Merge branch 'lukas/erts/forker'

* lukas/erts/forker: (28 commits)
  erts: Never abort in the forked child
  erts: Mend ASSERT makro for erl_child_setup
  erts: Allow enomem failures in port_SUITE
  erts: iter_port sleep longer on freebsd
  erts: Allow one dangling fd if there is a gethost port
  erts: Only use forker StackAck on freebsd
  erts: It is not possible to exit the forker driver
  erts: Add forker StartAck for port start flowcontrol
  erts: Fix large open_port arg segfault for win32
  erts: Fix memory leak at async open port
  kernel: Remove cmd server for unix os:cmd
  erts: Add testcase for huge port environment
  erts: Move os_pid to port hash to child setup
  erts: Handle all EINTR and EAGAIN cases in child setup
  erts: Make child_setup work with large environments
  erts: Fix forker driver ifdefs for win32
  erts: Fix uds socket handling for os x
  erts: Fix dereferencing of unaligned integer for sparc
  erts: Flatten too long io vectors in uds write
  erts: Add fd count test for spawn_driver
  ...

Conflicts:
	erts/emulator/beam/erl_node_tables.c
	erts/preloaded/src/erts_internal.erl

1 files changed, 1862 insertions, 0 deletions

diff --git a/erts/emulator/sys/unix/sys_drivers.c b/erts/emulator/sys/unix/sys_drivers.c
new file mode 100644
index 0000000000..2a7cd91265
--- /dev/null
+++ b/erts/emulator/sys/unix/sys_drivers.c
@@ -0,0 +1,1862 @@
+/*
+ * %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>
+#include <arpa/inet.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 WANT_NONBLOCKING    /* must define this to pull in defs from sys.h */
+#include "sys.h"
+
+#ifdef USE_THREADS
+#include "erl_threads.h"
+#endif
+
+extern char **environ;
+extern erts_smp_rwmtx_t environ_rwmtx;
+
+extern erts_smp_atomic_t sys_misc_mem_sz;
+
+static Eterm forker_port;
+
+#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_cpu_topology.h"
+
+#include "erl_sys_driver.h"
+#include "sys_uds.h"
+
+#include "erl_child_setup.h"
+
+#if defined IOV_MAX
+#define MAXIOV IOV_MAX
+#elif defined UIO_MAXIOV
+#define MAXIOV UIO_MAXIOV
+#else
+#define MAXIOV 16
+#endif
+
+#ifdef USE_THREADS
+#  define FDBLOCK 1
+#else
+#  define FDBLOCK 0
+#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;
+
+typedef struct fd_data {
+    int   fd;
+    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;
+
+typedef struct driver_data {
+    ErlDrvPort port_num;
+    ErtsSysFdData *ofd;
+    ErtsSysFdData *ifd;
+    int packet_bytes;
+    int pid;
+    int alive;
+    int status;
+    int terminating;
+    ErtsSysBlocking *blocking;
+} ErtsSysDriverData;
+
+#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
+
+#ifdef DEBUG
+#define close(fd) do { int res = close(fd); ASSERT(res > -1); } while(0)
+#endif
+
+#define CHILD_SETUP_PROG_NAME	"erl_child_setup" ERL_BUILD_TYPE_MARKER
+
+// #define HARD_DEBUG
+#ifdef HARD_DEBUG
+#define driver_select(port_num, fd, flags, onoff)                       \
+    do {                                                                \
+        if (((flags) & ERL_DRV_READ) && onoff)                          \
+            fprintf(stderr,"%010d %p: read select %d\r\n", __LINE__, port_num, (int)fd); \
+        if (((flags) & ERL_DRV_WRITE) && onoff)                         \
+            fprintf(stderr,"%010d %p: writ select %d\r\n", __LINE__, port_num, (int)fd); \
+        if (((flags) & ERL_DRV_READ) && !onoff)                          \
+            fprintf(stderr,"%010d %p: read unsele %d\r\n", __LINE__, port_num, (int)fd); \
+        if (((flags) & ERL_DRV_WRITE) && !onoff)                         \
+            fprintf(stderr,"%010d %p: writ unsele %d\r\n", __LINE__, port_num, (int)fd); \
+        driver_select_nkp(port_num, fd, flags, onoff);                  \
+    } while(0)
+#endif
+
+/*
+ * Decreasing the size of it below 16384 is not allowed.
