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[pv_ops_mirror.git] / fs / select.c

/*
 * This file contains the procedures for the handling of select and poll
 *
 * Created for Linux based loosely upon Mathius Lattner's minix
 * patches by Peter MacDonald. Heavily edited by Linus.
 *
 *  4 February 1994
 *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
 *     flag set in its personality we do *not* modify the given timeout
 *     parameter to reflect time remaining.
 *
 *  24 January 2000
 *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation 
 *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
 */

#include <linux/syscalls.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/poll.h>
#include <linux/personality.h> /* for STICKY_TIMEOUTS */
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/rcupdate.h>

#include <asm/uaccess.h>

#define ROUND_UP(x,y) (((x)+(y)-1)/(y))
#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)

struct poll_table_page {
        struct poll_table_page * next;
        struct poll_table_entry * entry;
        struct poll_table_entry entries[0];
};

#define POLL_TABLE_FULL(table) \
        ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))

/*
 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
 * I have rewritten this, taking some shortcuts: This code may not be easy to
 * follow, but it should be free of race-conditions, and it's practical. If you
 * understand what I'm doing here, then you understand how the linux
 * sleep/wakeup mechanism works.
 *
 * Two very simple procedures, poll_wait() and poll_freewait() make all the
 * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
 * as all select/poll functions have to call it to add an entry to the
 * poll table.
 */
static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
                       poll_table *p);

void poll_initwait(struct poll_wqueues *pwq)
{
        init_poll_funcptr(&pwq->pt, __pollwait);
        pwq->error = 0;
        pwq->table = NULL;
        pwq->inline_index = 0;
}

EXPORT_SYMBOL(poll_initwait);

static void free_poll_entry(struct poll_table_entry *entry)
{
        remove_wait_queue(entry->wait_address,&entry->wait);
        fput(entry->filp);
}

void poll_freewait(struct poll_wqueues *pwq)
{
        struct poll_table_page * p = pwq->table;
        int i;
        for (i = 0; i < pwq->inline_index; i++)
                free_poll_entry(pwq->inline_entries + i);
        while (p) {
                struct poll_table_entry * entry;
                struct poll_table_page *old;

                entry = p->entry;
                do {
                        entry--;
                        free_poll_entry(entry);
                } while (entry > p->entries);
                old = p;
                p = p->next;
                free_page((unsigned long) old);
        }
}

EXPORT_SYMBOL(poll_freewait);

static struct poll_table_entry *poll_get_entry(poll_table *_p)
{
        struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
        struct poll_table_page *table = p->table;

        if (p->inline_index < N_INLINE_POLL_ENTRIES)
                return p->inline_entries + p->inline_index++;

        if (!table || POLL_TABLE_FULL(table)) {
                struct poll_table_page *new_table;

                new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
                if (!new_table) {
                        p->error = -ENOMEM;
                        __set_current_state(TASK_RUNNING);
                        return NULL;
                }
                new_table->entry = new_table->entries;
                new_table->next = table;
                p->table = new_table;
                table = new_table;
        }

        return table->entry++;
}

/* Add a new entry */
static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
                                poll_table *p)
{
        struct poll_table_entry *entry = poll_get_entry(p);
        if (!entry)
                return;
        get_file(filp);
        entry->filp = filp;
        entry->wait_address = wait_address;
        init_waitqueue_entry(&entry->wait, current);
        add_wait_queue(wait_address,&entry->wait);
}

#define FDS_IN(fds, n)          (fds->in + n)
#define FDS_OUT(fds, n)         (fds->out + n)
#define FDS_EX(fds, n)          (fds->ex + n)

#define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))

static int max_select_fd(unsigned long n, fd_set_bits *fds)
{
        unsigned long *open_fds;
        unsigned long set;
        int max;
        struct fdtable *fdt;

