trace.c revision a8909f71e1421949c960f287217be6c42c286c0f 
1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4#include <errno.h>
5#include <unistd.h>
6#include <sys/types.h>
7#include <sys/wait.h>
8#include "ptrace.h"
9#include <asm/unistd.h>
10
11#include "ltrace.h"
12#include "options.h"
13#include "sysdep.h"
14#include "debug.h"
15
16/* If the system headers did not provide the constants, hard-code the normal
17   values.  */
18#ifndef PTRACE_EVENT_FORK
19
20#define PTRACE_OLDSETOPTIONS    21
21#define PTRACE_SETOPTIONS       0x4200
22#define PTRACE_GETEVENTMSG      0x4201
23
24/* options set using PTRACE_SETOPTIONS */
25#define PTRACE_O_TRACESYSGOOD   0x00000001
26#define PTRACE_O_TRACEFORK      0x00000002
27#define PTRACE_O_TRACEVFORK     0x00000004
28#define PTRACE_O_TRACECLONE     0x00000008
29#define PTRACE_O_TRACEEXEC      0x00000010
30#define PTRACE_O_TRACEVFORKDONE 0x00000020
31#define PTRACE_O_TRACEEXIT      0x00000040
32
33/* Wait extended result codes for the above trace options.  */
34#define PTRACE_EVENT_FORK       1
35#define PTRACE_EVENT_VFORK      2
36#define PTRACE_EVENT_CLONE      3
37#define PTRACE_EVENT_EXEC       4
38#define PTRACE_EVENT_VFORK_DONE 5
39#define PTRACE_EVENT_EXIT       6
40
41#endif /* PTRACE_EVENT_FORK */
42
43static int fork_exec_syscalls[][5] = {
44	{
45#ifdef __NR_fork
46	 __NR_fork,
47#else
48	 -1,
49#endif
50#ifdef __NR_clone
51	 __NR_clone,
52#else
53	 -1,
54#endif
55#ifdef __NR_clone2
56	 __NR_clone2,
57#else
58	 -1,
59#endif
60#ifdef __NR_vfork
61	 __NR_vfork,
62#else
63	 -1,
64#endif
65#ifdef __NR_execve
66	 __NR_execve,
67#else
68	 -1,
69#endif
70	 }
71#ifdef FORK_EXEC_SYSCALLS
72	FORK_EXEC_SYSCALLS
73#endif
74};
75
76#ifdef ARCH_HAVE_UMOVELONG
77extern int arch_umovelong (Process *, void *, long *, arg_type_info *);
78int
79umovelong (Process *proc, void *addr, long *result, arg_type_info *info) {
80	return arch_umovelong (proc, addr, result, info);
81}
82#else
83/* Read a single long from the process's memory address 'addr' */
84int
85umovelong (Process *proc, void *addr, long *result, arg_type_info *info) {
86	long pointed_to;
87
88	errno = 0;
89	pointed_to = ptrace (PTRACE_PEEKTEXT, proc->pid, addr, 0);
90	if (pointed_to == -1 && errno)
91		return -errno;
92
93	*result = pointed_to;
94	return 0;
95}
96#endif
97
98
99/* Returns 1 if the sysnum may make a new child to be created
100 * (ie, with fork() or clone())
101 * Returns 0 otherwise.
102 */
103int
104fork_p(Process *proc, int sysnum) {
105	unsigned int i;
106	if (proc->personality
107	    >= sizeof fork_exec_syscalls / sizeof(fork_exec_syscalls[0]))
108		return 0;
109	for (i = 0; i < sizeof(fork_exec_syscalls[0]) / sizeof(int) - 1; ++i)
110		if (sysnum == fork_exec_syscalls[proc->personality][i])
111			return 1;
112	return 0;
113}
114
115/* Returns 1 if the sysnum may make the process exec other program
116 */
117int
118exec_p(Process *proc, int sysnum) {
119	int i;
120	if (proc->personality
121	    >= sizeof fork_exec_syscalls / sizeof(fork_exec_syscalls[0]))
122		return 0;
123	i = sizeof(fork_exec_syscalls[0]) / sizeof(int) - 1;
124	if (sysnum == fork_exec_syscalls[proc->personality][i])
125		return 1;
126	return 0;
127}
128
129/* Check that we just hit an exec.