+ */
+
+#define ERTS_SYS_READ_BUF_SZ (64*1024)
+
+/* I. Initialization */
+
+void
+erl_sys_late_init(void)
+{
+    SysDriverOpts opts;
+#ifdef ERTS_SMP
+    Port *port;
+#endif
+
+    sys_signal(SIGPIPE, SIG_IGN); /* Ignore - we'll handle the write failure */
+
+    opts.packet_bytes = 0;
+    opts.use_stdio = 1;
+    opts.redir_stderr = 0;
+    opts.read_write = 0;
+    opts.hide_window = 0;
+    opts.wd = NULL;
+    opts.envir = NULL;
+    opts.exit_status = 0;
+    opts.overlapped_io = 0;
+    opts.spawn_type = ERTS_SPAWN_ANY;
+    opts.argv = NULL;
+    opts.parallelism = erts_port_parallelism;
+
+#ifdef ERTS_SMP
+    port =
+#endif
+        erts_open_driver(&forker_driver, make_internal_pid(0), "forker", &opts, NULL, NULL);
+#ifdef ERTS_SMP
+    erts_mtx_unlock(port->lock);
+#endif
+}
+
+/* II. Prototypes */
+
+/* II.I Spawn prototypes */
+static ErlDrvData spawn_start(ErlDrvPort, char*, SysDriverOpts*);
+static ErlDrvSSizeT spawn_control(ErlDrvData, unsigned int, char *,
+                                  ErlDrvSizeT, char **, ErlDrvSizeT);
+
+/* II.II Vanilla prototypes */
+static ErlDrvData vanilla_start(ErlDrvPort, char*, SysDriverOpts*);
+
+
+/* II.III FD prototypes */
+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 void fd_stop(ErlDrvData);
+static void fd_flush(ErlDrvData);
+
+/* II.IV Common prototypes */
+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*);
+
+/* II.V Forker prototypes */
+static ErlDrvData forker_start(ErlDrvPort, char*, SysDriverOpts*);
+static void forker_stop(ErlDrvData);
+static void forker_ready_input(ErlDrvData, ErlDrvEvent);
+static void forker_ready_output(ErlDrvData, ErlDrvEvent);
+static ErlDrvSSizeT forker_control(ErlDrvData, unsigned int, char *,
+                                   ErlDrvSizeT, char **, ErlDrvSizeT);
+
+/* III Driver entries */
+
+/* III.I The spawn driver */
+struct erl_drv_entry spawn_driver_entry = {
+    NULL,
+    spawn_start,
+    stop,
+    output,
+    ready_input,
+    ready_output,
+    "spawn",
+    NULL,
+    NULL,
+    spawn_control,
+    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 | ERL_DRV_FLAG_USE_INIT_ACK,
+    NULL, NULL,
+    stop_select
+};
+
+/* III.II The fd driver */
+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
+};
+
+/* III.III The vanilla driver */
+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
+};
+
+/* III.III The forker driver */
+struct erl_drv_entry forker_driver_entry = {
+    NULL,
+    forker_start,
+    forker_stop,
+    NULL,
+    forker_ready_input,
+    forker_ready_output,
+    "spawn_forker",
+    NULL,
+    NULL,
+    forker_control,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    ERL_DRV_EXTENDED_MARKER,
+    ERL_DRV_EXTENDED_MAJOR_VERSION,
+    ERL_DRV_EXTENDED_MINOR_VERSION,
+    0,
+    NULL, NULL,
+    stop_select
+};
+
+/* Untility functions */
+
+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 void init_fd_data(ErtsSysFdData *fd_data, int fd)
+{
+    fd_data->fd = fd;
+    fd_data->buf = NULL;
+    fd_data->cpos = NULL;
+    fd_data->remain = 0;
+    fd_data->sz = 0;
+    fd_data->psz = 0;
+}
+
+static ErtsSysDriverData *
+create_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;
+    ErtsSysDriverData *driver_data;
+    char *data;
+    int size = sizeof(ErtsSysDriverData);
+
+    if (read_write & DO_READ)
+        size += sizeof(ErtsSysFdData);
+
+    if ((read_write & DO_WRITE) &&
+        ((ifd != ofd || ofd == -1) || !(read_write & DO_READ)))
+        size += sizeof(ErtsSysFdData);
+
+    data = erts_alloc(ERTS_ALC_T_DRV_TAB,size);
+    erts_smp_atomic_add_nob(&sys_misc_mem_sz, size);
+
+    driver_data = (ErtsSysDriverData*)data;
+    data += sizeof(*driver_data);
+
+    prt = erts_drvport2port(port_num);
+    if (prt != ERTS_INVALID_ERL_DRV_PORT)
+	prt->os_pid = pid;
+
+    driver_data->packet_bytes = packet_bytes;
+    driver_data->port_num = port_num;
+    driver_data->pid = pid;
+    driver_data->alive = exit_status ? 1 : 0;
+    driver_data->status = 0;
+    driver_data->terminating = 0;
+    driver_data->blocking = NULL;
+
+    if (read_write & DO_READ) {
+        driver_data->ifd = (ErtsSysFdData*)data;
+        data += sizeof(*driver_data->ifd);
+        init_fd_data(driver_data->ifd, ifd);
+        driver_select(port_num, ifd, (ERL_DRV_READ|ERL_DRV_USE), 1);
+    } else {
+        driver_data->ifd = NULL;
+    }
+
+    if (read_write & DO_WRITE) {
+        if (ofd != -1 && ifd == ofd && read_write & DO_READ) {
+            /* This is for when ifd and ofd are the same fd */
+            driver_data->ofd = driver_data->ifd;
+        } else {
+            driver_data->ofd = (ErtsSysFdData*)data;
+            data += sizeof(*driver_data->ofd);
+            init_fd_data(driver_data->ofd, ofd);
+        }
+        if (is_blocking && FDBLOCK)
+            if (!set_blocking_data(driver_data)) {
+                erts_free(ERTS_ALC_T_DRV_TAB, driver_data);
+                return NULL;
+            }
+    } else {
+        driver_data->ofd = NULL;
+    }
+
+    return driver_data;
+}
+
+/* Spawn driver */
+
+static void close_pipes(int ifd[2], int ofd[2])
+{
+    close(ifd[0]);
+    close(ifd[1]);
+    close(ofd[0]);
+    close(ofd[1]);
+}
+
+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;
+
+	    /* check if cpp[j] equals old
+	       before the = sign,
+	       i.e.
