[GitHub/mt8127/android_kernel_alcatel_ttab.git] / kernel / kmod.c

/*
	kmod, the new module loader (replaces kerneld)
	Kirk Petersen

	Reorganized not to be a daemon by Adam Richter, with guidance
	from Greg Zornetzer.

	Modified to avoid chroot and file sharing problems.
	Mikael Pettersson

	Limit the concurrent number of kmod modprobes to catch loops from
	"modprobe needs a service that is in a module".
	Keith Owens <kaos@ocs.com.au> December 1999

	Unblock all signals when we exec a usermode process.
	Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000

	call_usermodehelper wait flag, and remove exec_usermodehelper.
	Rusty Russell <rusty@rustcorp.com.au>  Jan 2003
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/mnt_namespace.h>
#include <linux/completion.h>
#include <linux/file.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/resource.h>
#include <asm/uaccess.h>

extern int max_threads;

static struct workqueue_struct *khelper_wq;

#ifdef CONFIG_KMOD

/*
	modprobe_path is set via /proc/sys.
*/
char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";

/**
 * request_module - try to load a kernel module
 * @fmt:     printf style format string for the name of the module
 * @varargs: arguements as specified in the format string
 *
 * Load a module using the user mode module loader. The function returns
 * zero on success or a negative errno code on failure. Note that a
 * successful module load does not mean the module did not then unload
 * and exit on an error of its own. Callers must check that the service
 * they requested is now available not blindly invoke it.
 *
 * If module auto-loading support is disabled then this function
 * becomes a no-operation.
 */
int request_module(const char *fmt, ...)
{
	va_list args;
	char module_name[MODULE_NAME_LEN];
	unsigned int max_modprobes;
	int ret;
	char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
	static char *envp[] = { "HOME=/",
				"TERM=linux",
				"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
				NULL };
	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
#define MAX_KMOD_CONCURRENT 50	/* Completely arbitrary value - KAO */
	static int kmod_loop_msg;

	va_start(args, fmt);
	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
	va_end(args);
	if (ret >= MODULE_NAME_LEN)
		return -ENAMETOOLONG;

	/* If modprobe needs a service that is in a module, we get a recursive
	 * loop.  Limit the number of running kmod threads to max_threads/2 or
	 * MAX_KMOD_CONCURRENT, whichever is the smaller.  A cleaner method
	 * would be to run the parents of this process, counting how many times
	 * kmod was invoked.  That would mean accessing the internals of the
	 * process tables to get the command line, proc_pid_cmdline is static
	 * and it is not worth changing the proc code just to handle this case. 
	 * KAO.
	 *
	 * "trace the ppid" is simple, but will fail if someone's
	 * parent exits.  I think this is as good as it gets. --RR
	 */
	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
	atomic_inc(&kmod_concurrent);
	if (atomic_read(&kmod_concurrent) > max_modprobes) {
		/* We may be blaming an innocent here, but unlikely */
		if (kmod_loop_msg++ < 5)
			printk(KERN_ERR
			       "request_module: runaway loop modprobe %s\n",
			       module_name);
		atomic_dec(&kmod_concurrent);
		return -ENOMEM;
	}

	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
	atomic_dec(&kmod_concurrent);
	return ret;
}
EXPORT_SYMBOL(request_module);
#endif /* CONFIG_KMOD */

struct subprocess_info {
	struct work_struct work;
	struct completion *complete;
	char *path;
	char **argv;
	char **envp;
	struct key *ring;
	int wait;
	int retval;
	struct file *stdin;
};

/*
 * This is the task which runs the usermode application
 */
static int ____call_usermodehelper(void *data)
{
	struct subprocess_info *sub_info = data;
	struct key *new_session, *old_session;
	int retval;

	/* Unblock all signals and set the session keyring. */
	new_session = key_get(sub_info->ring);
	flush_signals(current);
	spin_lock_irq(&current->sighand->siglock);
	old_session = __install_session_keyring(current, new_session);
	flush_signal_handlers(current, 1);
	sigemptyset(&current->blocked);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	key_put(old_session);