130 */
131int
132was_exec(Process *proc, int status) {
133	if (!WIFSTOPPED (status))
134		return 0;
135
136	if (WSTOPSIG (status) == SIGTRAP
137	    && (status >> 16) == PTRACE_EVENT_EXEC) {
138		debug (1, "detected exec (PTRACE_EVENT_EXEC)");
139		return 1;
140	}
141
142	if (WSTOPSIG (status) == SIGTRAP
143	    && proc->callstack_depth > 0) {
144		/* Check whether this SIGTRAP is received just after
145		   execve is called for this process.  Ideally we'd
146		   like to check that the exec succeeded, but e.g. on
147		   s390 we have no way of knowing, because return
148		   value is not set to -1 (as it should).  Never mind,
149		   reseting breakpoints for current process doesn't
150		   hurt. */
151		struct callstack_element *elem;
152		elem = &proc->callstack[proc->callstack_depth - 1];
153		if (elem && elem->is_syscall &&  exec_p(proc, elem->c_un.syscall)) {
154			debug (1, "detected exec (callstack)");
155			return 1;
156		}
157	}
158
159	return 0;
160}
161
162void
163trace_me(void) {
164	if (ptrace(PTRACE_TRACEME, 0, 1, 0) < 0) {
165		perror("PTRACE_TRACEME");
166		exit(1);
167	}
168}
169
170int
171trace_pid(pid_t pid) {
172	if (ptrace(PTRACE_ATTACH, pid, 1, 0) < 0) {
173		return -1;
174	}
175
176	/* man ptrace: PTRACE_ATTACH attaches to the process specified
177	   in pid.  The child is sent a SIGSTOP, but will not
178	   necessarily have stopped by the completion of this call;
179	   use wait() to wait for the child to stop. */
180	if (waitpid (pid, NULL, 0) != pid) {
181		perror ("trace_pid: waitpid");
182		exit (1);
183	}
184
185	return 0;
186}
187
188void
189trace_set_options(Process *proc, pid_t pid) {
190	if (proc->tracesysgood & 0x80)
191		return;
192
193	long options = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEFORK |
194		PTRACE_O_TRACEVFORK | PTRACE_O_TRACECLONE |
195		PTRACE_O_TRACEEXEC;
196	if (ptrace(PTRACE_SETOPTIONS, pid, 0, options) < 0 &&
197	    ptrace(PTRACE_OLDSETOPTIONS, pid, 0, options) < 0) {
198		perror("PTRACE_SETOPTIONS");
199		return;
200	}
201	proc->tracesysgood |= 0x80;
202}
203
204void
205untrace_pid(pid_t pid) {
206	ptrace(PTRACE_DETACH, pid, 1, 0);
207}
208
209void
210continue_after_signal(pid_t pid, int signum) {
211	Process *proc;
212
213	proc = pid2proc(pid);
214	if (proc && proc->breakpoint_being_enabled) {
215#if defined __sparc__  || defined __ia64___
216		ptrace(PTRACE_SYSCALL, pid, 0, signum);
217#else
218		ptrace(PTRACE_SINGLESTEP, pid, 0, signum);
219#endif
220	} else {
221		ptrace(PTRACE_SYSCALL, pid, 0, signum);
222	}
223}
224
225void
226continue_process(pid_t pid) {
227	/* We always trace syscalls to control fork(), clone(), execve()... */
228
229	ptrace(PTRACE_SYSCALL, pid, 0, 0);
230}
231
232void
233continue_enabling_breakpoint(pid_t pid, struct breakpoint *sbp) {
234	enable_breakpoint(pid, sbp);
235	continue_process(pid);
236}
237
238void
239continue_after_breakpoint(Process *proc, struct breakpoint *sbp) {
240	if (sbp->enabled)
241		disable_breakpoint(proc->pid, sbp);
242	set_instruction_pointer(proc, sbp->addr);
243	if (sbp->enabled == 0) {
244		continue_process(proc->pid);
245	} else {
246		proc->breakpoint_being_enabled = sbp;
247#if defined __sparc__  || defined __ia64___
248		/* we don't want to singlestep here */
249		continue_process(proc->pid);
250#else
251		ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0);
252#endif
253	}
254}
255
256/* Read a series of bytes starting at the process's memory address
257   'addr' and continuing until a NUL ('\0') is seen or 'len' bytes
258   have been read.
259*/
260int
261umovestr(Process *proc, void *addr, int len, void *laddr) {
262	union {
263		long a;
264		char c[sizeof(long)];
265	} a;
266	int i;
267	int offset = 0;
268
269	while (offset < len) {
270		a.a = ptrace(PTRACE_PEEKTEXT, proc->pid, addr + offset, 0);
271		for (i = 0; i < sizeof(long); i++) {
272			if (a.c[i] && offset + (signed)i < len) {
273				*(char *)(laddr + offset + i) = a.c[i];
274			} else {
275				*(char *)(laddr + offset + i) = '\0';
276				return 0;
277			}
278		}
279		offset += sizeof(long);
280	}
281	*(char *)(laddr + offset) = '\0';
282	return 0;
283}
284