+	       "TMPDIR=/tmp/" */
+	    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;
+}
+
+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 len;
+    char **new_environ;
+    ErtsSysDriverData *dd;
+    char *cmd_line;
+    char wd_buff[MAXPATHLEN+1];
+    char *wd;
+    int ifd[2], ofd[2], stderrfd;
+
+    if (pipe(ifd) < 0) return ERL_DRV_ERROR_ERRNO;
+    errno = EMFILE;		/* default for next three conditions */
+    if (ifd[0] >= sys_max_files() || pipe(ofd) < 0) {
+        close(ifd[0]);
+        close(ifd[1]);
+        return ERL_DRV_ERROR_ERRNO;
+    }
+    if (ofd[1] >= sys_max_files()) {
+        close_pipes(ifd, ofd);
+        errno = EMFILE;
+        return ERL_DRV_ERROR_ERRNO;
+    }
+
+    SET_NONBLOCKING(ifd[0]);
+    SET_NONBLOCKING(ofd[1]);
+
+    stderrfd = opts->redir_stderr ? ifd[1] : dup(2);
+
+    if (stderrfd >= sys_max_files() || stderrfd < 0) {
+        close_pipes(ifd, ofd);
+        if (stderrfd > -1)
+            close(stderrfd);
+        return ERL_DRV_ERROR_ERRNO;
+    }
+
+    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);
+	    errno = ENOMEM;
+	    return ERL_DRV_ERROR_ERRNO;
+	}
+	memcpy((void *) cmd_line,(void *) name, len);
+	cmd_line[len] = '\0';
+	len = len + 1;
+	if (access(cmd_line,X_OK) != 0) {
+	    int save_errno = errno;
+	    erts_free(ERTS_ALC_T_TMP, cmd_line);
+            close_pipes(ifd, ofd);
+	    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);
+	    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';
+	len = CMD_LINE_PREFIX_STR_SZ + len + 1;
+    }
+
+    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);
+        close_pipes(ifd, ofd);
+	erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+	errno = ENOMEM;
+	return ERL_DRV_ERROR_ERRNO;
+    }
+
+    if (opts->wd == NULL) {
+        if ((wd = getcwd(wd_buff, MAXPATHLEN+1)) == NULL) {
+            /* on some OSs this call opens a fd in the
+               background which means that this can
+               return EMFILE */
+            int err = errno;
+            close_pipes(ifd, ofd);
+            erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+            if (new_environ != environ)
+                erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
+            erts_smp_rwmtx_runlock(&environ_rwmtx);
+            errno = err;
+            return ERL_DRV_ERROR_ERRNO;
+        }
+    } else {
+        wd = opts->wd;
+    }
+
+    {
+        struct iovec *io_vector;
+        int iov_len = 5;
+        char nullbuff[] = "\0";
+        int j, i = 0, res;
+        Sint32 buffsz = 0, env_len = 0, argv_len = 0,
+            flags = (opts->use_stdio ? FORKER_FLAG_USE_STDIO : 0)
+            | (opts->exit_status ? FORKER_FLAG_EXIT_STATUS : 0)
+            | (opts->read_write & DO_READ ? FORKER_FLAG_DO_READ : 0)
+            | (opts->read_write & DO_WRITE ? FORKER_FLAG_DO_WRITE : 0);
+
+        /* count number of elements in environment */
+        while(new_environ[env_len] != NULL)
+            env_len++;
+        iov_len += 1 + env_len; /* num envs including size int */
+
+        /* count number of element in argument list */
+        if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
+            if (opts->argv != NULL) {
+                while(opts->argv[argv_len] != NULL)
+                    argv_len++;
+            } else {
+                argv_len++;
+            }
+            iov_len += 1 + argv_len; /* num argvs including size int */
+        }
+
+        io_vector = erts_alloc_fnf(ERTS_ALC_T_TMP, sizeof(struct iovec) * iov_len);
+
+        if (!io_vector) {
+            close_pipes(ifd, ofd);
+            erts_smp_rwmtx_runlock(&environ_rwmtx);
+            erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+            if (new_environ != environ)
+                erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
+            errno = ENOMEM;
+            return ERL_DRV_ERROR_ERRNO;
+        }
+
+        io_vector[i].iov_base = (void*)&buffsz;
+        io_vector[i++].iov_len = sizeof(buffsz);
+
+        io_vector[i].iov_base = (void*)&flags;
+        flags = htonl(flags);
+        io_vector[i++].iov_len = sizeof(flags);
+        buffsz += sizeof(flags);
+
+        io_vector[i].iov_base = cmd_line;
+        io_vector[i++].iov_len = len;
+        buffsz += len;
+
+        io_vector[i].iov_base = wd;
+        io_vector[i].iov_len = strlen(io_vector[i].iov_base) + 1;
+        buffsz += io_vector[i++].iov_len;
+
+        io_vector[i].iov_base = nullbuff;
+        io_vector[i++].iov_len = 1;
+        buffsz += io_vector[i-1].iov_len;
+
+        io_vector[i].iov_base = (void*)&env_len;
+        env_len = htonl(env_len);
+        io_vector[i++].iov_len = sizeof(env_len);
+        buffsz += io_vector[i-1].iov_len;
+
+        for (j = 0; new_environ[j] != NULL; j++) {
