path: root/erts/emulator/sys/unix/sys_drivers.c

/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 1996-2014. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * %CopyrightEnd%
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#ifdef ISC32
#define _POSIX_SOURCE
#define _XOPEN_SOURCE
#endif

#include <sys/times.h>		/* ! */
#include <time.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/uio.h>
#include <termios.h>
#include <ctype.h>
#include <sys/utsname.h>
#include <sys/select.h>

#ifdef ISC32
#include <sys/bsdtypes.h>
#endif

#include <termios.h>
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#define NEED_CHILD_SETUP_DEFINES
#define WANT_NONBLOCKING    /* must define this to pull in defs from sys.h */
#include "sys.h"
#include "erl_thr_progress.h"

#if defined(__APPLE__) && defined(__MACH__) && !defined(__DARWIN__)
#define __DARWIN__ 1
#endif

#ifdef USE_THREADS
#include "erl_threads.h"
#endif

#include "erl_mseg.h"

extern char **environ;
extern erts_smp_rwmtx_t environ_rwmtx;

extern erts_smp_atomic_t sys_misc_mem_sz;

#define MAX_VSIZE 16		/* Max number of entries allowed in an I/O
				 * vector sock_sendv().
				 */
/*
 * Don't need global.h, but erl_cpu_topology.h won't compile otherwise
 */
#include "global.h"

#include "erl_sys_driver.h"
#include "erl_check_io.h"
#include "erl_cpu_topology.h"

#ifndef DISABLE_VFORK
#define DISABLE_VFORK 0
#endif

#if defined IOV_MAX
#define MAXIOV IOV_MAX
#elif defined UIO_MAXIOV
#define MAXIOV UIO_MAXIOV
#else
#define MAXIOV 16
#endif

/*
 * [OTP-3906]
 * Solaris signal management gets confused when threads are used and a
 * lot of child processes dies. The confusion results in that SIGCHLD
 * signals aren't delivered to the emulator which in turn results in
 * a lot of defunct processes in the system.
 *
 * The problem seems to appear when a signal is frequently
 * blocked/unblocked at the same time as the signal is frequently
 * propagated. The child waiter thread is a workaround for this problem.
 * The SIGCHLD signal is always blocked (in all threads), and the child
 * waiter thread fetches the signal by a call to sigwait(). See
 * child_waiter().
 */

typedef struct ErtsSysReportExit_ ErtsSysReportExit;
struct ErtsSysReportExit_ {
    ErtsSysReportExit *next;
    Eterm port;
    int pid;
    int ifd;
    int ofd;
#if CHLDWTHR && !defined(ERTS_SMP)
    int status;
#endif
};

/* Used by the fd driver iff the fd could not be set to non-blocking */
typedef struct ErtsSysBlocking_ {
    ErlDrvPDL pdl;
    int res;
    int err;
    unsigned int pkey;
} ErtsSysBlocking;


/* This data is shared by these drivers - initialized by spawn_init() */
typedef struct driver_data {
    ErlDrvPort port_num;
    int ofd, packet_bytes;
    ErtsSysReportExit *report_exit;
    int pid;
    int alive;
    int status;
    int terminating;
    ErtsSysBlocking *blocking;
} ErtsSysDriverData;

static ErtsSysDriverData *driver_data;			/* indexed by fd */

static ErtsSysReportExit *report_exit_list;
#if CHLDWTHR && !defined(ERTS_SMP)
static ErtsSysReportExit *report_exit_transit_list;
#endif

#define DIR_SEPARATOR_CHAR    '/'

#if defined(__ANDROID__)
#define SHELL "/system/bin/sh"
#else
#define SHELL "/bin/sh"
#endif /* __ANDROID__ */


#if defined(DEBUG)
#define ERL_BUILD_TYPE_MARKER ".debug"
#elif defined(PURIFY)
#define ERL_BUILD_TYPE_MARKER ".purify"
#elif defined(QUANTIFY)
#define ERL_BUILD_TYPE_MARKER ".quantify"
#elif defined(PURECOV)
#define ERL_BUILD_TYPE_MARKER ".purecov"
#elif defined(VALGRIND)
#define ERL_BUILD_TYPE_MARKER ".valgrind"
#else /* opt */
#define ERL_BUILD_TYPE_MARKER
#endif

#define CHILD_SETUP_PROG_NAME	"erl_child_setup" ERL_BUILD_TYPE_MARKER
static char *child_setup_prog;

#if CHLDWTHR || defined(ERTS_SMP)
erts_mtx_t chld_stat_mtx;
#endif
#if CHLDWTHR
static erts_tid_t child_waiter_tid;
/* chld_stat_mtx is used to protect against concurrent accesses
   of the driver_data fields pid, alive, and status. */
erts_cnd_t chld_stat_cnd;
static long children_alive;
#define CHLD_STAT_LOCK		erts_mtx_lock(&chld_stat_mtx)
#define CHLD_STAT_UNLOCK	erts_mtx_unlock(&chld_stat_mtx)
#define CHLD_STAT_WAIT		erts_cnd_wait(&chld_stat_cnd, &chld_stat_mtx)
#define CHLD_STAT_SIGNAL	erts_cnd_signal(&chld_stat_cnd)
#elif defined(ERTS_SMP) /* ------------------------------------------------- */
#define CHLD_STAT_LOCK		erts_mtx_lock(&chld_stat_mtx)
#define CHLD_STAT_UNLOCK	erts_mtx_unlock(&chld_stat_mtx)

#else /* ------------------------------------------------------------------- */
#define CHLD_STAT_LOCK
#define CHLD_STAT_UNLOCK
static volatile int children_died;
#endif

typedef struct ErtsSysFdData {
    char  pbuf[4];   /* hold partial packet bytes */
    int   psz;       /* size of pbuf */
    char  *buf;
    char  *cpos;
    int   sz;
    int   remain;  /* for input on fd */
} ErtsSysFdData;

static ErtsSysFdData *fd_data;			/* indexed by fd */

/* static FUNCTION(int, write_fill, (int, char*, int)); unused? */
static void note_child_death(int, int);

#if CHLDWTHR
static void* child_waiter(void *);
#endif

static void block_signals(void)
{
#if !CHLDWTHR
   sys_sigblock(SIGCHLD);
#endif
#ifndef ERTS_SMP
   sys_sigblock(SIGINT);
#ifndef ETHR_UNUSABLE_SIGUSRX
   sys_sigblock(SIGUSR1);
#endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
#endif /* #ifndef ERTS_SMP */

#if defined(ERTS_SMP) && !defined(ETHR_UNUSABLE_SIGUSRX)
   sys_sigblock(ERTS_SYS_SUSPEND_SIGNAL);
#endif

}

static void unblock_signals(void)
{
    /* Update erl_child_setup.c if changed */
#if !CHLDWTHR
   sys_sigrelease(SIGCHLD);
#endif
#ifndef ERTS_SMP
   sys_sigrelease(SIGINT);
#ifndef ETHR_UNUSABLE_SIGUSRX
   sys_sigrelease(SIGUSR1);
#endif /* #ifndef ETHR_UNUSABLE_SIGUSRX */
#endif /* #ifndef ERTS_SMP */

#if defined(ERTS_SMP) && !defined(ETHR_UNUSABLE_SIGUSRX)
   sys_sigrelease(ERTS_SYS_SUSPEND_SIGNAL);
#endif

}

/************************** Port I/O *******************************/



/* I. Common stuff */

/*
 * Decreasing the size of it below 16384 is not allowed.
 */

/* II. The spawn/fd/vanilla drivers */

#define ERTS_SYS_READ_BUF_SZ (64*1024)

