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 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 const int fpReg = 6; 50 const int spReg = 7; 51 52 Dwarf_Word fp; 53 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 Dwarf_Word sp; 58 if (!getfunc(spReg, 1, &sp, arg)) 59 sp = 0; 60 61 Dwarf_Word prev_fp; 62 if (!readfunc(fp, &prev_fp, arg)) 63 prev_fp = 0; 64 65 Dwarf_Word ret; 66 if (!readfunc(fp + 8, &ret, arg)) 67 return false; 68 69 if (!setfunc(fpReg, 1, &prev_fp, arg)) 70 return false; 71 72 fp += 16; // Pop fp and return address and write result to sp 73 if (!setfunc(spReg, 1, &fp, arg)) 74 return false; 75 76 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 if (sp >= fp) 83 return false; 84 85 return true; 86 } 87
