/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software written by Ken Arnold and
 * published in UNIX Review, Vol. 6, No. 8.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "namespace.h"
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/wait.h>

#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <paths.h>
#include <pthread.h>
#include "un-namespace.h"
#include "libc_private.h"

struct pid {
        SLIST_ENTRY(pid) next;
        FILE *fp;
        pid_t pid;
};
static SLIST_HEAD(, pid) pidlist = SLIST_HEAD_INITIALIZER(pidlist);
static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;

#define THREAD_LOCK()   if (__isthreaded) _pthread_mutex_lock(&pidlist_mutex)
#define THREAD_UNLOCK() if (__isthreaded) _pthread_mutex_unlock(&pidlist_mutex)

FILE *
popen(const char *command, const char *type)
{
        struct pid *cur;
        FILE *iop;
        int pdes[2], pid, twoway, cloexec;
        int pdes_unused_in_parent;
        char *argv[4];
        struct pid *p;

        cloexec = strchr(type, 'e') != NULL;
        /*
         * Lite2 introduced two-way popen() pipes using _socketpair().
         * FreeBSD's pipe() is bidirectional, so we use that.
         */
        if (strchr(type, '+')) {
                twoway = 1;
                type = "r+";
        } else  {
                twoway = 0;
                if ((*type != 'r' && *type != 'w') ||
                    (type[1] && (type[1] != 'e' || type[2])))
                        return (NULL);
        }
        if (pipe2(pdes, O_CLOEXEC) < 0)
                return (NULL);

        if ((cur = malloc(sizeof(struct pid))) == NULL) {
                (void)_close(pdes[0]);
                (void)_close(pdes[1]);
                return (NULL);
        }

        if (*type == 'r') {
                iop = fdopen(pdes[0], type);
                pdes_unused_in_parent = pdes[1];
        } else {
                iop = fdopen(pdes[1], type);
                pdes_unused_in_parent = pdes[0];
        }
        if (iop == NULL) {
                (void)_close(pdes[0]);
                (void)_close(pdes[1]);
                free(cur);
                return (NULL);
        }

        argv[0] = "sh";
        argv[1] = "-c";
        argv[2] = (char *)command;
        argv[3] = NULL;

        THREAD_LOCK();
        switch (pid = vfork()) {
        case -1:                        /* Error. */
                THREAD_UNLOCK();
                /*
                 * The _close() closes the unused end of pdes[], while
                 * the fclose() closes the used end of pdes[], *and* cleans
                 * up iop.
                 */
                (void)_close(pdes_unused_in_parent);
                free(cur);
                (void)fclose(iop);
                return (NULL);
                /* NOTREACHED */
        case 0:                         /* Child. */
                if (*type == 'r') {
                        /*
                         * The _dup2() to STDIN_FILENO is repeated to avoid
                         * writing to pdes[1], which might corrupt the
                         * parent's copy.  This isn't good enough in
                         * general, since the _exit() is no return, so
                         * the compiler is free to corrupt all the local
                         * variables.
                         */
                        if (pdes[1] != STDOUT_FILENO) {
                                (void)_dup2(pdes[1], STDOUT_FILENO);
                                if (twoway)
                                        (void)_dup2(STDOUT_FILENO, STDIN_FILENO);
                        } else if (twoway && (pdes[1] != STDIN_FILENO)) {
                                (void)_dup2(pdes[1], STDIN_FILENO);
                                (void)_fcntl(pdes[1], F_SETFD, 0);
                        } else
                                (void)_fcntl(pdes[1], F_SETFD, 0);
                } else {
                        if (pdes[0] != STDIN_FILENO) {
                                (void)_dup2(pdes[0], STDIN_FILENO);
                        } else
                                (void)_fcntl(pdes[0], F_SETFD, 0);
                }
                SLIST_FOREACH(p, &pidlist, next)
                        (void)_close(fileno(p->fp));
                _execve(_PATH_BSHELL, argv, environ);
                _exit(127);
                /* NOTREACHED */
        }
        THREAD_UNLOCK();

        /* Parent. */
        (void)_close(pdes_unused_in_parent);

        /* Link into list of file descriptors. */
        cur->fp = iop;
        cur->pid = pid;
        THREAD_LOCK();
        SLIST_INSERT_HEAD(&pidlist, cur, next);
        THREAD_UNLOCK();

        /*
         * To guard against undesired fd passing with concurrent calls,
         * only clear the close-on-exec flag after linking the file into
         * the list which will cause an explicit close.
         */
        if (!cloexec)
                (void)_fcntl(fileno(iop), F_SETFD, 0);

        return (iop);
}

/*
 * pclose --
 *      Pclose returns -1 if stream is not associated with a `popened' command,
 *      if already `pclosed', or waitpid returns an error.
 */
int
pclose(FILE *iop)
{
        struct pid *cur, *last = NULL;
        int pstat;
        pid_t pid;

        /*
         * Find the appropriate file pointer and remove it from the list.
         */
        THREAD_LOCK();
        SLIST_FOREACH(cur, &pidlist, next) {
                if (cur->fp == iop)
                        break;
                last = cur;
        }
        if (cur == NULL) {
                THREAD_UNLOCK();
                return (-1);
        }
        if (last == NULL)
                SLIST_REMOVE_HEAD(&pidlist, next);
        else
                SLIST_REMOVE_AFTER(last, next);
        THREAD_UNLOCK();

        (void)fclose(iop);

        do {
                pid = _wait4(cur->pid, &pstat, 0, (struct rusage *)0);
        } while (pid == -1 && errno == EINTR);

        free(cur);

        return (pid == -1 ? -1 : pstat);
}