+            io_vector[i].iov_base = new_environ[j];
+            io_vector[i++].iov_len = strlen(new_environ[j]) + 1;
+            buffsz += io_vector[i-1].iov_len;
+        }
+
+        /* only append arguments if this was a spawn_executable */
+        if (opts->spawn_type == ERTS_SPAWN_EXECUTABLE) {
+
+            io_vector[i].iov_base = (void*)&argv_len;
+            argv_len = htonl(argv_len);
+            io_vector[i++].iov_len = sizeof(argv_len);
+            buffsz += io_vector[i-1].iov_len;
+
+            if (opts->argv) {
+                /* If there are arguments we copy in the references to
+                   them into the iov */
+                for (j = 0; opts->argv[j]; j++) {
+                    if (opts->argv[j] == erts_default_arg0)
+                        io_vector[i].iov_base = cmd_line;
+                    else
+                        io_vector[i].iov_base = opts->argv[j];
+                    io_vector[i].iov_len = strlen(io_vector[i].iov_base) + 1;
+                    buffsz += io_vector[i++].iov_len;
+                }
+            } else {
+                io_vector[i].iov_base = cmd_line;
+                io_vector[i].iov_len = strlen(io_vector[i].iov_base) + 1;
+                buffsz += io_vector[i++].iov_len;
+            }
+        }
+
+        /* we send the request to do the fork */
+        if ((res = writev(ofd[1], io_vector, iov_len > MAXIOV ? MAXIOV : iov_len)) < 0) {
+            if (errno == ERRNO_BLOCK) {
+                res = 0;
+            } else {
+                int err = errno;
+                close_pipes(ifd, ofd);
+                erts_free(ERTS_ALC_T_TMP, io_vector);
+                if (new_environ != environ)
+                    erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
+                erts_smp_rwmtx_runlock(&environ_rwmtx);
+                erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+                errno = err;
+                return ERL_DRV_ERROR_ERRNO;
+            }
+        }
+
+        if (res < buffsz) {
+            /* we only wrote part of the command payload. Enqueue the rest. */
+            for (i = 0; i < iov_len; i++) {
+                driver_enq(port_num, io_vector[i].iov_base, io_vector[i].iov_len);
+            }
+            driver_deq(port_num, res);
+            driver_select(port_num, ofd[1], ERL_DRV_WRITE|ERL_DRV_USE, 1);
+        }
+
+        erts_free(ERTS_ALC_T_TMP, io_vector);
+    }
+
+    erts_free(ERTS_ALC_T_TMP, (void *) cmd_line);
+
+    if (new_environ != environ)
+	erts_free(ERTS_ALC_T_ENVIRONMENT, (void *) new_environ);
+
+    erts_smp_rwmtx_runlock(&environ_rwmtx);
+
+    dd = create_driver_data(port_num, ifd[0], ofd[1], opts->packet_bytes,
+                             DO_WRITE | DO_READ, opts->exit_status,
+                             0, 0);
+
+    {
+        /* send ofd[0] + ifd[1] + stderrfd to forker port */
+        ErtsSysForkerProto *proto =
+            erts_alloc(ERTS_ALC_T_DRV_CTRL_DATA,
+                       sizeof(ErtsSysForkerProto));
+        memset(proto, 0, sizeof(ErtsSysForkerProto));
+        proto->action = ErtsSysForkerProtoAction_Start;
+        proto->u.start.fds[0] = ofd[0];
+        proto->u.start.fds[1] = ifd[1];
+        proto->u.start.fds[2] = stderrfd;
+        proto->u.start.port_id = opts->exit_status ? erts_drvport2id(port_num) : THE_NON_VALUE;
+        if (erl_drv_port_control(forker_port, 'S', (char*)proto, sizeof(*proto))) {
+            /* The forker port has been killed, we close both fd's which will
+               make open_port throw an epipe error */
+            close(ofd[0]);
+            close(ifd[1]);
+        }
+    }
+
+    /* we set these fds to negative to mark if
+       they should be closed after the handshake */
+    if (!(opts->read_write & DO_READ))
+        dd->ifd->fd *= -1;
+
+    if (!(opts->read_write & DO_WRITE))
+        dd->ofd->fd *= -1;
+
+    return (ErlDrvData)dd;
+#undef CMD_LINE_PREFIX_STR
+#undef CMD_LINE_PREFIX_STR_SZ
+}
+
+static ErlDrvSSizeT spawn_control(ErlDrvData e, unsigned int cmd, char *buf,
+                                  ErlDrvSizeT len, char **rbuf, ErlDrvSizeT rlen)
+{
+    ErtsSysDriverData *dd = (ErtsSysDriverData*)e;
+    ErtsSysForkerProto *proto = (ErtsSysForkerProto *)buf;
+
+    ASSERT(len == sizeof(*proto));
+    ASSERT(proto->action == ErtsSysForkerProtoAction_SigChld);
+
+    dd->status = proto->u.sigchld.error_number;
+    dd->alive = -1;
+
+    if (dd->ifd)
+        driver_select(dd->port_num, abs(dd->ifd->fd), ERL_DRV_READ | ERL_DRV_USE, 1);
+
+    if (dd->ofd)
+        driver_select(dd->port_num, abs(dd->ofd->fd), ERL_DRV_WRITE | ERL_DRV_USE, 1);
+
+    return 0;
+}
+
+#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)
+{
+    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.
