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/*

 * 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/slab.h>

#include <linux/smp_lock.h>

#include <linux/poll.h>

#include <linux/personality.h> /* for STICKY_TIMEOUTS */

#include <linux/file.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 poll_freewait(poll_table* pt)

{

        struct poll_table_page * p = pt->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);

        }

}

void __pollwait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)

{

        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)

{

        poll_table table, *wait;

        int retval, i, off;

        long __timeout = *timeout;

        read_lock(&current->files->file_lock);

        retval = max_select_fd(n, fds);

        read_unlock(&current->files->file_lock);

        if (retval < 0)

                return retval;

        n = retval;

        poll_initwait(&table);

        wait = &table;

        if (!__timeout)

                wait = NULL;

        retval = 0;

        for (;;) {

                set_current_state(TASK_INTERRUPTIBLE);

                for (i = 0 ; i < n; i++) {

                        unsigned long bit = BIT(i);

                        unsigned long mask;

                        struct file *file;

                        off = i / __NFDBITS;

                        if (!(bit & BITS(fds, off)))

                                continue;

                        file = fget(i);

                        mask = POLLNVAL;

                        if (file) {

                                mask = DEFAULT_POLLMASK;

                                if (file->f_op && file->f_op->poll)

                                        mask = file->f_op->poll(file, wait);

                                fput(file);

                        }

                        if ((mask & POLLIN_SET) && ISSET(bit, __IN(fds,off))) {

                                SET(bit, __RES_IN(fds,off));

                                retval++;

                                wait = NULL;

                        }

                        if ((mask & POLLOUT_SET) && ISSET(bit, __OUT(fds,off))) {

                                SET(bit, __RES_OUT(fds,off));

                                retval++;

                                wait = NULL;

                        }

                        if ((mask & POLLEX_SET) && ISSET(bit, __EX(fds,off))) {

                                SET(bit, __RES_EX(fds,off));

                                retval++;

                                wait = NULL;

                        }

                }

                wait = NULL;

                if (retval || !__timeout || signal_pending(current))

                        break;

                if(table.error) {

                        retval = table.error;

                        break;

                }

                __timeout = schedule_timeout(__timeout);

        }

        current->state = TASK_RUNNING;

        poll_freewait(&table);

        /*

         * Up-to-date the caller timeout.

         */

        *timeout = __timeout;

        return retval;

}

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 *inp, fd_set *outp, fd_set *exp, struct timeval *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;

}

#define POLLFD_PER_PAGE  ((PAGE_SIZE) / 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, unsigned int nchunks, unsigned int nleft,

        struct pollfd *fds[], poll_table *wait, long timeout)

{

        int count;

        poll_table* pt = wait;

        for (;;) {

                unsigned int i;

                set_current_state(TASK_INTERRUPTIBLE);

                count = 0;

                for (i=0; i < nchunks; i++)

                        do_pollfd(POLLFD_PER_PAGE, fds[i], &pt, &count);

                if (nleft)

                        do_pollfd(nleft, fds[nchunks], &pt, &count);

                pt = NULL;

                if (count || !timeout || signal_pending(current))

                        break;

                count = wait->error;

                if (count)

                        break;

                timeout = schedule_timeout(timeout);

        }

        current->state = TASK_RUNNING;

        return count;

}

asmlinkage long sys_poll(struct pollfd * ufds, unsigned int nfds, long timeout)

{

        int i, j, fdcount, err;

        struct pollfd **fds;

        poll_table table, *wait;

        int nchunks, nleft;

        /* 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);

        wait = &table;

        if (!timeout)

                wait = NULL;

        err = -ENOMEM;

        fds = NULL;

        if (nfds != 0) {

                fds = (struct pollfd **)kmalloc(

                        (1 + (nfds - 1) / POLLFD_PER_PAGE) * sizeof(struct pollfd *),

                        GFP_KERNEL);

                if (fds == NULL)

                        goto out;

        }

        nchunks = 0;

        nleft = nfds;

        while (nleft > POLLFD_PER_PAGE) { /* allocate complete PAGE_SIZE chunks */

                fds[nchunks] = (struct pollfd *)__get_free_page(GFP_KERNEL);

                if (fds[nchunks] == NULL)

                        goto out_fds;

                nchunks++;

                nleft -= POLLFD_PER_PAGE;

        }

        if (nleft) { /* allocate last PAGE_SIZE chunk, only nleft elements used */

                fds[nchunks] = (struct pollfd *)__get_free_page(GFP_KERNEL);

                if (fds[nchunks] == NULL)

                        goto out_fds;

        }

        err = -EFAULT;

        for (i=0; i < nchunks; i++)

                if (copy_from_user(fds[i], ufds + i*POLLFD_PER_PAGE, PAGE_SIZE))

                        goto out_fds1;

        if (nleft) {

                if (copy_from_user(fds[nchunks], ufds + nchunks*POLLFD_PER_PAGE,

                                nleft * sizeof(struct pollfd)))

                        goto out_fds1;

        }

        fdcount = do_poll(nfds, nchunks, nleft, fds, wait, timeout);

        /* OK, now copy the revents fields back to user space. */

        for(i=0; i < nchunks; i++)

                for (j=0; j < POLLFD_PER_PAGE; j++, ufds++)

                        __put_user((fds[i] + j)->revents, &ufds->revents);

        if (nleft)

                for (j=0; j < nleft; j++, ufds++)

                        __put_user((fds[nchunks] + j)->revents, &ufds->revents);

        err = fdcount;

        if (!fdcount && signal_pending(current))

                err = -EINTR;

out_fds1:

        if (nleft)

                free_page((unsigned long)(fds[nchunks]));

out_fds:

        for (i=0; i < nchunks; i++)

                free_page((unsigned long)(fds[i]));

        if (nfds != 0)

                kfree(fds);

out:

        poll_freewait(&table);

        return err;

}