visor/pkg/sentry/syscalls/linux/sys_sched.go

// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package linux

import (
	"gvisor.dev/gvisor/pkg/abi/linux"
	"gvisor.dev/gvisor/pkg/errors/linuxerr"
	"gvisor.dev/gvisor/pkg/sentry/arch"
	"gvisor.dev/gvisor/pkg/sentry/kernel"
)

const (
	onlyPriority = 0
)

func isSchedulerSupported(policy uint) bool {
	// We only support SCHED_NORMAL (manpage refers to as SCHED_OTHER), SCHED_BATCH, or SCHED_IDLE
	return policy == linux.SCHED_NORMAL || policy == linux.SCHED_BATCH || policy == linux.SCHED_IDLE
}

// SchedParam replicates struct sched_param in sched.h.
//
// +marshal
type SchedParam struct {
	schedPriority int32
}

// SchedGetparam implements linux syscall sched_getparam(2).
func SchedGetparam(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
	pid := args[0].Int()
	param := args[1].Pointer()
	if param == 0 {
		return 0, nil, linuxerr.EINVAL
	}
	if pid < 0 {
		return 0, nil, linuxerr.EINVAL
	}
	if pid != 0 && t.PIDNamespace().TaskWithID(kernel.ThreadID(pid)) == nil {
		return 0, nil, linuxerr.ESRCH
	}
	r := SchedParam{schedPriority: onlyPriority}
	if _, err := r.CopyOut(t, param); err != nil {
		return 0, nil, err
	}

	return 0, nil, nil
}

// SchedGetscheduler implements linux syscall sched_getscheduler(2).
func SchedGetscheduler(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
	pid := kernel.ThreadID(args[0].Int())

	if pid < 0 {
		return 0, nil, linuxerr.EINVAL
	}

	var task *kernel.Task
	if pid == 0 {
		task = t
	} else {
		task = t.PIDNamespace().TaskWithID(pid)
		if task == nil {
			return 0, nil, linuxerr.ESRCH
		}
	}

	scheduler := uintptr(task.GetScheduler())

	return scheduler, nil, nil
}

// SchedSetscheduler implements linux syscall sched_setscheduler(2).
func SchedSetscheduler(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
	pid := kernel.ThreadID(args[0].Int())
	uPolicy := args[1].Int()
	param := args[2].Pointer()

	if pid < 0 || uPolicy < 0 {
		return 0, nil, linuxerr.EINVAL
	}
	policy := uint(uPolicy)
	if !isSchedulerSupported(policy) {
		return 0, nil, linuxerr.EINVAL
	}

	var task *kernel.Task
	if pid == 0 {
		task = t
	} else {
		task = t.PIDNamespace().TaskWithID(pid)
		if task == nil {
			return 0, nil, linuxerr.ESRCH
		}

		// See kernel/sched/syscalls.c:user_check_sched_setscheduler().
		if !canSetTaskNice(t, task) {
			return 0, nil, linuxerr.EPERM
		}
	}

	var r SchedParam
	if _, err := r.CopyIn(t, param); err != nil {
		return 0, nil, linuxerr.EINVAL
	}
	if r.schedPriority != onlyPriority {
		return 0, nil, linuxerr.EINVAL
	}

	task.SetScheduler(policy)

	return 0, nil, nil
}

// SchedGetPriorityMax implements linux syscall sched_get_priority_max(2).
func SchedGetPriorityMax(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
	return onlyPriority, nil, nil
}

// SchedGetPriorityMin implements linux syscall sched_get_priority_min(2).
func SchedGetPriorityMin(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
	return onlyPriority, nil, nil
}