+     */
+
+    /* Try to figure out if we can use non-blocking writes */
+    if (opts->read_write & DO_WRITE) {
+
+	/* 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);
+		    }
+		}
+	    }
+	}
+    }
+    return (ErlDrvData)create_driver_data(port_num, opts->ifd, opts->ofd,
+                                          opts->packet_bytes,
+                                          opts->read_write, 0, -1,
+                                          !non_blocking);
+}
+
+static void clear_fd_data(ErtsSysFdData *fdd)
+{
+    if (fdd->sz > 0) {
+	erts_free(ERTS_ALC_T_FD_ENTRY_BUF, (void *) fdd->buf);
+	ASSERT(erts_smp_atomic_read_nob(&sys_misc_mem_sz) >= fdd->sz);
+	erts_smp_atomic_add_nob(&sys_misc_mem_sz, -1*fdd->sz);
+    }
+    fdd->buf = NULL;
+    fdd->sz = 0;
+    fdd->remain = 0;
+    fdd->cpos = NULL;
+    fdd->psz = 0;
+}
+
+static void nbio_stop_fd(ErlDrvPort prt, ErtsSysFdData *fdd)
+{
+    driver_select(prt, abs(fdd->fd), DO_READ|DO_WRITE, 0);
+    clear_fd_data(fdd);
+    SET_BLOCKING(abs(fdd->fd));
+
+}
+
+static void fd_stop(ErlDrvData ev)  /* Does not close the fds */
+{
+    ErtsSysDriverData* dd = (ErtsSysDriverData*)ev;
+    ErlDrvPort prt = dd->port_num;
+    int sz = sizeof(ErtsSysDriverData);
+
+#if FDBLOCK
+    if (dd->blocking) {
+        erts_free(ERTS_ALC_T_SYS_BLOCKING, dd->blocking);
+        dd->blocking = NULL;
+        sz += sizeof(ErtsSysBlocking);
+    }
+#endif
+
+    if (dd->ifd) {
+        sz += sizeof(ErtsSysFdData);
+        nbio_stop_fd(prt, dd->ifd);
+    }
+    if (dd->ofd && dd->ofd != dd->ifd) {
+        sz += sizeof(ErtsSysFdData);
+        nbio_stop_fd(prt, dd->ofd);
+    }
+
+     erts_free(ERTS_ALC_T_DRV_TAB, dd);
+     erts_smp_atomic_add_nob(&sys_misc_mem_sz, -sz);
+}
+
+static void fd_flush(ErlDrvData ev)
+{
+    ErtsSysDriverData* dd = (ErtsSysDriverData*)ev;
+    if (!dd->terminating)
+        dd->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);
+
+    res = (ErlDrvData)(long)create_driver_data(port_num, fd, fd,
+                                               opts->packet_bytes,
+                                               opts->read_write, 0, -1, 0);
+    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 ev)
+{
+    ErtsSysDriverData* dd = (ErtsSysDriverData*)ev;
+    ErlDrvPort prt = dd->port_num;
+
+    if (dd->ifd) {
+        nbio_stop_fd(prt, dd->ifd);
+        driver_select(prt, abs(dd->ifd->fd), ERL_DRV_USE, 0);  /* close(ifd); */
+    }
+
+    if (dd->ofd && dd->ofd != dd->ifd) {
+	nbio_stop_fd(prt, dd->ofd);
+	driver_select(prt, abs(dd->ofd->fd), ERL_DRV_USE, 0);  /* close(ofd); */
+    }
+
+    erts_free(ERTS_ALC_T_DRV_TAB, dd);
+}
+
+/* used by fd_driver */
+static void outputv(ErlDrvData e, ErlIOVec* ev)
+{
+    ErtsSysDriverData *dd = (ErtsSysDriverData*)e;
+    ErlDrvPort ix = dd->port_num;
+    int pb = dd->packet_bytes;
+    int ofd = dd->ofd ? dd->ofd->fd : -1;
+    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 (dd->blocking && FDBLOCK)
+        driver_pdl_lock(dd->blocking->pdl);
+
+    if ((sz = driver_sizeq(ix)) > 0) {
+	driver_enqv(ix, ev, 0);
+
+        if (dd->blocking && FDBLOCK)
+            driver_pdl_unlock(dd->blocking->pdl);
+
+	if (sz + ev->size >= (1 << 13))
+	    set_busy_port(ix, 1);
+    }
+    else if (!dd->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(dd->blocking->pdl);
+            driver_async(ix, &dd->blocking->pkey,
+                         fd_async, dd, NULL);
+        } else {
+            driver_pdl_unlock(dd->blocking->pdl);
+        }
+    }
+#endif
+    /* return 0;*/
+}
+
+/* Used by spawn_driver and vanilla driver */
+static void output(ErlDrvData e, char* buf, ErlDrvSizeT len)
+{
+    ErtsSysDriverData *dd = (ErtsSysDriverData*)e;
+    ErlDrvPort ix = dd->port_num;
+    int pb = dd->packet_bytes;
+    int ofd = dd->ofd ? dd->ofd->fd : -1;
+    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)
+        || dd->pid == 0 /* Attempt at output before port is ready */) {
+	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(ErtsSysDriverData *dd, int res)
+				/* Result: 0 (eof) or -1 (error) */
+{
+    int err = errno;
+
+    ASSERT(res <= 0);
+    if (dd->ifd) {
+        driver_select(dd->port_num, dd->ifd->fd, ERL_DRV_READ|ERL_DRV_WRITE, 0);
+        clear_fd_data(dd->ifd);
+    }
+
+    if (dd->blocking && FDBLOCK) {
+        driver_pdl_lock(dd->blocking->pdl);
+        if (driver_sizeq(dd->port_num) > 0) {
+            driver_pdl_unlock(dd->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)
+                dd->terminating = 2;
+            else
+                dd->terminating = -err;
+            return 0;
+        }
+        driver_pdl_unlock(dd->blocking->pdl);
+    }
+
+    if (res == 0) {
+        if (dd->alive == 1) {
+            /*
+             * We have eof and want to report exit status, but the process
+             * hasn't exited yet. When it does ready_input will
+             * driver_select() this fd which will make sure that we get
+             * back here with dd->alive == -1 and dd->status set.
