1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2010 The FreeBSD Foundation
5 * All rights reserved.
6 *
7 * This software was developed by Rui Paulo under sponsorship from the
8 * FreeBSD Foundation.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34
35 #include <sys/types.h>
36 #include <sys/ptrace.h>
37 #include <sys/wait.h>
38
39 #include <assert.h>
40 #include <err.h>
41 #include <errno.h>
42 #include <signal.h>
43 #include <stdio.h>
44
45 #include "_libproc.h"
46
47 #if defined(__aarch64__)
48 #define AARCH64_BRK 0xd4200000
49 #define AARCH64_BRK_IMM16_SHIFT 5
50 #define AARCH64_BRK_IMM16_VAL (0xd << AARCH64_BRK_IMM16_SHIFT)
51 #define BREAKPOINT_INSTR (AARCH64_BRK | AARCH64_BRK_IMM16_VAL)
52 #define BREAKPOINT_INSTR_SZ 4
53 #elif defined(__amd64__) || defined(__i386__)
54 #define BREAKPOINT_INSTR 0xcc /* int 0x3 */
55 #define BREAKPOINT_INSTR_SZ 1
56 #define BREAKPOINT_ADJUST_SZ BREAKPOINT_INSTR_SZ
57 #elif defined(__arm__)
58 #define BREAKPOINT_INSTR 0xe7ffffff /* bkpt */
59 #define BREAKPOINT_INSTR_SZ 4
60 #elif defined(__mips__)
61 #define BREAKPOINT_INSTR 0xd /* break */
62 #define BREAKPOINT_INSTR_SZ 4
63 #elif defined(__powerpc__)
64 #define BREAKPOINT_INSTR 0x7fe00008 /* trap */
65 #define BREAKPOINT_INSTR_SZ 4
66 #elif defined(__riscv)
67 #define BREAKPOINT_INSTR 0x00100073 /* sbreak */
68 #define BREAKPOINT_INSTR_SZ 4
69 #else
70 #error "Add support for your architecture"
71 #endif
72
73 /*
74 * Use 4-bytes holder for breakpoint instruction on all the platforms.
75 * Works for x86 as well until it is endian-little platform.
76 * (We are coping one byte only on x86 from this 4-bytes piece of
77 * memory).
78 */
79 typedef uint32_t instr_t;
80
81 static int
proc_stop(struct proc_handle * phdl)82 proc_stop(struct proc_handle *phdl)
83 {
84 int status;
85
86 if (kill(proc_getpid(phdl), SIGSTOP) == -1) {
87 DPRINTF("kill %d", proc_getpid(phdl));
88 return (-1);
89 } else if (waitpid(proc_getpid(phdl), &status, WSTOPPED) == -1) {
90 DPRINTF("waitpid %d", proc_getpid(phdl));
91 return (-1);
92 } else if (!WIFSTOPPED(status)) {
93 DPRINTFX("waitpid: unexpected status 0x%x", status);
94 return (-1);
95 }
96
97 return (0);
98 }
99
100 int
proc_bkptset(struct proc_handle * phdl,uintptr_t address,unsigned long * saved)101 proc_bkptset(struct proc_handle *phdl, uintptr_t address,
102 unsigned long *saved)
103 {
104 struct ptrace_io_desc piod;
105 int ret = 0, stopped;
106 instr_t instr;
107
108 *saved = 0;
109 if (phdl->status == PS_DEAD || phdl->status == PS_UNDEAD ||
110 phdl->status == PS_IDLE) {
111 errno = ENOENT;
112 return (-1);
113 }
114
115 DPRINTFX("adding breakpoint at 0x%lx", (unsigned long)address);
116
117 stopped = 0;
118 if (phdl->status != PS_STOP) {
119 if (proc_stop(phdl) != 0)
120 return (-1);
121 stopped = 1;
122 }
123
124 /*
125 * Read the original instruction.
126 */
127 instr = 0;
128 piod.piod_op = PIOD_READ_I;
129 piod.piod_offs = (void *)address;
130 piod.piod_addr = &instr;
131 piod.piod_len = BREAKPOINT_INSTR_SZ;
132 if (ptrace(PT_IO, proc_getpid(phdl), (caddr_t)&piod, 0) < 0) {
133 DPRINTF("ERROR: couldn't read instruction at address 0x%jx",
134 (uintmax_t)address);
135 ret = -1;
136 goto done;
137 }
138 *saved = instr;
139 /*
140 * Write a breakpoint instruction to that address.
