/*-
 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

/*
FUNCTION
<<posix_spawn>>, <<posix_spawnp>>---spawn a process

INDEX
    posix_spawn
INDEX
    posix_spawnp

SYNOPSIS
    #include <spawn.h>

    int posix_spawn(pid_t *<[pid]>, const char *<[path]>,
            const posix_spawn_file_actions_t *<[file_actions]>,
            const posix_spawnattr_t *<[attrp]>,
            char *const <[argv]>, char *const <[envp]>);
    int posix_spawnp(pid_t *<[pid]>, const char *<[file]>,
            const posix_spawn_file_actions_t *<[file_actions]>,
            const posix_spawnattr_t *<[attrp]>,
            char *const <[argv]>, char *const <[envp]>);

DESCRIPTION
Use <<posix_spawn>> and <<posix_spawnp>> to create a new child process
from the specified process image file. <<argc>> is the argument count
and <<argv>> is an array of argument strings passed to the new program.
<<envp>> is an array of stings, which are passed as environment to the
new program.

The <<path>> argument to <<posix_spawn>> identifies the new process
image file to execute. The <<file>> argument to <<posix_spawnp>> is
used to construct a pathname that identifies the new process image
file by duplicating the actions of the shell in searching for an
executable file if the specified filename does not contain a `<</>>'
character. The <<file>> is sought in the colon-separated list of
directory pathnames specified in the <<PATH>> environment variable.

The file descriptors remain open across <<posix_spawn>> and
<<posix_spawnp>> except for those marked as close-on-exec. The open
file descriptors in the child process can be modified by the spawn file
actions object pointed to by <<file_actions>>.

The spawn attributes object type pointed to by <<attrp>> argument
may contain any of the attributes defined in <<spawn.h>>.

RETURNS
<<posix_spawn>> and <<posix_spawnp>> return the process ID of the newly
spawned child process in the variable pointed by a non-NULL <<*<[pid]>>>
argument and zero as the function return value upon successful
completion. Otherwise, <<posix_spawn>> and <<posix_spawnp>> return an
error number as the function return value to indicate the error; the
value stored into the variable pointed to by a non-NULL <<*<[pid]>>>
argument is unspecified.

PORTABILITY
POSIX.1-2008 requires <<posix_spawn>> and <<posix_spawnp>>.

Supporting OS subroutines required: <<_close>>, <<dup2>>, <<_fcntl>>,
<<_execve>>, <<execvpe>>, <<_exit>>, <<_open>>, <<sigaction>>,
<<sigprocmask>>, <<waitpid>>, <<sched_setscheduler>>,
<<sched_setparam>>, <<setegid>>, <<seteuid>>, <<setpgid>>, <<vfork>>.
*/

#ifndef _NO_POSIX_SPAWN

#include <sys/cdefs.h>

#include <sys/signal.h>
#include <sys/queue.h>
#include <sys/wait.h>

#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <spawn.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/* Only deal with a pointer to environ, to work around subtle bugs with shared
   libraries and/or small data systems where the user declares his own
   'environ'.  */
static char*** p_environ = &environ;

struct __posix_spawnattr {
    short sa_flags;
    pid_t sa_pgroup;
    struct sched_param sa_schedparam;
    int sa_schedpolicy;
    sigset_t sa_sigdefault;
    sigset_t sa_sigmask;
};

struct __posix_spawn_file_actions {
    STAILQ_HEAD(, __posix_spawn_file_actions_entry) fa_list;
};

typedef struct __posix_spawn_file_actions_entry {
    STAILQ_ENTRY(__posix_spawn_file_actions_entry) fae_list;
    enum { FAE_OPEN, FAE_DUP2, FAE_CLOSE } fae_action;

    int fae_fildes;
    union {
        struct {
            char* path;
#define fae_path fae_data.open.path
            int oflag;
#define fae_oflag fae_data.open.oflag
            mode_t mode;
#define fae_mode fae_data.open.mode
        } open;
        struct {
            int newfildes;
#define fae_newfildes fae_data.dup2.newfildes
        } dup2;
    } fae_data;
} posix_spawn_file_actions_entry_t;

/*
 * Spawn routines
 */

static int process_spawnattr(const posix_spawnattr_t sa)
{
    struct sigaction sigact = {.sa_flags = 0, .sa_handler = SIG_DFL};
    int i;

    /*
     * POSIX doesn't really describe in which order everything
     * should be set. We'll just set them in the order in which they
     * are mentioned.
     */

    /* Set process group */
    if (sa->sa_flags & POSIX_SPAWN_SETPGROUP) {
        if (setpgid(0, sa->sa_pgroup) != 0) return (errno);
    }

    /* Set scheduler policy */
    if (sa->sa_flags & POSIX_SPAWN_SETSCHEDULER) {
        if (sched_setscheduler(0, sa->sa_schedpolicy, &sa->sa_schedparam) != 0)
            return (errno);
    } else if (sa->sa_flags & POSIX_SPAWN_SETSCHEDPARAM) {
        if (sched_setparam(0, &sa->sa_schedparam) != 0) return (errno);
    }

