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TOMOYO Linux Cross Reference
Linux/fs/signalfd.c

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  1 /*
  2  *  fs/signalfd.c
  3  *
  4  *  Copyright (C) 2003  Linus Torvalds
  5  *
  6  *  Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org>
  7  *      Changed ->read() to return a siginfo strcture instead of signal number.
  8  *      Fixed locking in ->poll().
  9  *      Added sighand-detach notification.
 10  *      Added fd re-use in sys_signalfd() syscall.
 11  *      Now using anonymous inode source.
 12  *      Thanks to Oleg Nesterov for useful code review and suggestions.
 13  *      More comments and suggestions from Arnd Bergmann.
 14  *  Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br>
 15  *      Retrieve multiple signals with one read() call
 16  *  Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org>
 17  *      Attach to the sighand only during read() and poll().
 18  */
 19 
 20 #include <linux/file.h>
 21 #include <linux/poll.h>
 22 #include <linux/init.h>
 23 #include <linux/fs.h>
 24 #include <linux/sched.h>
 25 #include <linux/slab.h>
 26 #include <linux/kernel.h>
 27 #include <linux/signal.h>
 28 #include <linux/list.h>
 29 #include <linux/anon_inodes.h>
 30 #include <linux/signalfd.h>
 31 #include <linux/syscalls.h>
 32 #include <linux/proc_fs.h>
 33 #include <linux/compat.h>
 34 
 35 void signalfd_cleanup(struct sighand_struct *sighand)
 36 {
 37         wait_queue_head_t *wqh = &sighand->signalfd_wqh;
 38         /*
 39          * The lockless check can race with remove_wait_queue() in progress,
 40          * but in this case its caller should run under rcu_read_lock() and
 41          * sighand_cachep is SLAB_DESTROY_BY_RCU, we can safely return.
 42          */
 43         if (likely(!waitqueue_active(wqh)))
 44                 return;
 45 
 46         /* wait_queue_t->func(POLLFREE) should do remove_wait_queue() */
 47         wake_up_poll(wqh, POLLHUP | POLLFREE);
 48 }
 49 
 50 struct signalfd_ctx {
 51         sigset_t sigmask;
 52 };
 53 
 54 static int signalfd_release(struct inode *inode, struct file *file)
 55 {
 56         kfree(file->private_data);
 57         return 0;
 58 }
 59 
 60 static unsigned int signalfd_poll(struct file *file, poll_table *wait)
 61 {
 62         struct signalfd_ctx *ctx = file->private_data;
 63         unsigned int events = 0;
 64 
 65         poll_wait(file, &current->sighand->signalfd_wqh, wait);
 66 
 67         spin_lock_irq(&current->sighand->siglock);
 68         if (next_signal(&current->pending, &ctx->sigmask) ||
 69             next_signal(&current->signal->shared_pending,
 70                         &ctx->sigmask))
 71                 events |= POLLIN;
 72         spin_unlock_irq(&current->sighand->siglock);
 73 
 74         return events;
 75 }
 76 
 77 /*
 78  * Copied from copy_siginfo_to_user() in kernel/signal.c
 79  */
 80 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 81                              siginfo_t const *kinfo)
 82 {
 83         long err;
 84 
 85         BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
 86 
 87         /*
 88          * Unused members should be zero ...
 89          */
 90         err = __clear_user(uinfo, sizeof(*uinfo));
 91 
 92         /*
 93          * If you change siginfo_t structure, please be sure
 94          * this code is fixed accordingly.
 95          */
 96         err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
 97         err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
 98         err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
 99         switch (kinfo->si_code & __SI_MASK) {
100         case __SI_KILL:
101                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
102                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
103                 break;
104         case __SI_TIMER:
105                  err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
106                  err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
107                  err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
108                  err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
109                 break;
110         case __SI_POLL:
111                 err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
112                 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
113                 break;
114         case __SI_FAULT:
115                 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
116 #ifdef __ARCH_SI_TRAPNO
117                 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
118 #endif
119 #ifdef BUS_MCEERR_AO
120                 /* 
121                  * Other callers might not initialize the si_lsb field,
122                  * so check explicitly for the right codes here.
123                  */
124                 if (kinfo->si_code == BUS_MCEERR_AR ||
125                     kinfo->si_code == BUS_MCEERR_AO)
126                         err |= __put_user((short) kinfo->si_addr_lsb,
127                                           &uinfo->ssi_addr_lsb);
128 #endif
129                 break;
130         case __SI_CHLD:
131                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
132                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
133                 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
134                 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
135                 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
136                 break;
137         case __SI_RT: /* This is not generated by the kernel as of now. */
138         case __SI_MESGQ: /* But this is */
139                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
140                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
141                 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
142                 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
143                 break;
144         default:
145                 /*
146                  * This case catches also the signals queued by sigqueue().
