setup.c revision 85301 
1/*
2 * Copryight 1997 Sean Eric Fagan
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 * 3. All advertising materials mentioning features or use of this software
13 *    must display the following acknowledgement:
14 *	This product includes software developed by Sean Eric Fagan
15 * 4. Neither the name of the author may be used to endorse or promote
16 *    products derived from this software without specific prior written
17 *    permission.
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#ifndef lint
33static const char rcsid[] =
34  "$FreeBSD: head/usr.bin/truss/setup.c 85301 2001-10-22 02:02:00Z des $";
35#endif /* not lint */
36
37/*
38 * Various setup functions for truss.  Not the cleanest-written code,
39 * I'm afraid.
40 */
41
42#include <sys/param.h>
43#include <sys/ioctl.h>
44#include <sys/pioctl.h>
45#include <sys/proc.h>
46#include <sys/wait.h>
47
48#include <err.h>
49#include <errno.h>
50#include <fcntl.h>
51#include <signal.h>
52#include <stdio.h>
53#include <stdlib.h>
54#include <string.h>
55#include <unistd.h>
56
57static int evflags = 0;
58
59/*
60 * setup_and_wait() is called to start a process.  All it really does
61 * is fork(), set itself up to stop on exec or exit, and then exec
62 * the given command.  At that point, the child process stops, and
63 * the parent can wake up and deal with it.
64 */
65
66int
67setup_and_wait(char *command[]) {
68  struct procfs_status pfs;
69  char buf[32];
70  int fd;
71  int pid;
72  int flags;
73
74  pid = fork();
75  if (pid == -1) {
76    err(1, "fork failed");
77  }
78  if (pid == 0) {	/* Child */
79    int mask = S_EXEC | S_EXIT;
80    fd = open("/proc/curproc/mem", O_WRONLY);
81    if (fd == -1)
82      err(2, "cannot open /proc/curproc/mem");
83    fcntl(fd, F_SETFD, 1);
84    if (ioctl(fd, PIOCBIS, mask) == -1)
85      err(3, "PIOCBIS");
86    flags = PF_LINGER;
87    /*
88     * The PF_LINGER flag tells procfs not to wake up the
89     * process on last close; normally, this is the behaviour
90     * we want.
91     */
92    if (ioctl(fd, PIOCSFL, flags) == -1)
93      warn("cannot set PF_LINGER");
94    execvp(command[0], command);
95    mask = ~0;
96    ioctl(fd, PIOCBIC, ~0);
97    err(4, "execvp %s", command[0]);
98  }
99  /* Only in the parent here */
100
101  if (waitpid(pid, NULL, WNOHANG) != 0) {
102    /*
103     * Process exited before it got to us -- meaning the exec failed
104     * miserably -- so we just quietly exit.
105     */
106    exit(1);
107  }
108
109  sprintf(buf, "/proc/%d/mem", pid);
110  if ((fd = open(buf, O_RDWR)) == -1)
111    err(5, "cannot open %s", buf);
112  if (ioctl(fd, PIOCWAIT, &pfs) == -1)
113    err(6, "PIOCWAIT");
114  if (pfs.why == S_EXIT) {
115    fprintf(stderr, "process exited before exec'ing\n");
116    ioctl(fd, PIOCCONT, 0);
117    wait(0);
118    exit(7);
119  }
120  close(fd);
121  return pid;
122}
123
124/*
125 * start_tracing picks up where setup_and_wait() dropped off -- namely,
126 * it sets the event mask for the given process id.  Called for both
127 * monitoring an existing process and when we create our own.
128 */
129
130int
131start_tracing(int pid, int flags) {
132  int fd;
133  char buf[32];
134  struct procfs_status tmp;
135  sprintf(buf, "/proc/%d/mem", pid);
136
137  fd = open(buf, O_RDWR);
138  if (fd == -1) {
139    /*
140     * The process may have run away before we could start -- this
141     * happens with SUGID programs.  So we need to see if it still
142     * exists before we complain bitterly.
143     */
144    if (kill(pid, 0) == -1)
145      return -1;
146    err(8, "cannot open %s", buf);
147  }
148
149  if (ioctl(fd, PIOCSTATUS, &tmp) == -1) {
150    err(10, "cannot get procfs status struct");
151  }
152  evflags = tmp.events;
153
154  if (ioctl(fd, PIOCBIS, flags) == -1)
155    err(9, "cannot set procfs event bit mask");
156
157  /*
158   * This clears the PF_LINGER set above in setup_and_wait();
159   * if truss happens to die before this, then the process
160   * needs to be woken up via procctl.
161   */
162
163  if (ioctl(fd, PIOCSFL, 0) == -1)
164    warn("cannot clear PF_LINGER");
165
166  return fd;
167}
168
169/*
170 * Restore a process back to it's pre-truss state.
171 * Called for SIGINT, SIGTERM, SIGQUIT.  This only
172 * applies if truss was told to monitor an already-existing
173 * process.
174 */
175void
176restore_proc(int signo) {
177  extern int Procfd;
178
179  ioctl(Procfd, PIOCBIC, ~0);
180  if (evflags)
181    ioctl(Procfd, PIOCBIS, evflags);
182  exit(0);
183}
184