    /* Reset user ID's */
    if (sa->sa_flags & POSIX_SPAWN_RESETIDS) {
        if (setegid(getgid()) != 0) return (errno);
        if (seteuid(getuid()) != 0) return (errno);
    }

    /* Set signal masks/defaults */
    if (sa->sa_flags & POSIX_SPAWN_SETSIGMASK) {
        sigprocmask(SIG_SETMASK, &sa->sa_sigmask, NULL);
    }

    if (sa->sa_flags & POSIX_SPAWN_SETSIGDEF) {
        for (i = 1; i < NSIG; i++) {
            if (sigismember(&sa->sa_sigdefault, i))
                if (sigaction(i, &sigact, NULL) != 0) return (errno);
        }
    }

    return (0);
}

static int process_file_actions_entry(posix_spawn_file_actions_entry_t* fae)
{
    int fd;

    switch (fae->fae_action) {
    case FAE_OPEN:
        /* Perform an open(), make it use the right fd */
        fd = open(fae->fae_path, fae->fae_oflag, fae->fae_mode);
        if (fd < 0) return (errno);
        if (fd != fae->fae_fildes) {
            if (dup2(fd, fae->fae_fildes) == -1) return (errno);
            if (close(fd) != 0) {
                if (errno == EBADF) return (EBADF);
            }
        }
#ifdef HAVE_FCNTL
        if (_fcntl(fae->fae_fildes, F_SETFD, 0) == -1) return (errno);
#endif /* HAVE_FCNTL */
        break;
    case FAE_DUP2:
        /* Perform a dup2() */
        if (dup2(fae->fae_fildes, fae->fae_newfildes) == -1) return (errno);
#ifdef HAVE_FCNTL
        if (_fcntl(fae->fae_newfildes, F_SETFD, 0) == -1) return (errno);
#endif /* HAVE_FCNTL */
        break;
    case FAE_CLOSE:
        /* Perform a close(), do not fail if already closed */
        (void)close(fae->fae_fildes);
        break;
    }
    return (0);
}

static int process_file_actions(const posix_spawn_file_actions_t fa)
{
    posix_spawn_file_actions_entry_t* fae;
    int error;

    /* Replay all file descriptor modifications */
    STAILQ_FOREACH(fae, &fa->fa_list, fae_list)
    {
        error = process_file_actions_entry(fae);
        if (error) return (error);
    }
    return (0);
}

static int do_posix_spawn(pid_t* pid, const char* path,
                          const posix_spawn_file_actions_t* fa,
                          const posix_spawnattr_t* sa, char* const argv[],
                          char* const envp[], int use_env_path)
{
    pid_t p;
    volatile int error = 0;

    p = vfork();
    switch (p) {
    case -1:
        return (errno);
    case 0:
        if (sa != NULL) {
            error = process_spawnattr(*sa);
            if (error) _exit(127);
        }
        if (fa != NULL) {
            error = process_file_actions(*fa);
            if (error) _exit(127);
        }
        /* if (use_env_path) */
        /*      execvpe(path, argv, envp != NULL ? envp : *p_environ); */
        /* else */
        execve(path, argv, envp != NULL ? envp : *p_environ);
        error = errno;
        _exit(127);
    default:
        if (error != 0)
            waitpid(p, NULL, WNOHANG);
        else if (pid != NULL)
            *pid = p;
        return (error);
    }
}

int posix_spawn(pid_t* pid, const char* path,
                const posix_spawn_file_actions_t* fa,
                const posix_spawnattr_t* sa, char* const argv[],
                char* const envp[])
{
    return do_posix_spawn(pid, path, fa, sa, argv, envp, 0);
}

int posix_spawnp(pid_t* pid, const char* path,
                 const posix_spawn_file_actions_t* fa,
                 const posix_spawnattr_t* sa, char* const argv[],
                 char* const envp[])
{
    return do_posix_spawn(pid, path, fa, sa, argv, envp, 1);
}

/*
 * File descriptor actions
 */

int posix_spawn_file_actions_init(posix_spawn_file_actions_t* ret)
{
    posix_spawn_file_actions_t fa;

    fa = malloc(sizeof(struct __posix_spawn_file_actions));
    if (fa == NULL) return (-1);

    STAILQ_INIT(&fa->fa_list);
    *ret = fa;
    return (0);
}

int posix_spawn_file_actions_destroy(posix_spawn_file_actions_t* fa)
{
    posix_spawn_file_actions_entry_t* fae;

    while ((fae = STAILQ_FIRST(&(*fa)->fa_list)) != NULL) {
        /* Remove file action entry from the queue */
        STAILQ_REMOVE_HEAD(&(*fa)->fa_list, fae_list);

        /* Deallocate file action entry */
        if (fae->fae_action == FAE_OPEN) free(fae->fae_path);
        free(fae);
    }

    free(*fa);
    return (0);
}

int posix_spawn_file_actions_addopen(posix_spawn_file_actions_t* __restrict fa,
                                     int fildes, const char* __restrict path,
                                     int oflag, mode_t mode)
{
    posix_spawn_file_actions_entry_t* fae;
    int error;

    if (fildes < 0) return (EBADF);

