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 33 struct signalfd_ctx { 34 sigset_t sigmask; 35 }; 36 37 static int signalfd_release(struct inode *inode, struct file *file) 38 { 39 kfree(file->private_data); 40 return 0; 41 } 42 43 static unsigned int signalfd_poll(struct file *file, poll_table *wait) 44 { 45 struct signalfd_ctx *ctx = file->private_data; 46 unsigned int events = 0; 47 48 poll_wait(file, ¤t->sighand->signalfd_wqh, wait); 49 50 spin_lock_irq(¤t->sighand->siglock); 51 if (next_signal(¤t->pending, &ctx->sigmask) || 52 next_signal(¤t->signal->shared_pending, 53 &ctx->sigmask)) 54 events |= POLLIN; 55 spin_unlock_irq(¤t->sighand->siglock); 56 57 return events; 58 } 59 60 /* 61 * Copied from copy_siginfo_to_user() in kernel/signal.c 62 */ 63 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, 64 siginfo_t const *kinfo) 65 { 66 long err; 67 68 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); 69 70 /* 71 * Unused members should be zero ... 72 */ 73 err = __clear_user(uinfo, sizeof(*uinfo)); 74 75 /* 76 * If you change siginfo_t structure, please be sure 77 * this code is fixed accordingly. 78 */ 79 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo); 80 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno); 81 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code); 82 switch (kinfo->si_code & __SI_MASK) { 83 case __SI_KILL: 84 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 85 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 86 break; 87 case __SI_TIMER: 88 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid); 89 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun); 90 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 91 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 92 break; 93 case __SI_POLL: 94 err |= __put_user(kinfo->si_band, &uinfo->ssi_band); 95 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd); 96 break; 97 case __SI_FAULT: 98 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr); 99 #ifdef __ARCH_SI_TRAPNO 100 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno); 101 #endif 102 break; 103 case __SI_CHLD: 104 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 105 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 106 err |= __put_user(kinfo->si_status, &uinfo->ssi_status); 107 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); 108 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); 109 break; 110 case __SI_RT: /* This is not generated by the kernel as of now. */ 111 case __SI_MESGQ: /* But this is */ 112 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 113 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 114 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 115 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 116 break; 117 default: 118 /* 119 * This case catches also the signals queued by sigqueue(). 120 */ 121 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 122 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 123 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 124 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 125 break; 126 } 127 128 return err ? -EFAULT: sizeof(*uinfo); 129 } 130 131 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 132 int nonblock) 133 { 134 ssize_t ret; 135 DECLARE_WAITQUEUE(wait, current); 136 137 spin_lock_irq(¤t->sighand->siglock); 138 ret = dequeue_signal(current, &ctx->sigmask, info); 139 switch (ret) { 140 case 0: 141 if (!nonblock) 142 break; 143 ret = -EAGAIN; 144 default: 145 spin_unlock_irq(¤t->sighand->siglock); 146 return ret; 147 } 148 149 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 150 for (;;) { 151 set_current_state(TASK_INTERRUPTIBLE); 152 ret = dequeue_signal(current, &ctx->sigmask, info); 153 if (ret != 0) 154 break; 155 if (signal_pending(current)) { 156 ret = -ERESTARTSYS; 157 break; 158 } 159 spin_unlock_irq(¤t->sighand->siglock); 160 schedule(); 161 spin_lock_irq(¤t->sighand->siglock); 162 } 163 spin_unlock_irq(¤t->sighand->siglock); 164 165 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 166 __set_current_state(TASK_RUNNING); 167 168 return ret; 169 } 170 171 /* 172 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 173 * error code. The "count" parameter must be at least the size of a 174 * "struct signalfd_siginfo". 175 */ 176 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 177 loff_t *ppos) 178 { 179 struct signalfd_ctx *ctx = file->private_data; 180 struct signalfd_siginfo __user *siginfo; 181 int nonblock = file->f_flags & O_NONBLOCK; 182 ssize_t ret, total = 0; 183 siginfo_t info; 184 185 count /= sizeof(struct signalfd_siginfo); 186 if (!count) 187 return -EINVAL; 188 189 siginfo = (struct signalfd_siginfo __user *) buf; 190 do { 191 ret = signalfd_dequeue(ctx, &info, nonblock); 192 if (unlikely(ret <= 0)) 193 break; 194 ret = signalfd_copyinfo(siginfo, &info); 195 if (ret < 0) 196 break; 197 siginfo++; 198 total += ret; 199 nonblock = 1; 200 } while (--count); 201 202 return total ? total: ret; 203 } 204 205 static const struct file_operations signalfd_fops = { 206 .release = signalfd_release, 207 .poll = signalfd_poll, 208 .read = signalfd_read, 209 }; 210 211 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 212 size_t, sizemask, int, flags) 213 { 214 sigset_t sigmask; 215 struct signalfd_ctx *ctx; 216 217 /* Check the SFD_* constants for consistency. */ 218 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 219 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 220 221 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 222 return -EINVAL; 223 224 if (sizemask != sizeof(sigset_t) || 225 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 226 return -EINVAL; 227 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 228 signotset(&sigmask); 229 230 if (ufd == -1) { 231 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 232 if (!ctx) 233 return -ENOMEM; 234 235 ctx->sigmask = sigmask; 236 237 /* 238 * When we call this, the initialization must be complete, since 239 * anon_inode_getfd() will install the fd. 240 */ 241 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 242 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 243 if (ufd < 0) 244 kfree(ctx); 245 } else { 246 struct file *file = fget(ufd); 247 if (!file) 248 return -EBADF; 249 ctx = file->private_data; 250 if (file->f_op != &signalfd_fops) { 251 fput(file); 252 return -EINVAL; 253 } 254 spin_lock_irq(¤t->sighand->siglock); 255 ctx->sigmask = sigmask; 256 spin_unlock_irq(¤t->sighand->siglock); 257 258 wake_up(¤t->sighand->signalfd_wqh); 259 fput(file); 260 } 261 262 return ufd; 263 } 264 265 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 266 size_t, sizemask) 267 { 268 return sys_signalfd4(ufd, user_mask, sizemask, 0); 269 } 270