usr.bin/truss/setup.c

   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 1.3 2003/11/04 15:34:41 eirikn 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 "truss.h"
  55 #include "extern.h"
  56
  57 static 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
  66 int
  67 setup_and_wait(char *command[]) {
  68   struct procfs_status pfs;
  69   char *buf;
  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     asprintf(&buf, "%s/curproc/mem", procfs_path);
  81     if (buf == NULL)
  82       err(1, "Out of memory");
  83     fd = open(buf, O_WRONLY);
  84     free(buf);
  85     if (fd == -1)
  86       err(2, "cannot open %s", buf);
  87     fcntl(fd, F_SETFD, 1);
  88     if (ioctl(fd, PIOCBIS, mask) == -1)
  89       err(3, "PIOCBIS");
  90     flags = PF_LINGER;
  91     /*
  92      * The PF_LINGER flag tells procfs not to wake up the
  93      * process on last close; normally, this is the behaviour
  94      * we want.
  95      */
  96     if (ioctl(fd, PIOCSFL, flags) == -1)
  97       warn("cannot set PF_LINGER");
  98     execvp(command[0], command);
  99     mask = ~0;
 100     ioctl(fd, PIOCBIC, ~0);
 101     err(4, "execvp %s", command[0]);
 102   }
 103   /* Only in the parent here */
 104
 105   if (waitpid(pid, NULL, WNOHANG) != 0) {
 106     /*
 107      * Process exited before it got to us -- meaning the exec failed
 108      * miserably -- so we just quietly exit.
 109      */
 110     exit(1);
 111   }
 112
 113   asprintf(&buf, "%s/%d/mem", procfs_path, pid);
 114   if (buf == NULL)
 115     err(1, "Out of memory");
 116   do {
 117     fd = open(buf, O_RDWR);
 118   } while(fd == -1 && errno == EAGAIN);
 119   free(buf);
 120   if (fd == -1)
 121     err(5, "cannot open %s", buf);
 122   if (ioctl(fd, PIOCWAIT, &pfs) == -1)
 123     err(6, "PIOCWAIT");
 124   if (pfs.why == S_EXIT) {
 125     fprintf(stderr, "process exited before exec'ing\n");
 126     ioctl(fd, PIOCCONT, 0);
 127     wait(0);
 128     exit(7);
 129   }
 130   close(fd);
 131   return pid;
 132 }
 133
 134 /*
 135  * start_tracing picks up where setup_and_wait() dropped off -- namely,
 136  * it sets the event mask for the given process id.  Called for both
 137  * monitoring an existing process and when we create our own.
 138  */
 139
 140 int
 141 start_tracing(int pid, int flags) {
 142   int fd;
 143   char *buf;
 144   struct procfs_status tmp;
 145
 146   asprintf(&buf, "%s/%d/mem", procfs_path, pid);
 147   if (buf == NULL)
 148     err(1, "Out of memory");
 149   do {
 150     fd = open(buf, O_RDWR);
 151   } while(fd == -1 && errno == EAGAIN);
 152   free(buf);
 153   if (fd == -1) {
 154     /*
 155      * The process may have run away before we could start -- this
 156      * happens with SUGID programs.  So we need to see if it still
 157      * exists before we complain bitterly.
 158      */
 159     if (kill(pid, 0) == -1)
 160       return -1;
 161     err(8, "cannot open %s", buf);
 162   }
 163
 164   if (ioctl(fd, PIOCSTATUS, &tmp) == -1) {
 165     err(10, "cannot get procfs status struct");
 166   }
 167   evflags = tmp.events;
 168
 169   if (ioctl(fd, PIOCBIS, flags) == -1)
 170     err(9, "cannot set procfs event bit mask");
 171
 172   /*
 173    * This clears the PF_LINGER set above in setup_and_wait();
 174    * if truss happens to die before this, then the process
 175    * needs to be woken up via procctl.
 176    */
 177
 178   if (ioctl(fd, PIOCSFL, 0) == -1)
 179     warn("cannot clear PF_LINGER");
 180
 181   return fd;
 182 }
 183
 184 /*
 185  * Restore a process back to it's pre-truss state.
 186  * Called for SIGINT, SIGTERM, SIGQUIT.  This only
 187  * applies if truss was told to monitor an already-existing
 188  * process.
 189  */
 190 void
 191 restore_proc(int signo __unused) {
 192   ioctl(Procfd, PIOCBIC, ~0);
 193   if (evflags)
 194     ioctl(Procfd, PIOCBIS, evflags);
 195   exit(0);
 196 }