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 1.6 2018/07/20 20:50:34 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
54 static int
proc_stop(struct proc_handle * phdl)55 proc_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
73 int
proc_bkptset(struct proc_handle * phdl,uintptr_t address,proc_breakpoint_t * saved)74 proc_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%" PRIxPTR, 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 PRIxPTR, 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 PRIxPTR, address);
123 ret = -1;
124 goto done;
125 }
126
127 done:
128 if (stopped)
129 /* Restart the process if we had to stop it. */
130 proc_continue(phdl);
131
132 return (ret);
133 }
134
135 int
proc_bkptdel(struct proc_handle * phdl,uintptr_t address,proc_breakpoint_t * saved)136 proc_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%" PRIxPTR, 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 PRIxPTR, 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 */
187 void
proc_bkptregadj(unsigned long * pc)188 proc_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 */
200 int
proc_bkptexec(struct proc_handle * phdl,proc_breakpoint_t * saved)201 proc_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 #ifdef PT_STEP
222 if (ptrace(PT_STEP, proc_getpid(phdl), (void *)(intptr_t)1, 0) < 0) {
223 DPRINTFX("ERROR: ptrace step failed");
224 return (-1);
225 }
226 #endif
227 proc_wstatus(phdl);
228 status = proc_getwstat(phdl);
229 if (!WIFSTOPPED(status)) {
230 DPRINTFX("ERROR: don't know why process stopped");
231 return (-1);
232 }
233 /*
234 * Restore the breakpoint. The saved instruction should be
235 * the same as the one that we were passed in.
236 */
237 if (proc_bkptset(phdl, pc, &samesaved) < 0) {
238 DPRINTFX("ERROR: couldn't restore breakpoint");
239 return (-1);
240 }
241
242 assert(memcmp(saved, &samesaved, sizeof(samesaved)) == 0);
243
244 return (0);
245 }
246