip_count--;
} else {
result[n] = StacktracePowerPCGetLR(sp);
if (IS_STACK_FRAMES) {
if (next_sp > sp) {
sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
} else {
// A frame-size of 0 is used to indicate unknown frame size.
sizes[n] = 0;
}
}
n++;
}
sp = next_sp;
next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
}
if (min_dropped_frames != nullptr) {
// Implementation detail: we clamp the max of frames we are willing to
// count, so as not to spend too much time in the loop below.
const int kMaxUnwind = 1000;
int j = 0;
for (; next_sp != nullptr && j < kMaxUnwind; j++) {
next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(next_sp, ucp);
}
*min_dropped_frames = j;
}
return n;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_

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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_
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 (min_dropped_frames != nullptr) {
*min_dropped_frames = 0;
}
return 0;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_

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// 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
//
// http://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.
//
// Produces a stack trace for Windows. Normally, one could use
// stacktrace_x86-inl.h or stacktrace_x86_64-inl.h -- and indeed, that
// should work for binaries compiled using MSVC in "debug" mode.
// However, in "release" mode, Windows uses frame-pointer
// optimization, which makes getting a stack trace very difficult.
//
// There are several approaches one can take. One is to use Windows
// intrinsics like StackWalk64. These can work, but have restrictions
// on how successful they can be. Another attempt is to write a
// version of stacktrace_x86-inl.h that has heuristic support for
// dealing with FPO, similar to what WinDbg does (see
// http://www.nynaeve.net/?p=97). There are (non-working) examples of
// these approaches, complete with TODOs, in stacktrace_win32-inl.h#1
//
// The solution we've ended up doing is to call the undocumented
// windows function RtlCaptureStackBackTrace, which probably doesn't
// work with FPO but at least is fast, and doesn't require a symbol
// server.
//
// This code is inspired by a patch from David Vitek:
// http://code.google.com/p/google-perftools/issues/detail?id=83
#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_
#include <windows.h> // for GetProcAddress and GetModuleHandle
#include <cassert>
typedef USHORT NTAPI RtlCaptureStackBackTrace_Function(
IN ULONG frames_to_skip,
IN ULONG frames_to_capture,
OUT PVOID *backtrace,
OUT PULONG backtrace_hash);
// Load the function we need at static init time, where we don't have
// to worry about someone else holding the loader's lock.
static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn =
(RtlCaptureStackBackTrace_Function*)
GetProcAddress(GetModuleHandleA("ntdll.dll"), "RtlCaptureStackBackTrace");
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) {
int n = 0;
if (!RtlCaptureStackBackTrace_fn) {
// can't find a stacktrace with no function to call
} else {
n = (int)RtlCaptureStackBackTrace_fn(skip_count + 2, max_depth, result, 0);
}
if (IS_STACK_FRAMES) {
// No implementation for finding out the stack frame sizes yet.
memset(sizes, 0, sizeof(*sizes) * n);
}
if (min_dropped_frames != nullptr) {
// Not implemented.
*min_dropped_frames = 0;
}
return n;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_

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// 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
//
// http://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.
//
// Produce stack trace
#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_
#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_
#if defined(__linux__) && (defined(__i386__) || defined(__x86_64__))
#include <ucontext.h> // for ucontext_t
#endif
#if !defined(_WIN32)
#include <unistd.h>
#endif
#include <cassert>
#include <cstdint>
#if defined(__linux__) && defined(__i386__)
// Count "push %reg" instructions in VDSO __kernel_vsyscall(),
// preceeding "syscall" or "sysenter".
// If __kernel_vsyscall uses frame pointer, answer 0.
//
// kMaxBytes tells how many instruction bytes of __kernel_vsyscall
// to analyze before giving up. Up to kMaxBytes+1 bytes of
// instructions could be accessed.
//
// Here are known __kernel_vsyscall instruction sequences:
//
// SYSENTER (linux-2.6.26/arch/x86/vdso/vdso32/sysenter.S).
// Used on Intel.
// 0xffffe400 <__kernel_vsyscall+0>: push %ecx
// 0xffffe401 <__kernel_vsyscall+1>: push %edx
// 0xffffe402 <__kernel_vsyscall+2>: push %ebp
// 0xffffe403 <__kernel_vsyscall+3>: mov %esp,%ebp
// 0xffffe405 <__kernel_vsyscall+5>: sysenter
//
// SYSCALL (see linux-2.6.26/arch/x86/vdso/vdso32/syscall.S).
// Used on AMD.
// 0xffffe400 <__kernel_vsyscall+0>: push %ebp
// 0xffffe401 <__kernel_vsyscall+1>: mov %ecx,%ebp
// 0xffffe403 <__kernel_vsyscall+3>: syscall
//
// The sequence below isn't actually expected in Google fleet,
// here only for completeness. Remove this comment from OSS release.
