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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 #define BACKEND aarch64_
     34 #define FP_REG 29
     35 #define LR_REG 30
     36 #define SP_REG 31
     37 #define FP_OFFSET 0
     38 #define LR_OFFSET 8
     39 #define SP_OFFSET 16
     40 
     41 #include "libebl_CPU.h"
     42 
     43 /* There was no CFI. Maybe we happen to have a frame pointer and can unwind from that?  */
     44 
     45 bool
     46 EBLHOOK(unwind) (Ebl *ebl __attribute__ ((unused)), Dwarf_Addr pc __attribute__ ((unused)),
     47                  ebl_tid_registers_t *setfunc, ebl_tid_registers_get_t *getfunc,
     48                  ebl_pid_memory_read_t *readfunc, void *arg,
     49                  bool *signal_framep __attribute__ ((unused)))
     50 {
     51   Dwarf_Word fp, lr, sp;
     52 
     53   if (!getfunc(LR_REG, 1, &lr, arg))
     54     return false;
     55 
     56   if (lr == 0 || !setfunc(-1, 1, &lr, arg))
     57     return false;
     58 
     59   if (!getfunc(FP_REG, 1, &fp, arg))
     60     fp = 0;
     61 
     62   if (!getfunc(SP_REG, 1, &sp, arg))
     63     sp = 0;
     64 
     65   Dwarf_Word newLr, newFp, newSp;
     66 
     67   if (!readfunc(fp + LR_OFFSET, &newLr, arg))
     68     newLr = 0;
     69 
     70   if (!readfunc(fp + FP_OFFSET, &newFp, arg))
     71     newFp = 0;
     72 
     73   newSp = fp + SP_OFFSET;
     74 
     75   // These are not fatal if they don't work. They will just prevent unwinding at the next frame.
     76   setfunc(LR_REG, 1, &newLr, arg);
     77   setfunc(FP_REG, 1, &newFp, arg);
     78   setfunc(SP_REG, 1, &newSp, arg);
     79 
     80   // If the fp is invalid, we might still have a valid lr.
     81   // But if the fp is valid, then the stack should be moving in the right direction.
     82   return fp == 0 || newSp > sp;
     83 }
     84