librt: add posix_spawn support

Signed-off-by: Ismael Luceno <ismael.luceno@gmail.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

Makefile.in

@@ -290,6 +290,7 @@ HEADERS_RM-$(UCLIBC_SUPPORT_AI_ADDRCONFIG)   += ifaddrs.h
 HEADERS_RM-$(UCLIBC_SV4_DEPRECATED)          += ustat.h sys/ustat.h bits/ustat.h
 HEADERS_RM-$(UCLIBC_SUSV3_LEGACY)            += sys/timeb.h regexp.h
 HEADERS_RM-$(UCLIBC_SUSV4_LEGACY)            += utime.h ucontext.h
+HEADERS_RM-$(UCLIBC_HAS_ADVANCED_REALTIME)   += spawn.h
 
 ifneq ($(findstring install,$(MAKECMDGOALS)),)
 $(addprefix $(PREFIX)$(DEVEL_PREFIX),include $(MULTILIB_DIR)):

include/spawn.h

@@ -0,0 +1,266 @@
+/* Definitions for POSIX spawn interface.
+   Copyright (C) 2000,2003,2004,2009,2011,2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef	_SPAWN_H
+#define	_SPAWN_H	1
+
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <features.h>
+#include <sched.h>
+#define __need_sigset_t
+#include <signal.h>
+#include <sys/types.h>
+
+
+/* Data structure to contain attributes for thread creation.  */
+typedef struct {
+	short int __flags;
+	pid_t __pgrp;
+	sigset_t __sd;
+	sigset_t __ss;
+	struct sched_param __sp;
+	int __policy;
+	int __pad[16];
+} posix_spawnattr_t;
+
+
+/* Data structure to contain information about the actions to be
+   performed in the new process with respect to file descriptors.  */
+typedef struct {
+	int __allocated;
+	int __used;
+	struct __spawn_action *__actions;
+	int __pad[16];
+} posix_spawn_file_actions_t;
+
+
+/* Flags to be set in the `posix_spawnattr_t'.  */
+#define POSIX_SPAWN_RESETIDS		0x01
+#define POSIX_SPAWN_SETPGROUP		0x02
+#define POSIX_SPAWN_SETSIGDEF		0x04
+#define POSIX_SPAWN_SETSIGMASK		0x08
+#define POSIX_SPAWN_SETSCHEDPARAM	0x10
+#define POSIX_SPAWN_SETSCHEDULER	0x20
+#define POSIX_SPAWN_USEVFORK		0x40 /* GNU extension */
+
+
+#define __POSIX_SPAWN_MASK (POSIX_SPAWN_RESETIDS		\
+			    | POSIX_SPAWN_SETPGROUP		\
+			    | POSIX_SPAWN_SETSIGDEF		\
+			    | POSIX_SPAWN_SETSIGMASK		\
+			    | POSIX_SPAWN_SETSCHEDPARAM		\
+			    | POSIX_SPAWN_SETSCHEDULER		\
+			    | POSIX_SPAWN_USEVFORK)
+
+__BEGIN_DECLS
+
+/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS.
+
+   This function is a possible cancellation point and therefore not
+   marked with __THROW. */
+int posix_spawn(pid_t * restrict pid, const char * restrict path,
+		const posix_spawn_file_actions_t * restrict file_actions,
+		const posix_spawnattr_t * restrict attrp,
+		char * const argv[restrict],
+		char * const envp[restrict]);
+
+/* Similar to `posix_spawn' but search for FILE in the PATH.
+
+   This function is a possible cancellation point and therefore not
+   marked with __THROW.  */
+int posix_spawnp(pid_t *pid, const char *file,
+		 const posix_spawn_file_actions_t *file_actions,
+		 const posix_spawnattr_t *attrp,
+		 char * const argv[], char * const envp[]);
+
+/* Initialize data structure with attributes for `spawn' to default values. */
+inline static int
+posix_spawnattr_init(posix_spawnattr_t *attr)
+{
+	memset(attr, 0, sizeof(*attr));
+	return 0;
+}
+
+/* Free resources associated with ATTR.  */
+inline static int
+posix_spawnattr_destroy(posix_spawnattr_t *attr)
+{
+	return 0;
+}
+
+/* Store signal mask for signals with default handling from ATTR in
+   SIGDEFAULT.  */
+inline static int
+posix_spawnattr_getsigdefault(const posix_spawnattr_t *attr,
+			      sigset_t *sigdefault)
+{
+	memcpy(sigdefault, &attr->__sd, sizeof(sigset_t));
+	return 0;
+}
+
+
+/* Set signal mask for signals with default handling in ATTR to SIGDEFAULT.  */
+inline static int
+posix_spawnattr_setsigdefault(posix_spawnattr_t *attr,
+			      const sigset_t *sigdefault)
+{
+	memcpy(&attr->__sd, sigdefault, sizeof(sigset_t));