// i386 (see linux-2.6.26/arch/x86/vdso/vdso32/int80.S)
// 0xffffe400 <__kernel_vsyscall+0>: int $0x80
// 0xffffe401 <__kernel_vsyscall+1>: ret
//
static const int kMaxBytes = 10;
// We use assert()s instead of DCHECK()s -- this is too low level
// for DCHECK().
static int CountPushInstructions(const unsigned char *const addr) {
int result = 0;
for (int i = 0; i < kMaxBytes; ++i) {
if (addr[i] == 0x89) {
// "mov reg,reg"
if (addr[i + 1] == 0xE5) {
// Found "mov %esp,%ebp".
return 0;
}
++i; // Skip register encoding byte.
} else if (addr[i] == 0x0F &&
(addr[i + 1] == 0x34 || addr[i + 1] == 0x05)) {
// Found "sysenter" or "syscall".
return result;
} else if ((addr[i] & 0xF0) == 0x50) {
// Found "push %reg".
++result;
} else if (addr[i] == 0xCD && addr[i + 1] == 0x80) {
// Found "int $0x80"
assert(result == 0);
return 0;
} else {
// Unexpected instruction.
assert(false && "unexpected instruction in __kernel_vsyscall");
return 0;
}
}
// Unexpected: didn't find SYSENTER or SYSCALL in
// [__kernel_vsyscall, __kernel_vsyscall + kMaxBytes) interval.
assert(false && "did not find SYSENTER or SYSCALL in __kernel_vsyscall");
return 0;
}
#endif
// Assume stack frames larger than 100,000 bytes are bogus.
static const int kMaxFrameBytes = 100000;
// Returns the stack frame pointer from signal context, 0 if unknown.
// vuc is a ucontext_t *. We use void* to avoid the use
// of ucontext_t on non-POSIX systems.
static uintptr_t GetFP(const void *vuc) {
#if defined(__linux__)
if (vuc != nullptr) {
auto *uc = reinterpret_cast<const ucontext_t *>(vuc);
#if defined(__i386__)
const auto bp = uc->uc_mcontext.gregs[REG_EBP];
const auto sp = uc->uc_mcontext.gregs[REG_ESP];
#elif defined(__x86_64__)
const auto bp = uc->uc_mcontext.gregs[REG_RBP];
const auto sp = uc->uc_mcontext.gregs[REG_RSP];
#else
const uintptr_t bp = 0;
const uintptr_t sp = 0;
#endif
// Sanity-check that the base pointer is valid. It should be as long as
// SHRINK_WRAP_FRAME_POINTER is not set, but it's possible that some code in
// the process is compiled with --copt=-fomit-frame-pointer or
// --copt=-momit-leaf-frame-pointer.
//
// TODO(bcmills): -momit-leaf-frame-pointer is currently the default
// behavior when building with clang. Talk to the C++ toolchain team about
// fixing that.
if (bp >= sp && bp - sp <= kMaxFrameBytes) return bp;
// If bp isn't a plausible frame pointer, return the stack pointer instead.
// If we're lucky, it points to the start of a stack frame; otherwise, we'll
// get one frame of garbage in the stack trace and fail the sanity check on
// the next iteration.
return sp;
}
#endif
return 0;
}
// Given a pointer to a stack frame, locate and return the calling
// stackframe, or return null if no stackframe can be found. Perform sanity
// checks (the strictness of which is controlled by the boolean parameter
// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
template <bool STRICT_UNWINDING, bool WITH_CONTEXT>
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack.
ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack.
static void **NextStackFrame(void **old_fp, const void *uc) {
void **new_fp = (void **)*old_fp;
#if defined(__linux__) && defined(__i386__)
if (WITH_CONTEXT && uc != nullptr) {
// How many "push %reg" instructions are there at __kernel_vsyscall?
// This is constant for a given kernel and processor, so compute
// it only once.
static int num_push_instructions = -1; // Sentinel: not computed yet.
// Initialize with sentinel value: __kernel_rt_sigreturn can not possibly
// be there.
static const unsigned char *kernel_rt_sigreturn_address = nullptr;
static const unsigned char *kernel_vsyscall_address = nullptr;
if (num_push_instructions == -1) {
absl::debug_internal::VDSOSupport vdso;
if (vdso.IsPresent()) {
absl::debug_internal::VDSOSupport::SymbolInfo
rt_sigreturn_symbol_info;
absl::debug_internal::VDSOSupport::SymbolInfo vsyscall_symbol_info;
if (!vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.5", STT_FUNC,
&rt_sigreturn_symbol_info) ||
!vdso.LookupSymbol("__kernel_vsyscall", "LINUX_2.5", STT_FUNC,
&vsyscall_symbol_info) ||
rt_sigreturn_symbol_info.address == nullptr ||
vsyscall_symbol_info.address == nullptr) {
// Unexpected: 32-bit VDSO is present, yet one of the expected
// symbols is missing or null.
assert(false && "VDSO is present, but doesn't have expected symbols");
num_push_instructions = 0;
} else {
kernel_rt_sigreturn_address =
reinterpret_cast<const unsigned char *>(
rt_sigreturn_symbol_info.address);
kernel_vsyscall_address =
reinterpret_cast<const unsigned char *>(
vsyscall_symbol_info.address);
num_push_instructions =
CountPushInstructions(kernel_vsyscall_address);
}
} else {
num_push_instructions = 0;
}
}
if (num_push_instructions != 0 && kernel_rt_sigreturn_address != nullptr &&
old_fp[1] == kernel_rt_sigreturn_address) {
const ucontext_t *ucv = static_cast<const ucontext_t *>(uc);
// This kernel does not use frame pointer in its VDSO code,
// and so %ebp is not suitable for unwinding.
