[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
*/
#define __KERNEL_SYSCALLS__

#include <linux/config.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/kmod.h>
#include <linux/smp_lock.h>
#include <linux/slab.h>
#include <linux/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 <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 completion *complete;
	char *path;
	char **argv;
	char **envp;
	struct key *ring;
	int wait;
	int retval;
};

/*
 * 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);

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

	retval = -EPERM;
	if (current->fs->root)
		retval = 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, (struct k_sigaction *)0);
	allow_signal(SIGCHLD);

	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	if (pid < 0) {
		sub_info->retval = pid;
	} else {
		/*
		 * 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 *) &sub_info->retval, 0, NULL);
	}

	complete(sub_info->complete);
	return 0;
}

/* This is run by khelper thread  */
static void __call_usermodehelper(void *data)
{
	struct subprocess_info *sub_info = data;
	pid_t pid;

	/* CLONE_VFORK: wait until the usermode helper has execve'd
	 * successfully We need the data structures to stay around
	 * until that is done.  */
	if (sub_info->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 (pid < 0) {
		sub_info->retval = pid;
		complete(sub_info->complete);
	} else if (!sub_info->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.
 *
 * 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(done);
	struct subprocess_info sub_info = {
		.complete	= &done,
		.path		= path,
		.argv		= argv,
		.envp		= envp,
		.ring		= session_keyring,
		.wait		= wait,
		.retval		= 0,
	};
	DECLARE_WORK(work, __call_usermodehelper, &sub_info);

	if (!khelper_wq)
		return -EBUSY;