/* Driver interfaces */
static ErlDrvData spawn_start(ErlDrvPort, char*, SysDriverOpts*);
static ErlDrvData fd_start(ErlDrvPort, char*, SysDriverOpts*);
#if FDBLOCK
static void fd_async(void *);
static void fd_ready_async(ErlDrvData drv_data, ErlDrvThreadData thread_data);
#endif
static ErlDrvSSizeT fd_control(ErlDrvData, unsigned int, char *, ErlDrvSizeT,
			       char **, ErlDrvSizeT);
static ErlDrvData vanilla_start(ErlDrvPort, char*, SysDriverOpts*);
static int spawn_init(void);
static void fd_stop(ErlDrvData);
static void fd_flush(ErlDrvData);
static void stop(ErlDrvData);
static void ready_input(ErlDrvData, ErlDrvEvent);
static void ready_output(ErlDrvData, ErlDrvEvent);
static void output(ErlDrvData, char*, ErlDrvSizeT);
static void outputv(ErlDrvData, ErlIOVec*);
static void stop_select(ErlDrvEvent, void*);

struct erl_drv_entry spawn_driver_entry = {
    spawn_init,
    spawn_start,
    stop,
    output,
    ready_input,
    ready_output,
    "spawn",
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    ERL_DRV_EXTENDED_MARKER,
    ERL_DRV_EXTENDED_MAJOR_VERSION,
    ERL_DRV_EXTENDED_MINOR_VERSION,
    ERL_DRV_FLAG_USE_PORT_LOCKING,
    NULL, NULL,
    stop_select
};
struct erl_drv_entry fd_driver_entry = {
    NULL,
    fd_start,
    fd_stop,
    output,
    ready_input,
    ready_output, 
    "fd",
    NULL,
    NULL,
    fd_control,
    NULL,
    outputv,
#if FDBLOCK
    fd_ready_async, /* ready_async */
#else
    NULL,
#endif
    fd_flush, /* flush */
    NULL, /* call */
    NULL, /* event */
    ERL_DRV_EXTENDED_MARKER,
    ERL_DRV_EXTENDED_MAJOR_VERSION,
    ERL_DRV_EXTENDED_MINOR_VERSION,
    0, /* ERL_DRV_FLAGs */
    NULL, /* handle2 */
    NULL, /* process_exit */
    stop_select
};
struct erl_drv_entry vanilla_driver_entry = {
    NULL,
    vanilla_start,
    stop,
    output,
    ready_input,
    ready_output,
    "vanilla",
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL, /* flush */
    NULL, /* call */
    NULL, /* event */
    ERL_DRV_EXTENDED_MARKER,
    ERL_DRV_EXTENDED_MAJOR_VERSION,
    ERL_DRV_EXTENDED_MINOR_VERSION,
    0, /* ERL_DRV_FLAGs */
    NULL, /* handle2 */
    NULL, /* process_exit */
    stop_select
};

/* Handle SIGCHLD signals. */
#if (defined(SIG_SIGSET) || defined(SIG_SIGNAL))
static RETSIGTYPE onchld(void)
#else
static RETSIGTYPE onchld(int signum)
#endif
{
#if CHLDWTHR
    ASSERT(0); /* We should *never* catch a SIGCHLD signal */
#elif defined(ERTS_SMP)
    smp_sig_notify('C');
#else
    children_died = 1;
    ERTS_CHK_IO_AS_INTR(); /* Make sure we don't sleep in poll */
#endif
}

static int set_blocking_data(ErtsSysDriverData *dd) {

    dd->blocking = erts_alloc(ERTS_ALC_T_SYS_BLOCKING, sizeof(ErtsSysBlocking));

    erts_smp_atomic_add_nob(&sys_misc_mem_sz, sizeof(ErtsSysBlocking));

    dd->blocking->pdl = driver_pdl_create(dd->port_num);
    dd->blocking->res = 0;
    dd->blocking->err = 0;
    dd->blocking->pkey = driver_async_port_key(dd->port_num);

    return 1;
}

static int set_driver_data(ErlDrvPort port_num,
			   int ifd,
			   int ofd,
			   int packet_bytes,
			   int read_write,
			   int exit_status,
			   int pid,
                           int is_blocking)
{
    Port *prt;
    ErtsSysReportExit *report_exit;

    if (!exit_status)
	report_exit = NULL;
    else {
	report_exit = erts_alloc(ERTS_ALC_T_PRT_REP_EXIT,
				 sizeof(ErtsSysReportExit));
	report_exit->next = report_exit_list;
	report_exit->port = erts_drvport2id(port_num);
	report_exit->pid = pid;
	report_exit->ifd = read_write & DO_READ ? ifd : -1;
	report_exit->ofd = read_write & DO_WRITE ? ofd : -1;
#if CHLDWTHR && !defined(ERTS_SMP)
	report_exit->status = 0;
#endif
	report_exit_list = report_exit;
    }

    prt = erts_drvport2port(port_num);
    if (prt != ERTS_INVALID_ERL_DRV_PORT)
	prt->os_pid = pid;

    if (read_write & DO_READ) {
	driver_data[ifd].packet_bytes = packet_bytes;
	driver_data[ifd].port_num = port_num;
	driver_data[ifd].report_exit = report_exit;
	driver_data[ifd].pid = pid;
	driver_data[ifd].alive = 1;
	driver_data[ifd].status = 0;
        driver_data[ifd].terminating = 0;
        driver_data[ifd].blocking = NULL;
	if (read_write & DO_WRITE) {
	    driver_data[ifd].ofd = ofd;
            if (is_blocking && FDBLOCK)
                if (!set_blocking_data(driver_data+ifd))
                    return -1;
	    if (ifd != ofd)
		driver_data[ofd] = driver_data[ifd];  /* structure copy */
	} else {		/* DO_READ only */
	    driver_data[ifd].ofd = -1;
	}
	(void) driver_select(port_num, ifd, (ERL_DRV_READ|ERL_DRV_USE), 1);
	return(ifd);
    } else {			/* DO_WRITE only */
	driver_data[ofd].packet_bytes = packet_bytes;
	driver_data[ofd].port_num = port_num;
	driver_data[ofd].report_exit = report_exit;
	driver_data[ofd].ofd = ofd;
	driver_data[ofd].pid = pid;
	driver_data[ofd].alive = 1;
	driver_data[ofd].status = 0;
        driver_data[ofd].terminating = 0;
        driver_data[ofd].blocking = NULL;
        if (is_blocking && FDBLOCK)
            if (!set_blocking_data(driver_data+ofd))
                return -1;
	return(ofd);
    }
}

static int spawn_init()
{
   int i;
#if CHLDWTHR
   erts_thr_opts_t thr_opts = ERTS_THR_OPTS_DEFAULT_INITER;
#endif
   int res;
   char bindir[MAXPATHLEN];
   size_t bindirsz = sizeof(bindir);
   Uint csp_path_sz;

#if CHLDWTHR
   thr_opts.detached = 0;
   thr_opts.suggested_stack_size = 0; /* Smallest possible */
   thr_opts.name = "child_waiter";
#endif

#if !DISABLE_VFORK
   res = erts_sys_getenv_raw("BINDIR", bindir, &bindirsz);
   if (res != 0) {
    if (res < 0)
        erl_exit(-1,
        "Environment variable BINDIR is not set\n");
    if (res > 0)
        erl_exit(-1,
        "Value of environment variable BINDIR is too large\n");
   }
   if (bindir[0] != DIR_SEPARATOR_CHAR)
       erl_exit(-1,
                "Environment variable BINDIR does not contain an"
                " absolute path\n");
   csp_path_sz = (strlen(bindir)
                  + 1 /* DIR_SEPARATOR_CHAR */
                  + sizeof(CHILD_SETUP_PROG_NAME)
                  + 1);
   child_setup_prog = erts_alloc(ERTS_ALC_T_CS_PROG_PATH, csp_path_sz);
   erts_smp_atomic_add_nob(&sys_misc_mem_sz, csp_path_sz);
   erts_snprintf(child_setup_prog, csp_path_sz,
                 "%s%c%s",
                 bindir,
                 DIR_SEPARATOR_CHAR,
                 CHILD_SETUP_PROG_NAME);
#endif

   report_exit_list = NULL;

#ifdef USE_THREADS

#if CHLDWTHR || defined(ERTS_SMP)
    erts_mtx_init(&chld_stat_mtx, "child_status");
#endif
#if CHLDWTHR
#ifndef ERTS_SMP
    report_exit_transit_list = NULL;
#endif
    erts_cnd_init(&chld_stat_cnd);
    children_alive = 0;
#endif

