/*

 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#include <dirent.h>

#include <errno.h>

#include <fcntl.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <limits.h>

#include "childproc.h"

ssize_t

restartableWrite(int fd, const void *buf, size_t count)

{

    ssize_t result;

    RESTARTABLE(write(fd, buf, count), result);

    return result;

}

int

restartableDup2(int fd_from, int fd_to)

{

    int err;

    RESTARTABLE(dup2(fd_from, fd_to), err);

    return err;

}

int

closeSafely(int fd)

{

    return (fd == -1) ? 0 : close(fd);

}

int

isAsciiDigit(char c)

{

  return c >= '0' && c <= '9';

}

#ifdef _ALLBSD_SOURCE

#define FD_DIR "/dev/fd"

#define dirent64 dirent

#define readdir64 readdir

#else

#define FD_DIR "/proc/self/fd"

#endif

int

closeDescriptors(void)

{

    DIR *dp;

    struct dirent64 *dirp;

    int from_fd = FAIL_FILENO + 1;

    /* We're trying to close all file descriptors, but opendir() might

     * itself be implemented using a file descriptor, and we certainly

     * don't want to close that while it's in use.  We assume that if

     * opendir() is implemented using a file descriptor, then it uses

     * the lowest numbered file descriptor, just like open().  So we

     * close a couple explicitly.  */

    close(from_fd);          /* for possible use by opendir() */

    close(from_fd + 1);      /* another one for good luck */

    if ((dp = opendir(FD_DIR)) == NULL)

        return 0;

    /* We use readdir64 instead of readdir to work around Solaris bug

     * 6395699: /proc/self/fd fails to report file descriptors >= 1024 on Solaris 9

     */

    while ((dirp = readdir64(dp)) != NULL) {

        int fd;

        if (isAsciiDigit(dirp->d_name[0]) &&

            (fd = strtol(dirp->d_name, NULL, 10)) >= from_fd + 2)

            close(fd);

    }

    closedir(dp);

    return 1;

}

int

moveDescriptor(int fd_from, int fd_to)

{

    if (fd_from != fd_to) {

        if ((restartableDup2(fd_from, fd_to) == -1) ||

            (close(fd_from) == -1))

            return -1;

    }

    return 0;

}

int

magicNumber() {

    return 43110;

}

/*

 * Reads nbyte bytes from file descriptor fd into buf,

 * The read operation is retried in case of EINTR or partial reads.

 *

 * Returns number of bytes read (normally nbyte, but may be less in

 * case of EOF).  In case of read errors, returns -1 and sets errno.

 */

ssize_t

readFully(int fd, void *buf, size_t nbyte)

{

    ssize_t remaining = nbyte;

    for (;;) {

        ssize_t n = read(fd, buf, remaining);

        if (n == 0) {

            return nbyte - remaining;

        } else if (n > 0) {

            remaining -= n;

            if (remaining <= 0)

                return nbyte;

            /* We were interrupted in the middle of reading the bytes.

             * Unlikely, but possible. */

            buf = (void *) (((char *)buf) + n);

        } else if (errno == EINTR) {

            /* Strange signals like SIGJVM1 are possible at any time.

             * See http://www.dreamsongs.com/WorseIsBetter.html */

        } else {

            return -1;

        }

    }

}

void

initVectorFromBlock(const char**vector, const char* block, int count)

{

    int i;

    const char *p;

    for (i = 0, p = block; i < count; i++) {

        /* Invariant: p always points to the start of a C string. */

        vector[i] = p;

        while (*(p++));

    }

    vector[count] = NULL;

}

/**

 * Exec FILE as a traditional Bourne shell script (i.e. one without #!).

 * If we could do it over again, we would probably not support such an ancient

 * misfeature, but compatibility wins over sanity.  The original support for

 * this was imported accidentally from execvp().

 */

void

execve_as_traditional_shell_script(const char *file,

                                   const char *argv[],

                                   const char *const envp[])

{

    /* Use the extra word of space provided for us in argv by caller. */

    const char *argv0 = argv[0];

    const char *const *end = argv;

    while (*end != NULL)

        ++end;

    memmove(argv+2, argv+1, (end-argv) * sizeof(*end));

    argv[0] = "/bin/sh";

    argv[1] = file;

    execve(argv[0], (char **) argv, (char **) envp);

    /* Can't even exec /bin/sh?  Big trouble, but let's soldier on... */

    memmove(argv+1, argv+2, (end-argv) * sizeof(*end));

    argv[0] = argv0;

}

/**

 * Like execve(2), except that in case of ENOEXEC, FILE is assumed to

 * be a shell script and the system default shell is invoked to run it.

 */

void

execve_with_shell_fallback(int mode, const char *file,

                           const char *argv[],

                           const char *const envp[])

{

    if (mode == MODE_CLONE || mode == MODE_VFORK) {

        /* shared address space; be very careful. */

        execve(file, (char **) argv, (char **) envp);

        if (errno == ENOEXEC)

            execve_as_traditional_shell_script(file, argv, envp);

    } else {

        /* unshared address space; we can mutate environ. */

        environ = (char **) envp;

        execvp(file, (char **) argv);

    }

}

/**

 * 'execvpe' should have been included in the Unix standards,

 * and is a GNU extension in glibc 2.10.

 *

 * JDK_execvpe is identical to execvp, except that the child environment is

 * specified via the 3rd argument instead of being inherited from environ.