+	return 0;
+}
+
+/* Store signal mask for the new process from ATTR in SIGMASK.  */
+inline static int
+posix_spawnattr_getsigmask(const posix_spawnattr_t *attr,
+			   sigset_t *sigmask)
+{
+	memcpy(sigmask, &attr->__ss, sizeof(sigset_t));
+	return 0;
+}
+
+
+/* Set signal mask for the new process in ATTR to SIGMASK.  */
+inline static int
+posix_spawnattr_setsigmask(posix_spawnattr_t *attr,
+			   const sigset_t *sigmask)
+{
+	memcpy(&attr->__ss, sigmask, sizeof(sigset_t));
+	return 0;
+}
+
+/* Get flag word from the attribute structure.  */
+inline static int
+posix_spawnattr_getflags(const posix_spawnattr_t *attr, short int *flags)
+{
+	*flags = attr->__flags;
+	return 0;
+}
+
+/* Store flags in the attribute structure.  */
+inline static int
+posix_spawnattr_setflags(posix_spawnattr_t *attr, short int flags)
+{
+	/* Check no invalid bits are set.  */
+	if (flags & ~__POSIX_SPAWN_MASK)
+		return EINVAL;
+
+	attr->__flags = flags;
+	return 0;
+}
+
+/* Get process group ID from the attribute structure.  */
+inline static int
+posix_spawnattr_getpgroup(const posix_spawnattr_t *attr, pid_t *pgroup)
+{
+	*pgroup = attr->__pgrp;
+	return 0;
+}
+
+/* Store process group ID in the attribute structure.  */
+inline static int
+posix_spawnattr_setpgroup(posix_spawnattr_t *attr, pid_t pgroup)
+{
+	attr->__pgrp = pgroup;
+	return 0;
+}
+
+/* Get scheduling policy from the attribute structure.  */
+inline static int
+posix_spawnattr_getschedpolicy(const posix_spawnattr_t *attr,
+			       int *schedpolicy)
+{
+	*schedpolicy = attr->__policy;
+	return 0;
+}
+
+/* Store scheduling policy in the attribute structure.  */
+inline static int
+posix_spawnattr_setschedpolicy(posix_spawnattr_t *attr, int schedpolicy)
+{
+	switch (schedpolicy) {
+	case SCHED_OTHER:
+	case SCHED_FIFO:
+	case SCHED_RR:
+		break;
+	default:
+		return EINVAL;
+	}
+
+	attr->__policy = schedpolicy;
+	return 0;
+}
+
+/* Get scheduling parameters from the attribute structure.  */
+static inline int
+posix_spawnattr_getschedparam(const posix_spawnattr_t *attr,
+			      struct sched_param *schedparam)
+{
+	memcpy(schedparam, &attr->__sp, sizeof(attr->__sp));
+	return 0;
+}
+
+/* Store scheduling parameters in the attribute structure.  */
+static inline int
+posix_spawnattr_setschedparam(posix_spawnattr_t *attr,
+			      const struct sched_param *schedparam)
+{
+	attr->__sp = *schedparam;
+	return 0;
+}
+
+/* Initialize data structure for file attribute for `spawn' call.  */
+inline static int
+posix_spawn_file_actions_init(posix_spawn_file_actions_t *file_actions)
+{
+	memset(file_actions, 0, sizeof(*file_actions));
+	return 0;
+}
+
+/* Free resources associated with FILE-ACTIONS.  */
+inline static int
+posix_spawn_file_actions_destroy(posix_spawn_file_actions_t *file_actions)
+{
+	free(file_actions->__actions);
+	return 0;
+}
+
+/* Add an action to FILE-ACTIONS which tells the implementation to call
+   `open' for the given file during the `spawn' call.  */
+int posix_spawn_file_actions_addopen(posix_spawn_file_actions_t * restrict
+				     file_actions, int fd,
+				     const char * restrict path,
+				     int oflag, mode_t mode)
+     __THROW;
+
+/* Add an action to FILE-ACTIONS which tells the implementation to call
+   `close' for the given file descriptor during the `spawn' call.  */
+int posix_spawn_file_actions_addclose(posix_spawn_file_actions_t *file_actions,
+				      int fd)
+     __THROW;
+
+/* Add an action to FILE-ACTIONS which tells the implementation to call
+   `dup2' for the given file descriptors during the `spawn' call.  */
+int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *file_actions,
+				     int fd, int newfd) __THROW;
+
+__END_DECLS
+
+#endif /* spawn.h */

