/*      $NetBSD: popen.c,v 1.38 2022/04/19 20:32:15 rillig Exp $        */

/*
* 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 <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)popen.c     8.3 (Berkeley) 5/3/95";
#else
__RCSID("$NetBSD: popen.c,v 1.38 2022/04/19 20:32:15 rillig Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

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

#include <assert.h>
#include <errno.h>
#include <paths.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

#include "env.h"

#ifdef __weak_alias
__weak_alias(popen,_popen)
__weak_alias(pclose,_pclose)
#endif

static struct pid {
       struct pid *next;
       FILE *fp;
#ifdef _REENTRANT
       int fd;
#endif
       pid_t pid;
} *pidlist;

#ifdef _REENTRANT
static  mutex_t pidlist_mutex = MUTEX_INITIALIZER;
# define MUTEX_LOCK() \
   do { \
           if (__isthreaded) \
                   mutex_lock(&pidlist_mutex); \
   } while (0)
# define MUTEX_UNLOCK() \
   do { \
           if (__isthreaded) \
                   mutex_unlock(&pidlist_mutex); \
   } while (0)
#else
# define MUTEX_LOCK() __nothing
# define MUTEX_UNLOCK() __nothing
#endif

static struct pid *
pdes_get(int *pdes, const char **type)
{
       struct pid *cur;
       int flags = strchr(*type, 'e') ? O_CLOEXEC : 0;
       int serrno;

       if (strchr(*type, '+')) {
               int stype = flags ? (SOCK_STREAM | SOCK_CLOEXEC) : SOCK_STREAM;
               *type = "r+";
               if (socketpair(AF_LOCAL, stype, 0, pdes) < 0)
                       return NULL;
       } else  {
               *type = strrchr(*type, 'r') ? "r" : "w";
               if (pipe2(pdes, flags) == -1)
                       return NULL;
       }

       if ((cur = malloc(sizeof(*cur))) != NULL)
               return cur;
       serrno = errno;
       (void)close(pdes[0]);
       (void)close(pdes[1]);
       errno = serrno;
       return NULL;
}

static void
pdes_child(int *pdes, const char *type)
{
       struct pid *old;

       /* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
          from previous popen() calls that remain open in the
          parent process are closed in the new child process. */
       for (old = pidlist; old; old = old->next)
#ifdef _REENTRANT
               (void)close(old->fd); /* don't allow a flush */
#else
               (void)close(fileno(old->fp)); /* don't allow a flush */
#endif

       if (type[0] == 'r') {
               (void)close(pdes[0]);
               if (pdes[1] != STDOUT_FILENO) {
                       (void)dup2(pdes[1], STDOUT_FILENO);
                       (void)close(pdes[1]);
               }
               if (type[1] == '+')
                       (void)dup2(STDOUT_FILENO, STDIN_FILENO);
       } else {
               (void)close(pdes[1]);
               if (pdes[0] != STDIN_FILENO) {
                       (void)dup2(pdes[0], STDIN_FILENO);
                       (void)close(pdes[0]);
               }
       }
}

static void
pdes_parent(int *pdes, struct pid *cur, pid_t pid, const char *type)
{
       FILE *iop;

       /* Parent; assume fdopen can't fail. */
       if (*type == 'r') {
               iop = fdopen(pdes[0], type);
#ifdef _REENTRANT
               cur->fd = pdes[0];
#endif
               (void)close(pdes[1]);
       } else {
               iop = fdopen(pdes[1], type);
#ifdef _REENTRANT
               cur->fd = pdes[1];
#endif
               (void)close(pdes[0]);
       }

       /* Link into list of file descriptors. */
       cur->fp = iop;
       cur->pid =  pid;
       cur->next = pidlist;
       pidlist = cur;
}

static void
pdes_error(int *pdes, struct pid *cur)
{
       free(cur);
       (void)close(pdes[0]);
       (void)close(pdes[1]);
}

FILE *
popen(const char *cmd, const char *type)
{
       struct pid *cur;
       int pdes[2], serrno;
       pid_t pid;

       _DIAGASSERT(cmd != NULL);
       _DIAGASSERT(type != NULL);

       if ((cur = pdes_get(pdes, &type)) == NULL)
               return NULL;

       MUTEX_LOCK();
       (void)__readlockenv();
       switch (pid = vfork()) {
       case -1:                        /* Error. */
               serrno = errno;
               (void)__unlockenv();
               MUTEX_UNLOCK();
               pdes_error(pdes, cur);
               errno = serrno;
               return NULL;
               /* NOTREACHED */
       case 0:                         /* Child. */
               pdes_child(pdes, type);
               execl(_PATH_BSHELL, "sh", "-c", "--", cmd, NULL);
               _exit(127);
               /* NOTREACHED */
       }
       (void)__unlockenv();

       pdes_parent(pdes, cur, pid, type);

       MUTEX_UNLOCK();

       return cur->fp;
}

FILE *
popenve(const char *cmd, char *const *argv, char *const *envp, const char *type)
{
       struct pid *cur;
       int pdes[2], serrno;
       pid_t pid;

       _DIAGASSERT(cmd != NULL);
       _DIAGASSERT(type != NULL);

       if ((cur = pdes_get(pdes, &type)) == NULL)
               return NULL;

       MUTEX_LOCK();
       switch (pid = vfork()) {
       case -1:                        /* Error. */
               serrno = errno;
               MUTEX_UNLOCK();
               pdes_error(pdes, cur);
               errno = serrno;
               return NULL;
               /* NOTREACHED */
       case 0:                         /* Child. */
               pdes_child(pdes, type);
               execve(cmd, argv, envp);
               _exit(127);
               /* NOTREACHED */
       }

       pdes_parent(pdes, cur, pid, type);

       MUTEX_UNLOCK();

       return cur->fp;
}

/*
* 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;
       int pstat;
       pid_t pid;

       _DIAGASSERT(iop != NULL);

       MUTEX_LOCK();

       /* Find the appropriate file pointer. */
       for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
               if (cur->fp == iop)
                       break;
       if (cur == NULL) {
               MUTEX_UNLOCK();
               errno = ESRCH;
               return -1;
       }

       (void)fclose(iop);

       /* Remove the entry from the linked list. */
       if (last == NULL)
               pidlist = cur->next;
       else
               last->next = cur->next;

       MUTEX_UNLOCK();

       do {
               pid = waitpid(cur->pid, &pstat, 0);
       } while (pid == -1 && errno == EINTR);

       free(cur);

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

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