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       1                 :            : /* Get previous frame state for an existing frame state.
       2                 :            :    Copyright (C) 2016 The Qt Company Ltd.
       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 x86_64_
      37                 :            : #include "libebl_CPU.h"
      38                 :            : 
      39                 :            : /* There was no CFI. Maybe we happen to have a frame pointer and can unwind from that?  */
      40                 :            : 
      41                 :            : bool
      42                 :         17 : x86_64_unwind (Ebl *ebl __attribute__ ((unused)),
      43                 :            :                Dwarf_Addr pc __attribute__ ((unused)),
      44                 :            :                ebl_tid_registers_t *setfunc, ebl_tid_registers_get_t *getfunc,
      45                 :            :                ebl_pid_memory_read_t *readfunc, void *arg,
      46                 :            :                bool *signal_framep __attribute__ ((unused)))
      47                 :            : {
      48                 :            :   // Register 6 is supposed to be rbp, thus the conventional frame pointer
      49                 :         17 :   const int fpReg = 6;
      50                 :         17 :   const int spReg = 7;
      51                 :            : 
      52                 :         17 :   Dwarf_Word fp;
      53   [ +  -  +  + ]:         17 :   if (!getfunc(fpReg, 1, &fp, arg) || fp == 0)
      54                 :            :     return false;
      55                 :            : 
      56                 :            :   // Try to read old sp, so that we can avoid infinite loops below
      57                 :          7 :   Dwarf_Word sp;
      58         [ -  + ]:          7 :   if (!getfunc(spReg, 1, &sp, arg))
      59                 :          0 :     sp = 0;
      60                 :            : 
      61                 :          7 :   Dwarf_Word prev_fp;
      62         [ -  + ]:          7 :   if (!readfunc(fp, &prev_fp, arg))
      63                 :          0 :     prev_fp = 0;
      64                 :            : 
      65                 :          7 :   Dwarf_Word ret;
      66         [ +  - ]:          7 :   if (!readfunc(fp + 8, &ret, arg))
      67                 :            :     return false;
      68                 :            : 
      69         [ +  - ]:          7 :   if (!setfunc(fpReg, 1, &prev_fp, arg))
      70                 :            :     return false;
      71                 :            : 
      72                 :          7 :   fp += 16; // Pop fp and return address and write result to sp
      73         [ +  - ]:          7 :   if (!setfunc(spReg, 1, &fp, arg))
      74                 :            :     return false;
      75                 :            : 
      76         [ +  - ]:          7 :   if (!setfunc(-1, 1, &ret, arg))
      77                 :            :     return false;
      78                 :            : 
      79                 :            :   // If the sp didn't move up we don't actually have a new stack
      80                 :            :   // frame but rather some random data that doesn't include frame
      81                 :            :   // pointers. Break the unwinding then.
      82         [ +  + ]:          7 :   if (sp >= fp)
      83                 :          2 :     return false;
      84                 :            : 
      85                 :            :   return true;
      86                 :            : }