Linux kernel & device driver programming

Cross-Referenced Linux and Device Driver Code

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Version: [ 2.6.11.8 ] [ 2.6.25 ] [ 2.6.25.8 ] [ 2.6.31.13 ] Architecture: [ i386 ] 
  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/kernel.h>
 26 #include <linux/signal.h>
 27 #include <linux/list.h>
 28 #include <linux/anon_inodes.h>
 29 #include <linux/signalfd.h>
 30 #include <linux/syscalls.h>
 31 
 32 struct signalfd_ctx {
 33         sigset_t sigmask;
 34 };
 35 
 36 static int signalfd_release(struct inode *inode, struct file *file)
 37 {
 38         kfree(file->private_data);
 39         return 0;
 40 }
 41 
 42 static unsigned int signalfd_poll(struct file *file, poll_table *wait)
 43 {
 44         struct signalfd_ctx *ctx = file->private_data;
 45         unsigned int events = 0;
 46 
 47         poll_wait(file, &current->sighand->signalfd_wqh, wait);
 48 
 49         spin_lock_irq(&current->sighand->siglock);
 50         if (next_signal(&current->pending, &ctx->sigmask) ||
 51             next_signal(&current->signal->shared_pending,
 52                         &ctx->sigmask))
 53                 events |= POLLIN;
 54         spin_unlock_irq(&current->sighand->siglock);
 55 
 56         return events;
 57 }
 58 
 59 /*
 60  * Copied from copy_siginfo_to_user() in kernel/signal.c
 61  */
 62 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 63                              siginfo_t const *kinfo)
 64 {
 65         long err;
 66 
 67         BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
 68 
 69         /*
 70          * Unused members should be zero ...
 71          */
 72         err = __clear_user(uinfo, sizeof(*uinfo));
 73 
 74         /*
 75          * If you change siginfo_t structure, please be sure
 76          * this code is fixed accordingly.
 77          */
 78         err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
 79         err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
 80         err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
 81         switch (kinfo->si_code & __SI_MASK) {
 82         case __SI_KILL:
 83                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
 84                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
 85                 break;
 86         case __SI_TIMER:
 87                  err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
 88                  err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
 89                  err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
 90                 break;
 91         case __SI_POLL:
 92                 err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
 93                 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
 94                 break;
 95         case __SI_FAULT:
 96                 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
 97 #ifdef __ARCH_SI_TRAPNO
 98                 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
 99 #endif
100                 break;
101         case __SI_CHLD:
102                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
103                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
104                 err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
105                 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
106                 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
107                 break;
108         case __SI_RT: /* This is not generated by the kernel as of now. */
109         case __SI_MESGQ: /* But this is */
110                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
111                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
112                 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
113                 break;
114         default:
115                 /*
116                  * This case catches also the signals queued by sigqueue().
117                  */
118                 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
119                 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
120                 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
121                 err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
122                 break;
123         }
124 
125         return err ? -EFAULT: sizeof(*uinfo);
126 }
127 
128 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
129                                 int nonblock)
130 {
131         ssize_t ret;
132         DECLARE_WAITQUEUE(wait, current);
133 
134         spin_lock_irq(&current->sighand->siglock);
135         ret = dequeue_signal(current, &ctx->sigmask, info);
136         switch (ret) {
137         case 0:
138                 if (!nonblock)
139                         break;
140                 ret = -EAGAIN;
141         default:
142                 spin_unlock_irq(&current->sighand->siglock);
143                 return ret;
144         }
145 
146         add_wait_queue(&current->sighand->signalfd_wqh, &wait);
147         for (;;) {
148                 set_current_state(TASK_INTERRUPTIBLE);
149                 ret = dequeue_signal(current, &ctx->sigmask, info);
150                 if (ret != 0)
151                         break;
152                 if (signal_pending(current)) {
153                         ret = -ERESTARTSYS;
154                         break;
155                 }
156                 spin_unlock_irq(&current->sighand->siglock);
157                 schedule();
158                 spin_lock_irq(&current->sighand->siglock);
159         }
160         spin_unlock_irq(&current->sighand->siglock);
161 
162         remove_wait_queue(&current->sighand->signalfd_wqh, &wait);
163         __set_current_state(TASK_RUNNING);
164 
165         return ret;
166 }
167 
168 /*
169  * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative
170  * error code. The "count" parameter must be at least the size of a
171  * "struct signalfd_siginfo".
172  */
173 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
174                              loff_t *ppos)
175 {
176         struct signalfd_ctx *ctx = file->private_data;
177         struct signalfd_siginfo __user *siginfo;
178         int nonblock = file->f_flags & O_NONBLOCK;
179         ssize_t ret, total = 0;
180         siginfo_t info;
181 
182         count /= sizeof(struct signalfd_siginfo);
183         if (!count)
184                 return -EINVAL;
185 
186         siginfo = (struct signalfd_siginfo __user *) buf;
187         do {
188                 ret = signalfd_dequeue(ctx, &info, nonblock);
189                 if (unlikely(ret <= 0))
190                         break;
191                 ret = signalfd_copyinfo(siginfo, &info);
192                 if (ret < 0)
193                         break;
194                 siginfo++;
195                 total += ret;
196                 nonblock = 1;
197         } while (--count);
198 
199         return total ? total: ret;
200 }
201 
202 static const struct file_operations signalfd_fops = {
203         .release        = signalfd_release,
204         .poll           = signalfd_poll,
205         .read           = signalfd_read,
206 };
207 
208 asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
209 {
210         int error;
211         sigset_t sigmask;
212         struct signalfd_ctx *ctx;
213         struct file *file;
214         struct inode *inode;
215 
216         if (sizemask != sizeof(sigset_t) ||
217             copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
218                 return -EINVAL;
219         sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
220         signotset(&sigmask);
221 
222         if (ufd == -1) {
223                 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
224                 if (!ctx)
225                         return -ENOMEM;
226 
227                 ctx->sigmask = sigmask;
228 
229                 /*
230                  * When we call this, the initialization must be complete, since
231                  * anon_inode_getfd() will install the fd.
232                  */
233                 error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]",
234                                          &signalfd_fops, ctx);
235                 if (error)
236                         goto err_fdalloc;
237         } else {
238                 file = fget(ufd);
239                 if (!file)
240                         return -EBADF;
241                 ctx = file->private_data;
242                 if (file->f_op != &signalfd_fops) {
243                         fput(file);
244                         return -EINVAL;
245                 }
246                 spin_lock_irq(&current->sighand->siglock);
247                 ctx->sigmask = sigmask;
248                 spin_unlock_irq(&current->sighand->siglock);
249 
250                 wake_up(&current->sighand->signalfd_wqh);
251                 fput(file);
252         }
253 
254         return ufd;
255 
256 err_fdalloc:
257         kfree(ctx);
258         return error;
259 }
260 
261
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