+             */
+            return 0;
+        }
+        else if (dd->alive == -1) {
+            int status = dd->status;
+
+            /* We need not be prepared for stopped/continued processes. */
+            if (WIFSIGNALED(status))
+                status = 128 + WTERMSIG(status);
+            else
+                status = WEXITSTATUS(status);
+            driver_report_exit(dd->port_num, status);
+        }
+       driver_failure_eof(dd->port_num);
+    } else if (dd->ifd) {
+        erl_drv_init_ack(dd->port_num, ERL_DRV_ERROR_ERRNO);
+    } else {
+	driver_failure_posix(dd->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)
+{
+    ErtsSysDriverData *dd = (ErtsSysDriverData*)e;
+    ErlDrvPort port_num;
+    int packet_bytes;
+    int res;
+    Uint h;
+
+    port_num = dd->port_num;
+    packet_bytes = dd->packet_bytes;
+
+    ASSERT(abs(dd->ifd->fd) == ready_fd);
+
+    if (dd->pid == 0) {
+        /* the pid is sent from erl_child_setup. spawn driver only. */
+        ErtsSysForkerProto proto;
+        int res;
+
+        if((res = read(ready_fd, &proto, sizeof(proto))) <= 0) {
+            /* hmm, child setup seems to have closed the pipe too early...
+               we close the port as there is not much else we can do */
+            if (res < 0 && errno == ERRNO_BLOCK)
+                return;
+            driver_select(port_num, ready_fd, ERL_DRV_READ, 0);
+            if (res == 0)
+                errno = EPIPE;
+            port_inp_failure(dd, -1);
+            return;
+        }
+
+        ASSERT(proto.action == ErtsSysForkerProtoAction_Go);
+        dd->pid = proto.u.go.os_pid;
+
+        if (dd->pid == -1) {
+            /* Setup failed! The only reason why this should happen is if
+               the fork fails. */
+            errno = proto.u.go.error_number;
+            port_inp_failure(dd, -1);
+            return;
+        }
+
+        proto.action = ErtsSysForkerProtoAction_Ack;
+
+        if (driver_sizeq(port_num) > 0) {
+            driver_enq(port_num, (char*)&proto, sizeof(proto));
+            } else {
+                if (write(abs(dd->ofd->fd), &proto, sizeof(proto)) < 0)
+                    if (errno == ERRNO_BLOCK || errno == EINTR)
+                        driver_enq(port_num, (char*)&proto, sizeof(proto));
+                /* do nothing on failure here. If the ofd is broken, then
+                   the ifd will probably also be broken and trigger
+                   a port_inp_failure */
+            }
+
+            if (dd->ifd->fd < 0) {
+                driver_select(port_num, abs(dd->ifd->fd), ERL_DRV_READ|ERL_DRV_USE, 0);
+                erts_smp_atomic_add_nob(&sys_misc_mem_sz, -sizeof(ErtsSysFdData));
+                dd->ifd = NULL;
+            }
+
+            if (dd->ofd->fd < 0  || driver_sizeq(port_num) > 0)
+                /* we select in order to close fd or write to queue,
+                   child setup will close this fd if fd < 0 */
+                driver_select(port_num, abs(dd->ofd->fd), ERL_DRV_WRITE|ERL_DRV_USE, 1);
+
+            erl_drv_set_os_pid(port_num, dd->pid);
+            erl_drv_init_ack(port_num, e);
+            return;
+    }
+
+    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(dd, res);
+	}
+	else if (res == 0)
+	    port_inp_failure(dd, res);
+	else
+	    driver_output(port_num, (char*) read_buf, res);
+	erts_free(ERTS_ALC_T_SYS_READ_BUF, (void *) read_buf);
+    }
+    else if (dd->ifd->remain > 0) { /* We try to read the remainder */
+	/* space is allocated in buf */
+	res = read(ready_fd, dd->ifd->cpos,
+		   dd->ifd->remain);
+	if (res < 0) {
+	    if ((errno != EINTR) && (errno != ERRNO_BLOCK))
+		port_inp_failure(dd, res);
+	}
+	else if (res == 0) {
+	    port_inp_failure(dd, res);
+	}
+	else if (res == dd->ifd->remain) { /* we're done  */
+	    driver_output(port_num, dd->ifd->buf,
+			  dd->ifd->sz);
+	    clear_fd_data(dd->ifd);
+	}
+	else { /*  if (res < dd->ifd->remain) */
+	    dd->ifd->cpos += res;
+	    dd->ifd->remain -= res;
+	}
+    }
+    else if (dd->ifd->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(dd, res);
+	}
+	else if (res == 0) {     	/* eof */
+	    port_inp_failure(dd, res);
+	}
+	else if (res < packet_bytes - dd->ifd->psz) {
+	    memcpy(dd->ifd->pbuf+dd->ifd->psz,
+		   read_buf, res);
+	    dd->ifd->psz += res;
+	}
+	else  { /* if (res >= packet_bytes) */
+	    unsigned char* cpos = read_buf;
+	    int bytes_left = res;
+
+	    while (1) {
+		int psz = dd->ifd->psz;