void **const reg_ebp =
reinterpret_cast<void **>(ucv->uc_mcontext.gregs[REG_EBP]);
const unsigned char *const reg_eip =
reinterpret_cast<unsigned char *>(ucv->uc_mcontext.gregs[REG_EIP]);
if (new_fp == reg_ebp && kernel_vsyscall_address <= reg_eip &&
reg_eip - kernel_vsyscall_address < kMaxBytes) {
// We "stepped up" to __kernel_vsyscall, but %ebp is not usable.
// Restore from 'ucv' instead.
void **const reg_esp =
reinterpret_cast<void **>(ucv->uc_mcontext.gregs[REG_ESP]);
// Check that alleged %esp is not null and is reasonably aligned.
if (reg_esp &&
((uintptr_t)reg_esp & (sizeof(reg_esp) - 1)) == 0) {
// Check that alleged %esp is actually readable. This is to prevent
// "double fault" in case we hit the first fault due to e.g. stack
// corruption.
void *const reg_esp2 = reg_esp[num_push_instructions - 1];
if (absl::debug_internal::AddressIsReadable(reg_esp2)) {
// Alleged %esp is readable, use it for further unwinding.
new_fp = reinterpret_cast<void **>(reg_esp2);
}
}
}
}
}
#endif
const uintptr_t old_fp_u = reinterpret_cast<uintptr_t>(old_fp);
const uintptr_t new_fp_u = reinterpret_cast<uintptr_t>(new_fp);
// Check that the transition from frame pointer old_fp to frame
// pointer new_fp isn't clearly bogus. Skip the checks if new_fp
// matches the signal context, so that we don't skip out early when
// using an alternate signal stack.
//
// TODO(bcmills): The GetFP call should be completely unnecessary when
// SHRINK_WRAP_FRAME_POINTER is set (because we should be back in the thread's
// stack by this point), but it is empirically still needed (e.g. when the
// stack includes a call to abort). unw_get_reg returns UNW_EBADREG for some
// frames. Figure out why GetValidFrameAddr and/or libunwind isn't doing what
// it's supposed to.
if (STRICT_UNWINDING &&
(!WITH_CONTEXT || uc == nullptr || new_fp_u != GetFP(uc))) {
// With the stack growing downwards, older stack frame must be
// at a greater address that the current one.
if (new_fp_u <= old_fp_u) return nullptr;
if (new_fp_u - old_fp_u > kMaxFrameBytes) return nullptr;
} else {
if (new_fp == nullptr) return nullptr; // skip AddressIsReadable() below
// In the non-strict mode, allow discontiguous stack frames.
// (alternate-signal-stacks for example).
if (new_fp == old_fp) return nullptr;
}
if (new_fp_u & (sizeof(void *) - 1)) return nullptr;
#ifdef __i386__
// On 32-bit machines, the stack pointer can be very close to
// 0xffffffff, so we explicitly check for a pointer into the
// last two pages in the address space
if (new_fp_u >= 0xffffe000) return nullptr;
#endif
#if !defined(_WIN32)
if (!STRICT_UNWINDING) {
// Lax sanity checks cause a crash in 32-bit tcmalloc/crash_reason_test
// on AMD-based machines with VDSO-enabled kernels.
// Make an extra sanity check to insure new_fp is readable.
// Note: NextStackFrame<false>() is only called while the program
// is already on its last leg, so it's ok to be slow here.
if (!absl::debug_internal::AddressIsReadable(new_fp)) {
return nullptr;
}
}
#endif
return new_fp;
}
template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS // May read random elements from stack.
ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY // May read random elements from stack.
ABSL_ATTRIBUTE_NOINLINE
static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
const void *ucp, int *min_dropped_frames) {
int n = 0;
void **fp = reinterpret_cast<void **>(__builtin_frame_address(0));
while (fp && n < max_depth) {
if (*(fp + 1) == reinterpret_cast<void *>(0)) {
// In 64-bit code, we often see a frame that
// points to itself and has a return address of 0.
break;
}
void **next_fp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(fp, ucp);
if (skip_count > 0) {
skip_count--;
} else {
result[n] = *(fp + 1);
if (IS_STACK_FRAMES) {
if (next_fp > fp) {
sizes[n] = (uintptr_t)next_fp - (uintptr_t)fp;
} else {
// A frame-size of 0 is used to indicate unknown frame size.
sizes[n] = 0;
}
}
n++;
}
fp = next_fp;
}
if (min_dropped_frames != nullptr) {
// Implementation detail: we clamp the max of frames we are willing to
// count, so as not to spend too much time in the loop below.
const int kMaxUnwind = 1000;
int j = 0;
for (; fp != nullptr && j < kMaxUnwind; j++) {
fp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(fp, ucp);
}
*min_dropped_frames = j;
}
return n;
}
#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_