        /* handle last in-complete long-word first */
        set = ~(~0UL << (n & (__NFDBITS-1)));
        n /= __NFDBITS;
        fdt = files_fdtable(current->files);
        open_fds = fdt->open_fds->fds_bits+n;
        max = 0;
        if (set) {
                set &= BITS(fds, n);
                if (set) {
                        if (!(set & ~*open_fds))
                                goto get_max;
                        return -EBADF;
                }
        }
        while (n) {
                open_fds--;
                n--;
                set = BITS(fds, n);
                if (!set)
                        continue;
                if (set & ~*open_fds)
                        return -EBADF;
                if (max)
                        continue;
get_max:
                do {
                        max++;
                        set >>= 1;
                } while (set);
                max += n * __NFDBITS;
        }

        return max;
}

#define BIT(i)          (1UL << ((i)&(__NFDBITS-1)))
#define MEM(i,m)        ((m)+(unsigned)(i)/__NFDBITS)
#define ISSET(i,m)      (((i)&*(m)) != 0)
#define SET(i,m)        (*(m) |= (i))

#define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
#define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
#define POLLEX_SET (POLLPRI)

int do_select(int n, fd_set_bits *fds, s64 *timeout)
{
        struct poll_wqueues table;
        poll_table *wait;
        int retval, i;

        rcu_read_lock();
        retval = max_select_fd(n, fds);
        rcu_read_unlock();

        if (retval < 0)
                return retval;
        n = retval;

        poll_initwait(&table);
        wait = &table.pt;
        if (!*timeout)
                wait = NULL;
        retval = 0;
        for (;;) {
                unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
                long __timeout;

                set_current_state(TASK_INTERRUPTIBLE);

                inp = fds->in; outp = fds->out; exp = fds->ex;
                rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;

                for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
                        unsigned long in, out, ex, all_bits, bit = 1, mask, j;
                        unsigned long res_in = 0, res_out = 0, res_ex = 0;
                        const struct file_operations *f_op = NULL;
                        struct file *file = NULL;

                        in = *inp++; out = *outp++; ex = *exp++;
                        all_bits = in | out | ex;
                        if (all_bits == 0) {
                                i += __NFDBITS;
                                continue;
                        }

                        for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
                                int fput_needed;
                                if (i >= n)
                                        break;
                                if (!(bit & all_bits))
                                        continue;
                                file = fget_light(i, &fput_needed);
                                if (file) {
                                        f_op = file->f_op;
                                        mask = DEFAULT_POLLMASK;
                                        if (f_op && f_op->poll)
                                                mask = (*f_op->poll)(file, retval ? NULL : wait);
                                        fput_light(file, fput_needed);
                                        if ((mask & POLLIN_SET) && (in & bit)) {
                                                res_in |= bit;
                                                retval++;
                                        }
                                        if ((mask & POLLOUT_SET) && (out & bit)) {
                                                res_out |= bit;
                                                retval++;
                                        }
                                        if ((mask & POLLEX_SET) && (ex & bit)) {
                                                res_ex |= bit;
                                                retval++;
                                        }
                                }
                                cond_resched();
                        }
                        if (res_in)
                                *rinp = res_in;
                        if (res_out)
                                *routp = res_out;
                        if (res_ex)
                                *rexp = res_ex;
                }
                wait = NULL;
                if (retval || !*timeout || signal_pending(current))
                        break;
                if(table.error) {
                        retval = table.error;
                        break;
                }

                if (*timeout < 0) {
                        /* Wait indefinitely */
                        __timeout = MAX_SCHEDULE_TIMEOUT;
                } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT - 1)) {
                        /* Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in a loop */
                        __timeout = MAX_SCHEDULE_TIMEOUT - 1;
                        *timeout -= __timeout;
                } else {
                        __timeout = *timeout;
                        *timeout = 0;
                }
                __timeout = schedule_timeout(__timeout);
                if (*timeout >= 0)
                        *timeout += __timeout;
        }
        __set_current_state(TASK_RUNNING);

        poll_freewait(&table);