#if !CHLDWTHR && !defined(ERTS_SMP)
    children_died = 0;
#endif

#endif /* USE_THREADS */

   sys_signal(SIGPIPE, SIG_IGN); /* Ignore - we'll handle the write failure */
   driver_data = (ErtsSysDriverData *)
       erts_alloc(ERTS_ALC_T_DRV_TAB, sys_max_files() * sizeof(ErtsSysDriverData));
   erts_smp_atomic_add_nob(&sys_misc_mem_sz,
			   sys_max_files() * sizeof(ErtsSysDriverData));

   for (i = 0; i < sys_max_files(); i++)
      driver_data[i].pid = -1;

   fd_data = (ErtsSysFdData *)
       erts_alloc(ERTS_ALC_T_FD_TAB, sys_max_files() * sizeof(ErtsSysFdData));
   erts_smp_atomic_add_nob(&sys_misc_mem_sz,
        sys_max_files() * sizeof(ErtsSysFdData));

#if CHLDWTHR
   sys_sigblock(SIGCHLD);
#endif

   sys_signal(SIGCHLD, onchld); /* Reap children */

#if CHLDWTHR
   erts_thr_create(&child_waiter_tid, child_waiter, NULL, &thr_opts);
#endif

   return 1;
}

static void close_pipes(int ifd[2], int ofd[2], int read_write)
{
    if (read_write & DO_READ) {
	(void) close(ifd[0]);
	(void) close(ifd[1]);
    }
    if (read_write & DO_WRITE) {
	(void) close(ofd[0]);
	(void) close(ofd[1]);
    }
}

static void init_fd_data(int fd, ErlDrvPort port_num)
{
    fd_data[fd].buf = NULL;
    fd_data[fd].cpos = NULL;
    fd_data[fd].remain = 0;
    fd_data[fd].sz = 0;
    fd_data[fd].psz = 0;
}

static char **build_unix_environment(char *block)
{
    int i;
    int j;
    int len;
    char *cp;
    char **cpp;
    char** old_env;
    
    ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rlocked(&environ_rwmtx));

    cp = block;
    len = 0;
    while (*cp != '\0') {
	cp += strlen(cp) + 1;
	len++;
    }
    old_env = environ;
    while (*old_env++ != NULL) {
	len++;
    }
    
    cpp = (char **) erts_alloc_fnf(ERTS_ALC_T_ENVIRONMENT,
				   sizeof(char *) * (len+1));
    if (cpp == NULL) {
	return NULL;
    }

    cp = block;
    len = 0;
    while (*cp != '\0') {
	cpp[len] = cp;
	cp += strlen(cp) + 1;
	len++;
    }
    
    i = len;
    for (old_env = environ; *old_env; old_env++) {
	char* old = *old_env;

	for (j = 0; j < len; j++) {
	    char *s, *t;

	    s = cpp[j];
	    t = old;
	    while (*s == *t && *s != '=') {
		s++, t++;
	    }
	    if (*s == '=' && *t == '=') {
		break;
	    }
	}

	if (j == len) {		/* New version not found */
	    cpp[len++] = old;
	}
    }

    for (j = 0; j < i; ) {
        size_t last = strlen(cpp[j])-1;
	if (cpp[j][last] == '=' && strchr(cpp[j], '=') == cpp[j]+last) {
	    cpp[j] = cpp[--len];
	    if (len < i) {
		i--;
	    } else {
		j++;
	    }
	}
	else {
	    j++;
	}
    }

    cpp[len] = NULL;
    return cpp;
}

/*
  [arndt] In most Unix systems, including Solaris 2.5, 'fork' allocates memory
  in swap space for the child of a 'fork', whereas 'vfork' does not do this.
  The natural call to use here is therefore 'vfork'. Due to a bug in
  'vfork' in Solaris 2.5 (apparently fixed in 2.6), using 'vfork'
  can be dangerous in what seems to be these circumstances:
      If the child code under a vfork sets the signal action to SIG_DFL
      (or SIG_IGN)
      for any signal which was previously set to a signal handler, the
      state of the parent is clobbered, so that the later arrival of
      such a signal yields a sigsegv in the parent. If the signal was
      not set to a signal handler, but ignored, all seems to work.
  If you change the forking code below, beware of this.
 */

static ErlDrvData spawn_start(ErlDrvPort port_num, char* name, SysDriverOpts* opts)
{
#define CMD_LINE_PREFIX_STR "exec "
#define CMD_LINE_PREFIX_STR_SZ (sizeof(CMD_LINE_PREFIX_STR) - 1)

    int ifd[2], ofd[2], len, pid, i;
    char **volatile new_environ; /* volatile since a vfork() then cannot
				    cause 'new_environ' to be clobbered
				    in the parent process. */
    int saved_errno;
    long res;
    char *cmd_line;
#ifndef QNX
    int unbind;
#endif
#if !DISABLE_VFORK
    int no_vfork;
    size_t no_vfork_sz = sizeof(no_vfork);

    no_vfork = (erts_sys_getenv_raw("ERL_NO_VFORK",
				    (char *) &no_vfork,
				    &no_vfork_sz) >= 0);
#endif

    switch (opts->read_write) {
    case DO_READ:
	if (pipe(ifd) < 0)
	    return ERL_DRV_ERROR_ERRNO;
	if (ifd[0] >= sys_max_files()) {
	    close_pipes(ifd, ofd, opts->read_write);
	    errno = EMFILE;
	    return ERL_DRV_ERROR_ERRNO;
	}
	ofd[1] = -1;		/* keep purify happy */
	break;
    case DO_WRITE:
	if (pipe(ofd) < 0) return ERL_DRV_ERROR_ERRNO;
	if (ofd[1] >= sys_max_files()) {
	    close_pipes(ifd, ofd, opts->read_write);
	    errno = EMFILE;
	    return ERL_DRV_ERROR_ERRNO;
	}
	ifd[0] = -1;		/* keep purify happy */
	break;
    case DO_READ|DO_WRITE:
	if (pipe(ifd) < 0) return ERL_DRV_ERROR_ERRNO;
	errno = EMFILE;		/* default for next two conditions */
	if (ifd[0] >= sys_max_files() || pipe(ofd) < 0) {
	    close_pipes(ifd, ofd, DO_READ);
	    return ERL_DRV_ERROR_ERRNO;
	}
	if (ofd[1] >= sys_max_files()) {
	    close_pipes(ifd, ofd, opts->read_write);
	    errno = EMFILE;
	    return ERL_DRV_ERROR_ERRNO;
	}
	break;
    default:
	ASSERT(0);
	return ERL_DRV_ERROR_GENERAL;
    }

    if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
	/* started with spawn_executable, not with spawn */
	len = strlen(name);
	cmd_line = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP, len + 1);
	if (!cmd_line) {
	    close_pipes(ifd, ofd, opts->read_write);
	    errno = ENOMEM;
	    return ERL_DRV_ERROR_ERRNO;
	}
	memcpy((void *) cmd_line,(void *) name, len);
	cmd_line[len] = '\0';
	if (access(cmd_line,X_OK) != 0) {
	    int save_errno = errno;
	    erts_free(ERTS_ALC_T_TMP, cmd_line);
	    errno = save_errno;
	    return ERL_DRV_ERROR_ERRNO;
	}
    } else {
	/* make the string suitable for giving to "sh" */
	len = strlen(name);
	cmd_line = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP,
					   CMD_LINE_PREFIX_STR_SZ + len + 1);
	if (!cmd_line) {
	    close_pipes(ifd, ofd, opts->read_write);
	    errno = ENOMEM;
	    return ERL_DRV_ERROR_ERRNO;
	}
	memcpy((void *) cmd_line,
	       (void *) CMD_LINE_PREFIX_STR,
	       CMD_LINE_PREFIX_STR_SZ);
	memcpy((void *) (cmd_line + CMD_LINE_PREFIX_STR_SZ), (void *) name, len);
	cmd_line[CMD_LINE_PREFIX_STR_SZ + len] = '\0';
    }

    erts_smp_rwmtx_rlock(&environ_rwmtx);

    if (opts->envir == NULL) {
	new_environ = environ;
    } else if ((new_environ = build_unix_environment(opts->envir)) == NULL) {
	erts_smp_rwmtx_runlock(&environ_rwmtx);
	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
	errno = ENOMEM;
	return ERL_DRV_ERROR_ERRNO;
    } 

#ifndef QNX
    /* Block child from SIGINT and SIGUSR1. Must be before fork()
       to be safe. */
    block_signals();

    CHLD_STAT_LOCK;

    unbind = erts_sched_bind_atfork_prepare();

