proc_bkpt.c revision 1.4
1/* 2 * Copyright (c) 2010 The FreeBSD Foundation 3 * All rights reserved. 4 * 5 * This software was developed by Rui Paulo under sponsorship from the 6 * FreeBSD Foundation. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30#include <sys/cdefs.h> 31#ifdef __FBSDID 32__FBSDID("$FreeBSD: head/lib/libproc/proc_bkpt.c 287106 2015-08-24 12:17:15Z andrew $"); 33#else 34__RCSID("$NetBSD: proc_bkpt.c,v 1.4 2015/09/25 19:09:38 christos Exp $"); 35#endif 36 37#include <sys/types.h> 38#include <sys/ptrace.h> 39#include <sys/wait.h> 40 41#include <assert.h> 42#include <string.h> 43#include <err.h> 44#include <errno.h> 45#include <inttypes.h> 46#include <signal.h> 47#include <stdio.h> 48#include "_libproc.h" 49 50#ifndef PTRACE_BREAKPOINT 51#error "Add support for your architecture" 52#endif 53 54static int 55proc_stop(struct proc_handle *phdl) 56{ 57 int status; 58 59 if (kill(proc_getpid(phdl), SIGSTOP) == -1) { 60 DPRINTF("kill %d", proc_getpid(phdl)); 61 return (-1); 62 } else if (waitpid(proc_getpid(phdl), &status, WSTOPPED) == -1) { 63 DPRINTF("waitpid %d", proc_getpid(phdl)); 64 return (-1); 65 } else if (!WIFSTOPPED(status)) { 66 DPRINTFX("waitpid: unexpected status 0x%x", status); 67 return (-1); 68 } 69 70 return (0); 71} 72 73int 74proc_bkptset(struct proc_handle *phdl, uintptr_t address, 75 proc_breakpoint_t *saved) 76{ 77 struct ptrace_io_desc piod; 78 unsigned long paddr, caddr; 79 int ret = 0, stopped; 80 proc_breakpoint_t copy; 81 82 if (phdl->status == PS_DEAD || phdl->status == PS_UNDEAD || 83 phdl->status == PS_IDLE) { 84 errno = ENOENT; 85 return (-1); 86 } 87 88 DPRINTFX("adding breakpoint at 0x%lx", address); 89 90 stopped = 0; 91 if (phdl->status != PS_STOP) { 92 if (proc_stop(phdl) != 0) 93 return (-1); 94 stopped = 1; 95 } 96 97 /* 98 * Read the original instruction. 99 */ 100 caddr = address; 101 paddr = 0; 102 piod.piod_op = PIOD_READ_I; 103 piod.piod_offs = (void *)caddr; 104 piod.piod_addr = (void *)saved->data; 105 piod.piod_len = sizeof(saved->data); 106 if (ptrace(PT_IO, proc_getpid(phdl), &piod, 0) < 0) { 107 DPRINTF("ERROR: couldn't read instruction at address 0x%" 108 PRIuPTR, address); 109 ret = -1; 110 goto done; 111 } 112 /* 113 * Write a breakpoint instruction to that address. 114 */ 115 caddr = address; 116 piod.piod_op = PIOD_WRITE_I; 117 piod.piod_offs = (void *)caddr; 118 piod.piod_addr = (void *)PTRACE_BREAKPOINT; 119 piod.piod_len = sizeof(PTRACE_BREAKPOINT); 120 if (ptrace(PT_IO, proc_getpid(phdl), &piod, 0) < 0) { 121 DPRINTF("ERROR: couldn't write instruction at address 0x%" 122 PRIuPTR, address); 123 ret = -1; 124 goto done; 125 } 126 127done: 128 if (stopped) 129 /* Restart the process if we had to stop it. */ 130 proc_continue(phdl); 131 132 return (ret); 133} 134 135int 136proc_bkptdel(struct proc_handle *phdl, uintptr_t address, 137 proc_breakpoint_t *saved) 138{ 139 struct ptrace_io_desc piod; 140 unsigned long paddr, caddr; 141 int ret = 0, stopped; 142 143 if (phdl->status == PS_DEAD || phdl->status == PS_UNDEAD || 144 phdl->status == PS_IDLE) { 145 errno = ENOENT; 146 return (-1); 147 } 148 149 DPRINTFX("removing breakpoint at 0x%lx", address); 150 151 stopped = 0; 152 if (phdl->status != PS_STOP) { 153 if (proc_stop(phdl) != 0) 154 return (-1); 155 stopped = 1; 156 } 157 158 /* 159 * Overwrite the breakpoint instruction that we setup previously. 160 */ 161 caddr = address; 162 piod.piod_op = PIOD_WRITE_I; 163 piod.piod_offs = (void *)caddr; 164 piod.piod_addr = (void *)saved->data; 165 piod.piod_len = sizeof(saved->data); 166 if (ptrace(PT_IO, proc_getpid(phdl), &piod, 0) < 0) { 167 DPRINTF("ERROR: couldn't write instruction at address 0x%" 168 PRIuPTR, address); 169 ret = -1; 170 } 171 172 if (stopped) 173 /* Restart the process if we had to stop it. */ 174 proc_continue(phdl); 175 176 return (ret); 177} 178 179/* 180 * Decrement pc so that we delete the breakpoint at the correct 181 * address, i.e. at the breakpoint instruction address. 182 * 183 * This is only needed on some architectures where the pc value 184 * when reading registers points at the instruction after the 185 * breakpoint, e.g. x86. 186 */ 187void 188proc_bkptregadj(unsigned long *pc) 189{ 190 191 (void)pc; 192#ifdef PTRACE_BREAKPOINT_ADJ 193 *pc = *pc - PTRACE_BREAKPOINT_ADJ; 194#endif 195} 196 197/* 198 * Step over the breakpoint. 199 */ 200int 201proc_bkptexec(struct proc_handle *phdl, proc_breakpoint_t *saved) 202{ 203 unsigned long pc; 204 proc_breakpoint_t samesaved; 205 int status; 206 207 if (proc_regget(phdl, REG_PC, &pc) < 0) { 208 DPRINTFX("ERROR: couldn't get PC register"); 209 return (-1); 210 } 211 proc_bkptregadj(&pc); 212 if (proc_bkptdel(phdl, pc, saved) < 0) { 213 DPRINTFX("ERROR: couldn't delete breakpoint"); 214 return (-1); 215 } 216 /* 217 * Go back in time and step over the new instruction just 218 * set up by proc_bkptdel(). 219 */ 220 proc_regset(phdl, REG_PC, pc); 221 if (ptrace(PT_STEP, proc_getpid(phdl), (void *)(intptr_t)1, 0) < 0) { 222 DPRINTFX("ERROR: ptrace step failed"); 223 return (-1); 224 } 225 proc_wstatus(phdl); 226 status = proc_getwstat(phdl); 227 if (!WIFSTOPPED(status)) { 228 DPRINTFX("ERROR: don't know why process stopped"); 229 return (-1); 230 } 231 /* 232 * Restore the breakpoint. The saved instruction should be 233 * the same as the one that we were passed in. 234 */ 235 if (proc_bkptset(phdl, pc, &samesaved) < 0) { 236 DPRINTFX("ERROR: couldn't restore breakpoint"); 237 return (-1); 238 } 239 240 assert(memcmp(saved, &samesaved, sizeof(samesaved)) == 0); 241 242 return (0); 243} 244