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/*-
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 * Copyright (c) 1991, 1993
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 *        The Regents of the University of California.  All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the University nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include <sys/cdefs.h>
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#include <assert.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <limits.h>
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#include <paths.h>
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#include <unistd.h>
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extern char **environ;
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int
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execvp(const char *name, char * const *argv)
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{
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        const char **memp;
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        int cnt;
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        size_t lp, ln = 0;
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        int eacces = 0;
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        unsigned int etxtbsy = 0;
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        char buf[PATH_MAX];
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        const char *bp, *path, *p;
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        /* "" is not a valid filename; check this before traversing PATH. */
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        if (name[0] == '\0') {
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                errno = ENOENT;
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                goto done;
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        }
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        /* If it's an absolute or relative path name, it's easy. */
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        if (strchr(name, '/')) {
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                bp = name;
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                path = "";
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                goto retry;
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        }
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        bp = buf;
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        /* Get the path we're searching. */
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        if (!(path = getenv("PATH")))
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                path = _PATH_DEFPATH;
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        ln = strlen(name);
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        do {
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                /* Find the end of this path element. */
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                for (p = path; *path != 0 && *path != ':'; path++)
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                        continue;
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                /*
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                 * It's a SHELL path -- double, leading and trailing colons
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                 * mean the current directory.
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                 */
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                if (p == path) {
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                        p = ".";
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                        lp = 1;
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                } else
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                        lp = path - p;
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                /*
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                 * If the path is too long complain.  This is a possible
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                 * security issue; given a way to make the path too long
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                 * the user may execute the wrong program.
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                 */
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                if (lp + ln + 2 > sizeof(buf))
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                        continue;
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                memcpy(buf, p, lp);
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                buf[lp] = '/';
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                memcpy(buf + lp + 1, name, ln);
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                buf[lp + ln + 1] = '\0';
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retry:                (void)execve(bp, argv, environ);
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                switch (errno) {
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                case EACCES:
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                        eacces = 1;
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                        break;
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                case ENOTDIR:
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                case ENOENT:
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                        break;
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                case ENOEXEC:
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                        for (cnt = 0; argv[cnt] != NULL; ++cnt)
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                                continue;
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                        if ((memp = (const char **)(alloca((cnt + 2) * sizeof(*memp)))) == NULL)
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                                goto done;
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                        memp[0] = _PATH_BSHELL;
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                        memp[1] = bp;
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                        (void)memcpy(&memp[2], &argv[1], cnt * sizeof(*memp));
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                        (void)execve(_PATH_BSHELL, (char * const *)memp,
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                            environ);
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                        goto done;
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                case ETXTBSY:
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                        if (etxtbsy < 3)
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                                (void)sleep(++etxtbsy);
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                        goto retry;
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                default:
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                        goto done;
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                }
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        } while (*path++ == ':');        /* Otherwise, *path was NUL */
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        if (eacces)
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                errno = EACCES;
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        else if (!errno)
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                errno = ENOENT;
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done:
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        return (-1);
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}