Linux v2.6.13-rc3
[pohmelfs.git] / kernel / kmod.c
blob44166e3bb8afab469a61575946b46da45e215cc7
1 /*
2 kmod, the new module loader (replaces kerneld)
3 Kirk Petersen
5 Reorganized not to be a daemon by Adam Richter, with guidance
6 from Greg Zornetzer.
8 Modified to avoid chroot and file sharing problems.
9 Mikael Pettersson
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
15 Unblock all signals when we exec a usermode process.
16 Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
18 call_usermodehelper wait flag, and remove exec_usermodehelper.
19 Rusty Russell <rusty@rustcorp.com.au> Jan 2003
21 #define __KERNEL_SYSCALLS__
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>
41 extern int max_threads;
43 static struct workqueue_struct *khelper_wq;
45 #ifdef CONFIG_KMOD
48 modprobe_path is set via /proc/sys.
50 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
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
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.
63 * If module auto-loading support is disabled then this function
64 * becomes a no-operation.
66 int request_module(const char *fmt, ...)
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;
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;
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.
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
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;
111 ret = call_usermodehelper(modprobe_path, argv, envp, 1);
112 atomic_dec(&kmod_concurrent);
113 return ret;
115 EXPORT_SYMBOL(request_module);
116 #endif /* CONFIG_KMOD */
118 struct subprocess_info {
119 struct completion *complete;
120 char *path;
121 char **argv;
122 char **envp;
123 struct key *ring;
124 int wait;
125 int retval;
129 * This is the task which runs the usermode application
131 static int ____call_usermodehelper(void *data)
133 struct subprocess_info *sub_info = data;
134 struct key *old_session;
135 int retval;
137 /* Unblock all signals and set the session keyring. */
138 key_get(sub_info->ring);
139 flush_signals(current);
140 spin_lock_irq(&current->sighand->siglock);
141 old_session = __install_session_keyring(current, sub_info->ring);
142 flush_signal_handlers(current, 1);
143 sigemptyset(&current->blocked);
144 recalc_sigpending();
145 spin_unlock_irq(&current->sighand->siglock);
147 key_put(old_session);
149 /* We can run anywhere, unlike our parent keventd(). */
150 set_cpus_allowed(current, CPU_MASK_ALL);
152 retval = -EPERM;
153 if (current->fs->root)
154 retval = execve(sub_info->path, sub_info->argv,sub_info->envp);
156 /* Exec failed? */
157 sub_info->retval = retval;
158 do_exit(0);
161 /* Keventd can't block, but this (a child) can. */
162 static int wait_for_helper(void *data)
164 struct subprocess_info *sub_info = data;
165 pid_t pid;
166 struct k_sigaction sa;
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);
176 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
177 if (pid < 0) {
178 sub_info->retval = pid;
179 } else {
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.
187 * Thus the __user pointer cast is valid here.
189 sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL);
192 complete(sub_info->complete);
193 return 0;
196 /* This is run by khelper thread */
197 static void __call_usermodehelper(void *data)
199 struct subprocess_info *sub_info = data;
200 pid_t pid;
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);
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);
220 * call_usermodehelper_keys - start a usermode application
221 * @path: pathname for the application
222 * @argv: null-terminated argument list
223 * @envp: null-terminated environment list
224 * @session_keyring: session keyring for process (NULL for an empty keyring)
225 * @wait: wait for the application to finish and return status.
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).
231 * Must be called from process context. Returns a negative error code
232 * if program was not execed successfully, or 0.
234 int call_usermodehelper_keys(char *path, char **argv, char **envp,
235 struct key *session_keyring, int wait)
237 DECLARE_COMPLETION(done);
238 struct subprocess_info sub_info = {
239 .complete = &done,
240 .path = path,
241 .argv = argv,
242 .envp = envp,
243 .ring = session_keyring,
244 .wait = wait,
245 .retval = 0,
247 DECLARE_WORK(work, __call_usermodehelper, &sub_info);
249 if (!khelper_wq)
250 return -EBUSY;
252 if (path[0] == '\0')
253 return 0;
255 queue_work(khelper_wq, &work);
256 wait_for_completion(&done);
257 return sub_info.retval;
259 EXPORT_SYMBOL(call_usermodehelper_keys);
261 void __init usermodehelper_init(void)
263 khelper_wq = create_singlethread_workqueue("khelper");
264 BUG_ON(!khelper_wq);