	/* Install input pipe when needed */
	if (sub_info->stdin) {
		struct files_struct *f = current->files;
		struct fdtable *fdt;
		/* no races because files should be private here */
		sys_close(0);
		fd_install(0, sub_info->stdin);
		spin_lock(&f->file_lock);
		fdt = files_fdtable(f);
		FD_SET(0, fdt->open_fds);
		FD_CLR(0, fdt->close_on_exec);
		spin_unlock(&f->file_lock);

		/* and disallow core files too */
		current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
	}

	/* We can run anywhere, unlike our parent keventd(). */
	set_cpus_allowed(current, CPU_MASK_ALL);

	/*
	 * Our parent is keventd, which runs with elevated scheduling priority.
	 * Avoid propagating that into the userspace child.
	 */
	set_user_nice(current, 0);

	retval = -EPERM;
	if (current->fs->root)
		retval = kernel_execve(sub_info->path,
				sub_info->argv, sub_info->envp);

	/* Exec failed? */
	sub_info->retval = retval;
	do_exit(0);
}

/* Keventd can't block, but this (a child) can. */
static int wait_for_helper(void *data)
{
	struct subprocess_info *sub_info = data;
	pid_t pid;
	struct k_sigaction sa;

	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	 * populate the status, but will return -ECHILD. */
	sa.sa.sa_handler = SIG_IGN;
	sa.sa.sa_flags = 0;
	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
	do_sigaction(SIGCHLD, &sa, NULL);
	allow_signal(SIGCHLD);

	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	if (pid < 0) {
		sub_info->retval = pid;
	} else {
		int ret;

		/*
		 * Normally it is bogus to call wait4() from in-kernel because
		 * wait4() wants to write the exit code to a userspace address.
		 * But wait_for_helper() always runs as keventd, and put_user()
		 * to a kernel address works OK for kernel threads, due to their
		 * having an mm_segment_t which spans the entire address space.
		 *
		 * Thus the __user pointer cast is valid here.
		 */
		sys_wait4(pid, (int __user *)&ret, 0, NULL);

		/*
		 * If ret is 0, either ____call_usermodehelper failed and the
		 * real error code is already in sub_info->retval or
		 * sub_info->retval is 0 anyway, so don't mess with it then.
		 */
		if (ret)
			sub_info->retval = ret;
	}

	if (sub_info->wait < 0)
		kfree(sub_info);
	else
		complete(sub_info->complete);
	return 0;
}

/* This is run by khelper thread  */
static void __call_usermodehelper(struct work_struct *work)
{
	struct subprocess_info *sub_info =
		container_of(work, struct subprocess_info, work);
	pid_t pid;
	int wait = sub_info->wait;

	/* CLONE_VFORK: wait until the usermode helper has execve'd
	 * successfully We need the data structures to stay around
	 * until that is done.  */
	if (wait)
		pid = kernel_thread(wait_for_helper, sub_info,
				    CLONE_FS | CLONE_FILES | SIGCHLD);
	else
		pid = kernel_thread(____call_usermodehelper, sub_info,
				    CLONE_VFORK | SIGCHLD);

	if (wait < 0)
		return;

	if (pid < 0) {
		sub_info->retval = pid;
		complete(sub_info->complete);
	} else if (!wait)
		complete(sub_info->complete);
}

/**
 * call_usermodehelper_keys - start a usermode application
 * @path: pathname for the application
 * @argv: null-terminated argument list
 * @envp: null-terminated environment list
 * @session_keyring: session keyring for process (NULL for an empty keyring)
 * @wait: wait for the application to finish and return status.
 *        when -1 don't wait at all, but you get no useful error back when
 *        the program couldn't be exec'ed. This makes it safe to call
 *        from interrupt context.
 *
 * Runs a user-space application.  The application is started
 * asynchronously if wait is not set, and runs as a child of keventd.
 * (ie. it runs with full root capabilities).
 *
 * Must be called from process context.  Returns a negative error code
 * if program was not execed successfully, or 0.
 */
int call_usermodehelper_keys(char *path, char **argv, char **envp,
			     struct key *session_keyring, int wait)
{
	DECLARE_COMPLETION_ONSTACK(done);
	struct subprocess_info *sub_info;
	int retval;

	if (!khelper_wq)
		return -EBUSY;

	if (path[0] == '\0')
		return 0;

	sub_info = kzalloc(sizeof(struct subprocess_info),  GFP_ATOMIC);
	if (!sub_info)
		return -ENOMEM;

