/* 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 Library General Public License as

   published by the Free Software Foundation; either version 2 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

   Library General Public License for more details.

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

   License along with the GNU C Library; see the file COPYING.LIB.  If

   not, see <http://www.gnu.org/licenses/>.  */

#include <stddef.h>

#include <string.h>

#include <signal.h>

#include <stdint.h>

#include <execinfo.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

            |                |        |                 |

            | cr save        |        | cr save	  |

            |                |        |                 |

            | (unused)       |        | return address  |

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

*/

struct layout

{

  struct layout *next;

  long int condition_register;

  void *return_address;

};

/* 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_64 {

#define SIGNAL_FRAMESIZE 128

  char dummy[SIGNAL_FRAMESIZE];

  ucontext_t uc;

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

};

static inline int

is_sigtramp_address (void *nip)

{

#ifdef SHARED

  if (nip == VDSO_SYMBOL (sigtramp_rt64))

    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 ("ld %0,0(1)" : "=r"(current));

  for (				count = 0;

       current != NULL && 	count < size;

       current = current->next, count++)

    {

      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_64 *sigframe = (struct signal_frame_64*) current;

	  if (count + 1 == size)

	    break;

          array[++count] = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_NIP];

	  current = (void*) sigframe->uc.uc_mcontext.gp_regs[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)