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_TYPESAFE_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, ¤t->sighand->signalfd_wqh, wait); 66 67 spin_lock_irq(¤t->sighand->siglock); 68 if (next_signal(¤t->pending, &ctx->sigmask) || 69 next_signal(¤t->signal->shared_pending, 70 &ctx->sigmask)) 71 events |= POLLIN; 72 spin_unlock_irq(¤t->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_signo == SIGBUS && 125 (kinfo->si_code == BUS_MCEERR_AR || 126 kinfo->si_code == BUS_MCEERR_AO)) 127 err |= __put_user((short) kinfo->si_addr_lsb, 128 &uinfo->ssi_addr_lsb); 129 #endif 130 break; 131 case __SI_CHLD: 132 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 133 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 134 err |= __put_user(kinfo->si_status, &uinfo->ssi_status); 135 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); 136 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); 137 break; 138 case __SI_RT: /* This is not generated by the kernel as of now. */ 139 case __SI_MESGQ: /* But this is */ 140 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 141 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 142 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 143 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 144 break; 145 default: 146 /* 147 * This case catches also the signals queued by sigqueue(). 148 */ 149 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 150 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 151 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 152 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 153 break; 154 } 155 156 return err ? -EFAULT: sizeof(*uinfo); 157 } 158 159 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 160 int nonblock) 161 { 162 ssize_t ret; 163 DECLARE_WAITQUEUE(wait, current); 164 165 spin_lock_irq(¤t->sighand->siglock); 166 ret = dequeue_signal(current, &ctx->sigmask, info); 167 switch (ret) { 168 case 0: 169 if (!nonblock) 170 break; 171 ret = -EAGAIN; 172 default: 173 spin_unlock_irq(¤t->sighand->siglock); 174 return ret; 175 } 176 177 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 178 for (;;) { 179 set_current_state(TASK_INTERRUPTIBLE); 180 ret = dequeue_signal(current, &ctx->sigmask, info); 181 if (ret != 0) 182 break; 183 if (signal_pending(current)) { 184 ret = -ERESTARTSYS; 185 break; 186 } 187 spin_unlock_irq(¤t->sighand->siglock); 188 schedule(); 189 spin_lock_irq(¤t->sighand->siglock); 190 } 191 spin_unlock_irq(¤t->sighand->siglock); 192 193 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 194 __set_current_state(TASK_RUNNING); 195 196 return ret; 197 } 198 199 /* 200 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 201 * error code. The "count" parameter must be at least the size of a 202 * "struct signalfd_siginfo". 203 */ 204 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 205 loff_t *ppos) 206 { 207 struct signalfd_ctx *ctx = file->private_data; 208 struct signalfd_siginfo __user *siginfo; 209 int nonblock = file->f_flags & O_NONBLOCK; 210 ssize_t ret, total = 0; 211 siginfo_t info; 212 213 count /= sizeof(struct signalfd_siginfo); 214 if (!count) 215 return -EINVAL; 216 217 siginfo = (struct signalfd_siginfo __user *) buf; 218 do { 219 ret = signalfd_dequeue(ctx, &info, nonblock); 220 if (unlikely(ret <= 0)) 221 break; 222 ret = signalfd_copyinfo(siginfo, &info); 223 if (ret < 0) 224 break; 225 siginfo++; 226 total += ret; 227 nonblock = 1; 228 } while (--count); 229 230 return total ? total: ret; 231 } 232 233 #ifdef CONFIG_PROC_FS 234 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) 235 { 236 struct signalfd_ctx *ctx = f->private_data; 237 sigset_t sigmask; 238 239 sigmask = ctx->sigmask; 240 signotset(&sigmask); 241 render_sigset_t(m, "sigmask:\t", &sigmask); 242 } 243 #endif 244 245 static const struct file_operations signalfd_fops = { 246 #ifdef CONFIG_PROC_FS 247 .show_fdinfo = signalfd_show_fdinfo, 248 #endif 249 .release = signalfd_release, 250 .poll = signalfd_poll, 251 .read = signalfd_read, 252 .llseek = noop_llseek, 253 }; 254 255 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 256 size_t, sizemask, int, flags) 257 { 258 sigset_t sigmask; 259 struct signalfd_ctx *ctx; 260 261 /* Check the SFD_* constants for consistency. */ 262 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 263 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 264 265 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 266 return -EINVAL; 267 268 if (sizemask != sizeof(sigset_t) || 269 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 270 return -EINVAL; 271 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 272 signotset(&sigmask); 273 274 if (ufd == -1) { 275 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 276 if (!ctx) 277 return -ENOMEM; 278 279 ctx->sigmask = sigmask; 280 281 /* 282 * When we call this, the initialization must be complete, since 283 * anon_inode_getfd() will install the fd. 284 */ 285 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 286 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 287 if (ufd < 0) 288 kfree(ctx); 289 } else { 290 struct fd f = fdget(ufd); 291 if (!f.file) 292 return -EBADF; 293 ctx = f.file->private_data; 294 if (f.file->f_op != &signalfd_fops) { 295 fdput(f); 296 return -EINVAL; 297 } 298 spin_lock_irq(¤t->sighand->siglock); 299 ctx->sigmask = sigmask; 300 spin_unlock_irq(¤t->sighand->siglock); 301 302 wake_up(¤t->sighand->signalfd_wqh); 303 fdput(f); 304 } 305 306 return ufd; 307 } 308 309 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 310 size_t, sizemask) 311 { 312 return sys_signalfd4(ufd, user_mask, sizemask, 0); 313 } 314 315 #ifdef CONFIG_COMPAT 316 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, 317 const compat_sigset_t __user *,sigmask, 318 compat_size_t, sigsetsize, 319 int, flags) 320 { 321 compat_sigset_t ss32; 322 sigset_t tmp; 323 sigset_t __user *ksigmask; 324 325 if (sigsetsize != sizeof(compat_sigset_t)) 326 return -EINVAL; 327 if (copy_from_user(&ss32, sigmask, sizeof(ss32))) 328 return -EFAULT; 329 sigset_from_compat(&tmp, &ss32); 330 ksigmask = compat_alloc_user_space(sizeof(sigset_t)); 331 if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) 332 return -EFAULT; 333 334 return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); 335 } 336 337 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, 338 const compat_sigset_t __user *,sigmask, 339 compat_size_t, sigsetsize) 340 { 341 return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); 342 } 343 #endif 344