root/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/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 <asm/uaccess.h>

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

struct poll_table_entry {
        struct file * filp;
        wait_queue_t wait;
        wait_queue_head_t * wait_address;
};

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.
 */
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;
}

EXPORT_SYMBOL(poll_initwait);

void poll_freewait(struct poll_wqueues *pwq)
{
        struct poll_table_page * p = pwq->table;
        while (p) {
                struct poll_table_entry * entry;
                struct poll_table_page *old;

                entry = p->entry;
                do {
                        entry--;
                        remove_wait_queue(entry->wait_address,&entry->wait);
                        fput(entry->filp);
                } while (entry > p->entries);
                old = p;
                p = p->next;
                free_page((unsigned long) old);
        }
}

EXPORT_SYMBOL(poll_freewait);

//NEW FOR RING CYCLE
void mod_poll_wait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p)
{
    poll_wait(filp, wait_address, p);
}


void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *_p)
{
        struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
        struct poll_table_page *table = p->table;

        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;
                }
                new_table->entry = new_table->entries;
                new_table->next = table;
                p->table = new_table;
                table = new_table;
        }

        /* Add a new entry */
        {
                struct poll_table_entry * entry = table->entry;
                table->entry = entry+1;
                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 __IN(fds, n)            (fds->in + n)
#define __OUT(fds, n)           (fds->out + n)
#define __EX(fds, n)            (fds->ex + n)
#define __RES_IN(fds, n)        (fds->res_in + n)
#define __RES_OUT(fds, n)       (fds->res_out + n)
#define __RES_EX(fds, n)        (fds->res_ex + n)

#define BITS(fds, n)            (*__IN(fds, n)|*__OUT(fds, n)|*__EX(fds, n))

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

        /* handle last in-complete long-word first */
        set = ~(~0UL << (n & (__NFDBITS-1)));
        n /= __NFDBITS;
        open_fds = current->files->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, long *timeout)
{
        struct poll_wqueues table;
        poll_table *wait;
        int retval, i;
        long __timeout = *timeout;

        spin_lock(&current->files->file_lock);
        retval = max_select_fd(n, fds);
        spin_unlock(&current->files->file_lock);

        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;

                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;
                        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) {
                                if (i >= n)
                                        break;
                                if (!(bit & all_bits))
                                        continue;
                                file = fget(i);
                                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(file);
                                        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++;
                                        }
                                }
                        }
                        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;
                }
                __timeout = schedule_timeout(__timeout);
        }
        __set_current_state(TASK_RUNNING);

        poll_freewait(&table);

        /*
         * Up-to-date the caller timeout.
         */
        *timeout = __timeout;
        return retval;
}

EXPORT_SYMBOL(do_select);

static void *select_bits_alloc(int size)
{
        return kmalloc(6 * size, GFP_KERNEL);
}

static void select_bits_free(void *bits, int size)
{
        kfree(bits);
}

/*
 * 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)

asmlinkage long
sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp)
{
        fd_set_bits fds;
        char *bits;
        long timeout;
        int ret, size, max_fdset;

        timeout = MAX_SCHEDULE_TIMEOUT;
        if (tvp) {
                time_t sec, usec;

                if ((ret = verify_area(VERIFY_READ, tvp, sizeof(*tvp)))
                    || (ret = __get_user(sec, &tvp->tv_sec))
                    || (ret = __get_user(usec, &tvp->tv_usec)))
                        goto out_nofds;

                ret = -EINVAL;
                if (sec < 0 || usec < 0)
                        goto out_nofds;

                if ((unsigned long) sec < MAX_SELECT_SECONDS) {
                        timeout = ROUND_UP(usec, 1000000/HZ);
                        timeout += sec * (unsigned long) HZ;
                }
        }

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

        /* max_fdset can increase, so grab it once to avoid race */
        max_fdset = current->files->max_fdset;
        if (n > max_fdset)
                n = max_fdset;