#if !DISABLE_VFORK
    /* See fork/vfork discussion before this function. */
    if (no_vfork) {
#endif

	DEBUGF(("Using fork\n"));
	pid = fork();

	if (pid == 0) {
	    /* The child! Setup child... */

	    if (erts_sched_bind_atfork_child(unbind) != 0)
		goto child_error;

	    /* OBSERVE!
	     * Keep child setup after vfork() (implemented below and in
	     * erl_child_setup.c) up to date if changes are made here.
	     */

	    if (opts->use_stdio) {
		if (opts->read_write & DO_READ) {
		    /* stdout for process */
		    if (dup2(ifd[1], 1) < 0)
			goto child_error;
		    if(opts->redir_stderr)
			/* stderr for process */
			if (dup2(ifd[1], 2) < 0)
			    goto child_error;
		}
		if (opts->read_write & DO_WRITE)
		    /* stdin for process */
		    if (dup2(ofd[0], 0) < 0)
			goto child_error;
	    }
	    else {	/* XXX will fail if ofd[0] == 4 (unlikely..) */
		if (opts->read_write & DO_READ)
		    if (dup2(ifd[1], 4) < 0)
			goto child_error;
		if (opts->read_write & DO_WRITE)
		    if (dup2(ofd[0], 3) < 0)
			goto child_error;
	    }

#if defined(HAVE_CLOSEFROM)
	    closefrom(opts->use_stdio ? 3 : 5);
#else
	    for (i = opts->use_stdio ? 3 : 5; i < sys_max_files(); i++)
		(void) close(i);
#endif

	    if (opts->wd && chdir(opts->wd) < 0)
		goto child_error;

#if defined(USE_SETPGRP_NOARGS)		/* SysV */
	    (void) setpgrp();
#elif defined(USE_SETPGRP)		/* BSD */
	    (void) setpgrp(0, getpid());
#else					/* POSIX */
	    (void) setsid();
#endif
	    
	    unblock_signals();

	    if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
		if (opts->argv == NULL) {
		    execle(cmd_line,cmd_line,(char *) NULL, new_environ);
		} else {
		    if (opts->argv[0] == erts_default_arg0) {
			opts->argv[0] = cmd_line;
		    }
		    execve(cmd_line, opts->argv, new_environ);
		    if (opts->argv[0] == cmd_line) {
			opts->argv[0] = erts_default_arg0;
		    }
		}
	    } else {
		execle(SHELL, "sh", "-c", cmd_line, (char *) NULL, new_environ);
	    }
	child_error:
	    _exit(1);
	}
#if !DISABLE_VFORK
    }
#define ENOUGH_BYTES (44)
    else { /* Use vfork() */
	char **cs_argv= erts_alloc(ERTS_ALC_T_TMP,(CS_ARGV_NO_OF_ARGS + 1)*
				   sizeof(char *));
	char fd_close_range[ENOUGH_BYTES];                  /* 44 bytes are enough to  */
	char dup2_op[CS_ARGV_NO_OF_DUP2_OPS][ENOUGH_BYTES]; /* hold any "%d:%d" string */
                                                            /* on a 64-bit machine.    */

	/* Setup argv[] for the child setup program (implemented in
	   erl_child_setup.c) */
	i = 0;
	if (opts->use_stdio) {
	    if (opts->read_write & DO_READ){
		/* stdout for process */
		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 1);
		if(opts->redir_stderr)
		    /* stderr for process */
		    erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 2);
	    }
	    if (opts->read_write & DO_WRITE)
		/* stdin for process */
		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ofd[0], 0);
	} else {	/* XXX will fail if ofd[0] == 4 (unlikely..) */
	    if (opts->read_write & DO_READ)
		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ifd[1], 4);
	    if (opts->read_write & DO_WRITE)
		erts_snprintf(&dup2_op[i++][0], ENOUGH_BYTES, "%d:%d", ofd[0], 3);
	}
	for (; i < CS_ARGV_NO_OF_DUP2_OPS; i++)
	    strcpy(&dup2_op[i][0], "-");
	erts_snprintf(fd_close_range, ENOUGH_BYTES, "%d:%d", opts->use_stdio ? 3 : 5, sys_max_files()-1);

	cs_argv[CS_ARGV_PROGNAME_IX] = child_setup_prog;
	cs_argv[CS_ARGV_WD_IX] = opts->wd ? opts->wd : ".";
	cs_argv[CS_ARGV_UNBIND_IX] = erts_sched_bind_atvfork_child(unbind);
	cs_argv[CS_ARGV_FD_CR_IX] = fd_close_range;
	for (i = 0; i < CS_ARGV_NO_OF_DUP2_OPS; i++)
	    cs_argv[CS_ARGV_DUP2_OP_IX(i)] = &dup2_op[i][0];

	if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
	    int num = 0;
	    int j = 0;
	    if (opts->argv != NULL) {
		for(; opts->argv[num] != NULL; ++num)
		    ;
	    }
	    cs_argv = erts_realloc(ERTS_ALC_T_TMP,cs_argv, (CS_ARGV_NO_OF_ARGS + 1 + num + 1) * sizeof(char *));
	    cs_argv[CS_ARGV_CMD_IX] = "-";
	    cs_argv[CS_ARGV_NO_OF_ARGS] = cmd_line;
	    if (opts->argv != NULL) {
		for (;opts->argv[j] != NULL; ++j) {
		    if (opts->argv[j] == erts_default_arg0) {
			cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = cmd_line;
		    } else {
			cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = opts->argv[j];
		    }
		}
	    }
	    cs_argv[CS_ARGV_NO_OF_ARGS + 1 + j] = NULL;
	} else {
	    cs_argv[CS_ARGV_CMD_IX] = cmd_line; /* Command */
	    cs_argv[CS_ARGV_NO_OF_ARGS] = NULL;
	}
	DEBUGF(("Using vfork\n"));
	pid = vfork();

	if (pid == 0) {
	    /* The child! */

	    /* Observe!
	     * OTP-4389: The child setup program (implemented in
	     * erl_child_setup.c) will perform the necessary setup of the
	     * child before it execs to the user program. This because
	     * vfork() only allow an *immediate* execve() or _exit() in the
	     * child.
	     */
	    execve(child_setup_prog, cs_argv, new_environ);
	    _exit(1);
	}
	erts_free(ERTS_ALC_T_TMP,cs_argv);
    }
#undef ENOUGH_BYTES
#endif

    erts_sched_bind_atfork_parent(unbind);

    if (pid == -1) {
        saved_errno = errno;
	CHLD_STAT_UNLOCK;
	erts_smp_rwmtx_runlock(&environ_rwmtx);
	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
        unblock_signals();
        close_pipes(ifd, ofd, opts->read_write);
	errno = saved_errno;
	return ERL_DRV_ERROR_ERRNO;
    }
#else /* QNX */
    if (opts->use_stdio) {
	if (opts->read_write & DO_READ)
	    qnx_spawn_options.iov[1] = ifd[1];  /* stdout for process */
	if (opts->read_write & DO_WRITE)
	    qnx_spawn_options.iov[0] = ofd[0];  /* stdin for process */
	} 
    else {
	if (opts->read_write & DO_READ)
	    qnx_spawn_options.iov[4] = ifd[1];
	if (opts->read_write & DO_WRITE)
	    qnx_spawn_options.iov[3] = ofd[0];
    }
    /* Close fds on exec */
    for (i = 3; i < sys_max_files(); i++)
	fcntl(i, F_SETFD, 1);

    qnx_spawn_options.flags = _SPAWN_SETSID;
    if ((pid = spawnl(P_NOWAIT, SHELL, SHELL, "-c", cmd_line, 
                      (char *) 0)) < 0) {
	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
        reset_qnx_spawn();
	erts_smp_rwmtx_runlock(&environ_rwmtx);
	close_pipes(ifd, ofd, opts->read_write);
	return ERL_DRV_ERROR_GENERAL;
    }
    reset_qnx_spawn();
#endif /* QNX */

    erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);

    if (new_environ != environ)
	erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);

    if (opts->read_write & DO_READ) 
	(void) close(ifd[1]);
    if (opts->read_write & DO_WRITE)
	(void) close(ofd[0]);
	
    if (opts->read_write & DO_READ) {
	SET_NONBLOCKING(ifd[0]);
	init_fd_data(ifd[0], port_num);
    }
    if (opts->read_write & DO_WRITE) {
	SET_NONBLOCKING(ofd[1]);
        init_fd_data(ofd[1], port_num);
    }

    res = set_driver_data(port_num, ifd[0], ofd[1], opts->packet_bytes,
			  opts->read_write, opts->exit_status, pid, 0);
    /* Don't unblock SIGCHLD until now, since the call above must
       first complete putting away the info about our new subprocess. */
    unblock_signals();