        return retval;
}

/*
 * We can actually return ERESTARTSYS instead of EINTR, but I'd
 * like to be certain this leads to no problems. So I return
 * EINTR just for safety.
 *
 * Update: ERESTARTSYS breaks at least the xview clock binary, so
 * I'm trying ERESTARTNOHAND which restart only when you want to.
 */
#define MAX_SELECT_SECONDS \
        ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)

static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                           fd_set __user *exp, s64 *timeout)
{
        fd_set_bits fds;
        void *bits;
        int ret, max_fds;
        unsigned int size;
        struct fdtable *fdt;
        /* Allocate small arguments on the stack to save memory and be faster */
        long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];

        ret = -EINVAL;
        if (n < 0)
                goto out_nofds;

        /* max_fds can increase, so grab it once to avoid race */
        rcu_read_lock();
        fdt = files_fdtable(current->files);
        max_fds = fdt->max_fds;
        rcu_read_unlock();
        if (n > max_fds)
                n = max_fds;

        /*
         * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
         * since we used fdset we need to allocate memory in units of
         * long-words. 
         */
        size = FDS_BYTES(n);
        bits = stack_fds;
        if (size > sizeof(stack_fds) / 6) {
                /* Not enough space in on-stack array; must use kmalloc */
                ret = -ENOMEM;
                bits = kmalloc(6 * size, GFP_KERNEL);
                if (!bits)
                        goto out_nofds;
        }
        fds.in      = bits;
        fds.out     = bits +   size;
        fds.ex      = bits + 2*size;
        fds.res_in  = bits + 3*size;
        fds.res_out = bits + 4*size;
        fds.res_ex  = bits + 5*size;

        if ((ret = get_fd_set(n, inp, fds.in)) ||
            (ret = get_fd_set(n, outp, fds.out)) ||
            (ret = get_fd_set(n, exp, fds.ex)))
                goto out;
        zero_fd_set(n, fds.res_in);
        zero_fd_set(n, fds.res_out);
        zero_fd_set(n, fds.res_ex);

        ret = do_select(n, &fds, timeout);

        if (ret < 0)
                goto out;
        if (!ret) {
                ret = -ERESTARTNOHAND;
                if (signal_pending(current))
                        goto out;
                ret = 0;
        }

        if (set_fd_set(n, inp, fds.res_in) ||
            set_fd_set(n, outp, fds.res_out) ||
            set_fd_set(n, exp, fds.res_ex))
                ret = -EFAULT;

out:
        if (bits != stack_fds)
                kfree(bits);
out_nofds:
        return ret;
}

asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                        fd_set __user *exp, struct timeval __user *tvp)
{
        s64 timeout = -1;
        struct timeval tv;
        int ret;

        if (tvp) {
                if (copy_from_user(&tv, tvp, sizeof(tv)))
                        return -EFAULT;

                if (tv.tv_sec < 0 || tv.tv_usec < 0)
                        return -EINVAL;

                /* Cast to u64 to make GCC stop complaining */
                if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS)
                        timeout = -1;   /* infinite */
                else {
                        timeout = ROUND_UP(tv.tv_usec, USEC_PER_SEC/HZ);
                        timeout += tv.tv_sec * HZ;
                }
        }

        ret = core_sys_select(n, inp, outp, exp, &timeout);

        if (tvp) {
                struct timeval rtv;

                if (current->personality & STICKY_TIMEOUTS)
                        goto sticky;
                rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));
                rtv.tv_sec = timeout;
                if (timeval_compare(&rtv, &tv) >= 0)
                        rtv = tv;
                if (copy_to_user(tvp, &rtv, sizeof(rtv))) {
sticky:
                        /*
                         * If an application puts its timeval in read-only
                         * memory, we don't want the Linux-specific update to
                         * the timeval to cause a fault after the select has
                         * completed successfully. However, because we're not
                         * updating the timeval, we can't restart the system
                         * call.
                         */
                        if (ret == -ERESTARTNOHAND)
                                ret = -EINTR;
                }
        }

