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- // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
- // 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(),
- // preceding "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)
- static 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
- skip_count++; // skip parent's frame due to indirection in stacktrace.cc
- 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;
- }
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