lib/libc/gen/popen.c

   1 /*
   2  * Copyright (c) 1988, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software written by Ken Arnold and
   6  * published in UNIX Review, Vol. 6, No. 8.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)popen.c  8.3 (Berkeley) 5/3/95
  33  * $FreeBSD: src/lib/libc/gen/popen.c,v 1.20 2008/07/29 16:29:59 ed Exp $
  34  * $DragonFly: src/lib/libc/gen/popen.3,v 1.4 2006/04/08 08:17:06 swildner Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <sys/param.h>
  39 #include <sys/queue.h>
  40 #include <sys/wait.h>
  41
  42 #include <signal.h>
  43 #include <errno.h>
  44 #include <unistd.h>
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #include <string.h>
  48 #include <paths.h>
  49 #include <fcntl.h>
  50 #include <pthread.h>
  51 #include "un-namespace.h"
  52 #include "libc_private.h"
  53
  54 extern char **environ;
  55
  56 struct pid {
  57         SLIST_ENTRY(pid) next;
  58         FILE *fp;
  59         pid_t pid;
  60 };
  61 static SLIST_HEAD(, pid) pidlist = SLIST_HEAD_INITIALIZER(pidlist);
  62 static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;
  63
  64 #define THREAD_LOCK()   if (__isthreaded) _pthread_mutex_lock(&pidlist_mutex)
  65 #define THREAD_UNLOCK() if (__isthreaded) _pthread_mutex_unlock(&pidlist_mutex)
  66
  67 FILE *
  68 popen(const char *command, const char *type)
  69 {
  70         struct pid *cur;
  71         FILE *iop;
  72         int pdes[2], pid, twoway, cloexec;
  73         const char *argv[4];
  74         struct pid *p;
  75
  76         cloexec = (strchr(type, 'e') != NULL);
  77
  78         /*
  79          * Lite2 introduced two-way popen() pipes using _socketpair().
  80          * FreeBSD's pipe() is bidirectional, so we use that.
  81          */
  82         if (strchr(type, '+')) {
  83                 twoway = 1;
  84                 type = "r+";
  85         } else  {
  86                 twoway = 0;
  87                 if ((*type != 'r' && *type != 'w') ||
  88                     (type[1] && (type[1] != 'e' || type[2])))
  89                         return (NULL);
  90         }
  91         if (pipe2(pdes, O_CLOEXEC) < 0)
  92                 return (NULL);
  93
  94         if ((cur = malloc(sizeof(struct pid))) == NULL) {
  95                 _close(pdes[0]);
  96                 _close(pdes[1]);
  97                 return (NULL);
  98         }
  99
 100         argv[0] = "sh";
 101         argv[1] = "-c";
 102         argv[2] = command;
 103         argv[3] = NULL;
 104
 105         THREAD_LOCK();
 106         switch (pid = vfork()) {
 107         case -1:                        /* Error. */
 108                 THREAD_UNLOCK();
 109                 _close(pdes[0]);
 110                 _close(pdes[1]);
 111                 free(cur);
 112                 return (NULL);
 113                 /* NOTREACHED */
 114         case 0:                         /* Child. */
 115                 if (*type == 'r') {
 116                         /*
 117                          * The _dup2() to STDIN_FILENO is repeated to avoid
 118                          * writing to pdes[1], which might corrupt the
 119                          * parent's copy.  This isn't good enough in
 120                          * general, since the _exit() is no return, so
 121                          * the compiler is free to corrupt all the local
 122                          * variables.
 123                          */
 124                         _close(pdes[0]);
 125                         _fcntl(pdes[1], F_SETFD, 0);
 126                         if (pdes[1] != STDOUT_FILENO) {
 127                                 _dup2(pdes[1], STDOUT_FILENO);
 128                                 _close(pdes[1]);
 129                                 if (twoway)
 130                                         _dup2(STDOUT_FILENO, STDIN_FILENO);
 131                         } else if (twoway && (pdes[1] != STDIN_FILENO))
 132                                 _dup2(pdes[1], STDIN_FILENO);
 133                 } else {
 134                         _fcntl(pdes[0], F_SETFD, 0);
 135                         if (pdes[0] != STDIN_FILENO) {
 136                                 _dup2(pdes[0], STDIN_FILENO);
 137                                 _close(pdes[0]);
 138                         }
 139                         _close(pdes[1]);
 140                 }
 141                 SLIST_FOREACH(p, &pidlist, next)
 142                         _close(__sfileno(p->fp));
 143                 _execve(_PATH_BSHELL, __DECONST(char * const *, argv), environ);
 144                 _exit(127);
 145                 /* NOTREACHED */
 146         }
 147         THREAD_UNLOCK();
 148
 149         /* Parent; assume fdopen can't fail. */
 150         if (*type == 'r') {
 151                 iop = fdopen(pdes[0], type);
 152                 _close(pdes[1]);
 153         } else {
 154                 iop = fdopen(pdes[1], type);
 155                 _close(pdes[0]);
 156         }
 157
 158         /* Link into list of file descriptors. */
 159         cur->fp = iop;
 160         cur->pid = pid;
 161         THREAD_LOCK();
 162         SLIST_INSERT_HEAD(&pidlist, cur, next);
 163         THREAD_UNLOCK();
 164
 165         if (!cloexec) {
 166                 int fd = (*type == 'r') ? pdes[0] : pdes[1];
 167                 _fcntl(fd, F_SETFD, 0);
 168         }
 169
 170         return (iop);
 171 }
 172
 173 /*
 174  * pclose --
 175  *      Pclose returns -1 if stream is not associated with a `popened' command,
 176  *      if already `pclosed', or waitpid returns an error.
 177  */
 178 int
 179 pclose(FILE *iop)
 180 {
 181         struct pid *cur, *last = NULL;
 182         int pstat;
 183         pid_t pid;
 184
 185         /*
 186          * Find the appropriate file pointer and remove it from the list.
 187          */
 188         THREAD_LOCK();
 189         SLIST_FOREACH(cur, &pidlist, next) {
 190                 if (cur->fp == iop)
 191                         break;
 192                 last = cur;
 193         }
 194         if (cur == NULL) {
 195                 THREAD_UNLOCK();
 196                 return (-1);
 197         }
 198         if (last == NULL)
 199                 SLIST_REMOVE_HEAD(&pidlist, next);
 200         else
 201                 SLIST_REMOVE_AFTER(last, next);
 202
 203         /* re-apply close-on-exec for unlock/fclose race */
 204         _fcntl(__sfileno(iop), F_SETFD, FD_CLOEXEC);
 205
 206         THREAD_UNLOCK();
 207
 208         fclose(iop);
 209
 210         do {
 211                 pid = _wait4(cur->pid, &pstat, 0, NULL);
 212         } while (pid == -1 && errno == EINTR);
 213
 214         free(cur);
 215
 216         return (pid == -1 ? -1 : pstat);
 217 }