        return ret;
}

#ifdef TIF_RESTORE_SIGMASK
asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp,
                fd_set __user *exp, struct timespec __user *tsp,
                const sigset_t __user *sigmask, size_t sigsetsize)
{
        s64 timeout = MAX_SCHEDULE_TIMEOUT;
        sigset_t ksigmask, sigsaved;
        struct timespec ts;
        int ret;

        if (tsp) {
                if (copy_from_user(&ts, tsp, sizeof(ts)))
                        return -EFAULT;

                if (ts.tv_sec < 0 || ts.tv_nsec < 0)
                        return -EINVAL;

                /* Cast to u64 to make GCC stop complaining */
                if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
                        timeout = -1;   /* infinite */
                else {
                        timeout = ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
                        timeout += ts.tv_sec * HZ;
                }
        }

        if (sigmask) {
                /* XXX: Don't preclude handling different sized sigset_t's.  */
                if (sigsetsize != sizeof(sigset_t))
                        return -EINVAL;
                if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
                        return -EFAULT;

                sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
                sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
        }

        ret = core_sys_select(n, inp, outp, exp, &timeout);

        if (tsp) {
                struct timespec rts;

                if (current->personality & STICKY_TIMEOUTS)
                        goto sticky;
                rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
                                                1000;
                rts.tv_sec = timeout;
                if (timespec_compare(&rts, &ts) >= 0)
                        rts = ts;
                if (copy_to_user(tsp, &rts, sizeof(rts))) {
sticky:
                        /*
                         * If an application puts its timeval in read-only
                         * memory, we don't want the Linux-specific update to
                         * the timeval to cause a fault after the select has
                         * completed successfully. However, because we're not
                         * updating the timeval, we can't restart the system
                         * call.
                         */
                        if (ret == -ERESTARTNOHAND)
                                ret = -EINTR;
                }
        }

        if (ret == -ERESTARTNOHAND) {
                /*
                 * Don't restore the signal mask yet. Let do_signal() deliver
                 * the signal on the way back to userspace, before the signal
                 * mask is restored.
                 */
                if (sigmask) {
                        memcpy(&current->saved_sigmask, &sigsaved,
                                        sizeof(sigsaved));
                        set_thread_flag(TIF_RESTORE_SIGMASK);
                }
        } else if (sigmask)
                sigprocmask(SIG_SETMASK, &sigsaved, NULL);

        return ret;
}

/*
 * Most architectures can't handle 7-argument syscalls. So we provide a
 * 6-argument version where the sixth argument is a pointer to a structure
 * which has a pointer to the sigset_t itself followed by a size_t containing
 * the sigset size.
 */
asmlinkage long sys_pselect6(int n, fd_set __user *inp, fd_set __user *outp,
        fd_set __user *exp, struct timespec __user *tsp, void __user *sig)
{
        size_t sigsetsize = 0;
        sigset_t __user *up = NULL;

        if (sig) {
                if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
                    || __get_user(up, (sigset_t __user * __user *)sig)
                    || __get_user(sigsetsize,
                                (size_t __user *)(sig+sizeof(void *))))
                        return -EFAULT;
        }

        return sys_pselect7(n, inp, outp, exp, tsp, up, sigsetsize);
}
#endif /* TIF_RESTORE_SIGMASK */

struct poll_list {
        struct poll_list *next;
        int len;
        struct pollfd entries[0];
};

#define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))

