chromium/third_party/abseil-cpp/absl/debugging/internal/stacktrace_x86-inl.inc

// 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
//
//      https://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>
#include <limits>

#include "absl/base/attributes.h"
#include "absl/base/macros.h"
#include "absl/base/port.h"
#include "absl/debugging/internal/address_is_readable.h"
#include "absl/debugging/internal/vdso_support.h"  // a no-op on non-elf or non-glibc systems
#include "absl/debugging/stacktrace.h"

AddressIsReadable;

#if defined(__linux__) && defined(__i386__)
// 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
//

// 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 = …;
// Stack end to use when we don't know the actual stack end
// (effectively just the end of address space).
constexpr uintptr_t kUnknownStackEnd = …;

// 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) { … }

// 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,
                             size_t stack_low, size_t stack_high) { … }

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) { … }

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace debugging_internal {
bool StackTraceWorksForTest() { … }
}  // namespace debugging_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_