/*

 * Copyright (c) 1995, 2015, 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.

 */

#undef  _LARGEFILE64_SOURCE

#define _LARGEFILE64_SOURCE 1

#include "jni.h"

#include "jvm.h"

#include "jvm_md.h"

#include "jni_util.h"

#include "io_util.h"

/*

 * Platform-specific support for java.lang.Process

 */

#include <assert.h>

#include <stddef.h>

#include <stdlib.h>

#include <sys/types.h>

#include <ctype.h>

#include <sys/wait.h>

#include <signal.h>

#include <string.h>

#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)

#include <spawn.h>

#endif

#include "childproc.h"

/*

 * There are 4 possible strategies we might use to "fork":

 *

 * - fork(2).  Very portable and reliable but subject to

 *   failure due to overcommit (see the documentation on

 *   /proc/sys/vm/overcommit_memory in Linux proc(5)).

 *   This is the ancient problem of spurious failure whenever a large

 *   process starts a small subprocess.

 *

 * - vfork().  Using this is scary because all relevant man pages

 *   contain dire warnings, e.g. Linux vfork(2).  But at least it's

 *   documented in the glibc docs and is standardized by XPG4.

 *   http://www.opengroup.org/onlinepubs/000095399/functions/vfork.html

 *   On Linux, one might think that vfork() would be implemented using

 *   the clone system call with flag CLONE_VFORK, but in fact vfork is

 *   a separate system call (which is a good sign, suggesting that

 *   vfork will continue to be supported at least on Linux).

 *   Another good sign is that glibc implements posix_spawn using

 *   vfork whenever possible.  Note that we cannot use posix_spawn

 *   ourselves because there's no reliable way to close all inherited

 *   file descriptors.

 *

 * - clone() with flags CLONE_VM but not CLONE_THREAD.  clone() is

 *   Linux-specific, but this ought to work - at least the glibc

 *   sources contain code to handle different combinations of CLONE_VM

 *   and CLONE_THREAD.  However, when this was implemented, it

 *   appeared to fail on 32-bit i386 (but not 64-bit x86_64) Linux with

 *   the simple program

 *     Runtime.getRuntime().exec("/bin/true").waitFor();

 *   with:

 *     #  Internal Error (os_linux_x86.cpp:683), pid=19940, tid=2934639536

 *     #  Error: pthread_getattr_np failed with errno = 3 (ESRCH)

 *   We believe this is a glibc bug, reported here:

 *     http://sources.redhat.com/bugzilla/show_bug.cgi?id=10311

 *   but the glibc maintainers closed it as WONTFIX.

 *

 * - posix_spawn(). While posix_spawn() is a fairly elaborate and

 *   complicated system call, it can't quite do everything that the old

 *   fork()/exec() combination can do, so the only feasible way to do

 *   this, is to use posix_spawn to launch a new helper executable

 *   "jprochelper", which in turn execs the target (after cleaning

 *   up file-descriptors etc.) The end result is the same as before,

 *   a child process linked to the parent in the same way, but it

 *   avoids the problem of duplicating the parent (VM) process

 *   address space temporarily, before launching the target command.

 *

 * Based on the above analysis, we are currently using vfork() on

 * Linux and posix_spawn() on other Unix systems.

 */

static void

setSIGCHLDHandler(JNIEnv *env)

{

    /* There is a subtle difference between having the signal handler

     * for SIGCHLD be SIG_DFL and SIG_IGN.  We cannot obtain process

     * termination information for child processes if the signal

     * handler is SIG_IGN.  It must be SIG_DFL.

     *

     * We used to set the SIGCHLD handler only on Linux, but it's

     * safest to set it unconditionally.

     *

     * Consider what happens if java's parent process sets the SIGCHLD

     * handler to SIG_IGN.  Normally signal handlers are inherited by

     * children, but SIGCHLD is a controversial case.  Solaris appears

     * to always reset it to SIG_DFL, but this behavior may be

     * non-standard-compliant, and we shouldn't rely on it.