147                  */
148                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
149                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
150                 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
151                 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
152                 break;
153         }
154 
155         return err ? -EFAULT: sizeof(*uinfo);
156 }
157 
158 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
159                                 int nonblock)
160 {
161         ssize_t ret;
162         DECLARE_WAITQUEUE(wait, current);
163 
164         spin_lock_irq(&current->sighand->siglock);
165         ret = dequeue_signal(current, &ctx->sigmask, info);
166         switch (ret) {
167         case 0:
168                 if (!nonblock)
169                         break;
170                 ret = -EAGAIN;
171         default:
172                 spin_unlock_irq(&current->sighand->siglock);
173                 return ret;
174         }
175 
176         add_wait_queue(&current->sighand->signalfd_wqh, &wait);
177         for (;;) {
178                 set_current_state(TASK_INTERRUPTIBLE);
179                 ret = dequeue_signal(current, &ctx->sigmask, info);
180                 if (ret != 0)
181                         break;
182                 if (signal_pending(current)) {
183                         ret = -ERESTARTSYS;
184                         break;
185                 }
186                 spin_unlock_irq(&current->sighand->siglock);
187                 schedule();
188                 spin_lock_irq(&current->sighand->siglock);
189         }
190         spin_unlock_irq(&current->sighand->siglock);
191 
192         remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
193         __set_current_state(TASK_RUNNING);
194 
195         return ret;
196 }
197 
198 /*
199  * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
200  * error code. The "count" parameter must be at least the size of a
201  * "struct signalfd_siginfo".
202  */
203 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
204                              loff_t *ppos)
205 {
206         struct signalfd_ctx *ctx = file->private_data;
207         struct signalfd_siginfo __user *siginfo;
208         int nonblock = file->f_flags & O_NONBLOCK;
209         ssize_t ret, total = 0;
210         siginfo_t info;
211 
212         count /= sizeof(struct signalfd_siginfo);
213         if (!count)
214                 return -EINVAL;
215 
216         siginfo = (struct signalfd_siginfo __user *) buf;
217         do {
218                 ret = signalfd_dequeue(ctx, &info, nonblock);
219                 if (unlikely(ret <= 0))
220                         break;
221                 ret = signalfd_copyinfo(siginfo, &info);
222                 if (ret < 0)
223                         break;
224                 siginfo++;
225                 total += ret;
226                 nonblock = 1;
227         } while (--count);
228 
229         return total ? total: ret;
230 }
231 
232 #ifdef CONFIG_PROC_FS
233 static int signalfd_show_fdinfo(struct seq_file *m, struct file *f)
234 {
235         struct signalfd_ctx *ctx = f->private_data;
236         sigset_t sigmask;
237 
238         sigmask = ctx->sigmask;
239         signotset(&sigmask);
240         render_sigset_t(m, "sigmask:\t", &sigmask);
241 
242         return 0;
243 }
244 #endif
245 
246 static const struct file_operations signalfd_fops = {
247 #ifdef CONFIG_PROC_FS
248         .show_fdinfo    = signalfd_show_fdinfo,
249 #endif
250         .release        = signalfd_release,
251         .poll           = signalfd_poll,
252         .read           = signalfd_read,
253         .llseek         = noop_llseek,
254 };
255 
256 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
257                 size_t, sizemask, int, flags)
258 {
259         sigset_t sigmask;
260         struct signalfd_ctx *ctx;
261 
262         /* Check the SFD_* constants for consistency.  */
263         BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
264         BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
265 
266         if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
267                 return -EINVAL;
268 
269         if (sizemask != sizeof(sigset_t) ||
270             copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
271                 return -EINVAL;
272         sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
273         signotset(&sigmask);
274 
275         if (ufd == -1) {
276                 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
277                 if (!ctx)
278                         return -ENOMEM;
279 
280                 ctx->sigmask = sigmask;
281 
282                 /*
283                  * When we call this, the initialization must be complete, since
284                  * anon_inode_getfd() will install the fd.
285                  */
286                 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
287                                        O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
288                 if (ufd < 0)
289                         kfree(ctx);
290         } else {
291                 struct fd f = fdget(ufd);
292                 if (!f.file)
293                         return -EBADF;
294                 ctx = f.file->private_data;
295                 if (f.file->f_op != &signalfd_fops) {
296                         fdput(f);
297                         return -EINVAL;
298                 }
299                 spin_lock_irq(&current->sighand->siglock);
300                 ctx->sigmask = sigmask;
301                 spin_unlock_irq(&current->sighand->siglock);
302 
303                 wake_up(&current->sighand->signalfd_wqh);
304                 fdput(f);
305         }
306 
307         return ufd;
308 }
309 
310 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
311                 size_t, sizemask)
312 {
313         return sys_signalfd4(ufd, user_mask, sizemask, 0);
314 }
315 
316 #ifdef CONFIG_COMPAT
317 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd,
318                      const compat_sigset_t __user *,sigmask,
319                      compat_size_t, sigsetsize,
320                      int, flags)
321 {
322         compat_sigset_t ss32;
323         sigset_t tmp;
324         sigset_t __user *ksigmask;
325 
326         if (sigsetsize != sizeof(compat_sigset_t))
327                 return -EINVAL;
328         if (copy_from_user(&ss32, sigmask, sizeof(ss32)))
329                 return -EFAULT;
330         sigset_from_compat(&tmp, &ss32);
331         ksigmask = compat_alloc_user_space(sizeof(sigset_t));
332         if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t)))
333                 return -EFAULT;
334 
335         return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags);
336 }
337 
338 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd,
339                      const compat_sigset_t __user *,sigmask,
340                      compat_size_t, sigsetsize)
341 {
342         return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0);
343 }
344 #endif
345 

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