graphene/LibOS/shim/src/sys/shim_sched.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/>.  */

/*
 * shim_sched.c
 *
 * Implementation of system call "sched_yield".
 */

#include <api.h>
#include <errno.h>
#include <pal.h>
#include <shim_internal.h>
#include <shim_table.h>

int shim_do_sched_yield(void) {
    DkThreadYieldExecution();
    return 0;
}

int shim_do_sched_getaffinity(pid_t pid, size_t len, __kernel_cpu_set_t* user_mask_ptr) {
    __UNUSED(pid);
    int ncpus = PAL_CB(cpu_info.cpu_num);

    /* Check that user_mask_ptr is valid; if not, should return -EFAULT */
    if (test_user_memory(user_mask_ptr, len, 1))
        return -EFAULT;

    /* Linux kernel bitmap is based on long. So according to its
     * implementation, round up the result to sizeof(long) */
    size_t bitmask_long_count    = (ncpus + sizeof(long) * 8 - 1) / (sizeof(long) * 8);
    size_t bitmask_size_in_bytes = bitmask_long_count * sizeof(long);
    if (len < bitmask_size_in_bytes)
        return -EINVAL;
    /* Linux kernel also rejects non-natural size */
    if (len & (sizeof(long) - 1))
        return -EINVAL;

    memset(user_mask_ptr, 0, len);
    for (int i = 0; i < ncpus; i++) {
        ((uint8_t*)user_mask_ptr)[i / 8] |= 1 << (i % 8);
    }
    /* imitate the Linux kernel implementation
     * See SYSCALL_DEFINE3(sched_getaffinity) */
    return bitmask_size_in_bytes;
}