+		char* pbp = dd->ifd->pbuf + psz;
+
+		while(bytes_left && (psz < packet_bytes)) {
+		    *pbp++ = *cpos++;
+		    bytes_left--;
+		    psz++;
+		}
+
+		if (psz < packet_bytes) {
+		    dd->ifd->psz = psz;
+		    break;
+		}
+		dd->ifd->psz = 0;
+
+		switch (packet_bytes) {
+		case 1: h = get_int8(dd->ifd->pbuf);  break;
+		case 2: h = get_int16(dd->ifd->pbuf); break;
+		case 4: h = get_int32(dd->ifd->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(dd, -1);
+		    }
+		    else {
+			erts_smp_atomic_add_nob(&sys_misc_mem_sz, h);
+			sys_memcpy(buf, cpos, bytes_left);
+			dd->ifd->buf = buf;
+			dd->ifd->sz = h;
+			dd->ifd->remain = h - bytes_left;
+			dd->ifd->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)
+{
+    ErtsSysDriverData *dd = (ErtsSysDriverData*)e;
+    ErlDrvPort ix = dd->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 (dd->pid > 0 && dd->ofd->fd < 0) {
+            /* The port was opened with 'in' option, which means we
+               should close the output fd as soon as the command has
+               been sent. */
+            driver_select(ix, ready_fd, ERL_DRV_WRITE|ERL_DRV_USE, 0);
+            erts_smp_atomic_add_nob(&sys_misc_mem_sz, -sizeof(ErtsSysFdData));
+            dd->ofd = NULL;
+        }
+        if (dd->terminating)
+            driver_failure_atom(dd->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->fd, 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);
+
+    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
+
+/* Forker driver */
+
+static int forker_fd;
+
+static ErlDrvData forker_start(ErlDrvPort port_num, char* name,
+                               SysDriverOpts* opts)
+{
+
+    int i;
+    int fds[2];
+    int res, unbind;
+    char bindir[MAXPATHLEN];
+    size_t bindirsz = sizeof(bindir);
+    Uint csp_path_sz;
+    char *child_setup_prog;
+
+    forker_port = erts_drvport2id(port_num);
+
+    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_snprintf(child_setup_prog, csp_path_sz,
+                  "%s%c%s",
+                  bindir,
+                  DIR_SEPARATOR_CHAR,
+                  CHILD_SETUP_PROG_NAME);
+    if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) < 0) {
+        erl_exit(ERTS_ABORT_EXIT,
+                 "Could not open unix domain socket in spawn_init: %d\n",
+                 errno);
+    }
+
+    forker_fd = fds[0];
+
+    unbind = erts_sched_bind_atfork_prepare();
+
+    i = fork();
+
+    if (i == 0) {
+        /* The child */
+        char *cs_argv[FORKER_ARGV_NO_OF_ARGS] =
+            {CHILD_SETUP_PROG_NAME, NULL, NULL};
+        char buff[128];
+
+        erts_sched_bind_atfork_child(unbind);
+
+        snprintf(buff, 128, "%d", sys_max_files());
+        cs_argv[FORKER_ARGV_MAX_FILES] = buff;
+
+        /* We preallocate fd 3 for the uds fd */
+        if (fds[1] != 3) {
+            dup2(fds[1], 3);
+        }
+
+#if defined(USE_SETPGRP_NOARGS)		/* SysV */
+    (void) setpgrp();
+#elif defined(USE_SETPGRP)		/* BSD */
+    (void) setpgrp(0, getpid());
+#else					/* POSIX */
+    (void) setsid();
+#endif
+
+        execv(child_setup_prog, cs_argv);
+        _exit(1);
+    }
+
+    erts_sched_bind_atfork_parent(unbind);
+
+    erts_free(ERTS_ALC_T_CS_PROG_PATH, child_setup_prog);
+
+    close(fds[1]);
+
+    SET_NONBLOCKING(forker_fd);
+
+    driver_select(port_num, forker_fd, ERL_DRV_READ|ERL_DRV_USE, 1);
+
+    return (ErlDrvData)port_num;
+}
+
+static void forker_stop(ErlDrvData e)
+{
+    /* we probably should do something here,
+       the port has been closed by the user. */
+}
+
+static void forker_ready_input(ErlDrvData e, ErlDrvEvent fd)
+{
+    int res;
+    ErtsSysForkerProto *proto;
+
+    proto = erts_alloc(ERTS_ALC_T_DRV_CTRL_DATA, sizeof(*proto));
+
+    if ((res = read(fd, proto, sizeof(*proto))) < 0) {
+        if (errno == ERRNO_BLOCK)
+            return;
+        erl_exit(ERTS_DUMP_EXIT, "Failed to read from erl_child_setup: %d\n", errno);
+    }
+
+    if (res == 0)
+        erl_exit(ERTS_DUMP_EXIT, "erl_child_setup closed\n");
+
+    ASSERT(res == sizeof(*proto));
+
+#ifdef FORKER_PROTO_START_ACK
+    if (proto->action == ErtsSysForkerProtoAction_StartAck) {
+        /* Ideally we would like to not have to ack each Start
+           command being sent over the uds, but it would seem
+           that some operating systems (only observed on FreeBSD)
+           throw away data on the uds when the socket becomes full,
+           so we have to.
