proc_bkpt.c revision 1.2 
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 1.2 2015/09/24 14:12:48 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 <err.h>
43#include <errno.h>
44#include <inttypes.h>
45#include <signal.h>
46#include <stdio.h>
47#include "_libproc.h"
48
49#if defined(__aarch64__)
50#define	AARCH64_BRK		0xd4200000
51#define	AARCH64_BRK_IMM16_SHIFT	5
52#define	AARCH64_BRK_IMM16_VAL	(0xd << AARCH64_BRK_IMM16_SHIFT)
53#define	BREAKPOINT_INSTR	(AARCH64_BRK | AARCH64_BRK_IMM16_VAL)
54#define	BREAKPOINT_INSTR_SZ	4
55#elif defined(__amd64__) || defined(__i386__)
56#define	BREAKPOINT_INSTR	0xcc	/* int 0x3 */
57#define	BREAKPOINT_INSTR_SZ	1
58#define	BREAKPOINT_ADJUST_SZ	BREAKPOINT_INSTR_SZ
59#elif defined(__arm__)
60#define	BREAKPOINT_INSTR	0xe7ffffff	/* bkpt */
61#define	BREAKPOINT_INSTR_SZ	4
62#elif defined(__mips__)
63#define	BREAKPOINT_INSTR	0xd	/* break */
64#define	BREAKPOINT_INSTR_SZ	4
65#elif defined(__powerpc__)
66#define	BREAKPOINT_INSTR	0x7fe00008	/* trap */
67#define	BREAKPOINT_INSTR_SZ	4
68#else
69#error "Add support for your architecture"
70#endif
71
72static int
73proc_stop(struct proc_handle *phdl)
74{
75	int status;
76
77	if (kill(proc_getpid(phdl), SIGSTOP) == -1) {
78		DPRINTF("kill %d", proc_getpid(phdl));
79		return (-1);
80	} else if (waitpid(proc_getpid(phdl), &status, WSTOPPED) == -1) {
81		DPRINTF("waitpid %d", proc_getpid(phdl));
82		return (-1);
83	} else if (!WIFSTOPPED(status)) {
84		DPRINTFX("waitpid: unexpected status 0x%x", status);
85		return (-1);
86	}
87
88	return (0);
89}
90
91int
92proc_bkptset(struct proc_handle *phdl, uintptr_t address,
93    unsigned long *saved)
94{
95	struct ptrace_io_desc piod;
96	unsigned long paddr, caddr;
97	int ret = 0, stopped;
98
99	*saved = 0;
100	if (phdl->status == PS_DEAD || phdl->status == PS_UNDEAD ||
101	    phdl->status == PS_IDLE) {
102		errno = ENOENT;
103		return (-1);
104	}
105
106	DPRINTFX("adding breakpoint at 0x%lx", address);
107
108	stopped = 0;
109	if (phdl->status != PS_STOP) {
110		if (proc_stop(phdl) != 0)
111			return (-1);
112		stopped = 1;
113	}
114
115	/*
116	 * Read the original instruction.
117	 */
118	caddr = address;
119	paddr = 0;
120	piod.piod_op = PIOD_READ_I;
121	piod.piod_offs = (void *)caddr;
122	piod.piod_addr = &paddr;
123	piod.piod_len  = BREAKPOINT_INSTR_SZ;
124	if (ptrace(PT_IO, proc_getpid(phdl), (caddr_t)&piod, 0) < 0) {
125		DPRINTF("ERROR: couldn't read instruction at address 0x%"
126		    PRIuPTR, address);
127		ret = -1;
128		goto done;
129	}
130	*saved = paddr;
131	/*
132	 * Write a breakpoint instruction to that address.
133	 */
134	caddr = address;
135	paddr = BREAKPOINT_INSTR;
136	piod.piod_op = PIOD_WRITE_I;
137	piod.piod_offs = (void *)caddr;
138	piod.piod_addr = &paddr;
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%"
142		    PRIuPTR, address);
143		ret = -1;
144		goto done;
145	}
146
147done:
148	if (stopped)
149		/* Restart the process if we had to stop it. */
150		proc_continue(phdl);
151
152	return (ret);
153}
154
155int
156proc_bkptdel(struct proc_handle *phdl, uintptr_t address,
157    unsigned long saved)
158{
159	struct ptrace_io_desc piod;
160	unsigned long paddr, caddr;
161	int ret = 0, stopped;
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", 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	caddr = address;
182	paddr = saved;
183	piod.piod_op = PIOD_WRITE_I;
184	piod.piod_offs = (void *)caddr;
185	piod.piod_addr = &paddr;
186	piod.piod_len  = BREAKPOINT_INSTR_SZ;
187	if (ptrace(PT_IO, proc_getpid(phdl), (caddr_t)&piod, 0) < 0) {
188		DPRINTF("ERROR: couldn't write instruction at address 0x%"
189		    PRIuPTR, address);
190		ret = -1;
191	}
192
193	if (stopped)
194		/* Restart the process if we had to stop it. */
195		proc_continue(phdl);
196
197	return (ret);
198}
199
200/*
201 * Decrement pc so that we delete the breakpoint at the correct
202 * address, i.e. at the BREAKPOINT_INSTR address.
203 *
204 * This is only needed on some architectures where the pc value
205 * when reading registers points at the instruction after the
206 * breakpoint, e.g. x86.
207 */
208void
209proc_bkptregadj(unsigned long *pc)
210{
211
212	(void)pc;
213#ifdef BREAKPOINT_ADJUST_SZ
214	*pc = *pc - BREAKPOINT_ADJUST_SZ;
215#endif
216}
217
218/*
219 * Step over the breakpoint.
220 */
221int
222proc_bkptexec(struct proc_handle *phdl, unsigned long saved)
223{
224	unsigned long pc;
225	unsigned long samesaved;
226	int status;
227
228	if (proc_regget(phdl, REG_PC, &pc) < 0) {
229		DPRINTFX("ERROR: couldn't get PC register");
230		return (-1);
231	}
232	proc_bkptregadj(&pc);
233	if (proc_bkptdel(phdl, pc, saved) < 0) {
234		DPRINTFX("ERROR: couldn't delete breakpoint");
235		return (-1);
236	}
237	/*
238	 * Go back in time and step over the new instruction just
239	 * set up by proc_bkptdel().
240	 */
241	proc_regset(phdl, REG_PC, pc);
242	if (ptrace(PT_STEP, proc_getpid(phdl), (caddr_t)1, 0) < 0) {
243		DPRINTFX("ERROR: ptrace step failed");
244		return (-1);
245	}
246	proc_wstatus(phdl);
247	status = proc_getwstat(phdl);
248	if (!WIFSTOPPED(status)) {
249		DPRINTFX("ERROR: don't know why process stopped");
250		return (-1);
251	}
252	/*
253	 * Restore the breakpoint. The saved instruction should be
254	 * the same as the one that we were passed in.
255	 */
256	if (proc_bkptset(phdl, pc, &samesaved) < 0) {
257		DPRINTFX("ERROR: couldn't restore breakpoint");
258		return (-1);
259	}
260	assert(samesaved == saved);
261
262	return (0);
263}
264