 */

void

JDK_execvpe(int mode, const char *file,

            const char *argv[],

            const char *const envp[])

{

    if (envp == NULL || (char **) envp == environ) {

        execvp(file, (char **) argv);

        return;

    }

    if (*file == '\0') {

        errno = ENOENT;

        return;

    }

    if (strchr(file, '/') != NULL) {

        execve_with_shell_fallback(mode, file, argv, envp);

    } else {

        /* We must search PATH (parent's, not child's) */

        char expanded_file[PATH_MAX];

        int filelen = strlen(file);

        int sticky_errno = 0;

        const char * const * dirs;

        for (dirs = parentPathv; *dirs; dirs++) {

            const char * dir = *dirs;

            int dirlen = strlen(dir);

            if (filelen + dirlen + 2 >= PATH_MAX) {

                errno = ENAMETOOLONG;

                continue;

            }

            memcpy(expanded_file, dir, dirlen);

            if (expanded_file[dirlen - 1] != '/')

                expanded_file[dirlen++] = '/';

            memcpy(expanded_file + dirlen, file, filelen);

            expanded_file[dirlen + filelen] = '\0';

            execve_with_shell_fallback(mode, expanded_file, argv, envp);

            /* There are 3 responses to various classes of errno:

             * return immediately, continue (especially for ENOENT),

             * or continue with "sticky" errno.

             *

             * From exec(3):

             *

             * If permission is denied for a file (the attempted

             * execve returned EACCES), these functions will continue

             * searching the rest of the search path.  If no other

             * file is found, however, they will return with the

             * global variable errno set to EACCES.

             */

            switch (errno) {

            case EACCES:

                sticky_errno = errno;

                /* FALLTHRU */

            case ENOENT:

            case ENOTDIR:

#ifdef ELOOP

            case ELOOP:

#endif

#ifdef ESTALE

            case ESTALE:

#endif

#ifdef ENODEV

            case ENODEV:

#endif

#ifdef ETIMEDOUT

            case ETIMEDOUT:

#endif

                break; /* Try other directories in PATH */

            default:

                return;

            }

        }

        if (sticky_errno != 0)

            errno = sticky_errno;

    }

}

/**

 * Child process after a successful fork() or clone().

 * This function must not return, and must be prepared for either all

 * of its address space to be shared with its parent, or to be a copy.

 * It must not modify global variables such as "environ".

 */

int

childProcess(void *arg)

{

    const ChildStuff* p = (const ChildStuff*) arg;

    /* Close the parent sides of the pipes.

       Closing pipe fds here is redundant, since closeDescriptors()

       would do it anyways, but a little paranoia is a good thing. */

    if ((closeSafely(p->in[1])   == -1) ||

        (closeSafely(p->out[0])  == -1) ||

        (closeSafely(p->err[0])  == -1) ||

        (closeSafely(p->childenv[0])  == -1) ||

        (closeSafely(p->childenv[1])  == -1) ||

        (closeSafely(p->fail[0]) == -1))

        goto WhyCantJohnnyExec;

    /* Give the child sides of the pipes the right fileno's. */

    /* Note: it is possible for in[0] == 0 */

    if ((moveDescriptor(p->in[0] != -1 ?  p->in[0] : p->fds[0],

                        STDIN_FILENO) == -1) ||

        (moveDescriptor(p->out[1]!= -1 ? p->out[1] : p->fds[1],

                        STDOUT_FILENO) == -1))

        goto WhyCantJohnnyExec;

    if (p->redirectErrorStream) {

        if ((closeSafely(p->err[1]) == -1) ||

            (restartableDup2(STDOUT_FILENO, STDERR_FILENO) == -1))

            goto WhyCantJohnnyExec;

    } else {

        if (moveDescriptor(p->err[1] != -1 ? p->err[1] : p->fds[2],

                           STDERR_FILENO) == -1)

            goto WhyCantJohnnyExec;

    }

    if (moveDescriptor(p->fail[1], FAIL_FILENO) == -1)

        goto WhyCantJohnnyExec;

    /* close everything */

    if (closeDescriptors() == 0) { /* failed,  close the old way */

        int max_fd = (int)sysconf(_SC_OPEN_MAX);

        int fd;

        for (fd = FAIL_FILENO + 1; fd < max_fd; fd++)

            if (close(fd) == -1 && errno != EBADF)

                goto WhyCantJohnnyExec;

    }

    /* change to the new working directory */

    if (p->pdir != NULL && chdir(p->pdir) < 0)

        goto WhyCantJohnnyExec;

    if (fcntl(FAIL_FILENO, F_SETFD, FD_CLOEXEC) == -1)

        goto WhyCantJohnnyExec;

    JDK_execvpe(p->mode, p->argv[0], p->argv, p->envv);

 WhyCantJohnnyExec:

    /* We used to go to an awful lot of trouble to predict whether the

     * child would fail, but there is no reliable way to predict the

     * success of an operation without *trying* it, and there's no way

     * to try a chdir or exec in the parent.  Instead, all we need is a

     * way to communicate any failure back to the parent.  Easy; we just

     * send the errno back to the parent over a pipe in case of failure.

     * The tricky thing is, how do we communicate the *success* of exec?

     * We use FD_CLOEXEC together with the fact that a read() on a pipe

     * yields EOF when the write ends (we have two of them!) are closed.

     */

    {

        int errnum = errno;

        restartableWrite(FAIL_FILENO, &errnum, sizeof(errnum));

    }

    close(FAIL_FILENO);

    _exit(-1);

    return 0;  /* Suppress warning "no return value from function" */

}