     *

     * References:

     * http://www.opengroup.org/onlinepubs/7908799/xsh/exec.html

     * http://www.pasc.org/interps/unofficial/db/p1003.1/pasc-1003.1-132.html

     */

    struct sigaction sa;

    sa.sa_handler = SIG_DFL;

    sigemptyset(&sa.sa_mask);

    sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;

    if (sigaction(SIGCHLD, &sa, NULL) < 0)

        JNU_ThrowInternalError(env, "Can't set SIGCHLD handler");

}

static void*

xmalloc(JNIEnv *env, size_t size)

{

    void *p = malloc(size);

    if (p == NULL)

        JNU_ThrowOutOfMemoryError(env, NULL);

    return p;

}

#define NEW(type, n) ((type *) xmalloc(env, (n) * sizeof(type)))

/**

 * If PATH is not defined, the OS provides some default value.

 * Unfortunately, there's no portable way to get this value.

 * Fortunately, it's only needed if the child has PATH while we do not.

 */

static const char*

defaultPath(void)

{

#ifdef __solaris__

    /* These really are the Solaris defaults! */

    return (geteuid() == 0 || getuid() == 0) ?

        "/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin:/usr/sbin" :

        "/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin:";

#else

    return ":/bin:/usr/bin";    /* glibc */

#endif

}

static const char*

effectivePath(void)

{

    const char *s = getenv("PATH");

    return (s != NULL) ? s : defaultPath();

}

static int

countOccurrences(const char *s, char c)

{

    int count;

    for (count = 0; *s != '\0'; s++)

        count += (*s == c);

    return count;

}

static const char * const *

effectivePathv(JNIEnv *env)

{

    char *p;

    int i;

    const char *path = effectivePath();

    int count = countOccurrences(path, ':') + 1;

    size_t pathvsize = sizeof(const char *) * (count+1);

    size_t pathsize = strlen(path) + 1;

    const char **pathv = (const char **) xmalloc(env, pathvsize + pathsize);

    if (pathv == NULL)

        return NULL;

    p = (char *) pathv + pathvsize;

    memcpy(p, path, pathsize);

    /* split PATH by replacing ':' with NULs; empty components => "." */

    for (i = 0; i < count; i++) {

        char *q = p + strcspn(p, ":");

        pathv[i] = (p == q) ? "." : p;

        *q = '\0';

        p = q + 1;

    }

    pathv[count] = NULL;

    return pathv;

}

JNIEXPORT void JNICALL

Java_java_lang_ProcessImpl_init(JNIEnv *env, jclass clazz)

{

    parentPathv = effectivePathv(env);

    CHECK_NULL(parentPathv);

    setSIGCHLDHandler(env);

}

#ifndef WIFEXITED

#define WIFEXITED(status) (((status)&0xFF) == 0)

#endif

#ifndef WEXITSTATUS

#define WEXITSTATUS(status) (((status)>>8)&0xFF)

#endif

#ifndef WIFSIGNALED

#define WIFSIGNALED(status) (((status)&0xFF) > 0 && ((status)&0xFF00) == 0)

#endif

#ifndef WTERMSIG

#define WTERMSIG(status) ((status)&0x7F)

#endif

/* Block until a child process exits and return its exit code.

   Note, can only be called once for any given pid. */

JNIEXPORT jint JNICALL

Java_java_lang_ProcessImpl_waitForProcessExit(JNIEnv* env,

                                              jobject junk,

                                              jint pid)

{

    /* We used to use waitid() on Solaris, waitpid() on Linux, but

     * waitpid() is more standard, so use it on all POSIX platforms. */

    int status;

    /* Wait for the child process to exit.  This returns immediately if

       the child has already exited. */

    while (waitpid(pid, &status, 0) < 0) {

        switch (errno) {

        case ECHILD: return 0;

        case EINTR: break;

        default: return -1;

        }

    }

    if (WIFEXITED(status)) {

        /*

         * The child exited normally; get its exit code.

