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