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// Copyright 2018 Google Inc.
//
// 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 kvm
import (
"sync/atomic"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform/interrupt"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
// context is an implementation of the platform context.
//
// This is a thin wrapper around the machine.
type context struct {
// machine is the parent machine, and is immutable.
machine *machine
// interrupt is the interrupt context.
interrupt interrupt.Forwarder
}
// Switch runs the provided context in the given address space.
func (c *context) Switch(as platform.AddressSpace, ac arch.Context, _ int32) (*arch.SignalInfo, usermem.AccessType, error) {
// Extract data.
localAS := as.(*addressSpace)
regs := &ac.StateData().Regs
fp := (*byte)(ac.FloatingPointData())
// Grab a vCPU.
cpu, err := c.machine.Get()
if err != nil {
return nil, usermem.NoAccess, err
}
// Enable interrupts (i.e. calls to vCPU.Notify).
if !c.interrupt.Enable(cpu) {
c.machine.Put(cpu) // Already preempted.
return nil, usermem.NoAccess, platform.ErrContextInterrupt
}
// Mark the address space as dirty.
flags := ring0.Flags(0)
dirty := localAS.Touch(cpu)
if v := atomic.SwapUint32(dirty, 1); v == 0 {
flags |= ring0.FlagFlush
}
if ac.FullRestore() {
flags |= ring0.FlagFull
}
// Take the blue pill.
si, at, err := cpu.SwitchToUser(regs, fp, localAS.pageTables, flags)
// Release resources.
c.machine.Put(cpu)
// All done.
c.interrupt.Disable()
return si, at, err
}
// Interrupt interrupts the running context.
func (c *context) Interrupt() {
c.interrupt.NotifyInterrupt()
}
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