Line data    Source code

       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             : }