trace.c revision aee093126654f722523b47848a0c5449e39cf4bb 
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/* Returns 1 if the sysnum may make a new child to be created
77 * (ie, with fork() or clone())
78 * Returns 0 otherwise.
79 */
80int fork_p(struct process *proc, int sysnum)
81{
82	unsigned int i;
83	if (proc->personality
84	    >= sizeof fork_exec_syscalls / sizeof(fork_exec_syscalls[0]))
85		return 0;
86	for (i = 0; i < sizeof(fork_exec_syscalls[0]) / sizeof(int) - 1; ++i)
87		if (sysnum == fork_exec_syscalls[proc->personality][i])
88			return 1;
89	return 0;
90}
91
92/* Returns 1 if the sysnum may make the process exec other program
93 */
94int exec_p(struct process *proc, int sysnum)
95{
96	int i;
97	if (proc->personality
98	    >= sizeof fork_exec_syscalls / sizeof(fork_exec_syscalls[0]))
99		return 0;
100	i = sizeof(fork_exec_syscalls[0]) / sizeof(int) - 1;
101	if (sysnum == fork_exec_syscalls[proc->personality][i])
102		return 1;
103	return 0;
104}
105
106/* Check that we just hit an exec.
107 */
108int was_exec(struct process *proc, int status)
109{
110	if (!WIFSTOPPED (status))
111		return 0;
112
113	if (WSTOPSIG (status) == SIGTRAP
114	    && (status >> 16) == PTRACE_EVENT_EXEC) {
115		debug (1, "detected exec (PTRACE_EVENT_EXEC)");
116		return 1;
117	}
118
119	if (WSTOPSIG (status) == SIGTRAP
120	    && proc->callstack_depth > 0) {
121		/* Check whether this SIGTRAP is received just after
122		   execve is called for this process.  Ideally we'd
123		   like to check that the exec succeeded, but e.g. on
124		   s390 we have no way of knowing, because return
125		   value is not set to -1 (as it should).  Never mind,
126		   reseting breakpoints for current process doesn't
127		   hurt. */
128		struct callstack_element *elem;
129		elem = &proc->callstack[proc->callstack_depth - 1];
130		if (elem && elem->is_syscall &&  exec_p(proc, elem->c_un.syscall)) {
131			debug (1, "detected exec (callstack)");
132			return 1;
133		}
134	}
135
136	return 0;
137}
138
139void trace_me(void)
140{
141	if (ptrace(PTRACE_TRACEME, 0, 1, 0) < 0) {
142		perror("PTRACE_TRACEME");
143		exit(1);
144	}
145}
146
147int trace_pid(pid_t pid)
148{
149	if (ptrace(PTRACE_ATTACH, pid, 1, 0) < 0) {
150		return -1;
151	}
152
153	return 0;
154}
155
156void trace_set_options(struct process *proc, pid_t pid)
157{
158	if (proc->tracesysgood & 0x80)
159		return;
160
161	long options = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC;
162	if (ptrace(PTRACE_SETOPTIONS, pid, 0, options) < 0 &&
163	    ptrace(PTRACE_OLDSETOPTIONS, pid, 0, options) < 0) {
164		perror("PTRACE_SETOPTIONS");
165		return;
166	}
167	proc->tracesysgood |= 0x80;
168}
169
170void untrace_pid(pid_t pid)
171{
172	ptrace(PTRACE_DETACH, pid, 1, 0);
173}
174
175void continue_after_signal(pid_t pid, int signum)
176{
177	/* We should always trace syscalls to be able to control fork(), clone(), execve()... */
178	ptrace(PTRACE_SYSCALL, pid, 0, signum);
179}
180
181void continue_process(pid_t pid)
182{
183	continue_after_signal(pid, 0);
184}
185
186void continue_enabling_breakpoint(pid_t pid, struct breakpoint *sbp)
187{
188	enable_breakpoint(pid, sbp);
189	continue_process(pid);
190}
191
192void continue_after_breakpoint(struct process *proc, struct breakpoint *sbp)
193{
194	if (sbp->enabled)
195		disable_breakpoint(proc->pid, sbp);
196	set_instruction_pointer(proc, sbp->addr);
197	if (sbp->enabled == 0) {
198		continue_process(proc->pid);
199	} else {
200		proc->breakpoint_being_enabled = sbp;
201#if defined __sparc__  || defined __ia64___
202		/* we don't want to singlestep here */
203		continue_process(proc->pid);
204#else
205		ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0);
206#endif
207	}
208}
209
210/* Read a single long from the process's memory address 'addr' */
211int umovelong(struct process *proc, void *addr, long *result)
212{
213	long pointed_to;
214
215        errno = 0;
216        pointed_to = ptrace(PTRACE_PEEKTEXT, proc->pid, addr, 0);
217        if (pointed_to == -1 && errno)
218          return -errno;
219
220        *result = pointed_to;
221        return 0;
222}
223
224/* Read a series of bytes starting at the process's memory address
225   'addr' and continuing until a NUL ('\0') is seen or 'len' bytes
226   have been read.
227*/
228int umovestr(struct process *proc, void *addr, int len, void *laddr)
229{
230	union {
231		long a;
232		char c[sizeof(long)];
233	} a;
234	int i;
235	int offset = 0;
236
237	while (offset < len) {
238		a.a = ptrace(PTRACE_PEEKTEXT, proc->pid, addr + offset, 0);
239		for (i = 0; i < sizeof(long); i++) {
240			if (a.c[i] && offset + (signed)i < len) {
241				*(char *)(laddr + offset + i) = a.c[i];
242			} else {
243				*(char *)(laddr + offset + i) = '\0';
244				return 0;
245			}
246		}
247		offset += sizeof(long);
248	}
249	*(char *)(laddr + offset) = '\0';
250	return 0;
251}
252