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: /* this is just in case for now ... */ 115 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 116 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 117 break; 118 } 119 120 return err ? -EFAULT: sizeof(*uinfo); 121 } 122 123 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 124 int nonblock) 125 { 126 ssize_t ret; 127 DECLARE_WAITQUEUE(wait, current); 128 129 spin_lock_irq(¤t->sighand->siglock); 130 ret = dequeue_signal(current, &ctx->sigmask, info); 131 switch (ret) { 132 case 0: 133 if (!nonblock) 134 break; 135 ret = -EAGAIN; 136 default: 137 spin_unlock_irq(¤t->sighand->siglock); 138 return ret; 139 } 140 141 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 142 for (;;) { 143 set_current_state(TASK_INTERRUPTIBLE); 144 ret = dequeue_signal(current, &ctx->sigmask, info); 145 if (ret != 0) 146 break; 147 if (signal_pending(current)) { 148 ret = -ERESTARTSYS; 149 break; 150 } 151 spin_unlock_irq(¤t->sighand->siglock); 152 schedule(); 153 spin_lock_irq(¤t->sighand->siglock); 154 } 155 spin_unlock_irq(¤t->sighand->siglock); 156 157 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 158 __set_current_state(TASK_RUNNING); 159 160 return ret; 161 } 162 163 /* 164 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 165 * error code. The "count" parameter must be at least the size of a 166 * "struct signalfd_siginfo". 167 */ 168 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 169 loff_t *ppos) 170 { 171 struct signalfd_ctx *ctx = file->private_data; 172 struct signalfd_siginfo __user *siginfo; 173 int nonblock = file->f_flags & O_NONBLOCK; 174 ssize_t ret, total = 0; 175 siginfo_t info; 176 177 count /= sizeof(struct signalfd_siginfo); 178 if (!count) 179 return -EINVAL; 180 181 siginfo = (struct signalfd_siginfo __user *) buf; 182 do { 183 ret = signalfd_dequeue(ctx, &info, nonblock); 184 if (unlikely(ret <= 0)) 185 break; 186 ret = signalfd_copyinfo(siginfo, &info); 187 if (ret < 0) 188 break; 189 siginfo++; 190 total += ret; 191 nonblock = 1; 192 } while (--count); 193 194 return total ? total: ret; 195 } 196 197 static const struct file_operations signalfd_fops = { 198 .release = signalfd_release, 199 .poll = signalfd_poll, 200 .read = signalfd_read, 201 }; 202 203 asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask) 204 { 205 int error; 206 sigset_t sigmask; 207 struct signalfd_ctx *ctx; 208 struct file *file; 209 struct inode *inode; 210 211 if (sizemask != sizeof(sigset_t) || 212 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 213 return -EINVAL; 214 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 215 signotset(&sigmask); 216 217 if (ufd == -1) { 218 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 219 if (!ctx) 220 return -ENOMEM; 221 222 ctx->sigmask = sigmask; 223 224 /* 225 * When we call this, the initialization must be complete, since 226 * anon_inode_getfd() will install the fd. 227 */ 228 error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]", 229 &signalfd_fops, ctx); 230 if (error) 231 goto err_fdalloc; 232 } else { 233 file = fget(ufd); 234 if (!file) 235 return -EBADF; 236 ctx = file->private_data; 237 if (file->f_op != &signalfd_fops) { 238 fput(file); 239 return -EINVAL; 240 } 241 spin_lock_irq(¤t->sighand->siglock); 242 ctx->sigmask = sigmask; 243 spin_unlock_irq(¤t->sighand->siglock); 244 245 wake_up(¤t->sighand->signalfd_wqh); 246 fput(file); 247 } 248 249 return ufd; 250 251 err_fdalloc: 252 kfree(ctx); 253 return error; 254 } 255 256