/* Return backtrace of current program state.

   Copyright (C) 1998-2018 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 <execinfo.h>

#include <stddef.h>

#include <string.h>

#include <signal.h>

#include <libc-vdso.h>

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

   Note that every routine is required by the ABI to lay out the stack

   like this.

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

    %r1  -> | %r1 last frame--------> | %r1 last frame--->...  --> NULL

            |                |        |                 |

            | (unused)       |        | return address  |

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

*/

struct layout

{

  struct layout *next;

  void *return_address;

};

#define SIGNAL_FRAMESIZE 64

/* Since the signal handler is just like any other function it needs to

   save/restore its LR and it will save it into callers stack frame.

   Since a signal handler doesn't have a caller, the kernel creates a

   dummy frame to make it look like it has a caller.  */

struct signal_frame_32 {

  char               dummy[SIGNAL_FRAMESIZE];

  struct sigcontext  sctx;

  mcontext_t         mctx;

  /* We don't care about the rest, since IP value is at 'mctx' field.  */

};

static inline int

is_sigtramp_address (void *nip)

{

#ifdef SHARED

  if (nip == VDSO_SYMBOL (sigtramp32))

    return 1;

#endif

  return 0;

}

struct rt_signal_frame_32 {

  char               dummy[SIGNAL_FRAMESIZE + 16];

  siginfo_t          info;

  ucontext_t         uc;

  /* We don't care about the rest, since IP value is at 'uc' field.  */

};

static inline int

is_sigtramp_address_rt (void * nip)

{

#ifdef SHARED

  if (nip == VDSO_SYMBOL (sigtramp_rt32))

    return 1;

#endif

  return 0;

}

int

__backtrace (void **array, int size)

{

  struct layout *current;

  int count;

  /* Force gcc to spill LR.  */

  asm volatile ("" : "=l"(current));

  /* Get the address on top-of-stack.  */

  asm volatile ("lwz %0,0(1)" : "=r"(current));

  for (				count = 0;

       current != NULL && 	count < size;

       current = current->next, count++)

    {

      gregset_t *gregset = NULL;

      array[count] = current->return_address;

      /* Check if the symbol is the signal trampoline and get the interrupted

       * symbol address from the trampoline saved area.  */

      if (is_sigtramp_address (current->return_address))

	{

	  struct signal_frame_32 *sigframe =

	    (struct signal_frame_32*) current;

          gregset = &sigframe->mctx.gregs;

        }

      else if (is_sigtramp_address_rt (current->return_address))

	{

	  struct rt_signal_frame_32 *sigframe =

            (struct rt_signal_frame_32*) current;

          gregset = &sigframe->uc.uc_mcontext.uc_regs->gregs;

        }

      if (gregset)

	{

	  if (count + 1 == size)

	    break;

	  array[++count] = (void*)((*gregset)[PT_NIP]);

	  current = (void*)((*gregset)[PT_R1]);

	}

    }

  /* It's possible the second-last stack frame can't return

     (that is, it's __libc_start_main), in which case

     the CRT startup code will have set its LR to 'NULL'.  */

  if (count > 0 && array[count-1] == NULL)

    count--;

  return count;

}

weak_alias (__backtrace, backtrace)

libc_hidden_def (__backtrace)