         */

        return WEXITSTATUS(status);

    } else if (WIFSIGNALED(status)) {

        /* The child exited because of a signal.

         * The best value to return is 0x80 + signal number,

         * because that is what all Unix shells do, and because

         * it allows callers to distinguish between process exit and

         * process death by signal.

         * Unfortunately, the historical behavior on Solaris is to return

         * the signal number, and we preserve this for compatibility. */

#ifdef __solaris__

        return WTERMSIG(status);

#else

        return 0x80 + WTERMSIG(status);

#endif

    } else {

        /*

         * Unknown exit code; pass it through.

         */

        return status;

    }

}

static const char *

getBytes(JNIEnv *env, jbyteArray arr)

{

    return arr == NULL ? NULL :

        (const char*) (*env)->GetByteArrayElements(env, arr, NULL);

}

static void

releaseBytes(JNIEnv *env, jbyteArray arr, const char* parr)

{

    if (parr != NULL)

        (*env)->ReleaseByteArrayElements(env, arr, (jbyte*) parr, JNI_ABORT);

}

static void

throwIOException(JNIEnv *env, int errnum, const char *defaultDetail)

{

    const char *detail = defaultDetail;

    char *errmsg;

    jstring s;

    if (errnum != 0) {

        const char *s = strerror(errnum);

        if (strcmp(s, "Unknown error") != 0)

            detail = s;

    }

    /* ASCII Decimal representation uses 2.4 times as many bits as binary. */

    if (errmsg == NULL)

        return;

    s = JNU_NewStringPlatform(env, errmsg);

    if (s != NULL) {

        jobject x = JNU_NewObjectByName(env, "java/io/IOException",

                                        "(Ljava/lang/String;)V", s);

        if (x != NULL)

            (*env)->Throw(env, x);

    }

    free(errmsg);

}

#ifdef DEBUG_PROCESS

/* Debugging process code is difficult; where to write debug output? */

static void

debugPrint(char *format, ...)

{

    FILE *tty = fopen("/dev/tty", "w");

    va_list ap;

    va_start(ap, format);

    vfprintf(tty, format, ap);

    va_end(ap);

    fclose(tty);

}

#endif /* DEBUG_PROCESS */

static void

copyPipe(int from[2], int to[2])

{

    to[0] = from[0];

    to[1] = from[1];

}

/* arg is an array of pointers to 0 terminated strings. array is terminated

 * by a null element.

 *

 * *nelems and *nbytes receive the number of elements of array (incl 0)

 * and total number of bytes (incl. 0)

 * Note. An empty array will have one null element

 * But if arg is null, then *nelems set to 0, and *nbytes to 0

 */

static void arraysize(const char * const *arg, int *nelems, int *nbytes)

{

    int i, bytes, count;

    const char * const *a = arg;

    char *p;

    int *q;

    if (arg == 0) {

        *nelems = 0;

        *nbytes = 0;

        return;

    }

    /* count the array elements and number of bytes */

    for (count=0, bytes=0; *a != 0; count++, a++) {

        bytes += strlen(*a)+1;

    }

    *nbytes = bytes;

    *nelems = count+1;

}

/* copy the strings from arg[] into buf, starting at given offset

 * return new offset to next free byte

 */

static int copystrings(char *buf, int offset, const char * const *arg) {

    char *p;

    const char * const *a;

    int count=0;

    if (arg == 0) {

        return offset;

    }

    for (p=buf+offset, a=arg; *a != 0; a++) {

        int len = strlen(*a) +1;

        memcpy(p, *a, len);

        p += len;

        count += len;

    }

    return offset+count;

}

/**

 * We are unusually paranoid; use of vfork is

 * especially likely to tickle gcc/glibc bugs.