	INIT_WORK(&sub_info->work, __call_usermodehelper);
	sub_info->complete = &done;
	sub_info->path = path;
	sub_info->argv = argv;
	sub_info->envp = envp;
	sub_info->ring = session_keyring;
	sub_info->wait = wait;

	queue_work(khelper_wq, &sub_info->work);
	if (wait < 0) /* task has freed sub_info */
		return 0;
	wait_for_completion(&done);
	retval = sub_info->retval;
	kfree(sub_info);
	return retval;
}
EXPORT_SYMBOL(call_usermodehelper_keys);

int call_usermodehelper_pipe(char *path, char **argv, char **envp,
			     struct file **filp)
{
	DECLARE_COMPLETION(done);
	struct subprocess_info sub_info = {
		.work		= __WORK_INITIALIZER(sub_info.work,
						     __call_usermodehelper),
		.complete	= &done,
		.path		= path,
		.argv		= argv,
		.envp		= envp,
		.retval		= 0,
	};
	struct file *f;

	if (!khelper_wq)
		return -EBUSY;

	if (path[0] == '\0')
		return 0;

	f = create_write_pipe();
	if (IS_ERR(f))
		return PTR_ERR(f);
	*filp = f;

	f = create_read_pipe(f);
	if (IS_ERR(f)) {
		free_write_pipe(*filp);
		return PTR_ERR(f);
	}
	sub_info.stdin = f;

	queue_work(khelper_wq, &sub_info.work);
	wait_for_completion(&done);
	return sub_info.retval;
}
EXPORT_SYMBOL(call_usermodehelper_pipe);