/*
 * Fish for pollable events on the pollfd->fd file descriptor. We're only
 * interested in events matching the pollfd->events mask, and the result
 * matching that mask is both recorded in pollfd->revents and returned. The
 * pwait poll_table will be used by the fd-provided poll handler for waiting,
 * if non-NULL.
 */
static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
{
        unsigned int mask;
        int fd;

        mask = 0;
        fd = pollfd->fd;
        if (fd >= 0) {
                int fput_needed;
                struct file * file;

                file = fget_light(fd, &fput_needed);
                mask = POLLNVAL;
                if (file != NULL) {
                        mask = DEFAULT_POLLMASK;
                        if (file->f_op && file->f_op->poll)
                                mask = file->f_op->poll(file, pwait);
                        /* Mask out unneeded events. */
                        mask &= pollfd->events | POLLERR | POLLHUP;
                        fput_light(file, fput_needed);
                }
        }
        pollfd->revents = mask;

        return mask;
}

static int do_poll(unsigned int nfds,  struct poll_list *list,
                   struct poll_wqueues *wait, s64 *timeout)
{
        int count = 0;
        poll_table* pt = &wait->pt;

        /* Optimise the no-wait case */
        if (!(*timeout))
                pt = NULL;
 
        for (;;) {
                struct poll_list *walk;
                long __timeout;

                set_current_state(TASK_INTERRUPTIBLE);
                for (walk = list; walk != NULL; walk = walk->next) {
                        struct pollfd * pfd, * pfd_end;

                        pfd = walk->entries;
                        pfd_end = pfd + walk->len;
                        for (; pfd != pfd_end; pfd++) {
                                /*
                                 * Fish for events. If we found one, record it
                                 * and kill the poll_table, so we don't
                                 * needlessly register any other waiters after
                                 * this. They'll get immediately deregistered
                                 * when we break out and return.
                                 */
                                if (do_pollfd(pfd, pt)) {
                                        count++;
                                        pt = NULL;
                                }
                        }
                }
                /*
                 * All waiters have already been registered, so don't provide
                 * a poll_table to them on the next loop iteration.
                 */
                pt = NULL;
                if (count || !*timeout || signal_pending(current))
                        break;
                count = wait->error;
                if (count)
                        break;

                if (*timeout < 0) {
                        /* Wait indefinitely */
                        __timeout = MAX_SCHEDULE_TIMEOUT;
                } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT-1)) {
                        /*
                         * Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in
                         * a loop
                         */
                        __timeout = MAX_SCHEDULE_TIMEOUT - 1;
                        *timeout -= __timeout;
                } else {
                        __timeout = *timeout;
                        *timeout = 0;
                }

                __timeout = schedule_timeout(__timeout);
                if (*timeout >= 0)
                        *timeout += __timeout;
        }
        __set_current_state(TASK_RUNNING);
        return count;
}

#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
                        sizeof(struct pollfd))

int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
{
        struct poll_wqueues table;
        int fdcount, err;
        unsigned int i;
        struct poll_list *head;
        struct poll_list *walk;
        /* Allocate small arguments on the stack to save memory and be
           faster - use long to make sure the buffer is aligned properly
           on 64 bit archs to avoid unaligned access */
        long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
        struct poll_list *stack_pp = NULL;

        /* Do a sanity check on nfds ... */
        if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
                return -EINVAL;

        poll_initwait(&table);

        head = NULL;
        walk = NULL;
        i = nfds;
        err = -ENOMEM;
        while(i!=0) {
                struct poll_list *pp;
                int num, size;
                if (stack_pp == NULL)
                        num = N_STACK_PPS;
                else
                        num = POLLFD_PER_PAGE;
                if (num > i)
                        num = i;
                size = sizeof(struct poll_list) + sizeof(struct pollfd)*num;
                if (!stack_pp)
                        stack_pp = pp = (struct poll_list *)stack_pps;
                else {
                        pp = kmalloc(size, GFP_KERNEL);
                        if (!pp)
                                goto out_fds;
                }
                pp->next=NULL;
                pp->len = num;
                if (head == NULL)
                        head = pp;
                else
                        walk->next = pp;

                walk = pp;
                if (copy_from_user(pp->entries, ufds + nfds-i, 
                                sizeof(struct pollfd)*num)) {
                        err = -EFAULT;
                        goto out_fds;
                }
                i -= pp->len;
        }

        fdcount = do_poll(nfds, head, &table, timeout);

