xref: /dragonfly/usr.bin/truss/setup.c (revision 1de703da)
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  * $FreeBSD: src/usr.bin/truss/setup.c,v 1.10.2.2 2002/02/15 11:43:51 des Exp $
32  * $DragonFly: src/usr.bin/truss/setup.c,v 1.2 2003/06/17 04:29:33 dillon Exp $
33  */
34 
35 /*
36  * Various setup functions for truss.  Not the cleanest-written code,
37  * I'm afraid.
38  */
39 
40 #include <sys/param.h>
41 #include <sys/ioctl.h>
42 #include <sys/pioctl.h>
43 #include <sys/wait.h>
44 
45 #include <err.h>
46 #include <errno.h>
47 #include <fcntl.h>
48 #include <signal.h>
49 #include <stdio.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #include <unistd.h>
53 
54 #include "extern.h"
55 
56 static int evflags = 0;
57 
58 /*
59  * setup_and_wait() is called to start a process.  All it really does
60  * is fork(), set itself up to stop on exec or exit, and then exec
61  * the given command.  At that point, the child process stops, and
62  * the parent can wake up and deal with it.
63  */
64 
65 int
66 setup_and_wait(char *command[]) {
67   struct procfs_status pfs;
68   char buf[32];
69   int fd;
70   int pid;
71   int flags;
72 
73   pid = fork();
74   if (pid == -1) {
75     err(1, "fork failed");
76   }
77   if (pid == 0) {	/* Child */
78     int mask = S_EXEC | S_EXIT;
79     fd = open("/proc/curproc/mem", O_WRONLY);
80     if (fd == -1)
81       err(2, "cannot open /proc/curproc/mem");
82     fcntl(fd, F_SETFD, 1);
83     if (ioctl(fd, PIOCBIS, mask) == -1)
84       err(3, "PIOCBIS");
85     flags = PF_LINGER;
86     /*
87      * The PF_LINGER flag tells procfs not to wake up the
88      * process on last close; normally, this is the behaviour
89      * we want.
90      */
91     if (ioctl(fd, PIOCSFL, flags) == -1)
92       warn("cannot set PF_LINGER");
93     execvp(command[0], command);
94     mask = ~0;
95     ioctl(fd, PIOCBIC, ~0);
96     err(4, "execvp %s", command[0]);
97   }
98   /* Only in the parent here */
99 
100   if (waitpid(pid, NULL, WNOHANG) != 0) {
101     /*
102      * Process exited before it got to us -- meaning the exec failed
103      * miserably -- so we just quietly exit.
104      */
105     exit(1);
106   }
107 
108   sprintf(buf, "/proc/%d/mem", pid);
109   if ((fd = open(buf, O_RDWR)) == -1)
110     err(5, "cannot open %s", buf);
111   if (ioctl(fd, PIOCWAIT, &pfs) == -1)
112     err(6, "PIOCWAIT");
113   if (pfs.why == S_EXIT) {
114     fprintf(stderr, "process exited before exec'ing\n");
115     ioctl(fd, PIOCCONT, 0);
116     wait(0);
117     exit(7);
118   }
119   close(fd);
120   return pid;
121 }
122 
123 /*
124  * start_tracing picks up where setup_and_wait() dropped off -- namely,
125  * it sets the event mask for the given process id.  Called for both
126  * monitoring an existing process and when we create our own.
127  */
128 
129 int
130 start_tracing(int pid, int flags) {
131   int fd;
132   char buf[32];
133   struct procfs_status tmp;
134   sprintf(buf, "/proc/%d/mem", pid);
135 
136   fd = open(buf, O_RDWR);
137   if (fd == -1) {
138     /*
139      * The process may have run away before we could start -- this
140      * happens with SUGID programs.  So we need to see if it still
141      * exists before we complain bitterly.
142      */
143     if (kill(pid, 0) == -1)
144       return -1;
145     err(8, "cannot open %s", buf);
146   }
147 
148   if (ioctl(fd, PIOCSTATUS, &tmp) == -1) {
149     err(10, "cannot get procfs status struct");
150   }
151   evflags = tmp.events;
152 
153   if (ioctl(fd, PIOCBIS, flags) == -1)
154     err(9, "cannot set procfs event bit mask");
155 
156   /*
157    * This clears the PF_LINGER set above in setup_and_wait();
158    * if truss happens to die before this, then the process
159    * needs to be woken up via procctl.
160    */
161 
162   if (ioctl(fd, PIOCSFL, 0) == -1)
163     warn("cannot clear PF_LINGER");
164 
165   return fd;
166 }
167 
168 /*
169  * Restore a process back to it's pre-truss state.
170  * Called for SIGINT, SIGTERM, SIGQUIT.  This only
171  * applies if truss was told to monitor an already-existing
172  * process.
173  */
174 void
175 restore_proc(int signo __unused) {
176   extern int Procfd;
177 
178   ioctl(Procfd, PIOCBIC, ~0);
179   if (evflags)
180     ioctl(Procfd, PIOCBIS, evflags);
181   exit(0);
182 }
183