LXR linux/fs/signalfd.c

   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
  32struct signalfd_ctx {
  33        sigset_t sigmask;
  34};
  35
  36static int signalfd_release(struct inode *inode, struct file *file)
  37{
  38        kfree(file->private_data);
  39        return 0;
  40}
  41
  42static 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, &current->sighand->signalfd_wqh, wait);
  48
  49        spin_lock_irq(&current->sighand->siglock);
  50        if (next_signal(&current->pending, &ctx->sigmask) ||
  51            next_signal(&current->signal->shared_pending,
  52                        &ctx->sigmask))
  53                events |= POLLIN;
  54        spin_unlock_irq(&current->sighand->siglock);
  55
  56        return events;
  57}
  58
  59/*
  60 * Copied from copy_siginfo_to_user() in kernel/signal.c
  61 */
  62static 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
 128static 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(&current->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(&current->sighand->siglock);
 143                return ret;
 144        }
 145
 146        add_wait_queue(&current->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(&current->sighand->siglock);
 157                schedule();
 158                spin_lock_irq(&current->sighand->siglock);
 159        }
 160        spin_unlock_irq(&current->sighand->siglock);
 161
 162        remove_wait_queue(&current->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 */
 173static 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
 202static const struct file_operations signalfd_fops = {
 203        .release        = signalfd_release,
 204        .poll           = signalfd_poll,
 205        .read           = signalfd_read,
 206};
 207
 208SYSCALL_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                                       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(&current->sighand->siglock);
 252                ctx->sigmask = sigmask;
 253                spin_unlock_irq(&current->sighand->siglock);
 254
 255                wake_up(&current->sighand->signalfd_wqh);
 256                fput(file);
 257        }
 258
 259        return ufd;
 260}
 261
 262SYSCALL_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