void __init usermodehelper_init(void)
{
	khelper_wq = create_singlethread_workqueue("khelper");
	BUG_ON(!khelper_wq);
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	kmod, the new module loader (replaces kerneld)
	3	Kirk Petersen
	4
	5	Reorganized not to be a daemon by Adam Richter, with guidance
	6	from Greg Zornetzer.
	7
	8	Modified to avoid chroot and file sharing problems.
	9	Mikael Pettersson
	10
	11	Limit the concurrent number of kmod modprobes to catch loops from
	12	"modprobe needs a service that is in a module".
	13	Keith Owens <kaos@ocs.com.au> December 1999
	14
	15	Unblock all signals when we exec a usermode process.
	16	Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
	17
	18	call_usermodehelper wait flag, and remove exec_usermodehelper.
	19	Rusty Russell <rusty@rustcorp.com.au> Jan 2003
	20	*/
1da177e4 LT	21	#include <linux/module.h>
	22	#include <linux/sched.h>
	23	#include <linux/syscalls.h>
	24	#include <linux/unistd.h>
	25	#include <linux/kmod.h>
1da177e4	26	#include <linux/slab.h>
6b3286ed	27	#include <linux/mnt_namespace.h>
1da177e4 LT	28	#include <linux/completion.h>
	29	#include <linux/file.h>
	30	#include <linux/workqueue.h>
	31	#include <linux/security.h>
	32	#include <linux/mount.h>
	33	#include <linux/kernel.h>
	34	#include <linux/init.h>
d025c9db	35	#include <linux/resource.h>
1da177e4 LT	36	#include <asm/uaccess.h>
	37
	38	extern int max_threads;
	39
	40	static struct workqueue_struct *khelper_wq;
	41
	42	#ifdef CONFIG_KMOD
	43
	44	/*
	45	modprobe_path is set via /proc/sys.
	46	*/
	47	char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
	48
	49	/**
	50	* request_module - try to load a kernel module
	51	* @fmt: printf style format string for the name of the module
	52	* @varargs: arguements as specified in the format string
	53	*
	54	* Load a module using the user mode module loader. The function returns
	55	* zero on success or a negative errno code on failure. Note that a
	56	* successful module load does not mean the module did not then unload
	57	* and exit on an error of its own. Callers must check that the service
	58	* they requested is now available not blindly invoke it.
	59	*
	60	* If module auto-loading support is disabled then this function
	61	* becomes a no-operation.
	62	*/
	63	int request_module(const char *fmt, ...)
	64	{
	65	va_list args;
	66	char module_name[MODULE_NAME_LEN];
	67	unsigned int max_modprobes;
	68	int ret;
	69	char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
	70	static char *envp[] = { "HOME=/",
	71	"TERM=linux",
	72	"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
	73	NULL };
	74	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
	75	#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
	76	static int kmod_loop_msg;
	77
	78	va_start(args, fmt);
	79	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
	80	va_end(args);
	81	if (ret >= MODULE_NAME_LEN)
	82	return -ENAMETOOLONG;
	83
	84	/* If modprobe needs a service that is in a module, we get a recursive
	85	* loop. Limit the number of running kmod threads to max_threads/2 or
	86	* MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
	87	* would be to run the parents of this process, counting how many times
	88	* kmod was invoked. That would mean accessing the internals of the
	89	* process tables to get the command line, proc_pid_cmdline is static
	90	* and it is not worth changing the proc code just to handle this case.
	91	* KAO.
	92	*
	93	* "trace the ppid" is simple, but will fail if someone's
	94	* parent exits. I think this is as good as it gets. --RR
	95	*/
	96	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
	97	atomic_inc(&kmod_concurrent);
	98	if (atomic_read(&kmod_concurrent) > max_modprobes) {
	99	/* We may be blaming an innocent here, but unlikely */
100	if (kmod_loop_msg++ < 5)
101	printk(KERN_ERR
102	"request_module: runaway loop modprobe %s\n",
103	module_name);
104	atomic_dec(&kmod_concurrent);
105	return -ENOMEM;
106	}
107
108	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
109	atomic_dec(&kmod_concurrent);
