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execvp.c revision 1.20 
      1 /*	$NetBSD: execvp.c,v 1.20 2001/12/08 00:30:59 enami Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)exec.c	8.1 (Berkeley) 6/4/93";
     40 #else
     41 __RCSID("$NetBSD: execvp.c,v 1.20 2001/12/08 00:30:59 enami Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include "namespace.h"
     46 #include <assert.h>
     47 #include <errno.h>
     48 #include <stdio.h>
     49 #include <stdlib.h>
     50 #include <string.h>
     51 #include <limits.h>
     52 #include <unistd.h>
     53 #include <paths.h>
     54 #include "reentrant.h"
     55 
     56 #ifdef __weak_alias
     57 __weak_alias(execvp,_execvp)
     58 #endif
     59 
     60 extern char **environ;
     61 #ifdef _REENT
     62 extern rwlock_t __environ_lock;
     63 #endif
     64 
     65 int
     66 execvp(const char *name, char * const *argv)
     67 {
     68 	const char **memp;
     69 	int cnt;
     70 	size_t lp, ln;
     71 	int eacces = 0;
     72 	unsigned int etxtbsy = 0;
     73 	char buf[PATH_MAX];
     74 	const char *bp, *path, *p;
     75 
     76 	_DIAGASSERT(name != NULL);
     77 
     78 	/* "" is not a valid filename; check this before traversing PATH. */
     79 	if (name[0] == '\0') {
     80 		errno = ENOENT;
     81 		goto done;
     82 	}
     83 	/* If it's an absolute or relative path name, it's easy. */
     84 	if (strchr(name, '/')) {
     85 		bp = name;
     86 		path = "";
     87 		goto retry;
     88 	}
     89 	bp = buf;
     90 
     91 	/* Get the path we're searching. */
     92 	if (!(path = getenv("PATH")))
     93 		path = _PATH_DEFPATH;
     94 
     95 	ln = strlen(name);
     96 	do {
     97 		/* Find the end of this path element. */
     98 		for (p = path; *path != 0 && *path != ':'; path++)
     99 			continue;
    100 		/*
    101 		 * It's a SHELL path -- double, leading and trailing colons
    102 		 * mean the current directory.
    103 		 */
    104 		if (p == path) {
    105 			p = ".";
    106 			lp = 1;
    107 		} else
    108 			lp = path - p;
    109 
    110 		/*
    111 		 * If the path is too long complain.  This is a possible
    112 		 * security issue; given a way to make the path too long
    113 		 * the user may execute the wrong program.
    114 		 */
    115 		if (lp + ln + 2 > sizeof(buf)) {
    116 			(void)write(STDERR_FILENO, "execvp: ", 8);
    117 			(void)write(STDERR_FILENO, p, lp);
    118 			(void)write(STDERR_FILENO, ": path too long\n", 16);
    119 			continue;
    120 		}
    121 		memcpy(buf, p, lp);
    122 		buf[lp] = '/';
    123 		memcpy(buf + lp + 1, name, ln);
    124 		buf[lp + ln + 1] = '\0';
    125 
    126 retry:		rwlock_rdlock(&__environ_lock);
    127 		(void)execve(bp, argv, environ);
    128 		rwlock_unlock(&__environ_lock);
    129 		switch (errno) {
    130 		case EACCES:
    131 			eacces = 1;
    132 			break;
    133 		case ENOENT:
    134 			break;
    135 		case ENOEXEC:
    136 			for (cnt = 0; argv[cnt] != NULL; ++cnt)
    137 				continue;
    138 			if ((memp = alloca((cnt + 2) * sizeof(*memp))) == NULL)
    139 				goto done;
    140 			memp[0] = _PATH_BSHELL;
    141 			memp[1] = bp;
    142 			(void)memcpy(&memp[2], &argv[1], cnt * sizeof(*memp));
    143 			rwlock_rdlock(&__environ_lock);
    144 			(void)execve(_PATH_BSHELL, (char * const *)memp,
    145 			    environ);
    146 			rwlock_unlock(&__environ_lock);
    147 			goto done;
    148 		case ETXTBSY:
    149 			if (etxtbsy < 3)
    150 				(void)sleep(++etxtbsy);
    151 			goto retry;
    152 		default:
    153 			goto done;
    154 		}
    155 	} while (*path++ == ':');	/* Otherwise, *path was NUL */
    156 	if (eacces)
    157 		errno = EACCES;
    158 	else if (!errno)
    159 		errno = ENOENT;
    160 done:
    161 	return (-1);
    162 }
    163