    /* Allocate object */
    fae = malloc(sizeof(posix_spawn_file_actions_entry_t));
    if (fae == NULL) return (errno);

    /* Set values and store in queue */
    fae->fae_action = FAE_OPEN;
    fae->fae_path = strdup(path);
    if (fae->fae_path == NULL) {
        error = errno;
        free(fae);
        return (error);
    }
    fae->fae_fildes = fildes;
    fae->fae_oflag = oflag;
    fae->fae_mode = mode;

    STAILQ_INSERT_TAIL(&(*fa)->fa_list, fae, fae_list);
    return (0);
}

int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t* fa, int fildes,
                                     int newfildes)
{
    posix_spawn_file_actions_entry_t* fae;

    if (fildes < 0 || newfildes < 0) return (EBADF);

    /* Allocate object */
    fae = malloc(sizeof(posix_spawn_file_actions_entry_t));
    if (fae == NULL) return (errno);

    /* Set values and store in queue */
    fae->fae_action = FAE_DUP2;
    fae->fae_fildes = fildes;
    fae->fae_newfildes = newfildes;

    STAILQ_INSERT_TAIL(&(*fa)->fa_list, fae, fae_list);
    return (0);
}

int posix_spawn_file_actions_addclose(posix_spawn_file_actions_t* fa,
                                      int fildes)
{
    posix_spawn_file_actions_entry_t* fae;

    if (fildes < 0) return (EBADF);

    /* Allocate object */
    fae = malloc(sizeof(posix_spawn_file_actions_entry_t));
    if (fae == NULL) return (errno);

    /* Set values and store in queue */
    fae->fae_action = FAE_CLOSE;
    fae->fae_fildes = fildes;

    STAILQ_INSERT_TAIL(&(*fa)->fa_list, fae, fae_list);
    return (0);
}

/*
 * Spawn attributes
 */

int posix_spawnattr_init(posix_spawnattr_t* ret)
{
    posix_spawnattr_t sa;

    sa = calloc(1, sizeof(struct __posix_spawnattr));
    if (sa == NULL) return (errno);

    /* Set defaults as specified by POSIX, cleared above */
    *ret = sa;
    return (0);
}

int posix_spawnattr_destroy(posix_spawnattr_t* sa)
{
    free(*sa);
    return (0);
}

int posix_spawnattr_getflags(const posix_spawnattr_t* __restrict sa,
                             short* __restrict flags)
{
    *flags = (*sa)->sa_flags;
    return (0);
}

int posix_spawnattr_getpgroup(const posix_spawnattr_t* __restrict sa,
                              pid_t* __restrict pgroup)
{
    *pgroup = (*sa)->sa_pgroup;
    return (0);
}

int posix_spawnattr_getschedparam(const posix_spawnattr_t* __restrict sa,
                                  struct sched_param* __restrict schedparam)
{
    *schedparam = (*sa)->sa_schedparam;
    return (0);
}

int posix_spawnattr_getschedpolicy(const posix_spawnattr_t* __restrict sa,
                                   int* __restrict schedpolicy)
{
    *schedpolicy = (*sa)->sa_schedpolicy;
    return (0);
}

int posix_spawnattr_getsigdefault(const posix_spawnattr_t* __restrict sa,
                                  sigset_t* __restrict sigdefault)
{
    *sigdefault = (*sa)->sa_sigdefault;
    return (0);
}

int posix_spawnattr_getsigmask(const posix_spawnattr_t* __restrict sa,
                               sigset_t* __restrict sigmask)
{
    *sigmask = (*sa)->sa_sigmask;
    return (0);
}

int posix_spawnattr_setflags(posix_spawnattr_t* sa, short flags)
{
    (*sa)->sa_flags = flags;
    return (0);
}

int posix_spawnattr_setpgroup(posix_spawnattr_t* sa, pid_t pgroup)
{
    (*sa)->sa_pgroup = pgroup;
    return (0);
}

int posix_spawnattr_setschedparam(
    posix_spawnattr_t* __restrict sa,
    const struct sched_param* __restrict schedparam)
{
    (*sa)->sa_schedparam = *schedparam;
    return (0);
}

int posix_spawnattr_setschedpolicy(posix_spawnattr_t* sa, int schedpolicy)
{
    (*sa)->sa_schedpolicy = schedpolicy;
    return (0);
}

int posix_spawnattr_setsigdefault(posix_spawnattr_t* __restrict sa,
                                  const sigset_t* __restrict sigdefault)
{
    (*sa)->sa_sigdefault = *sigdefault;
    return (0);
}

int posix_spawnattr_setsigmask(posix_spawnattr_t* __restrict sa,
                               const sigset_t* __restrict sigmask)
{
    (*sa)->sa_sigmask = *sigmask;
    return (0);
}

#endif /* !_NO_POSIX_SPAWN */