110	return ret;
111	}
112	EXPORT_SYMBOL(request_module);
113	#endif /* CONFIG_KMOD */
114
115	struct subprocess_info {
65f27f38	116	struct work_struct work;
1da177e4 LT	117	struct completion *complete;
	118	char *path;
	119	char **argv;
	120	char **envp;
7888e7ff	121	struct key *ring;
1da177e4 LT	122	int wait;
1da177e4 LT	123	int retval;
e239ca54	124	struct file *stdin;
1da177e4 LT	125	};
	126
	127	/*
	128	* This is the task which runs the usermode application
	129	*/
	130	static int ____call_usermodehelper(void *data)
	131	{
	132	struct subprocess_info *sub_info = data;
20e1129a	133	struct key new_session, old_session;
1da177e4 LT	134	int retval;
1da177e4 LT	135
7888e7ff	136	/* Unblock all signals and set the session keyring. */
20e1129a	137	new_session = key_get(sub_info->ring);
1da177e4 LT	138	flush_signals(current);
1da177e4 LT	139	spin_lock_irq(&current->sighand->siglock);
20e1129a	140	old_session = __install_session_keyring(current, new_session);
1da177e4 LT	141	flush_signal_handlers(current, 1);
	142	sigemptyset(&current->blocked);
	143	recalc_sigpending();
	144	spin_unlock_irq(&current->sighand->siglock);
	145
7888e7ff DH	146	key_put(old_session);
7888e7ff DH	147
e239ca54 AK	148	/* Install input pipe when needed */
	149	if (sub_info->stdin) {
	150	struct files_struct *f = current->files;
	151	struct fdtable *fdt;
	152	/* no races because files should be private here */
	153	sys_close(0);
	154	fd_install(0, sub_info->stdin);
	155	spin_lock(&f->file_lock);
	156	fdt = files_fdtable(f);
	157	FD_SET(0, fdt->open_fds);
	158	FD_CLR(0, fdt->close_on_exec);
	159	spin_unlock(&f->file_lock);
d025c9db AK	160
	161	/* and disallow core files too */
	162	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
e239ca54 AK	163	}
e239ca54 AK	164
1da177e4 LT	165	/* We can run anywhere, unlike our parent keventd(). */
	166	set_cpus_allowed(current, CPU_MASK_ALL);
	167
b73a7e76 JE	168	/*
	169	* Our parent is keventd, which runs with elevated scheduling priority.
	170	* Avoid propagating that into the userspace child.
	171	*/
	172	set_user_nice(current, 0);
	173
1da177e4 LT	174	retval = -EPERM;
1da177e4 LT	175	if (current->fs->root)
67608567 AB	176	retval = kernel_execve(sub_info->path,
67608567 AB	177	sub_info->argv, sub_info->envp);
1da177e4 LT	178
	179	/* Exec failed? */
	180	sub_info->retval = retval;
	181	do_exit(0);
	182	}
	183
	184	/* Keventd can't block, but this (a child) can. */
	185	static int wait_for_helper(void *data)
	186	{
	187	struct subprocess_info *sub_info = data;
	188	pid_t pid;
	189	struct k_sigaction sa;
	190
	191	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	192	* populate the status, but will return -ECHILD. */
	193	sa.sa.sa_handler = SIG_IGN;
	194	sa.sa.sa_flags = 0;
	195	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
8292d633	196	do_sigaction(SIGCHLD, &sa, NULL);
1da177e4 LT	197	allow_signal(SIGCHLD);
	198
	199	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	200	if (pid < 0) {
	201	sub_info->retval = pid;
	202	} else {
111dbe0c BS	203	int ret;
111dbe0c BS	204
1da177e4 LT	205	/*
	206	* Normally it is bogus to call wait4() from in-kernel because
	207	* wait4() wants to write the exit code to a userspace address.
	208	* But wait_for_helper() always runs as keventd, and put_user()
	209	* to a kernel address works OK for kernel threads, due to their
	210	* having an mm_segment_t which spans the entire address space.
	211	*
	212	* Thus the __user pointer cast is valid here.
	213	*/
111dbe0c BS	214	sys_wait4(pid, (int __user *)&ret, 0, NULL);
	215
	216	/*
	217	* If ret is 0, either ____call_usermodehelper failed and the
	218	* real error code is already in sub_info->retval or
	219	* sub_info->retval is 0 anyway, so don't mess with it then.
	220	*/
	221	if (ret)
	222	sub_info->retval = ret;
1da177e4 LT	223	}
1da177e4 LT	224
a98f0dd3 AK	225	if (sub_info->wait < 0)
	226	kfree(sub_info);
	227	else
	228	complete(sub_info->complete);
1da177e4 LT	229	return 0;
	230	}
	231
	232	/* This is run by khelper thread */