librt/Makefile.in

@@ -33,6 +33,14 @@ else
 librt_filter_SRC += clock_nanosleep.c clock_getcpuclockid.c clock_gettime.c
 librt_SSRC :=
 endif
+
+librt_filter_SRC += $(if $(UCLIBC_HAS_ADVANCED_REALTIME),, \
+	spawn.c \
+	spawn_faction_addclose.c \
+	spawn_faction_adddup2.c \
+	spawn_faction_addopen.c \
+	spawn_faction_init.c)
+
 librt_SRC := $(filter-out $(librt_filter_SRC),$(librt_SRC))
 
 librt_OBJ := $(patsubst %.c,$(librt_OUT)/%.o,$(librt_SRC))

librt/spawn.c

@@ -0,0 +1,259 @@
+/* Copyright (C) 2000, 2011 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <alloca.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <fcntl.h>
+
+#include <sys/resource.h>
+#include <not-cancel.h>
+
+#include <spawn.h>
+#include "spawn_int.h"
+
+/* The Unix standard contains a long explanation of the way to signal
+   an error after the fork() was successful.  Since no new wait status
+   was wanted there is no way to signal an error using one of the
+   available methods.  The committee chose to signal an error by a
+   normal program exit with the exit code 127.  */
+#define SPAWN_ERROR	127
+
+/* Execute file actions.
+ * Returns true on error.
+ */
+inline static bool execute_file_actions(const posix_spawn_file_actions_t *fa)
+{
+	struct rlimit64 fdlimit;
+	bool have_fdlimit = false;
+
+	for (int cnt = 0; cnt < fa->__used; ++cnt) {
+		struct __spawn_action *action = &fa->__actions[cnt];
+
+		switch (action->tag) {
+		case spawn_do_close:
+			if (close_not_cancel(action->action.close_action.fd) != 0) {
+				if (!have_fdlimit) {
+					getrlimit64(RLIMIT_NOFILE, &fdlimit);
+					have_fdlimit = true;
+				}
+
+				/* Only signal errors for file descriptors out of range.  */
+				if (0 > action->action.close_action.fd
+				    || action->action.close_action.fd >= fdlimit.rlim_cur)
+					/* Signal the error.  */
+					return true;
+			}
+			break;
+
+		case spawn_do_open:;
+			int new_fd = open_not_cancel(action->action.open_action.path,
+						     action->action.open_action.oflag
+						     | O_LARGEFILE,
+						     action->action.open_action.mode);
+
+			if (new_fd == -1)
+				return true;
+
+			/* Make sure the desired file descriptor is used.  */
+			if (new_fd != action->action.open_action.fd) {
+				if (dup2(new_fd, action->action.open_action.fd)
+				    != action->action.open_action.fd)
+					return true;
+
+				if (close_not_cancel(new_fd) != 0)
+					return true;
+			}
+			break;
+
+		case spawn_do_dup2:
+			if (dup2(action->action.dup2_action.fd,
+				   action->action.dup2_action.newfd)
+			    != action->action.dup2_action.newfd)
+				return true;
+			break;
+		}
+	}
+
+	return false;
+}
+
+#define DANGEROUS (POSIX_SPAWN_SETSIGMASK		\
+		   | POSIX_SPAWN_SETSIGDEF		\
+		   | POSIX_SPAWN_SETSCHEDPARAM		\
+		   | POSIX_SPAWN_SETSCHEDULER		\
+		   | POSIX_SPAWN_SETPGROUP		\
+		   | POSIX_SPAWN_RESETIDS)
+inline static bool is_vfork_safe(short int flags)
+{
+	return ((flags & POSIX_SPAWN_USEVFORK) || !(flags & DANGEROUS));
+}
+
+
+/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS. */
+static int
+__spawni(pid_t *pid, const char *file,
+	 const posix_spawn_file_actions_t *fa,
+	 const posix_spawnattr_t *attrp, char *const argv[],
+	 char *const envp[], const char *path)
+{
+	short int flags = attrp ? attrp->__flags : 0;
+
+	pid_t new_pid;
+	if (is_vfork_safe(flags) && !fa)
+		new_pid = vfork();
+	else
+		new_pid = fork();
+
+	if (new_pid) {
+		if (new_pid < 0)
+			return errno;
+
+		if (pid)
+			*pid = new_pid;
+
+		return 0;
+	}
+
+	if (flags & POSIX_SPAWN_SETSIGMASK) {
+		if (sigprocmask(SIG_SETMASK, &attrp->__ss, NULL) != 0)
+			goto error;
+	}
+
+	if (flags & POSIX_SPAWN_SETSIGDEF) {
+		/* We have to iterate over all signals.  This could possibly be
+		   done better but it requires system specific solutions since
