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_entry_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(kinfo->si_code, &uinfo->ssi_code); 99 switch (siginfo_layout(kinfo->si_signo, kinfo->si_code)) { 100 case SIL_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 SIL_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 SIL_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 SIL_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 SIL_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 SIL_RT: 139 default: 140 /* 141 * This case catches also the signals queued by sigqueue(). 142 */ 143 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 144 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 145 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 146 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 147 break; 148 } 149 150 return err ? -EFAULT: sizeof(*uinfo); 151 } 152 153 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 154 int nonblock) 155 { 156 ssize_t ret; 157 DECLARE_WAITQUEUE(wait, current); 158 159 spin_lock_irq(¤t->sighand->siglock); 160 ret = dequeue_signal(current, &ctx->sigmask, info); 161 switch (ret) { 162 case 0: 163 if (!nonblock) 164 break; 165 ret = -EAGAIN; 166 default: 167 spin_unlock_irq(¤t->sighand->siglock); 168 return ret; 169 } 170 171 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 172 for (;;) { 173 set_current_state(TASK_INTERRUPTIBLE); 174 ret = dequeue_signal(current, &ctx->sigmask, info); 175 if (ret != 0) 176 break; 177 if (signal_pending(current)) { 178 ret = -ERESTARTSYS; 179 break; 180 } 181 spin_unlock_irq(¤t->sighand->siglock); 182 schedule(); 183 spin_lock_irq(¤t->sighand->siglock); 184 } 185 spin_unlock_irq(¤t->sighand->siglock); 186 187 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 188 __set_current_state(TASK_RUNNING); 189 190 return ret; 191 } 192 193 /* 194 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 195 * error code. The "count" parameter must be at least the size of a 196 * "struct signalfd_siginfo". 197 */ 198 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 199 loff_t *ppos) 200 { 201 struct signalfd_ctx *ctx = file->private_data; 202 struct signalfd_siginfo __user *siginfo; 203 int nonblock = file->f_flags & O_NONBLOCK; 204 ssize_t ret, total = 0; 205 siginfo_t info; 206 207 count /= sizeof(struct signalfd_siginfo); 208 if (!count) 209 return -EINVAL; 210 211 siginfo = (struct signalfd_siginfo __user *) buf; 212 do { 213 ret = signalfd_dequeue(ctx, &info, nonblock); 214 if (unlikely(ret <= 0)) 215 break; 216 ret = signalfd_copyinfo(siginfo, &info); 217 if (ret < 0) 218 break; 219 siginfo++; 220 total += ret; 221 nonblock = 1; 222 } while (--count); 223 224 return total ? total: ret; 225 } 226 227 #ifdef CONFIG_PROC_FS 228 static void signalfd_show_fdinfo(struct seq_file *m, struct file *f) 229 { 230 struct signalfd_ctx *ctx = f->private_data; 231 sigset_t sigmask; 232 233 sigmask = ctx->sigmask; 234 signotset(&sigmask); 235 render_sigset_t(m, "sigmask:\t", &sigmask); 236 } 237 #endif 238 239 static const struct file_operations signalfd_fops = { 240 #ifdef CONFIG_PROC_FS 241 .show_fdinfo = signalfd_show_fdinfo, 242 #endif 243 .release = signalfd_release, 244 .poll = signalfd_poll, 245 .read = signalfd_read, 246 .llseek = noop_llseek, 247 }; 248 249 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 250 size_t, sizemask, int, flags) 251 { 252 sigset_t sigmask; 253 struct signalfd_ctx *ctx; 254 255 /* Check the SFD_* constants for consistency. */ 256 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 257 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 258 259 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 260 return -EINVAL; 261 262 if (sizemask != sizeof(sigset_t) || 263 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 264 return -EINVAL; 265 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 266 signotset(&sigmask); 267 268 if (ufd == -1) { 269 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 270 if (!ctx) 271 return -ENOMEM; 272 273 ctx->sigmask = sigmask; 274 275 /* 276 * When we call this, the initialization must be complete, since 277 * anon_inode_getfd() will install the fd. 278 */ 279 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 280 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 281 if (ufd < 0) 282 kfree(ctx); 283 } else { 284 struct fd f = fdget(ufd); 285 if (!f.file) 286 return -EBADF; 287 ctx = f.file->private_data; 288 if (f.file->f_op != &signalfd_fops) { 289 fdput(f); 290 return -EINVAL; 291 } 292 spin_lock_irq(¤t->sighand->siglock); 293 ctx->sigmask = sigmask; 294 spin_unlock_irq(¤t->sighand->siglock); 295 296 wake_up(¤t->sighand->signalfd_wqh); 297 fdput(f); 298 } 299 300 return ufd; 301 } 302 303 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 304 size_t, sizemask) 305 { 306 return sys_signalfd4(ufd, user_mask, sizemask, 0); 307 } 308 309 #ifdef CONFIG_COMPAT 310 COMPAT_SYSCALL_DEFINE4(signalfd4, int, ufd, 311 const compat_sigset_t __user *,sigmask, 312 compat_size_t, sigsetsize, 313 int, flags) 314 { 315 compat_sigset_t ss32; 316 sigset_t tmp; 317 sigset_t __user *ksigmask; 318 319 if (sigsetsize != sizeof(compat_sigset_t)) 320 return -EINVAL; 321 if (copy_from_user(&ss32, sigmask, sizeof(ss32))) 322 return -EFAULT; 323 sigset_from_compat(&tmp, &ss32); 324 ksigmask = compat_alloc_user_space(sizeof(sigset_t)); 325 if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t))) 326 return -EFAULT; 327 328 return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags); 329 } 330 331 COMPAT_SYSCALL_DEFINE3(signalfd, int, ufd, 332 const compat_sigset_t __user *,sigmask, 333 compat_size_t, sigsetsize) 334 { 335 return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0); 336 } 337 #endif 338