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       1                 :             : /* Get previous frame state for an existing frame state using frame pointers.
       2                 :             :    Copyright (C) 2017 Red Hat, Inc.
       3                 :             :    This file is part of elfutils.
       4                 :             : 
       5                 :             :    This file is free software; you can redistribute it and/or modify
       6                 :             :    it under the terms of either
       7                 :             : 
       8                 :             :      * the GNU Lesser General Public License as published by the Free
       9                 :             :        Software Foundation; either version 3 of the License, or (at
      10                 :             :        your option) any later version
      11                 :             : 
      12                 :             :    or
      13                 :             : 
      14                 :             :      * the GNU General Public License as published by the Free
      15                 :             :        Software Foundation; either version 2 of the License, or (at
      16                 :             :        your option) any later version
      17                 :             : 
      18                 :             :    or both in parallel, as here.
      19                 :             : 
      20                 :             :    elfutils is distributed in the hope that it will be useful, but
      21                 :             :    WITHOUT ANY WARRANTY; without even the implied warranty of
      22                 :             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      23                 :             :    General Public License for more details.
      24                 :             : 
      25                 :             :    You should have received copies of the GNU General Public License and
      26                 :             :    the GNU Lesser General Public License along with this program.  If
      27                 :             :    not, see <http://www.gnu.org/licenses/>.  */
      28                 :             : 
      29                 :             : #ifdef HAVE_CONFIG_H
      30                 :             : # include <config.h>
      31                 :             : #endif
      32                 :             : 
      33                 :             : #include <stdlib.h>
      34                 :             : #include <assert.h>
      35                 :             : 
      36                 :             : #define BACKEND i386_
      37                 :             : #include "libebl_CPU.h"
      38                 :             : 
      39                 :             : /* Register numbers for frame and stack pointers.  We take advantage of
      40                 :             :    them being next to each other when calling getfunc and setfunc.  */
      41                 :             : #define ESP 4
      42                 :             : #define EBP (ESP + 1)
      43                 :             : 
      44                 :             : /* Most basic frame pointer chasing with EBP as frame pointer.
      45                 :             :    PC = *(FP + 4), SP = FP + 8, FP = *FP.  */
      46                 :             : bool
      47                 :          18 : i386_unwind (Ebl *ebl __attribute__ ((unused)),
      48                 :             :              Dwarf_Addr pc __attribute__ ((unused)),
      49                 :             :              ebl_tid_registers_t *setfunc, ebl_tid_registers_get_t *getfunc,
      50                 :             :              ebl_pid_memory_read_t *readfunc, void *arg,
      51                 :             :              bool *signal_framep __attribute__ ((unused)))
      52                 :             : {
      53                 :             :   /* sp = 0, fp = 1 */
      54                 :          18 :   Dwarf_Word regs[2];
      55                 :             : 
      56                 :             :   /* Get current stack and frame pointers.  */
      57         [ +  - ]:          18 :   if (! getfunc (ESP, 2, regs, arg))
      58                 :             :     return false;
      59                 :             : 
      60                 :          18 :   Dwarf_Word sp = regs[0];
      61                 :          18 :   Dwarf_Word fp = regs[1];
      62                 :             : 
      63                 :             :   /* Sanity check.  We only support traditional stack frames.  */
      64   [ +  +  +  - ]:          18 :   if (fp == 0 || sp == 0 || fp < sp)
      65                 :             :     return false;
      66                 :             : 
      67                 :             :   /* Get the return address from the stack, it is our new pc.  */
      68                 :          10 :   Dwarf_Word ret_addr;
      69   [ +  -  +  - ]:          10 :   if (! readfunc (fp + 4, &ret_addr, arg) || ret_addr == 0)
      70                 :             :     return false;
      71                 :             : 
      72                 :             :   /* Get new sp and fp.  Sanity check again.  */
      73                 :          10 :   sp = fp + 8;
      74   [ +  -  +  -  :          10 :   if (! readfunc (fp, &fp, arg) || fp == 0 || sp >= fp)
                   +  - ]
      75                 :             :     return false;
      76                 :             : 
      77                 :             :   /* Set new sp, fp and pc.  */
      78                 :          10 :   regs[0] = sp;
      79                 :          10 :   regs[1] = fp;
      80   [ +  -  -  + ]:          10 :   if (! setfunc (ESP, 2, regs, arg) || ! setfunc (-1, 1, &ret_addr, arg))
      81                 :           0 :     return false;
      82                 :             : 
      83                 :             :   return true;
      84                 :             : }