/* Return backtrace of current program state.

   Copyright (C) 2003-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.

   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 <gnu/lib-names.h>

#include <stdlib.h>

#include <unwind.h>

struct trace_arg

{

  void **array;

  _Unwind_Word cfa;

  int cnt;

  int size;

};

#ifdef SHARED

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

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

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

static void *libgcc_handle;

/* Dummy version in case libgcc_s does not contain the real code.  */

static _Unwind_Word

dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))

{

  return 0;

}

static void

init (void)

{

  libgcc_handle = __libc_dlopen (LIBGCC_S_SO);

  if (libgcc_handle == NULL)

    return;

  unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");

  unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");

  if (unwind_getip == NULL)

    unwind_backtrace = NULL;

  unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")

		  ?: dummy_getcfa);

}

#else

# define unwind_backtrace _Unwind_Backtrace

# define unwind_getip _Unwind_GetIP

# define unwind_getcfa _Unwind_GetCFA

#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);

      /* Check whether we make any progress.  */

      _Unwind_Word cfa = unwind_getcfa (ctx);

      if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]

	 && cfa == arg->cfa)

       return _URC_END_OF_STACK;

      arg->cfa = cfa;

    }

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

    return _URC_END_OF_STACK;

  return _URC_NO_REASON;

}

int

__backtrace (void **array, int size)

{

  struct trace_arg arg = { .array = array, .cfa = 0, .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;;

  /* _Unwind_Backtrace seems to put NULL address above

     _start.  Fix it up here.  */

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

    --arg.cnt;

  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