141 */
142 instr = BREAKPOINT_INSTR;
143 piod.piod_op = PIOD_WRITE_I;
144 piod.piod_offs = (void *)address;
145 piod.piod_addr = &instr;
146 piod.piod_len = BREAKPOINT_INSTR_SZ;
147 if (ptrace(PT_IO, proc_getpid(phdl), (caddr_t)&piod, 0) < 0) {
148 DPRINTF("ERROR: couldn't write instruction at address 0x%jx",
149 (uintmax_t)address);
150 ret = -1;
151 goto done;
152 }
153
154 done:
155 if (stopped)
156 /* Restart the process if we had to stop it. */
157 proc_continue(phdl);
158
159 return (ret);
160 }
161
162 int
proc_bkptdel(struct proc_handle * phdl,uintptr_t address,unsigned long saved)163 proc_bkptdel(struct proc_handle *phdl, uintptr_t address,
164 unsigned long saved)
165 {
166 struct ptrace_io_desc piod;
167 int ret = 0, stopped;
168 instr_t instr;
169
170 if (phdl->status == PS_DEAD || phdl->status == PS_UNDEAD ||
171 phdl->status == PS_IDLE) {
172 errno = ENOENT;
173 return (-1);
174 }
175
176 DPRINTFX("removing breakpoint at 0x%lx", (unsigned long)address);
177
178 stopped = 0;
179 if (phdl->status != PS_STOP) {
180 if (proc_stop(phdl) != 0)
181 return (-1);
182 stopped = 1;
183 }
184
185 /*
186 * Overwrite the breakpoint instruction that we setup previously.
187 */
188 instr = saved;
189 piod.piod_op = PIOD_WRITE_I;
190 piod.piod_offs = (void *)address;
191 piod.piod_addr = &instr;
192 piod.piod_len = BREAKPOINT_INSTR_SZ;
193 if (ptrace(PT_IO, proc_getpid(phdl), (caddr_t)&piod, 0) < 0) {
194 DPRINTF("ERROR: couldn't write instruction at address 0x%jx",
195 (uintmax_t)address);
196 ret = -1;
197 }
198
199 if (stopped)
200 /* Restart the process if we had to stop it. */
201 proc_continue(phdl);
202
203 return (ret);
204 }
205
206 /*
207 * Decrement pc so that we delete the breakpoint at the correct
208 * address, i.e. at the BREAKPOINT_INSTR address.
209 *
210 * This is only needed on some architectures where the pc value
211 * when reading registers points at the instruction after the
212 * breakpoint, e.g. x86.
213 */
214 void
proc_bkptregadj(unsigned long * pc)215 proc_bkptregadj(unsigned long *pc)
216 {
217
218 (void)pc;
219 #ifdef BREAKPOINT_ADJUST_SZ
220 *pc = *pc - BREAKPOINT_ADJUST_SZ;
221 #endif
222 }
223
224 /*
225 * Step over the breakpoint.
226 */
227 int
proc_bkptexec(struct proc_handle * phdl,unsigned long saved)228 proc_bkptexec(struct proc_handle *phdl, unsigned long saved)
229 {
230 unsigned long pc;
231 unsigned long samesaved;
232 int status;
233
234 if (proc_regget(phdl, REG_PC, &pc) < 0) {
235 DPRINTFX("ERROR: couldn't get PC register");
236 return (-1);
237 }
238 proc_bkptregadj(&pc);
239 if (proc_bkptdel(phdl, pc, saved) < 0) {
240 DPRINTFX("ERROR: couldn't delete breakpoint");
241 return (-1);
242 }
243 /*
244 * Go back in time and step over the new instruction just
245 * set up by proc_bkptdel().
246 */
247 proc_regset(phdl, REG_PC, pc);
248 if (ptrace(PT_STEP, proc_getpid(phdl), (caddr_t)1, 0) < 0) {
249 DPRINTFX("ERROR: ptrace step failed");
250 return (-1);
251 }
252 proc_wstatus(phdl);
253 status = proc_getwstat(phdl);
254 if (!WIFSTOPPED(status)) {
255 DPRINTFX("ERROR: don't know why process stopped");
256 return (-1);
257 }
258 /*
259 * Restore the breakpoint. The saved instruction should be
260 * the same as the one that we were passed in.
261 */
262 if (proc_bkptset(phdl, pc, &samesaved) < 0) {
263 DPRINTFX("ERROR: couldn't restore breakpoint");
264 return (-1);
265 }
266 assert(samesaved == saved);
267
268 return (0);
269 }
270