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

/* Copyright (C) 2019 Intel Corporation
   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_eventfd.c
 *
 * This file contains operations to handle streams with URIs that have "eventfd:".
 */

#include <asm/fcntl.h>
#include <asm/poll.h>
#include <linux/types.h>
#include <linux/un.h>
#include <sys/eventfd.h>

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

static inline int eventfd_type(int options) {
    int type = 0;
    if (options & PAL_OPTION_NONBLOCK)
        type |= EFD_NONBLOCK;

    if (options & PAL_OPTION_CLOEXEC)
        type |= EFD_CLOEXEC;

    if (options & PAL_OPTION_EFD_SEMAPHORE)
        type |= EFD_SEMAPHORE;

    return type;
}

/* `type` must be eventfd, `uri` & `access` & `share` are unused, `create` holds eventfd's initval,
 * `options` holds eventfd's flags */
static int eventfd_pal_open(PAL_HANDLE* handle, const char* type, const char* uri, int access,
                            int share, int create, int options) {
    int ret;
    __UNUSED(access);
    __UNUSED(share);

    if ((strcmp_static(type, URI_TYPE_EVENTFD) != 0) || (*uri != '\0')) {
        return -PAL_ERROR_INVAL;
    }

    /* Using create arg as a work-around (note: initval is uint32 but create is int32).*/
    ret = ocall_eventfd(create, eventfd_type(options));

    if (IS_ERR(ret))
        return unix_to_pal_error(ERRNO(ret));

    PAL_HANDLE hdl = malloc(HANDLE_SIZE(eventfd));
    SET_HANDLE_TYPE(hdl, eventfd);

    /* Note: using index 0, given that there is only 1 eventfd FD per pal-handle. */
    HANDLE_HDR(hdl)->flags = RFD(0) | WFD(0);

    hdl->eventfd.fd          = ret;
    hdl->eventfd.nonblocking = (options & PAL_OPTION_NONBLOCK) ? PAL_TRUE : PAL_FALSE;
    *handle = hdl;

    return 0;
}

static int64_t eventfd_pal_read(PAL_HANDLE handle, uint64_t offset, uint64_t len, void* buffer) {
    if (offset)
        return -PAL_ERROR_INVAL;

    if (!IS_HANDLE_TYPE(handle, eventfd))
        return -PAL_ERROR_NOTCONNECTION;

    if (len < sizeof(uint64_t))
        return -PAL_ERROR_INVAL;

    /* TODO: verify that the value returned in buffer is somehow meaningful (to prevent Iago
     * attacks) */
    ssize_t bytes = ocall_read(handle->eventfd.fd, buffer, len);

    if (IS_ERR(bytes))
        return unix_to_pal_error(ERRNO(bytes));

    if (!bytes)
        return -PAL_ERROR_ENDOFSTREAM;

    return bytes;
}

static int64_t eventfd_pal_write(PAL_HANDLE handle, uint64_t offset, uint64_t len,
                                 const void* buffer) {
    if (offset)
        return -PAL_ERROR_INVAL;

    if (!IS_HANDLE_TYPE(handle, eventfd))
        return -PAL_ERROR_NOTCONNECTION;

    if (len < sizeof(uint64_t))
        return -PAL_ERROR_INVAL;

    ssize_t bytes = ocall_write(handle->eventfd.fd, buffer, len);
    if (IS_ERR(bytes))
        return unix_to_pal_error(ERRNO(bytes));

    return bytes;
}

/* invoked during poll operation on eventfd from LibOS. */
static int eventfd_pal_attrquerybyhdl(PAL_HANDLE handle, PAL_STREAM_ATTR* attr) {
    int ret;

    if (handle->eventfd.fd == PAL_IDX_POISON)
        return -PAL_ERROR_BADHANDLE;

    attr->handle_type  = HANDLE_HDR(handle)->type;
    attr->nonblocking  = handle->eventfd.nonblocking;
    attr->disconnected = HANDLE_HDR(handle)->flags & ERROR(0);

    /* get number of bytes available for reading */
    ret = ocall_fionread(handle->eventfd.fd);
    if (IS_ERR(ret))
        return unix_to_pal_error(ERRNO(ret));

    attr->pending_size = ret;

    /* query if there is data available for reading */
    struct pollfd pfd = {.fd = handle->eventfd.fd, .events = POLLIN | POLLOUT, .revents = 0};
    ret = ocall_poll(&pfd, 1, 0);
    if (IS_ERR(ret))
        return unix_to_pal_error(ERRNO(ret));

    attr->readable = ret == 1 && (pfd.revents & (POLLIN | POLLERR | POLLHUP)) == POLLIN;
    attr->writable = ret == 1 && (pfd.revents & (POLLOUT | POLLERR | POLLHUP)) == POLLOUT;

    /* For future use, so that Linux host kernel can send notifications to user-space apps. App
     * receives virtual FD from LibOS, but the Linux-host eventfd is memorized here, such that this
     * Linux-host eventfd can be retrieved (by LibOS) during app's ioctl(). */
    attr->no_of_fds = 1;
    attr->fds[0]    = handle->eventfd.fd;

    return 0;
}

static int eventfd_pal_close(PAL_HANDLE handle) {
    if (IS_HANDLE_TYPE(handle, eventfd)) {
        if (handle->eventfd.fd != PAL_IDX_POISON) {
            ocall_close(handle->eventfd.fd);
            handle->eventfd.fd = PAL_IDX_POISON;
        }
        return 0;
    }

    return 0;
}

struct handle_ops eventfd_ops = {
    .open           = &eventfd_pal_open,
    .read           = &eventfd_pal_read,
    .write          = &eventfd_pal_write,
    .close          = &eventfd_pal_close,
    .attrquerybyhdl = &eventfd_pal_attrquerybyhdl,
};