        /* OK, now copy the revents fields back to user space. */
        walk = head;
        err = -EFAULT;
        while(walk != NULL) {
                struct pollfd *fds = walk->entries;
                int j;

                for (j=0; j < walk->len; j++, ufds++) {
                        if(__put_user(fds[j].revents, &ufds->revents))
                                goto out_fds;
                }
                walk = walk->next;
        }
        err = fdcount;
        if (!fdcount && signal_pending(current))
                err = -EINTR;
out_fds:
        walk = head;
        while(walk!=NULL) {
                struct poll_list *pp = walk->next;
                if (walk != stack_pp)
                        kfree(walk);
                walk = pp;
        }
        poll_freewait(&table);
        return err;
}

asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
                        long timeout_msecs)
{
        s64 timeout_jiffies;

        if (timeout_msecs > 0) {
#if HZ > 1000
                /* We can only overflow if HZ > 1000 */
                if (timeout_msecs / 1000 > (s64)0x7fffffffffffffffULL / (s64)HZ)
                        timeout_jiffies = -1;
                else
#endif
                        timeout_jiffies = msecs_to_jiffies(timeout_msecs);
        } else {
                /* Infinite (< 0) or no (0) timeout */
                timeout_jiffies = timeout_msecs;
        }

        return do_sys_poll(ufds, nfds, &timeout_jiffies);
}

#ifdef TIF_RESTORE_SIGMASK
asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
        struct timespec __user *tsp, const sigset_t __user *sigmask,
        size_t sigsetsize)
{
        sigset_t ksigmask, sigsaved;
        struct timespec ts;
        s64 timeout = -1;
        int ret;

        if (tsp) {
                if (copy_from_user(&ts, tsp, sizeof(ts)))
                        return -EFAULT;

                /* Cast to u64 to make GCC stop complaining */
                if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
                        timeout = -1;   /* infinite */
                else {
                        timeout = ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
                        timeout += ts.tv_sec * HZ;
                }
        }

        if (sigmask) {
                /* XXX: Don't preclude handling different sized sigset_t's.  */
                if (sigsetsize != sizeof(sigset_t))
                        return -EINVAL;
                if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
                        return -EFAULT;

                sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
                sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
        }

        ret = do_sys_poll(ufds, nfds, &timeout);

        /* We can restart this syscall, usually */
        if (ret == -EINTR) {
                /*
                 * Don't restore the signal mask yet. Let do_signal() deliver
                 * the signal on the way back to userspace, before the signal
                 * mask is restored.
                 */
                if (sigmask) {
                        memcpy(&current->saved_sigmask, &sigsaved,
                                        sizeof(sigsaved));
                        set_thread_flag(TIF_RESTORE_SIGMASK);
                }
                ret = -ERESTARTNOHAND;
        } else if (sigmask)
                sigprocmask(SIG_SETMASK, &sigsaved, NULL);

        if (tsp && timeout >= 0) {
                struct timespec rts;

                if (current->personality & STICKY_TIMEOUTS)
                        goto sticky;
                /* Yes, we know it's actually an s64, but it's also positive. */
                rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
                                                1000;
                rts.tv_sec = timeout;
                if (timespec_compare(&rts, &ts) >= 0)
                        rts = ts;
                if (copy_to_user(tsp, &rts, sizeof(rts))) {
                sticky:
                        /*
                         * If an application puts its timeval in read-only
                         * memory, we don't want the Linux-specific update to
                         * the timeval to cause a fault after the select has
                         * completed successfully. However, because we're not
                         * updating the timeval, we can't restart the system
                         * call.
                         */
                        if (ret == -ERESTARTNOHAND && timeout >= 0)
                                ret = -EINTR;
                }
        }

        return ret;
}
#endif /* TIF_RESTORE_SIGMASK */