+        */
+        ErlDrvPort port_num = (ErlDrvPort)e;
+        int vlen;
+        SysIOVec *iov = driver_peekq(port_num, &vlen);
+        ErtsSysForkerProto *proto = (ErtsSysForkerProto *)iov[0].iov_base;
+
+        close(proto->u.start.fds[0]);
+        close(proto->u.start.fds[1]);
+        if (proto->u.start.fds[1] != proto->u.start.fds[2])
+            close(proto->u.start.fds[2]);
+
+        driver_deq(port_num, sizeof(*proto));
+
+        if (driver_sizeq(port_num) > 0)
+            driver_select(port_num, forker_fd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
+    } else
+#endif
+    {
+        ASSERT(proto->action == ErtsSysForkerProtoAction_SigChld);
+
+        /* ideally this would be a port_command call, but as command is
+           already used by the spawn_driver, we use control instead.
+           Note that when using erl_drv_port_control it is an asynchronous
+           control. */
+        erl_drv_port_control(proto->u.sigchld.port_id, 'S',
+                             (char*)proto, sizeof(*proto));
+    }
+
+}
+
+static void forker_ready_output(ErlDrvData e, ErlDrvEvent fd)
+{
+    ErlDrvPort port_num = (ErlDrvPort)e;
+
+#ifndef FORKER_PROTO_START_ACK
+    while (driver_sizeq(port_num) > 0) {
+#endif
+        int vlen;
+        SysIOVec *iov = driver_peekq(port_num, &vlen);
+        ErtsSysForkerProto *proto = (ErtsSysForkerProto *)iov[0].iov_base;
+        ASSERT(iov[0].iov_len >= (sizeof(*proto)));
+        if (sys_uds_write(forker_fd, (char*)proto, sizeof(*proto),
+                          proto->u.start.fds, 3, 0) < 0) {
+            if (errno == ERRNO_BLOCK)
+                return;
+            erl_exit(ERTS_DUMP_EXIT, "Failed to write to erl_child_setup: %d\n", errno);
+        }
+#ifndef FORKER_PROTO_START_ACK
+        close(proto->u.start.fds[0]);
+        close(proto->u.start.fds[1]);
+        if (proto->u.start.fds[1] != proto->u.start.fds[2])
+            close(proto->u.start.fds[2]);
+        driver_deq(port_num, sizeof(*proto));
+    }
+#endif
+
+    driver_select(port_num, forker_fd, ERL_DRV_WRITE, 0);
+}
+
+static ErlDrvSSizeT forker_control(ErlDrvData e, unsigned int cmd, char *buf,
+                                   ErlDrvSizeT len, char **rbuf, ErlDrvSizeT rlen)
+{
+    ErtsSysForkerProto *proto = (ErtsSysForkerProto *)buf;
+    ErlDrvPort port_num = (ErlDrvPort)e;
+    int res;
+
+    driver_enq(port_num, buf, len);
+    if (driver_sizeq(port_num) > sizeof(*proto)) {
+        return 0;
+    }
+
+    if ((res = sys_uds_write(forker_fd, (char*)proto, sizeof(*proto),
+                             proto->u.start.fds, 3, 0)) < 0) {
+        if (errno == ERRNO_BLOCK) {
+            driver_select(port_num, forker_fd, ERL_DRV_WRITE|ERL_DRV_USE, 1);
+            return 0;
+        }
+        erl_exit(ERTS_DUMP_EXIT, "Failed to write to erl_child_setup: %d\n", errno);
+    }
+
+#ifndef FORKER_PROTO_START_ACK
+    ASSERT(res == sizeof(*proto));
+    close(proto->u.start.fds[0]);
+    close(proto->u.start.fds[1]);
+    if (proto->u.start.fds[1] != proto->u.start.fds[2])
+        close(proto->u.start.fds[2]);
+    driver_deq(port_num, sizeof(*proto));
+#endif
+
+    return 0;
+}