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

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

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	*/
	21	#define __KERNEL_SYSCALLS__
	22
	23	#include <linux/config.h>
	24	#include <linux/module.h>
	25	#include <linux/sched.h>
	26	#include <linux/syscalls.h>
	27	#include <linux/unistd.h>
	28	#include <linux/kmod.h>
	29	#include <linux/smp_lock.h>
	30	#include <linux/slab.h>
	31	#include <linux/namespace.h>
	32	#include <linux/completion.h>
	33	#include <linux/file.h>
	34	#include <linux/workqueue.h>
	35	#include <linux/security.h>
	36	#include <linux/mount.h>
	37	#include <linux/kernel.h>
	38	#include <linux/init.h>
	39	#include <asm/uaccess.h>
	40
	41	extern int max_threads;
	42
	43	static struct workqueue_struct *khelper_wq;
	44
	45	#ifdef CONFIG_KMOD
	46
	47	/*
	48	modprobe_path is set via /proc/sys.
	49	*/
	50	char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
	51
	52	/**
	53	* request_module - try to load a kernel module
	54	* @fmt: printf style format string for the name of the module
	55	* @varargs: arguements as specified in the format string
	56	*
	57	* Load a module using the user mode module loader. The function returns
	58	* zero on success or a negative errno code on failure. Note that a
	59	* successful module load does not mean the module did not then unload
	60	* and exit on an error of its own. Callers must check that the service
	61	* they requested is now available not blindly invoke it.
	62	*
	63	* If module auto-loading support is disabled then this function
	64	* becomes a no-operation.
65	*/
66	int request_module(const char *fmt, ...)
67	{
68	va_list args;
69	char module_name[MODULE_NAME_LEN];
70	unsigned int max_modprobes;
71	int ret;
72	char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
73	static char *envp[] = { "HOME=/",
74	"TERM=linux",
75	"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
76	NULL };
77	static atomic_t kmod_concurrent = ATOMIC_INIT(0);
78	#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
79	static int kmod_loop_msg;
80
81	va_start(args, fmt);
82	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
83	va_end(args);
84	if (ret >= MODULE_NAME_LEN)
85	return -ENAMETOOLONG;
86
87	/* If modprobe needs a service that is in a module, we get a recursive
88	* loop. Limit the number of running kmod threads to max_threads/2 or
89	* MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
90	* would be to run the parents of this process, counting how many times
91	* kmod was invoked. That would mean accessing the internals of the
92	* process tables to get the command line, proc_pid_cmdline is static
93	* and it is not worth changing the proc code just to handle this case.
94	* KAO.
95	*
96	* "trace the ppid" is simple, but will fail if someone's
97	* parent exits. I think this is as good as it gets. --RR
98	*/
99	max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
100	atomic_inc(&kmod_concurrent);
101	if (atomic_read(&kmod_concurrent) > max_modprobes) {
102	/* We may be blaming an innocent here, but unlikely */
103	if (kmod_loop_msg++ < 5)
104	printk(KERN_ERR
105	"request_module: runaway loop modprobe %s\n",
106	module_name);
107	atomic_dec(&kmod_concurrent);
108	return -ENOMEM;
109	}
110
111	ret = call_usermodehelper(modprobe_path, argv, envp, 1);
112	atomic_dec(&kmod_concurrent);
113	return ret;
114	}
115	EXPORT_SYMBOL(request_module);
116	#endif /* CONFIG_KMOD */
117
118	struct subprocess_info {
119	struct completion *complete;
120	char *path;
121	char **argv;
122	char **envp;
7888e7ff	123	struct key *ring;
1da177e4 LT	124	int wait;
	125	int retval;
	126	};
	127
	128	/*
	129	* This is the task which runs the usermode application
	130	*/
	131	static int ____call_usermodehelper(void *data)
	132	{
	133	struct subprocess_info *sub_info = data;
20e1129a	134	struct key new_session, old_session;
1da177e4 LT	135	int retval;
1da177e4 LT	136
7888e7ff	137	/* Unblock all signals and set the session keyring. */
20e1129a	138	new_session = key_get(sub_info->ring);
1da177e4 LT	139	flush_signals(current);
1da177e4 LT	140	spin_lock_irq(&current->sighand->siglock);
20e1129a	141	old_session = __install_session_keyring(current, new_session);
1da177e4 LT	142	flush_signal_handlers(current, 1);
	143	sigemptyset(&current->blocked);
	144	recalc_sigpending();
	145	spin_unlock_irq(&current->sighand->siglock);
	146
7888e7ff DH	147	key_put(old_session);
7888e7ff DH	148
1da177e4 LT	149	/* We can run anywhere, unlike our parent keventd(). */
	150	set_cpus_allowed(current, CPU_MASK_ALL);
	151
	152	retval = -EPERM;
	153	if (current->fs->root)
	154	retval = execve(sub_info->path, sub_info->argv,sub_info->envp);
	155
	156	/* Exec failed? */
	157	sub_info->retval = retval;
	158	do_exit(0);
	159	}
	160
	161	/* Keventd can't block, but this (a child) can. */
	162	static int wait_for_helper(void *data)
	163	{
	164	struct subprocess_info *sub_info = data;
	165	pid_t pid;
	166	struct k_sigaction sa;
	167
	168	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
	169	* populate the status, but will return -ECHILD. */
	170	sa.sa.sa_handler = SIG_IGN;
	171	sa.sa.sa_flags = 0;
	172	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
	173	do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
	174	allow_signal(SIGCHLD);
	175
	176	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
	177	if (pid < 0) {
	178	sub_info->retval = pid;
	179	} else {
	180	/*
	181	* Normally it is bogus to call wait4() from in-kernel because
	182	* wait4() wants to write the exit code to a userspace address.
	183	* But wait_for_helper() always runs as keventd, and put_user()
	184	* to a kernel address works OK for kernel threads, due to their
	185	* having an mm_segment_t which spans the entire address space.
	186	*
	187	* Thus the __user pointer cast is valid here.
	188	*/
	189	sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL);
	190	}
	191
	192	complete(sub_info->complete);
	193	return 0;
	194	}
	195
	196	/* This is run by khelper thread */
	197	static void __call_usermodehelper(void *data)
	198	{
	199	struct subprocess_info *sub_info = data;
	200	pid_t pid;
	201
	202	/* CLONE_VFORK: wait until the usermode helper has execve'd
	203	* successfully We need the data structures to stay around
	204	* until that is done. */
	205	if (sub_info->wait)
	206	pid = kernel_thread(wait_for_helper, sub_info,
	207	CLONE_FS \| CLONE_FILES \| SIGCHLD);
	208	else
	209	pid = kernel_thread(____call_usermodehelper, sub_info,
	210	CLONE_VFORK \| SIGCHLD);
	211
	212	if (pid < 0) {
213	sub_info->retval = pid;
214	complete(sub_info->complete);
215	} else if (!sub_info->wait)
216	complete(sub_info->complete);
217	}
218
219	/**
7888e7ff	220	* call_usermodehelper_keys - start a usermode application
1da177e4 LT	221	* @path: pathname for the application
	222	* @argv: null-terminated argument list
	223	* @envp: null-terminated environment list
7888e7ff	224	* @session_keyring: session keyring for process (NULL for an empty keyring)
1da177e4 LT	225	* @wait: wait for the application to finish and return status.
	226	*
	227	* Runs a user-space application. The application is started
	228	* asynchronously if wait is not set, and runs as a child of keventd.
	229	* (ie. it runs with full root capabilities).
	230	*
	231	* Must be called from process context. Returns a negative error code
	232	* if program was not execed successfully, or 0.
	233	*/
7888e7ff DH	234	int call_usermodehelper_keys(char path, char argv, char *envp,
7888e7ff DH	235	struct key *session_keyring, int wait)
1da177e4 LT	236	{
	237	DECLARE_COMPLETION(done);
	238	struct subprocess_info sub_info = {
	239	.complete = &done,
	240	.path = path,
	241	.argv = argv,
	242	.envp = envp,
7888e7ff	243	.ring = session_keyring,
1da177e4 LT	244	.wait = wait,
	245	.retval = 0,
	246	};
	247	DECLARE_WORK(work, __call_usermodehelper, &sub_info);
	248
	249	if (!khelper_wq)
	250	return -EBUSY;
	251
	252	if (path[0] == '\0')
	253	return 0;
	254
	255	queue_work(khelper_wq, &work);
	256	wait_for_completion(&done);
	257	return sub_info.retval;
	258	}
7888e7ff	259	EXPORT_SYMBOL(call_usermodehelper_keys);
1da177e4 LT	260
	261	void __init usermodehelper_init(void)
	262	{
	263	khelper_wq = create_singlethread_workqueue("khelper");
	264	BUG_ON(!khelper_wq);
	265	}