ia64/linux-2.6.18-xen.hg

view kernel/kmod.c @ 562:66faefe721eb

pvSCSI backend driver

Signed-off-by: Tomonari Horikoshi <t.horikoshi@jp.fujitsu.com>
Signed-off-by: Jun Kamada <kama@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Jun 02 09:58:27 2008 +0100 (2008-06-02)
parents 831230e53067
children
line source
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
20 */
21 #define __KERNEL_SYSCALLS__
23 #include <linux/module.h>
24 #include <linux/sched.h>
25 #include <linux/syscalls.h>
26 #include <linux/unistd.h>
27 #include <linux/kmod.h>
28 #include <linux/smp_lock.h>
29 #include <linux/slab.h>
30 #include <linux/namespace.h>
31 #include <linux/completion.h>
32 #include <linux/file.h>
33 #include <linux/workqueue.h>
34 #include <linux/security.h>
35 #include <linux/mount.h>
36 #include <linux/kernel.h>
37 #include <linux/init.h>
38 #include <asm/uaccess.h>
40 extern int max_threads;
42 static struct workqueue_struct *khelper_wq;
44 #ifdef CONFIG_KMOD
46 /*
47 modprobe_path is set via /proc/sys.
48 */
49 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
51 /**
52 * request_module - try to load a kernel module
53 * @fmt: printf style format string for the name of the module
54 * @varargs: arguements as specified in the format string
55 *
56 * Load a module using the user mode module loader. The function returns
57 * zero on success or a negative errno code on failure. Note that a
58 * successful module load does not mean the module did not then unload
59 * and exit on an error of its own. Callers must check that the service
60 * they requested is now available not blindly invoke it.
61 *
62 * If module auto-loading support is disabled then this function
63 * becomes a no-operation.
64 */
65 int request_module(const char *fmt, ...)
66 {
67 va_list args;
68 char module_name[MODULE_NAME_LEN];
69 unsigned int max_modprobes;
70 int ret;
71 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
72 static char *envp[] = { "HOME=/",
73 "TERM=linux",
74 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
75 NULL };
76 static atomic_t kmod_concurrent = ATOMIC_INIT(0);
77 #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
78 static int kmod_loop_msg;
80 va_start(args, fmt);
81 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
82 va_end(args);
83 if (ret >= MODULE_NAME_LEN)
84 return -ENAMETOOLONG;
86 /* If modprobe needs a service that is in a module, we get a recursive
87 * loop. Limit the number of running kmod threads to max_threads/2 or
88 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
89 * would be to run the parents of this process, counting how many times
90 * kmod was invoked. That would mean accessing the internals of the
91 * process tables to get the command line, proc_pid_cmdline is static
92 * and it is not worth changing the proc code just to handle this case.
93 * KAO.
94 *
95 * "trace the ppid" is simple, but will fail if someone's
96 * parent exits. I think this is as good as it gets. --RR
97 */
98 max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
99 atomic_inc(&kmod_concurrent);
100 if (atomic_read(&kmod_concurrent) > max_modprobes) {
101 /* We may be blaming an innocent here, but unlikely */
102 if (kmod_loop_msg++ < 5)
103 printk(KERN_ERR
104 "request_module: runaway loop modprobe %s\n",
105 module_name);
106 atomic_dec(&kmod_concurrent);
107 return -ENOMEM;
108 }
110 ret = call_usermodehelper(modprobe_path, argv, envp, 1);
111 atomic_dec(&kmod_concurrent);
112 return ret;
113 }
114 EXPORT_SYMBOL(request_module);
115 #endif /* CONFIG_KMOD */
117 struct subprocess_info {
118 struct completion *complete;
119 char *path;
120 char **argv;
121 char **envp;
122 struct key *ring;
123 int wait;
124 int retval;
125 };
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;
133 struct key *new_session, *old_session;
134 int retval;
136 /* Unblock all signals and set the session keyring. */
137 new_session = key_get(sub_info->ring);
138 flush_signals(current);
139 spin_lock_irq(&current->sighand->siglock);
140 old_session = __install_session_keyring(current, new_session);
141 flush_signal_handlers(current, 1);
142 sigemptyset(&current->blocked);
143 recalc_sigpending();
144 spin_unlock_irq(&current->sighand->siglock);
146 key_put(old_session);
148 /* We can run anywhere, unlike our parent keventd(). */
149 set_cpus_allowed(current, CPU_MASK_ALL);
151 retval = -EPERM;
152 if (current->fs->root)
153 retval = execve(sub_info->path, sub_info->argv,sub_info->envp);
155 /* Exec failed? */
156 sub_info->retval = retval;
157 do_exit(0);
158 }
160 /* Keventd can't block, but this (a child) can. */
161 static int wait_for_helper(void *data)
162 {
163 struct subprocess_info *sub_info = data;
164 pid_t pid;
165 struct k_sigaction sa;
167 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
168 * populate the status, but will return -ECHILD. */
169 sa.sa.sa_handler = SIG_IGN;
170 sa.sa.sa_flags = 0;
171 siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
172 do_sigaction(SIGCHLD, &sa, NULL);
173 allow_signal(SIGCHLD);
175 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
176 if (pid < 0) {
177 sub_info->retval = pid;
178 } else {
179 /*
180 * Normally it is bogus to call wait4() from in-kernel because
181 * wait4() wants to write the exit code to a userspace address.
182 * But wait_for_helper() always runs as keventd, and put_user()
183 * to a kernel address works OK for kernel threads, due to their
184 * having an mm_segment_t which spans the entire address space.
185 *
186 * Thus the __user pointer cast is valid here.
187 */
188 sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL);
189 }
191 complete(sub_info->complete);
192 return 0;
193 }
195 /* This is run by khelper thread */
196 static void __call_usermodehelper(void *data)
197 {
198 struct subprocess_info *sub_info = data;
199 pid_t pid;
200 int wait = sub_info->wait;
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 (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 (!wait)
216 complete(sub_info->complete);
217 }
219 /**
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.
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 */
234 int call_usermodehelper_keys(char *path, char **argv, char **envp,
235 struct key *session_keyring, int wait)
236 {
237 DECLARE_COMPLETION_ONSTACK(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,
246 };
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;
258 }
259 EXPORT_SYMBOL(call_usermodehelper_keys);
261 void __init usermodehelper_init(void)
262 {
263 khelper_wq = create_singlethread_workqueue("khelper");
264 BUG_ON(!khelper_wq);
265 }