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, ¤t->sighand->signalfd_wqh, wait); 48 49 spin_lock_irq(¤t->sighand->siglock); 50 if (next_signal(¤t->pending, &ctx->sigmask) || 51 next_signal(¤t->signal->shared_pending, 52 &ctx->sigmask)) 53 events |= POLLIN; 54 spin_unlock_irq(¤t->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(¤t->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(¤t->sighand->siglock); 143 return ret; 144 } 145 146 add_wait_queue(¤t->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(¤t->sighand->siglock); 157 schedule(); 158 spin_lock_irq(¤t->sighand->siglock); 159 } 160 spin_unlock_irq(¤t->sighand->siglock); 161 162 remove_wait_queue(¤t->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 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 209 size_t, sizemask, int, flags) 210 { 211 sigset_t sigmask; 212 struct signalfd_ctx *ctx; 213 214 /* Check the SFD_* constants for consistency. */ 215 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 216 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 217 218 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 219 return -EINVAL; 220 221 if (sizemask != sizeof(sigset_t) || 222 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 223 return -EINVAL; 224 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 225 signotset(&sigmask); 226 227 if (ufd == -1) { 228 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 229 if (!ctx) 230 return -ENOMEM; 231 232 ctx->sigmask = sigmask; 233 234 /* 235 * When we call this, the initialization must be complete, since 236 * anon_inode_getfd() will install the fd. 237 */ 238 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 239 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 240 if (ufd < 0) 241 kfree(ctx); 242 } else { 243 struct file *file = fget(ufd); 244 if (!file) 245 return -EBADF; 246 ctx = file->private_data; 247 if (file->f_op != &signalfd_fops) { 248 fput(file); 249 return -EINVAL; 250 } 251 spin_lock_irq(¤t->sighand->siglock); 252 ctx->sigmask = sigmask; 253 spin_unlock_irq(¤t->sighand->siglock); 254 255 wake_up(¤t->sighand->signalfd_wqh); 256 fput(file); 257 } 258 259 return ufd; 260 } 261 262 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 263 size_t, sizemask) 264 { 265 return sys_signalfd4(ufd, user_mask, sizemask, 0); 266 } 267