/* Return backtrace of current program state.

   Copyright (C) 2013-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <libc-lock.h>

#include <dlfcn.h>

#include <execinfo.h>

#include <stdlib.h>

#include <unwind.h>

struct trace_arg

{

  void **array;

  int cnt, size;

  void *lastfp, *lastsp;

};

#ifdef SHARED

static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);

static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);

static _Unwind_Ptr (*unwind_getcfa) (struct _Unwind_Context *);

static _Unwind_Ptr (*unwind_getgr) (struct _Unwind_Context *, int);

static void *libgcc_handle;

static void

init (void)

{

  libgcc_handle = __libc_dlopen ("libgcc_s.so.2");

  if (libgcc_handle == NULL)

    return;

  unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");

  unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");

  unwind_getcfa = __libc_dlsym (libgcc_handle, "_Unwind_GetCFA");

  unwind_getgr = __libc_dlsym (libgcc_handle, "_Unwind_GetGR");

  if (unwind_getip == NULL || unwind_getgr == NULL || unwind_getcfa == NULL)

    {

      unwind_backtrace = NULL;

      __libc_dlclose (libgcc_handle);

      libgcc_handle = NULL;

    }

}

#else

# define unwind_backtrace _Unwind_Backtrace

# define unwind_getip _Unwind_GetIP

# define unwind_getcfa _Unwind_GetCFA

# define unwind_getgr _Unwind_GetGR

#endif

static _Unwind_Reason_Code

backtrace_helper (struct _Unwind_Context *ctx, void *a)

{

  struct trace_arg *arg = a;

  /* We are first called with address in the __backtrace function.

     Skip it.  */

  if (arg->cnt != -1)

    arg->array[arg->cnt] = (void *) unwind_getip (ctx);

  if (++arg->cnt == arg->size)

    return _URC_END_OF_STACK;

  /* %fp is DWARF2 register 14 on M68K.  */

  arg->lastfp = (void *) unwind_getgr (ctx, 14);

  arg->lastsp = (void *) unwind_getcfa (ctx);

  return _URC_NO_REASON;

}

/* This is a global variable set at program start time.  It marks the

   highest used stack address.  */

extern void *__libc_stack_end;

/* This is the stack layout we see with every stack frame

   if not compiled without frame pointer.

           +-----------------+       +-----------------+

    %fp -> | %fp last frame--------> | %fp last frame--->...

           |                 |       |                 |

           | return address  |       | return address  |

           +-----------------+       +-----------------+

   First try as far to get as far as possible using

   _Unwind_Backtrace which handles -fomit-frame-pointer

   as well, but requires .eh_frame info.  Then fall back to

   walking the stack manually.  */

struct layout

{

  struct layout *fp;

  void *ret;

};

int

__backtrace (void **array, int size)

{

  struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };

  if (size <= 0)

    return 0;

#ifdef SHARED

  __libc_once_define (static, once);

  __libc_once (once, init);

  if (unwind_backtrace == NULL)

    return 0;

#endif

  unwind_backtrace (backtrace_helper, &arg;;

  if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)

    --arg.cnt;

  else if (arg.cnt < size)

    {

      struct layout *fp = (struct layout *) arg.lastfp;

      while (arg.cnt < size)

	{

	  /* Check for out of range.  */

	  if ((void *) fp < arg.lastsp || (void *) fp > __libc_stack_end

	      || ((long) fp & 1))

	    break;

	  array[arg.cnt++] = fp->ret;

	  fp = fp->fp;

	}

    }

  return arg.cnt != -1 ? arg.cnt : 0;

}

weak_alias (__backtrace, backtrace)

libc_hidden_def (__backtrace)

#ifdef SHARED

/* Free all resources if necessary.  */

libc_freeres_fn (free_mem)

{

  unwind_backtrace = NULL;

  if (libgcc_handle != NULL)

    {

      __libc_dlclose (libgcc_handle);

      libgcc_handle = NULL;

    }

}

#endif