+		   the sigset_t data type can be very different on different
+		   architectures.  */
+		struct sigaction sa;
+
+		memset(&sa, 0, sizeof(sa));
+		sa.sa_handler = SIG_DFL;
+
+		for (int sig = 1; sig <= _NSIG; ++sig) {
+			if (sigismember(&attrp->__sd, sig)) {
+				if (sigaction(sig, &sa, NULL) != 0)
+					goto error;
+			}
+		}
+	}
+
+	if (flags & POSIX_SPAWN_SETSCHEDULER) {
+		if (sched_setscheduler(0, attrp->__policy, &attrp->__sp) == -1)
+			goto error;
+	} else if (flags & POSIX_SPAWN_SETSCHEDPARAM) {
+		if (sched_setparam(0, &attrp->__sp) == -1)
+			goto error;
+	}
+
+	if (flags & POSIX_SPAWN_SETPGROUP) {
+		if (setpgid(0, attrp->__pgrp) != 0)
+			goto error;
+	}
+
+	if (flags & POSIX_SPAWN_RESETIDS) {
+		if (seteuid(getuid()) || setegid(getgid()))
+			goto error;
+	}
+
+	if (fa && execute_file_actions(fa))
+		goto error;
+
+	if (!path || strchr(file, '/')) {
+		execve(file, argv, envp);
+		goto error;
+	}
+
+
+	char *name;
+	{
+		size_t filelen = strlen(file) + 1;
+		size_t pathlen = strlen(path) + 1;
+		name = alloca(pathlen + filelen);
+
+		/* Copy the file name at the top. */
+		name = (char *) memcpy(name + pathlen, file, filelen);
+
+		/* And add the slash.  */
+		*--name = '/';
+	}
+
+	char *p;
+	do {
+		char *startp;
+		p = strchrnul(path, ':');
+
+		/* Two adjacent colons, or a colon at the beginning or the end
+		   of `PATH' means to search the current directory.  */
+		if (p == path)
+			startp = name + 1;
+		else
+			startp = (char *) memcpy(name - (p - path), path, p - path);
+
+		execve(startp, argv, envp);
+
+		switch (errno) {
+		case EACCES:
+		case ENOENT:
+		case ESTALE:
+		case ENOTDIR:
+			/* Those errors indicate the file is missing or not
+			   executable by us, in which case we want to just try
+			   the next path directory. */
+			break;
+		default:
+			/* Some other error means we found an executable file,
+			   but something went wrong executing it; return the
+			   error to our caller. */
+			goto error;
+		}
+
+		path = p;
+	} while (*p++ != '\0');
+
+error:
+	_exit(SPAWN_ERROR);
+}
+
+/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS. */
+int posix_spawn (pid_t *pid, const char *path,
+	       const posix_spawn_file_actions_t *fa,
+	       const posix_spawnattr_t *attrp, char *const argv[],
+	       char *const envp[])
+{
+	return __spawni(pid, path, fa, attrp, argv, envp, NULL);
+}
+
+/* Spawn a new process executing FILE with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS. */
+int
+posix_spawnp(pid_t *pid, const char *file,
+	     const posix_spawn_file_actions_t *fa,
+	     const posix_spawnattr_t *attrp, char *const argv[],
+	     char *const envp[])
+{
+	const char *path = getenv("PATH");
+
+	if (!path)
+		path = ":/bin:/usr/bin";
+
+	return __spawni(pid, file, fa, attrp, argv, envp, path);
+}

librt/spawn_faction_addclose.c

@@ -0,0 +1,51 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <spawn.h>
+#include <unistd.h>
+
+#include "spawn_int.h"
+
+/* Add an action to FILE-ACTIONS which tells the implementation to call
+   `close' for the given file descriptor during the `spawn' call.  */
+int
+posix_spawn_file_actions_addclose(posix_spawn_file_actions_t *file_actions,
+				  int fd)
+{
+	int maxfd = sysconf(_SC_OPEN_MAX);
+	struct __spawn_action *rec;
+
+	/* Test for the validity of the file descriptor.  */
+	if (fd < 0 || fd >= maxfd)
+		return EBADF;
+
+	/* Allocate more memory if needed.  */
+	if (file_actions->__used == file_actions->__allocated
+	    && __posix_spawn_file_actions_realloc(file_actions) != 0)
+		/* This can only mean we ran out of memory.  */
+		return ENOMEM;
+
+	/* Add the new value.  */
+	rec = &file_actions->__actions[file_actions->__used];
+	rec->tag = spawn_do_close;
+	rec->action.open_action.fd = fd;
+
+	/* Account for the new entry.  */
+	++file_actions->__used;
+	return 0;
+}