#if CHLDWTHR
    ASSERT(children_alive >= 0);

    if (!(children_alive++))
	CHLD_STAT_SIGNAL; /* Wake up child waiter thread if no children
			     was alive before we fork()ed ... */
#endif
    /* Don't unlock chld_stat_mtx until now of the same reason as above */
    CHLD_STAT_UNLOCK;

    erts_smp_rwmtx_runlock(&environ_rwmtx);

    return (ErlDrvData)res;
#undef CMD_LINE_PREFIX_STR
#undef CMD_LINE_PREFIX_STR_SZ
}

#ifdef QNX
static reset_qnx_spawn()
{
    int i;

    /* Reset qnx_spawn_options */
    qnx_spawn_options.flags = 0; 
    qnx_spawn_options.iov[0] = 0xff;
    qnx_spawn_options.iov[1] = 0xff;
    qnx_spawn_options.iov[2] = 0xff;
    qnx_spawn_options.iov[3] = 0xff;
}
#endif

#define FD_DEF_HEIGHT 24
#define FD_DEF_WIDTH 80
/* Control op */
#define FD_CTRL_OP_GET_WINSIZE 100

static int fd_get_window_size(int fd, Uint32 *width, Uint32 *height)
{
#ifdef TIOCGWINSZ 
    struct winsize ws;
    if (ioctl(fd,TIOCGWINSZ,&ws) == 0) {
	*width = (Uint32) ws.ws_col;
	*height = (Uint32) ws.ws_row;
	return 0;
    }
#endif
    return -1;
}

static ErlDrvSSizeT fd_control(ErlDrvData drv_data,
			       unsigned int command,
			       char *buf, ErlDrvSizeT len,
			       char **rbuf, ErlDrvSizeT rlen)
{
    int fd = (int)(long)drv_data;
    char resbuff[2*sizeof(Uint32)];
    switch (command) {
    case FD_CTRL_OP_GET_WINSIZE:
	{
	    Uint32 w,h;
	    if (fd_get_window_size(fd,&w,&h)) 
		return 0;
	    memcpy(resbuff,&w,sizeof(Uint32));
	    memcpy(resbuff+sizeof(Uint32),&h,sizeof(Uint32));
	}
	break;
    default:
	return 0;
    }
    if (rlen < 2*sizeof(Uint32)) {
	*rbuf = driver_alloc(2*sizeof(Uint32));
    }
    memcpy(*rbuf,resbuff,2*sizeof(Uint32));
    return 2*sizeof(Uint32);
}

static ErlDrvData fd_start(ErlDrvPort port_num, char* name,
			   SysDriverOpts* opts)
{
    ErlDrvData res;
    int non_blocking = 0;

    if (((opts->read_write & DO_READ) && opts->ifd >= sys_max_files()) ||
	((opts->read_write & DO_WRITE) && opts->ofd >= sys_max_files()))
	return ERL_DRV_ERROR_GENERAL;

    /*
     * Historical:
     *
     * "Note about nonblocking I/O.
     *
     * At least on Solaris, setting the write end of a TTY to nonblocking,
     * will set the input end to nonblocking as well (and vice-versa).
     * If erl is run in a pipeline like this:  cat | erl
     * the input end of the TTY will be the standard input of cat.
     * And cat is not prepared to handle nonblocking I/O."
     *
     * Actually, the reason for this is not that the tty itself gets set
     * in non-blocking mode, but that the "input end" (cat's stdin) and
     * the "output end" (erlang's stdout) are typically the "same" file
     * descriptor, dup()'ed from a single fd by one of this process'
     * ancestors.
     *
     * The workaround for this problem used to be a rather bad kludge,
     * interposing an extra process ("internal cat") between erlang's
     * stdout and the original stdout, allowing erlang to set its stdout
     * in non-blocking mode without affecting the stdin of the preceding
     * process in the pipeline - and being a kludge, it caused all kinds
     * of weird problems.
     *
     * So, this is the current logic:
     *
     * The only reason to set non-blocking mode on the output fd at all is
     * if it's something that can cause a write() to block, of course,
     * i.e. primarily if it points to a tty, socket, pipe, or fifo. 
     *
     * If we don't set non-blocking mode when we "should" have, and output
     * becomes blocked, the entire runtime system will be suspended - this
     * is normally bad of course, and can happen fairly "easily" - e.g. user
     * hits ^S on tty - but doesn't necessarily happen.
     * 
     * If we do set non-blocking mode when we "shouldn't" have, the runtime
     * system will end up seeing EOF on the input fd (due to the preceding
     * process dying), which typically will cause the entire runtime system
     * to terminate immediately (due to whatever erlang process is seeing
     * the EOF taking it as a signal to halt the system). This is *very* bad.
     * 
     * I.e. we should take a conservative approach, and only set non-
     * blocking mode when we a) need to, and b) are reasonably certain
     * that it won't be a problem. And as in the example above, the problem
     * occurs when input fd and output fd point to different "things".
     *
     * However, determining that they are not just the same "type" of
     * "thing", but actually the same instance of that type of thing, is
     * unreasonably complex in many/most cases.
     *
     * Also, with pipes, sockets, and fifos it's far from obvious that the
     * user *wants* non-blocking output: If you're running erlang inside
     * some complex pipeline, you're probably not running a real-time system
     * that must never stop, but rather *want* it to suspend if the output
     * channel is "full".
     *
     * So, the bottom line: We will only set the output fd non-blocking if
     * it points to a tty, and either a) the input fd also points to a tty,
     * or b) we can make sure that setting the output fd non-blocking
     * doesn't interfere with someone else's input, via a somewhat milder
     * kludge than the above.
     *
     * Also keep in mind that while this code is almost exclusively run as
     * a result of an erlang open_port({fd,0,1}, ...), that isn't the only
     * case - it can be called with any old pre-existing file descriptors,
     * the relations between which (if they're even two) we can only guess
     * at - still, we try our best...
     *
     * Added note OTP 18: Some systems seem to use stdout/stderr to log data
     * using unix pipes, so we cannot allow the system to block on a write.
     * Therefore we use an async thread to write the data to fd's that could
     * not be set to non-blocking. When no async threads are available we
     * fall back on the old behaviour.
     *
     * Also the guarantee about what is delivered to the OS has changed.
     * Pre 18 the fd driver did no flushing of data before terminating.
     * Now it does. This is because we want to be able to guarantee that things
     * such as escripts and friends really have outputted all data before
     * terminating. This could potentially block the termination of the system
     * for a very long time, but if the user wants to terminate fast she should
     * use erlang:halt with flush=false.
     */

    if (opts->read_write & DO_READ) {
	init_fd_data(opts->ifd, port_num);
    }
    if (opts->read_write & DO_WRITE) {
	init_fd_data(opts->ofd, port_num);

	/* If we don't have a read end, all bets are off - no non-blocking. */
	if (opts->read_write & DO_READ) {

	    if (isatty(opts->ofd)) { /* output fd is a tty:-) */

		if (isatty(opts->ifd)) { /* input fd is also a tty */

		    /* To really do this "right", we should also check that
		       input and output fd point to the *same* tty - but
		       this seems like overkill; ttyname() isn't for free,
		       and this is a very common case - and it's hard to
		       imagine a scenario where setting non-blocking mode
		       here would cause problems - go ahead and do it. */

                    non_blocking = 1;
		    SET_NONBLOCKING(opts->ofd);

		} else {	/* output fd is a tty, input fd isn't */

		    /* This is a "problem case", but also common (see the
		       example above) - i.e. it makes sense to try a bit
		       harder before giving up on non-blocking mode: Try to
		       re-open the tty that the output fd points to, and if
		       successful replace the original one with the "new" fd
		       obtained this way, and set *that* one in non-blocking
		       mode. (Yes, this is a kludge.)

