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