librt/spawn_faction_adddup2.c

@@ -0,0 +1,52 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <spawn.h>
+#include <unistd.h>
+
+#include "spawn_int.h"
+
+/* Add an action to FILE-ACTIONS which tells the implementation to call
+   `dup2' for the given file descriptors during the `spawn' call.  */
+int
+posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *file_actions,
+				 int fd, int newfd)
+{
+	int maxfd = sysconf(_SC_OPEN_MAX);
+	struct __spawn_action *rec;
+
+	/* Test for the validity of the file descriptor.  */
+	if (fd < 0 || newfd < 0 || fd >= maxfd || newfd >= maxfd)
+		return EBADF;
+
+	/* Allocate more memory if needed.  */
+	if (file_actions->__used == file_actions->__allocated
+	    && __posix_spawn_file_actions_realloc (file_actions) != 0)
+		/* This can only mean we ran out of memory.  */
+		return ENOMEM;
+
+	/* Add the new value.  */
+	rec = &file_actions->__actions[file_actions->__used];
+	rec->tag = spawn_do_dup2;
+	rec->action.dup2_action.fd = fd;
+	rec->action.dup2_action.newfd = newfd;
+
+	/* Account for the new entry.  */
+	++file_actions->__used;
+	return 0;
+}

librt/spawn_faction_addopen.c

@@ -0,0 +1,55 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <spawn.h>
+#include <unistd.h>
+
+#include "spawn_int.h"
+
+/* Add an action to FILE-ACTIONS which tells the implementation to call
+   `open' for the given file during the `spawn' call.  */
+int
+posix_spawn_file_actions_addopen(posix_spawn_file_actions_t *file_actions,
+				 int fd, const char *path, int oflag,
+				 mode_t mode)
+{
+	int maxfd = sysconf(_SC_OPEN_MAX);
+	struct __spawn_action *rec;
+
+	/* Test for the validity of the file descriptor.  */
+	if (fd < 0 || fd >= maxfd)
+		return EBADF;
+
+	/* Allocate more memory if needed.  */
+	if (file_actions->__used == file_actions->__allocated
+	    && __posix_spawn_file_actions_realloc (file_actions) != 0)
+		/* This can only mean we ran out of memory.  */
+		return ENOMEM;
+
+	/* Add the new value.  */
+	rec = &file_actions->__actions[file_actions->__used];
+	rec->tag = spawn_do_open;
+	rec->action.open_action.fd = fd;
+	rec->action.open_action.path = path;
+	rec->action.open_action.oflag = oflag;
+	rec->action.open_action.mode = mode;
+
+	/* Account for the new entry.  */
+	++file_actions->__used;
+	return 0;
+}

librt/spawn_faction_init.c

@@ -0,0 +1,42 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <spawn.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "spawn_int.h"
+
+
+/* Function used to increase the size of the allocated array.  This
+   function is called from the `add'-functions.  */
+int
+__posix_spawn_file_actions_realloc(posix_spawn_file_actions_t *file_actions)
+{
+	int newalloc = file_actions->__allocated + 8;
+	void *newmem = realloc(file_actions->__actions,
+			       newalloc * sizeof(struct __spawn_action));
+
+	if (newmem == NULL)
+		/* Not enough memory.  */
+		return ENOMEM;
+
+	file_actions->__actions = (struct __spawn_action *)newmem;
+	file_actions->__allocated = newalloc;
+	return 0;
+}

librt/spawn_int.h

@@ -0,0 +1,26 @@
+/* Data structure to contain the action information.  */
+struct __spawn_action {
+	enum {
+		spawn_do_close,
+		spawn_do_dup2,
+		spawn_do_open
+	} tag;
+
+	union {
+		struct {
+			int fd;
+		} close_action;
+		struct {
+			int fd;
+			int newfd;
+		} dup2_action;
+		struct {
+			int fd;
+			const char *path;
+			int oflag;
+			mode_t mode;
+		} open_action;
+	} action;
+};
+
+int __posix_spawn_file_actions_realloc(posix_spawn_file_actions_t *fa);