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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 : : }