// Copyright (c) 2000 - 2007, 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.

//

// Produce stack trace

#include <stdint.h>   // for uintptr_t

#include "utilities.h"   // for OS_* macros

#if !defined(OS_WINDOWS)

#include <unistd.h>

#include <sys/mman.h>

#endif

#include <stdio.h>  // for NULL

#include "stacktrace.h"

_START_GOOGLE_NAMESPACE_

// 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>

static void **NextStackFrame(void **old_sp) {

  void **new_sp = (void **) *old_sp;

  // 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;

    // And allow frames upto about 1MB.

    if ((new_sp > old_sp)

        && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) 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

#if !defined(OS_WINDOWS)

  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_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;

}

// If you change this function, also change GetStackFrames below.

int GetStackTrace(void** result, int max_depth, int skip_count) {

  void **sp;

#ifdef __i386__

  // Stack frame format:

  //    sp[0]   pointer to previous frame

  //    sp[1]   caller address

  //    sp[2]   first argument

  //    ...

  sp = (void **)&result - 2;

#endif

#ifdef __x86_64__

  // __builtin_frame_address(0) can return the wrong address on gcc-4.1.0-k8

  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;

#endif

  int n = 0;

  while (sp && n < max_depth) {

    if (*(sp+1) == (void *)0) {

      // In 64-bit code, we often see a frame that

      // points to itself and has a return address of 0.

      break;

    }

    if (skip_count > 0) {

      skip_count--;

    } else {

      result[n++] = *(sp+1);

    }

    // Use strict unwinding rules.

    sp = NextStackFrame<true>(sp);

  }

  return n;

}

_END_GOOGLE_NAMESPACE_