        /*
         * 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. 
         */
        ret = -ENOMEM;
        size = FDS_BYTES(n);
        bits = select_bits_alloc(size);
        if (!bits)
                goto out_nofds;
        fds.in      = (unsigned long *)  bits;
        fds.out     = (unsigned long *) (bits +   size);
        fds.ex      = (unsigned long *) (bits + 2*size);
        fds.res_in  = (unsigned long *) (bits + 3*size);
        fds.res_out = (unsigned long *) (bits + 4*size);
        fds.res_ex  = (unsigned long *) (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 (tvp && !(current->personality & STICKY_TIMEOUTS)) {
                time_t sec = 0, usec = 0;
                if (timeout) {
                        sec = timeout / HZ;
                        usec = timeout % HZ;
                        usec *= (1000000/HZ);
                }
                put_user(sec, &tvp->tv_sec);
                put_user(usec, &tvp->tv_usec);
        }

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

        set_fd_set(n, inp, fds.res_in);
        set_fd_set(n, outp, fds.res_out);
        set_fd_set(n, exp, fds.res_ex);

out:
        select_bits_free(bits, size);
out_nofds:
        return ret;
}

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))

static void do_pollfd(unsigned int num, struct pollfd * fdpage,
        poll_table ** pwait, int *count)
{
        int i;

        for (i = 0; i < num; i++) {
                int fd;
                unsigned int mask;
                struct pollfd *fdp;

                mask = 0;
                fdp = fdpage+i;
                fd = fdp->fd;
                if (fd >= 0) {
                        struct file * file = fget(fd);
                        mask = POLLNVAL;
                        if (file != NULL) {
                                mask = DEFAULT_POLLMASK;
                                if (file->f_op && file->f_op->poll)
                                        mask = file->f_op->poll(file, *pwait);
                                mask &= fdp->events | POLLERR | POLLHUP;
                                fput(file);
                        }
                        if (mask) {
                                *pwait = NULL;
                                (*count)++;
                        }
                }
                fdp->revents = mask;
        }
}

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

        if (!timeout)
                pt = NULL;
 
        for (;;) {
                struct poll_list *walk;
                set_current_state(TASK_INTERRUPTIBLE);
                walk = list;
                while(walk != NULL) {
                        do_pollfd( walk->len, walk->entries, &pt, &count);
                        walk = walk->next;
                }
                pt = NULL;
                if (count || !timeout || signal_pending(current))
                        break;
                count = wait->error;
                if (count)
                        break;
                timeout = schedule_timeout(timeout);
        }
        __set_current_state(TASK_RUNNING);
        return count;
}

asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
{
        struct poll_wqueues table;
        int fdcount, err;
        unsigned int i;
        struct poll_list *head;
        struct poll_list *walk;

        /* Do a sanity check on nfds ... */
        if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
                return -EINVAL;

        if (timeout) {
                /* Careful about overflow in the intermediate values */
                if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
                        timeout = (unsigned long)(timeout*HZ+999)/1000+1;
                else /* Negative or overflow */
                        timeout = MAX_SCHEDULE_TIMEOUT;
        }

        poll_initwait(&table);

        head = NULL;
        walk = NULL;
        i = nfds;
        err = -ENOMEM;
        while(i!=0) {
                struct poll_list *pp;
                pp = kmalloc(sizeof(struct poll_list)+
                                sizeof(struct pollfd)*
                                (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
                                        GFP_KERNEL);
                if(pp==NULL)
                        goto out_fds;
                pp->next=NULL;
                pp->len = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
                if (head == NULL)
                        head = pp;
                else
                        walk->next = pp;

                walk = pp;
                if (copy_from_user(pp->entries, ufds + nfds-i, 
                                sizeof(struct pollfd)*pp->len)) {
                        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;
                kfree(walk);
                walk = pp;
        }
        poll_freewait(&table);
        return err;
}