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