/* Return backtrace of current program state.  64 bit S/390 version.

   Copyright (C) 2001-2018 Free Software Foundation, Inc.

   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.

   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 <stddef.h>

#include <stdlib.h>

#include <unwind.h>

/* 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 for every non-leaf function.

           size                    offset

    %r15 ->    +------------------+

             8 | back chain       |   0

             8 | end of stack     |   8

            32 | scratch          |  16

            80 | save area r6-r15 |  48

            16 | save area f4,f6  | 128

            16 | empty            | 144

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

   r14 in the save area holds the return address.

*/

struct layout

{

  long back_chain;

  long end_of_stack;

  long scratch[4];

  long save_grps[10];

  long save_fp[2];

  long empty[2];

};

struct trace_arg

{

  void **array;

  int cnt, size;

};

#ifdef SHARED

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

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

static void

init (void)

{

  void *handle = __libc_dlopen ("libgcc_s.so.1");

  if (handle == NULL)

    return;

  unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");

  unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");

  if (unwind_getip == NULL)

    unwind_backtrace = NULL;

}

static int

__backchain_backtrace (void **array, int size)

{

  /* We assume that all the code is generated with frame pointers set.  */

  struct layout *stack;

  int cnt = 0;

  __asm__ ("LGR  %0,%%r15" : "=d" (stack) );

  /* We skip the call to this function, it makes no sense to record it.  */

  stack = (struct layout *) stack->back_chain;

  while (cnt < size)

    {

      if (stack == NULL || (void *) stack > __libc_stack_end)

	/* This means the address is out of range.  Note that for the

	   toplevel we see a frame pointer with value NULL which clearly is

	   out of range.  */

	break;

      array[cnt++] = (void *) stack->save_grps[8];

      stack = (struct layout *) stack->back_chain;

    }

  return cnt;

}

#else

# define unwind_backtrace _Unwind_Backtrace

# define unwind_getip _Unwind_GetIP

#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;

  return _URC_NO_REASON;

}

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 __backchain_backtrace (array, size);

#endif

  unwind_backtrace (backtrace_helper, &arg;;

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

}

weak_alias (__backtrace, backtrace)

libc_hidden_def (__backtrace)