		       However, re-opening the tty may fail in a couple of
		       (unusual) cases:

		       1) The name of the tty (or an equivalent one, i.e.
			  same major/minor number) can't be found, because
			  it actually lives somewhere other than /dev (or
			  wherever ttyname() looks for it), and isn't
			  equivalent to any of those that do live in the
			  "standard" place - this should be *very* unusual.

		       2) Permissions on the tty don't allow us to open it -
			  it's perfectly possible to have an fd open to an
			  object whose permissions wouldn't allow us to open
			  it. This is not as unusual as it sounds, one case
			  is if the user has su'ed to someone else (not
			  root) - we have a read/write fd open to the tty
			  (because it has been inherited all the way down
			  here), but we have neither read nor write
			  permission for the tty.

		       In these cases, we finally give up, and don't set the
		       output fd in non-blocking mode. */

		    char *tty;
		    int nfd;

		    if ((tty = ttyname(opts->ofd)) != NULL &&
			(nfd = open(tty, O_WRONLY)) != -1) {
			dup2(nfd, opts->ofd);
			close(nfd);
                        non_blocking = 1;
			SET_NONBLOCKING(opts->ofd);
		    }
		}
	    }
	}
    }
    CHLD_STAT_LOCK;
    res = (ErlDrvData)(long)set_driver_data(port_num, opts->ifd, opts->ofd,
                                            opts->packet_bytes,
                                            opts->read_write, 0, -1,
                                            !non_blocking);
    CHLD_STAT_UNLOCK;
    return res;
}

static void clear_fd_data(int fd) 
{
    if (fd_data[fd].sz > 0) {
	erts_free(ERTS_ALC_T_FD_ENTRY_BUF, (void *) fd_data[fd].buf);
	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= fd_data[fd].sz);
	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*fd_data[fd].sz);
    }
    fd_data[fd].buf = NULL;
    fd_data[fd].sz = 0;
    fd_data[fd].remain = 0;
    fd_data[fd].cpos = NULL;
    fd_data[fd].psz = 0;
}

static void nbio_stop_fd(ErlDrvPort prt, int fd)
{
    driver_select(prt,fd,DO_READ|DO_WRITE,0);
    clear_fd_data(fd);
    SET_BLOCKING(fd);
}

static void fd_stop(ErlDrvData ev)  /* Does not close the fds */
{
    int ofd;
    int fd = (int)(long)ev;
    ErlDrvPort prt = driver_data[fd].port_num;
    
#if FDBLOCK
    if (driver_data[fd].blocking) {
        erts_free(ERTS_ALC_T_SYS_BLOCKING,driver_data[fd].blocking);
        driver_data[fd].blocking = NULL;
        erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*sizeof(ErtsSysBlocking));
    }
#endif

    nbio_stop_fd(prt, fd);
    ofd = driver_data[fd].ofd;
    if (ofd != fd && ofd != -1)
	nbio_stop_fd(prt, ofd);
}

static void fd_flush(ErlDrvData fd)
{
    if (!driver_data[(int)(long)fd].terminating)
        driver_data[(int)(long)fd].terminating = 1;
}

static ErlDrvData vanilla_start(ErlDrvPort port_num, char* name,
				SysDriverOpts* opts)
{
    int flags, fd;
    ErlDrvData res;

    flags = (opts->read_write == DO_READ ? O_RDONLY :
	     opts->read_write == DO_WRITE ? O_WRONLY|O_CREAT|O_TRUNC :
	     O_RDWR|O_CREAT);
    if ((fd = open(name, flags, 0666)) < 0)
	return ERL_DRV_ERROR_GENERAL;
    if (fd >= sys_max_files()) {
	close(fd);
	return ERL_DRV_ERROR_GENERAL;
    }
    SET_NONBLOCKING(fd);
    init_fd_data(fd, port_num);

    CHLD_STAT_LOCK;
    res = (ErlDrvData)(long)set_driver_data(port_num, fd, fd,
                                            opts->packet_bytes,
                                            opts->read_write, 0, -1, 0);
    CHLD_STAT_UNLOCK;
    return res;
}

/* Note that driver_data[fd].ifd == fd if the port was opened for reading, */
/* otherwise (i.e. write only) driver_data[fd].ofd = fd.  */

static void stop(ErlDrvData fd)
{
    ErlDrvPort prt;
    int ofd;

    prt = driver_data[(int)(long)fd].port_num;
    nbio_stop_fd(prt, (int)(long)fd);

    ofd = driver_data[(int)(long)fd].ofd;
    if (ofd != (int)(long)fd && (int)(long)ofd != -1)
	nbio_stop_fd(prt, ofd);
    else
	ofd = -1;

    CHLD_STAT_LOCK;

    /* Mark as unused. */
    driver_data[(int)(long)fd].pid = -1;

    CHLD_STAT_UNLOCK;

    /* SMP note: Close has to be last thing done (open file descriptors work
       as locks on driver_data[] entries) */
    driver_select(prt, (int)(long)fd, ERL_DRV_USE, 0);  /* close(fd); */
    if (ofd >= 0) {
	driver_select(prt, (int)(long)ofd, ERL_DRV_USE, 0);  /* close(ofd); */
    }
}

/* used by fd_driver */
static void outputv(ErlDrvData e, ErlIOVec* ev)
{
    int fd = (int)(long)e;
    ErlDrvPort ix = driver_data[fd].port_num;
    int pb = driver_data[fd].packet_bytes;
    int ofd = driver_data[fd].ofd;
    ssize_t n;
    ErlDrvSizeT sz;
    char lb[4];
    char* lbp;
    ErlDrvSizeT len = ev->size;

    /* (len > ((unsigned long)-1 >> (4-pb)*8)) */
    /*    if (pb >= 0 && (len & (((ErlDrvSizeT)1 << (pb*8))) - 1) != len) {*/
    if (((pb == 2) && (len > 0xffff)) || (pb == 1 && len > 0xff)) {
	driver_failure_posix(ix, EINVAL);
	return; /* -1; */
    }
    /* Handles 0 <= pb <= 4 only */
    put_int32((Uint32) len, lb);
    lbp = lb + (4-pb);

    ev->iov[0].iov_base = lbp;
    ev->iov[0].iov_len = pb;
    ev->size += pb;

    if (driver_data[fd].blocking && FDBLOCK)
        driver_pdl_lock(driver_data[fd].blocking->pdl);

    if ((sz = driver_sizeq(ix)) > 0) {
	driver_enqv(ix, ev, 0);

        if (driver_data[fd].blocking && FDBLOCK)
            driver_pdl_unlock(driver_data[fd].blocking->pdl);

	if (sz + ev->size >= (1 << 13))
	    set_busy_port(ix, 1);
    }
    else if (!driver_data[fd].blocking || !FDBLOCK) {
        /* We try to write directly if the fd in non-blocking */
	int vsize = ev->vsize > MAX_VSIZE ? MAX_VSIZE : ev->vsize;

	n = writev(ofd, (const void *) (ev->iov), vsize);
	if (n == ev->size)
	    return; /* 0;*/
	if (n < 0) {
	    if ((errno != EINTR) && (errno != ERRNO_BLOCK)) {
		driver_failure_posix(ix, errno);
		return; /* -1;*/
	    }
	    n = 0;
	}
	driver_enqv(ix, ev, n);  /* n is the skip value */
	driver_select(ix, ofd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
    }
#if FDBLOCK
    else {
        if (ev->size != 0) {
            driver_enqv(ix, ev, 0);
            driver_pdl_unlock(driver_data[fd].blocking->pdl);
            driver_async(ix, &driver_data[fd].blocking->pkey,
                         fd_async, driver_data+fd, NULL);
        } else {
            driver_pdl_unlock(driver_data[fd].blocking->pdl);
        }
    }
#endif
    /* return 0;*/
}

/* Used by spawn_driver and vanilla driver */
static void output(ErlDrvData e, char* buf, ErlDrvSizeT len)
{
    int fd = (int)(long)e;
    ErlDrvPort ix = driver_data[fd].port_num;
    int pb = driver_data[fd].packet_bytes;
    int ofd = driver_data[fd].ofd;
    ssize_t n;
    ErlDrvSizeT sz;
    char lb[4];
    char* lbp;
    struct iovec iv[2];

