// Copyright (c) 2005, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ---
// Author: Sanjay Ghemawat
//
// Produce stack trace
#ifndef BASE_STACKTRACE_X86_INL_H_
#define BASE_STACKTRACE_X86_INL_H_
// Note: this file is included into stacktrace.cc more than once.
// Anything that should only be defined once should be here:
#include "config.h"
#include <stdlib.h> // for NULL
#include <assert.h>
#if defined(HAVE_SYS_UCONTEXT_H)
#include <sys/ucontext.h>
#elif defined(HAVE_UCONTEXT_H)
#include <ucontext.h> // for ucontext_t
#elif defined(HAVE_CYGWIN_SIGNAL_H)
// cygwin/signal.h has a buglet where it uses pthread_attr_t without
// #including <pthread.h> itself. So we have to do it.
# ifdef HAVE_PTHREAD
# include <pthread.h>
# endif
#include <cygwin/signal.h>
typedef ucontext ucontext_t;
#endif
#ifdef HAVE_STDINT_H
#include <stdint.h> // for uintptr_t
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_MMAP
#include <sys/mman.h> // for msync
#include "base/vdso_support.h"
#endif
#include "gperftools/stacktrace.h"
#if defined(__linux__) && defined(__i386__) && defined(__ELF__) && defined(HAVE_MMAP)
// 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
//
// 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(0 == "unexpected instruction in __kernel_vsyscall");
return 0;
}
}
// Unexpected: didn't find SYSENTER or SYSCALL in
// [__kernel_vsyscall, __kernel_vsyscall + kMaxBytes) interval.
assert(0 == "did not find SYSENTER or SYSCALL in __kernel_vsyscall");
return 0;
}
#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 WITH_CONTEXT>
static void **NextStackFrame(void **old_sp, const void *uc) {
void **new_sp = (void **) *old_sp;
#if defined(__linux__) && defined(__i386__) && defined(HAVE_VDSO_SUPPORT)
if (WITH_CONTEXT && uc != NULL) {
// 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 = NULL;
static const unsigned char *kernel_vsyscall_address = NULL;
if (num_push_instructions == -1) {
base::VDSOSupport vdso;
if (vdso.IsPresent()) {
base::VDSOSupport::SymbolInfo rt_sigreturn_symbol_info;
base::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 == NULL ||
vsyscall_symbol_info.address == NULL) {
// Unexpected: 32-bit VDSO is present, yet one of the expected
// symbols is missing or NULL.
assert(0 == "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 != NULL &&
old_sp[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_sp == 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.
//
// page_size is linker-initalized to avoid async-unsafe locking
// that GCC would otherwise insert (__cxa_guard_acquire etc).
static int page_size;
if (page_size == 0) {
// First time through.
page_size = getpagesize();
}
void *const reg_esp_aligned =
reinterpret_cast<void *>(
(uintptr_t)(reg_esp + num_push_instructions - 1) &
~(page_size - 1));
if (msync(reg_esp_aligned, page_size, MS_ASYNC) == 0) {
// Alleged %esp is readable, use it for further unwinding.
new_sp = reinterpret_cast<void **>(
reg_esp[num_push_instructions - 1]);
}
}
}
}
}
#endif
// 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 NULL;
// Assume stack frames larger than 100,000 bytes are bogus.
if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return NULL;
} else {
// In the non-strict mode, allow discontiguous stack frames.
// (alternate-signal-stacks for example).
if (new_sp == old_sp) return NULL;
if (new_sp > old_sp) {
// And allow frames upto about 1MB.
const uintptr_t delta = (uintptr_t)new_sp - (uintptr_t)old_sp;
const uintptr_t acceptable_delta = 1000000;
if (delta > acceptable_delta) {
return NULL;
}
}
}
if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return NULL;
#ifdef __i386__
// On 64-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 ((uintptr_t)new_sp >= 0xffffe000) return NULL;
#endif
#ifdef HAVE_MMAP
if (!STRICT_UNWINDING) {
// Lax sanity checks cause a crash on AMD-based machines with
// VDSO-enabled kernels.
// Make an extra sanity check to insure new_sp 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.
static int page_size = getpagesize();
void *new_sp_aligned = (void *)((uintptr_t)new_sp & ~(page_size - 1));
if (msync(new_sp_aligned, page_size, MS_ASYNC) == -1)
return NULL;
}
#endif
return new_sp;
}
#endif // BASE_STACKTRACE_X86_INL_H_
// Note: this part of the file is included several times.
// Do not put globals below.
// The following 4 functions are generated from the code below:
// GetStack{Trace,Frames}()
// GetStack{Trace,Frames}WithContext()
//
// These functions take the following args:
// void** result: the stack-trace, as an array
// int* sizes: the size of each stack frame, as an array
// (GetStackFrames* only)
// int max_depth: the size of the result (and sizes) array(s)
// int skip_count: how many stack pointers to skip before storing in result
// void* ucp: a ucontext_t* (GetStack{Trace,Frames}WithContext only)
int GET_STACK_TRACE_OR_FRAMES {
void **sp;
#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2) || __llvm__
// __builtin_frame_address(0) can return the wrong address on gcc-4.1.0-k8.
// It's always correct on llvm, and the techniques below aren't (in
// particular, llvm-gcc will make a copy of pcs, so it's not in sp[2]),
// so we also prefer __builtin_frame_address when running under llvm.
sp = reinterpret_cast<void**>(__builtin_frame_address(0));
#elif defined(__i386__)
// Stack frame format:
// sp[0] pointer to previous frame
// sp[1] caller address
// sp[2] first argument
// ...
// NOTE: This will break under llvm, since result is a copy and not in sp[2]
sp = (void **)&result - 2;
#elif defined(__x86_64__)
unsigned long rbp;
// Move the value of the register %rbp into the local variable rbp.
// We need 'volatile' to prevent this instruction from getting moved
// around during optimization to before function prologue is done.
// An alternative way to achieve this
// would be (before this __asm__ instruction) to call Noop() defined as
// static void Noop() __attribute__ ((noinline)); // prevent inlining
// static void Noop() { asm(""); } // prevent optimizing-away
__asm__ volatile ("mov %%rbp, %0" : "=r" (rbp));
// Arguments are passed in registers on x86-64, so we can't just
// offset from &result
sp = (void **) rbp;
#else
# error Using stacktrace_x86-inl.h on a non x86 architecture!
#endif
int n = 0;
while (sp && n < max_depth) {
if (*(sp+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;
}
#if !IS_WITH_CONTEXT
const void *const ucp = NULL;
#endif
void **next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
if (skip_count > 0) {
skip_count--;
} else {
result[n] = *(sp+1);
#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;
}
#endif
n++;
}
sp = next_sp;
}
return n;
}