graphene/Pal/src/host/Linux-SGX/db_object.c

/* Copyright (C) 2014 Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * db_object.c
 *
 * This file contains APIs for closing or polling PAL handles.
 */

#include "pal_defs.h"
#include "pal_linux_defs.h"
#include "pal.h"
#include "pal_internal.h"
#include "pal_linux.h"
#include "pal_linux_error.h"
#include "pal_error.h"
#include "pal_debug.h"
#include "api.h"

#include <linux/time.h>
#include <linux/poll.h>
#include <linux/wait.h>
#include <atomic.h>

#define DEFAULT_QUANTUM 500

/* internally to wait for one object. Also used as a shortcut to wait
   on events and semaphores */
static int _DkObjectWaitOne(PAL_HANDLE handle, int64_t timeout_us) {
    /* only for all these handle which has a file descriptor, or
       a eventfd. events and semaphores will skip this part */
    if (HANDLE_HDR(handle)->flags & HAS_FDS) {
        struct pollfd fds[MAX_FDS];
        int off[MAX_FDS];
        int nfds = 0;
        for (int i = 0 ; i < MAX_FDS ; i++) {
            int events = 0;

            if ((HANDLE_HDR(handle)->flags & RFD(i)) &&
                !(HANDLE_HDR(handle)->flags & ERROR(i)))
                events |= POLLIN;

            if ((HANDLE_HDR(handle)->flags & WFD(i)) &&
                !(HANDLE_HDR(handle)->flags & WRITABLE(i)) &&
                !(HANDLE_HDR(handle)->flags & ERROR(i)))
                events |= POLLOUT;

            if (events) {
                fds[nfds].fd = handle->generic.fds[i];
                fds[nfds].events = events|POLLHUP|POLLERR;
                fds[nfds].revents = 0;
                off[nfds] = i;
                nfds++;
            }
        }

        if (!nfds)
            return -PAL_ERROR_TRYAGAIN;

        int ret = ocall_poll(fds, nfds, timeout_us);
        if (IS_ERR(ret))
            return unix_to_pal_error(ERRNO(ret));

        if (!ret)
            return -PAL_ERROR_TRYAGAIN;

        for (int i = 0 ; i < nfds ; i++) {
            if (!fds[i].revents)
                continue;
            if (fds[i].revents & POLLOUT)
                HANDLE_HDR(handle)->flags |= WRITABLE(off[i]);
            if (fds[i].revents & (POLLHUP|POLLERR))
                HANDLE_HDR(handle)->flags |= ERROR(off[i]);
        }

        return 0;
    }

    const struct handle_ops * ops = HANDLE_OPS(handle);

    if (!ops || !ops->wait)
        return -PAL_ERROR_NOTSUPPORT;

    return ops->wait(handle, timeout_us);
}

/* _DkObjectsWaitAny for internal use. The function wait for any of the handle
   in the handle array. timeout_us can be set for the wait. */
int _DkObjectsWaitAny(int count, PAL_HANDLE* handleArray, int64_t timeout_us,
                      PAL_HANDLE* polled) {
    if (count <= 0)
        return 0;

    if (count == 1) {
        // It is possible to have NULL pointers in the handle array.
        // In this case, assume nothing is polled.
        if (!handleArray[0])
            return -PAL_ERROR_TRYAGAIN;

        int rv = _DkObjectWaitOne(handleArray[0], timeout_us);
        if (rv == 0)
            *polled = handleArray[0];
        return rv;
    }

    int i, j, ret, maxfds = 0, nfds = 0;

    /* we are not gonna to allow any polling on muliple synchronous
       objects, doing this is simply violating the division of
       labor between PAL and library OS */
    for (i = 0 ; i < count ; i++) {
        PAL_HANDLE hdl = handleArray[i];

        if (!hdl)
            continue;

        if (!(HANDLE_HDR(hdl)->flags & HAS_FDS))
            return -PAL_ERROR_NOTSUPPORT;

        /* eliminate repeated entries */
        for (j = 0 ; j < i ; j++)
            if (hdl == handleArray[j])
                break;
        if (j == i) {
            for (j = 0 ; j < MAX_FDS ; j++)
                if (HANDLE_HDR(hdl)->flags & (RFD(j)|WFD(j)))
                    maxfds++;
        }
    }

    struct pollfd * fds = __alloca(sizeof(struct pollfd) * maxfds);
    PAL_HANDLE * hdls = __alloca(sizeof(PAL_HANDLE) * maxfds);

    for (i = 0 ; i < count ; i++) {
        PAL_HANDLE hdl = handleArray[i];

        if (!hdl)
            continue;

        for (j = 0 ; j < i ; j++)
            if (hdl == handleArray[j])
                break;
        if (j < i)
            continue;

        for (j = 0 ; j < MAX_FDS ; j++) {
            int events = 0;

            if ((HANDLE_HDR(hdl)->flags & RFD(j)) &&
                !(HANDLE_HDR(hdl)->flags & ERROR(j)))
                events |= POLLIN;

            if ((HANDLE_HDR(hdl)->flags & WFD(j)) &&
                !(HANDLE_HDR(hdl)->flags & WRITABLE(j)) &&
                !(HANDLE_HDR(hdl)->flags & ERROR(j)))
                events |= POLLOUT;

            if (events && hdl->generic.fds[j] != PAL_IDX_POISON) {
                fds[nfds].fd = hdl->generic.fds[j];
                fds[nfds].events = events|POLLHUP|POLLERR;
                fds[nfds].revents = 0;
                hdls[nfds] = hdl;
                nfds++;
            }
        }
    }

    if (!nfds)
        return -PAL_ERROR_TRYAGAIN;

    ret = ocall_poll(fds, nfds, timeout_us);
    if (IS_ERR(ret))
        return unix_to_pal_error(ERRNO(ret));

    if (!ret)
        return -PAL_ERROR_TRYAGAIN;

    PAL_HANDLE polled_hdl = NULL;

    for (i = 0 ; i < nfds ; i++) {
        if (!fds[i].revents)
            continue;

        PAL_HANDLE hdl = hdls[i];

        if (polled_hdl) {
            if (hdl != polled_hdl)
                continue;
        } else {
            polled_hdl = hdl;
        }

        for (j = 0 ; j < MAX_FDS ; j++)
            if ((HANDLE_HDR(hdl)->flags & (RFD(j)|WFD(j))) &&
                hdl->generic.fds[j] == (PAL_IDX)fds[i].fd)
                break;

        if (j == MAX_FDS)
            continue;

        if (fds[i].revents & POLLOUT)
            HANDLE_HDR(hdl)->flags |= WRITABLE(j);
        if (fds[i].revents & (POLLHUP|POLLERR))
            HANDLE_HDR(hdl)->flags |= ERROR(j);
    }

    *polled = polled_hdl;
    return polled_hdl ? 0 : -PAL_ERROR_TRYAGAIN;
}