 */

#ifdef __attribute_noinline__  /* See: sys/cdefs.h */

__attribute_noinline__

#endif

static pid_t

vforkChild(ChildStuff *c) {

    volatile pid_t resultPid;

    /*

     * We separate the call to vfork into a separate function to make

     * very sure to keep stack of child from corrupting stack of parent,

     * as suggested by the scary gcc warning:

     *  warning: variable 'foo' might be clobbered by 'longjmp' or 'vfork'

     */

    resultPid = vfork();

    if (resultPid == 0) {

        childProcess(c);

    }

    assert(resultPid != 0);  /* childProcess never returns */

    return resultPid;

}

static pid_t

forkChild(ChildStuff *c) {

    pid_t resultPid;

    /*

     * From Solaris fork(2): In Solaris 10, a call to fork() is

     * identical to a call to fork1(); only the calling thread is

     * replicated in the child process. This is the POSIX-specified

     * behavior for fork().

     */

    resultPid = fork();

    if (resultPid == 0) {

        childProcess(c);

    }

    assert(resultPid != 0);  /* childProcess never returns */

    return resultPid;

}

#if defined(__solaris__) || defined(_ALLBSD_SOURCE) || defined(_AIX)

static pid_t

spawnChild(JNIEnv *env, jobject process, ChildStuff *c, const char *helperpath) {

    pid_t resultPid;

    jboolean isCopy;

    int i, offset, rval, bufsize, magic;

    char *buf, buf1[16];

    char *hlpargs[2];

    SpawnInfo sp;

    /* need to tell helper which fd is for receiving the childstuff

     * and which fd to send response back on

     */

    snprintf(buf1, sizeof(buf1), "%d:%d", c->childenv[0], c->fail[1]);

    /* put the fd string as argument to the helper cmd */

    hlpargs[0] = buf1;

    hlpargs[1] = 0;

    /* Following items are sent down the pipe to the helper

     * after it is spawned.

     * All strings are null terminated. All arrays of strings

     * have an empty string for termination.

     * - the ChildStuff struct

     * - the SpawnInfo struct

     * - the argv strings array

     * - the envv strings array

     * - the home directory string

     * - the parentPath string

     * - the parentPathv array

     */

    /* First calculate the sizes */

    arraysize(c->argv, &sp.nargv, &sp.argvBytes);

    bufsize = sp.argvBytes;

    arraysize(c->envv, &sp.nenvv, &sp.envvBytes);

    bufsize += sp.envvBytes;

    sp.dirlen = c->pdir == 0 ? 0 : strlen(c->pdir)+1;

    bufsize += sp.dirlen;

    arraysize(parentPathv, &sp.nparentPathv, &sp.parentPathvBytes);

    bufsize += sp.parentPathvBytes;

    /* We need to clear FD_CLOEXEC if set in the fds[].

     * Files are created FD_CLOEXEC in Java.

     * Otherwise, they will be closed when the target gets exec'd */

    for (i=0; i<3; i++) {

        if (c->fds[i] != -1) {

            int flags = fcntl(c->fds[i], F_GETFD);

            if (flags & FD_CLOEXEC) {

                fcntl(c->fds[i], F_SETFD, flags & (~1));

            }

        }

    }

    rval = posix_spawn(&resultPid, helperpath, 0, 0, (char * const *) hlpargs, environ);

    if (rval != 0) {

        return -1;

    }

    /* now the lengths are known, copy the data */

    buf = NEW(char, bufsize);

    if (buf == 0) {

        return -1;

    }

    offset = copystrings(buf, 0, &c->argv[0]);

    offset = copystrings(buf, offset, &c->envv[0]);

    memcpy(buf+offset, c->pdir, sp.dirlen);

    offset += sp.dirlen;

    offset = copystrings(buf, offset, parentPathv);

    assert(offset == bufsize);

    magic = magicNumber();