65f27f38	233	static void __call_usermodehelper(struct work_struct *work)
1da177e4	234	{
65f27f38 DH	235	struct subprocess_info *sub_info =
65f27f38 DH	236	container_of(work, struct subprocess_info, work);
1da177e4	237	pid_t pid;
e4b69aa2	238	int wait = sub_info->wait;
1da177e4 LT	239
	240	/* CLONE_VFORK: wait until the usermode helper has execve'd
	241	* successfully We need the data structures to stay around
	242	* until that is done. */
e4b69aa2	243	if (wait)
1da177e4 LT	244	pid = kernel_thread(wait_for_helper, sub_info,
	245	CLONE_FS \| CLONE_FILES \| SIGCHLD);
	246	else
	247	pid = kernel_thread(____call_usermodehelper, sub_info,
	248	CLONE_VFORK \| SIGCHLD);
	249
a98f0dd3 AK	250	if (wait < 0)
	251	return;
	252
1da177e4 LT	253	if (pid < 0) {
	254	sub_info->retval = pid;
	255	complete(sub_info->complete);
e4b69aa2	256	} else if (!wait)
1da177e4 LT	257	complete(sub_info->complete);
	258	}
	259
	260	/**
7888e7ff	261	* call_usermodehelper_keys - start a usermode application
1da177e4 LT	262	* @path: pathname for the application
	263	* @argv: null-terminated argument list
	264	* @envp: null-terminated environment list
7888e7ff	265	* @session_keyring: session keyring for process (NULL for an empty keyring)
1da177e4	266	* @wait: wait for the application to finish and return status.
a98f0dd3 AK	267	* when -1 don't wait at all, but you get no useful error back when
	268	* the program couldn't be exec'ed. This makes it safe to call
	269	* from interrupt context.
1da177e4 LT	270	*
	271	* Runs a user-space application. The application is started
	272	* asynchronously if wait is not set, and runs as a child of keventd.
	273	* (ie. it runs with full root capabilities).
	274	*
	275	* Must be called from process context. Returns a negative error code
	276	* if program was not execed successfully, or 0.
	277	*/
7888e7ff DH	278	int call_usermodehelper_keys(char path, char argv, char *envp,
7888e7ff DH	279	struct key *session_keyring, int wait)
1da177e4	280	{
60be6b9a	281	DECLARE_COMPLETION_ONSTACK(done);
a98f0dd3 AK	282	struct subprocess_info *sub_info;
a98f0dd3 AK	283	int retval;
1da177e4 LT	284
	285	if (!khelper_wq)
	286	return -EBUSY;
	287
	288	if (path[0] == '\0')
	289	return 0;
	290
a98f0dd3 AK	291	sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
	292	if (!sub_info)
	293	return -ENOMEM;
	294
	295	INIT_WORK(&sub_info->work, __call_usermodehelper);
	296	sub_info->complete = &done;
	297	sub_info->path = path;
	298	sub_info->argv = argv;
	299	sub_info->envp = envp;
	300	sub_info->ring = session_keyring;
	301	sub_info->wait = wait;
	302
	303	queue_work(khelper_wq, &sub_info->work);
	304	if (wait < 0) /* task has freed sub_info */
	305	return 0;
1da177e4	306	wait_for_completion(&done);
a98f0dd3 AK	307	retval = sub_info->retval;
	308	kfree(sub_info);
	309	return retval;
1da177e4	310	}
7888e7ff	311	EXPORT_SYMBOL(call_usermodehelper_keys);
1da177e4	312
e239ca54 AK	313	int call_usermodehelper_pipe(char path, char argv, char *envp,
	314	struct file **filp)
	315	{
	316	DECLARE_COMPLETION(done);
	317	struct subprocess_info sub_info = {
65f27f38 DH	318	.work = __WORK_INITIALIZER(sub_info.work,
65f27f38 DH	319	__call_usermodehelper),
e239ca54 AK	320	.complete = &done,
	321	.path = path,
	322	.argv = argv,
	323	.envp = envp,
	324	.retval = 0,
	325	};
	326	struct file *f;
e239ca54 AK	327
	328	if (!khelper_wq)
	329	return -EBUSY;
	330
	331	if (path[0] == '\0')
	332	return 0;
	333
	334	f = create_write_pipe();
3cce4856 AM	335	if (IS_ERR(f))
3cce4856 AM	336	return PTR_ERR(f);
e239ca54 AK	337	*filp = f;
	338
	339	f = create_read_pipe(f);
3cce4856	340	if (IS_ERR(f)) {
e239ca54	341	free_write_pipe(*filp);
3cce4856	342	return PTR_ERR(f);
e239ca54 AK	343	}
	344	sub_info.stdin = f;
	345
65f27f38	346	queue_work(khelper_wq, &sub_info.work);
e239ca54 AK	347	wait_for_completion(&done);
	348	return sub_info.retval;
	349	}
	350	EXPORT_SYMBOL(call_usermodehelper_pipe);
	351
1da177e4 LT	352	void __init usermodehelper_init(void)
	353	{
	354	khelper_wq = create_singlethread_workqueue("khelper");
	355	BUG_ON(!khelper_wq);
	356	}