    /* (len > ((unsigned long)-1 >> (4-pb)*8)) */
    if (((pb == 2) && (len > 0xffff)) || (pb == 1 && len > 0xff)) {
	driver_failure_posix(ix, EINVAL);
	return; /* -1; */
    }
    put_int32(len, lb);
    lbp = lb + (4-pb);

    if ((sz = driver_sizeq(ix)) > 0) {
	driver_enq(ix, lbp, pb);
	driver_enq(ix, buf, len);
	if (sz + len + pb >= (1 << 13))
	    set_busy_port(ix, 1);
    }
    else {
	iv[0].iov_base = lbp;
	iv[0].iov_len = pb;  /* should work for pb=0 */
	iv[1].iov_base = buf;
	iv[1].iov_len = len;
	n = writev(ofd, iv, 2);
	if (n == pb+len)
	    return; /* 0; */
	if (n < 0) {
	    if ((errno != EINTR) && (errno != ERRNO_BLOCK)) {
		driver_failure_posix(ix, errno);
		return; /* -1; */
	    }
	    n = 0;
	}
	if (n < pb) {
	    driver_enq(ix, lbp+n, pb-n);
	    driver_enq(ix, buf, len);
	}
	else {
	    n -= pb;
	    driver_enq(ix, buf+n, len-n);
	}
	driver_select(ix, ofd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
    }
    return; /* 0; */
}

static int port_inp_failure(ErlDrvPort port_num, int ready_fd, int res)
				/* Result: 0 (eof) or -1 (error) */
{
    int err = errno;

    ASSERT(res <= 0);
    (void) driver_select(port_num, ready_fd, ERL_DRV_READ|ERL_DRV_WRITE, 0); 
    clear_fd_data(ready_fd);

    if (driver_data[ready_fd].blocking && FDBLOCK) {
        driver_pdl_lock(driver_data[ready_fd].blocking->pdl);
        if (driver_sizeq(driver_data[ready_fd].port_num) > 0) {
            driver_pdl_unlock(driver_data[ready_fd].blocking->pdl);
            /* We have stuff in the output queue, so we just
               set the state to terminating and wait for fd_async_ready
               to terminate the port */
            if (res == 0)
                driver_data[ready_fd].terminating = 2;
            else
                driver_data[ready_fd].terminating = -err;
            return 0;
        }
        driver_pdl_unlock(driver_data[ready_fd].blocking->pdl);
    }

    if (res == 0) {
	if (driver_data[ready_fd].report_exit) {
	    CHLD_STAT_LOCK;

	    if (driver_data[ready_fd].alive) {
		/*
		 * We have eof and want to report exit status, but the process
		 * hasn't exited yet. When it does report_exit_status() will
		 * driver_select() this fd which will make sure that we get
		 * back here with driver_data[ready_fd].alive == 0 and
		 * driver_data[ready_fd].status set.
		 */
		CHLD_STAT_UNLOCK;
		return 0;
	    }
	    else {
		int status = driver_data[ready_fd].status;
		CHLD_STAT_UNLOCK;

		/* We need not be prepared for stopped/continued processes. */
		if (WIFSIGNALED(status))
		    status = 128 + WTERMSIG(status);
		else
		    status = WEXITSTATUS(status);

		driver_report_exit(driver_data[ready_fd].port_num, status);
	    }
       }
       driver_failure_eof(port_num);
    } else {
	driver_failure_posix(port_num, err);
    }
    return 0;
}

/* fd is the drv_data that is returned from the */
/* initial start routine                        */
/* ready_fd is the descriptor that is ready to read */

static void ready_input(ErlDrvData e, ErlDrvEvent ready_fd)
{
    int fd = (int)(long)e;
    ErlDrvPort port_num;
    int packet_bytes;
    int res;
    Uint h;

    port_num = driver_data[fd].port_num;
    packet_bytes = driver_data[fd].packet_bytes;


    if (packet_bytes == 0) {
	byte *read_buf = (byte *) erts_alloc(ERTS_ALC_T_SYS_READ_BUF,
					     ERTS_SYS_READ_BUF_SZ);
	res = read(ready_fd, read_buf, ERTS_SYS_READ_BUF_SZ);
	if (res < 0) {
	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
		port_inp_failure(port_num, ready_fd, res);
	}
	else if (res == 0)
	    port_inp_failure(port_num, ready_fd, res);
	else 
	    driver_output(port_num, (char*) read_buf, res);
	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
    }
    else if (fd_data[ready_fd].remain > 0) { /* We try to read the remainder */
	/* space is allocated in buf */
	res = read(ready_fd, fd_data[ready_fd].cpos, 
		   fd_data[ready_fd].remain);
	if (res < 0) {
	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
		port_inp_failure(port_num, ready_fd, res);
	}
	else if (res == 0) {
	    port_inp_failure(port_num, ready_fd, res);
	}
	else if (res == fd_data[ready_fd].remain) { /* we're done  */
	    driver_output(port_num, fd_data[ready_fd].buf, 
			  fd_data[ready_fd].sz);
	    clear_fd_data(ready_fd);
	}
	else { /*  if (res < fd_data[ready_fd].remain) */
	    fd_data[ready_fd].cpos += res;
	    fd_data[ready_fd].remain -= res;
	}
    }
    else if (fd_data[ready_fd].remain == 0) { /* clean fd */
	byte *read_buf = (byte *) erts_alloc(ERTS_ALC_T_SYS_READ_BUF,
					     ERTS_SYS_READ_BUF_SZ);
	/* We make one read attempt and see what happens */
	res = read(ready_fd, read_buf, ERTS_SYS_READ_BUF_SZ);
	if (res < 0) {  
	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
		port_inp_failure(port_num, ready_fd, res);
	}
	else if (res == 0) {     	/* eof */
	    port_inp_failure(port_num, ready_fd, res);
	} 
	else if (res < packet_bytes - fd_data[ready_fd].psz) { 
	    memcpy(fd_data[ready_fd].pbuf+fd_data[ready_fd].psz,
		   read_buf, res);
	    fd_data[ready_fd].psz += res;
	}
	else  { /* if (res >= packet_bytes) */
	    unsigned char* cpos = read_buf;
	    int bytes_left = res;

	    while (1) {
		int psz = fd_data[ready_fd].psz;
		char* pbp = fd_data[ready_fd].pbuf + psz;

		while(bytes_left && (psz < packet_bytes)) {
		    *pbp++ = *cpos++;
		    bytes_left--;
		    psz++;
		}
		
		if (psz < packet_bytes) {
		    fd_data[ready_fd].psz = psz;
		    break;
		}
		fd_data[ready_fd].psz = 0;

		switch (packet_bytes) {
		case 1: h = get_int8(fd_data[ready_fd].pbuf);  break;
		case 2: h = get_int16(fd_data[ready_fd].pbuf); break;
		case 4: h = get_int32(fd_data[ready_fd].pbuf); break;
		default: ASSERT(0); return; /* -1; */
		}

		if (h <= (bytes_left)) {
		    driver_output(port_num, (char*) cpos, h);
		    cpos += h;
		    bytes_left -= h;
		    continue;
		}
		else {		/* The last message we got was split */
		        char *buf = erts_alloc_fnf(ERTS_ALC_T_FD_ENTRY_BUF, h);
		    if (!buf) {
			errno = ENOMEM;
			port_inp_failure(port_num, ready_fd, -1);
		    }
		    else {
			erts_smp_atomic_add_nob(&sys_misc_mem_sz, h);
			sys_memcpy(buf, cpos, bytes_left);
			fd_data[ready_fd].buf = buf;
			fd_data[ready_fd].sz = h;
			fd_data[ready_fd].remain = h - bytes_left;
			fd_data[ready_fd].cpos = buf + bytes_left;
		    }
		    break;
		}
	    }
	}
	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
    }
}


/* fd is the drv_data that is returned from the */
/* initial start routine                        */
/* ready_fd is the descriptor that is ready to read */

static void ready_output(ErlDrvData e, ErlDrvEvent ready_fd)
{
    int fd = (int)(long)e;
    ErlDrvPort ix = driver_data[fd].port_num;
    int n;
    struct iovec* iv;
    int vsize;
    

    if ((iv = (struct iovec*) driver_peekq(ix, &vsize)) == NULL) {
	driver_select(ix, ready_fd, ERL_DRV_WRITE, 0);
        if (driver_data[fd].terminating)
            driver_failure_atom(driver_data[fd].port_num,"normal");
	return; /* 0; */
    }
    vsize = vsize > MAX_VSIZE ? MAX_VSIZE : vsize;
    if ((n = writev(ready_fd, iv, vsize)) > 0) {
	if (driver_deq(ix, n) == 0)
	    set_busy_port(ix, 0);
    }
    else if (n < 0) {
	if (errno == ERRNO_BLOCK || errno == EINTR)
	    return; /* 0; */
	else {
	    int res = errno;
	    driver_select(ix, ready_fd, ERL_DRV_WRITE, 0);
	    driver_failure_posix(ix, res);
	    return; /* -1; */
	}
    }
    return; /* 0; */
}

static void stop_select(ErlDrvEvent fd, void* _)
{
    close((int)fd);
}

#if FDBLOCK

static void
fd_async(void *async_data)
{
    int res;
    ErtsSysDriverData *dd = (ErtsSysDriverData*)async_data;
    SysIOVec      *iov0;
    SysIOVec      *iov;
    int            iovlen;
    int            err = 0;
    /* much of this code is stolen from efile_drv:invoke_writev */
    driver_pdl_lock(dd->blocking->pdl);
    iov0 = driver_peekq(dd->port_num, &iovlen);
    iovlen = iovlen < MAXIOV ? iovlen : MAXIOV;
    iov = erts_alloc_fnf(ERTS_ALC_T_SYS_WRITE_BUF,
                         sizeof(SysIOVec)*iovlen);
    if (!iov) {
        res = -1;
        err = ENOMEM;
        driver_pdl_unlock(dd->blocking->pdl);
    } else {
        memcpy(iov,iov0,iovlen*sizeof(SysIOVec));
        driver_pdl_unlock(dd->blocking->pdl);

        do {
            res = writev(dd->ofd, iov, iovlen);
        } while (res < 0 && errno == EINTR);
        if (res < 0)
            err = errno;
        err = errno;

        erts_free(ERTS_ALC_T_SYS_WRITE_BUF, iov);
    }
    dd->blocking->res = res;
    dd->blocking->err = err;
}

void fd_ready_async(ErlDrvData drv_data,
                    ErlDrvThreadData thread_data) {
    ErtsSysDriverData *dd = (ErtsSysDriverData *)thread_data;
    ErlDrvPort port_num = dd->port_num;

    ASSERT(dd->blocking);
    ASSERT(dd == (driver_data + (int)(long)drv_data));

    if (dd->blocking->res > 0) {
        driver_pdl_lock(dd->blocking->pdl);
        if (driver_deq(port_num, dd->blocking->res) == 0) {
            driver_pdl_unlock(dd->blocking->pdl);
            set_busy_port(port_num, 0);
            if (dd->terminating) {
                /* The port is has been ordered to terminate
                   from either fd_flush or port_inp_failure */
                if (dd->terminating == 1)
                    driver_failure_atom(port_num, "normal");
                else if (dd->terminating == 2)
                    driver_failure_eof(port_num);
                else if (dd->terminating < 0)
                    driver_failure_posix(port_num, -dd->terminating);
                return; /* -1; */
            }
        } else {
            driver_pdl_unlock(dd->blocking->pdl);
            /* still data left to write in queue */
            driver_async(port_num, &dd->blocking->pkey, fd_async, dd, NULL);
            return /* 0; */;
        }
    } else if (dd->blocking->res < 0) {
        if (dd->blocking->err == ERRNO_BLOCK) {
            set_busy_port(port_num, 1);
            /* still data left to write in queue */
            driver_async(port_num, &dd->blocking->pkey, fd_async, dd, NULL);
        } else
            driver_failure_posix(port_num, dd->blocking->err);
        return; /* -1; */
    }
    return; /* 0; */
}

#endif

static ERTS_INLINE void
report_exit_status(ErtsSysReportExit *rep, int status)
{
    Port *pp;
#ifdef ERTS_SMP
    CHLD_STAT_UNLOCK;
    pp = erts_thr_id2port_sflgs(rep->port,
				ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP);
    CHLD_STAT_LOCK;
#else
    pp = erts_id2port_sflgs(rep->port,
			    NULL,
			    0,
			    ERTS_PORT_SFLGS_INVALID_DRIVER_LOOKUP);
#endif
    if (pp) {
	if (rep->ifd >= 0) {
	    driver_data[rep->ifd].alive = 0;
	    driver_data[rep->ifd].status = status;
	    (void) driver_select(ERTS_Port2ErlDrvPort(pp),
				 rep->ifd,
				 (ERL_DRV_READ|ERL_DRV_USE),
				 1);
	}
	if (rep->ofd >= 0) {
	    driver_data[rep->ofd].alive = 0;
	    driver_data[rep->ofd].status = status;
	    (void) driver_select(ERTS_Port2ErlDrvPort(pp),
				 rep->ofd,
				 (ERL_DRV_WRITE|ERL_DRV_USE),
				 1);
	}
#ifdef ERTS_SMP
	erts_thr_port_release(pp);
#else
	erts_port_release(pp);
#endif
    }
    erts_free(ERTS_ALC_T_PRT_REP_EXIT, rep);
}

#if !CHLDWTHR  /* ---------------------------------------------------------- */

#define ERTS_REPORT_EXIT_STATUS report_exit_status

int check_children(void)
{
    int res = 0;
    int pid;
    int status;

#ifndef ERTS_SMP
    if (children_died)
#endif
    {
	sys_sigblock(SIGCHLD);
	CHLD_STAT_LOCK;
	while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
	    note_child_death(pid, status);
#ifndef ERTS_SMP
	children_died = 0;
#endif
	CHLD_STAT_UNLOCK;
	sys_sigrelease(SIGCHLD);
	res = 1;
    }
    return res;
}

#ifdef ERTS_SMP

void
erts_check_children(void)
{
    (void) check_children();
}

#endif

#elif CHLDWTHR && defined(ERTS_SMP) /* ------------------------------------- */

#define ERTS_REPORT_EXIT_STATUS report_exit_status

int check_children(void)
{
    return 0;
}

#else /* CHLDWTHR && !defined(ERTS_SMP) ------------------------------------ */

#define ERTS_REPORT_EXIT_STATUS initiate_report_exit_status

static ERTS_INLINE void
initiate_report_exit_status(ErtsSysReportExit *rep, int status)
{
    rep->next = report_exit_transit_list;
    rep->status = status;
    report_exit_transit_list = rep;
    erts_sys_schedule_interrupt(1);
}

int check_children(void)
{
    int res;
    ErtsSysReportExit *rep;
    CHLD_STAT_LOCK;
    rep = report_exit_transit_list;
    res = rep != NULL;
    while (rep) {
	ErtsSysReportExit *curr_rep = rep;
	rep = rep->next;
	report_exit_status(curr_rep, curr_rep->status);
    }
    report_exit_transit_list = NULL;
    CHLD_STAT_UNLOCK;
    return res;
}

#endif /* ------------------------------------------------------------------ */

static void note_child_death(int pid, int status)
{
    ErtsSysReportExit **repp = &report_exit_list;
    ErtsSysReportExit *rep = report_exit_list;

    while (rep) {
	if (pid == rep->pid) {
	    *repp = rep->next;
	    ERTS_REPORT_EXIT_STATUS(rep, status);
	    break;
	}
	repp = &rep->next;
	rep = rep->next;
    }
}

#if CHLDWTHR

static void *
child_waiter(void *unused)
{
  int pid;
  int status;

#ifdef ERTS_ENABLE_LOCK_CHECK
  erts_lc_set_thread_name("child waiter");
#endif

  while(1) {
#ifdef DEBUG
      int waitpid_errno;
#endif
      pid = waitpid(-1, &status, 0);
#ifdef DEBUG
      waitpid_errno = errno;
#endif
      CHLD_STAT_LOCK;
      if (pid < 0) {
	  ASSERT(waitpid_errno == ECHILD);
      }
      else {
	  children_alive--;
	  ASSERT(children_alive >= 0);
	  note_child_death(pid, status);
      }
      while (!children_alive)
	  CHLD_STAT_WAIT; /* Wait for children to wait on... :) */
      CHLD_STAT_UNLOCK;
  }

  return NULL;
}

#endif