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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 (
"fmt"
"sync/atomic"
"syscall"
"unsafe"
"gvisor.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0/pagetables"
)
//go:linkname entersyscall runtime.entersyscall
func entersyscall()
//go:linkname exitsyscall runtime.exitsyscall
func exitsyscall()
// TranslateToVirtual implements pagetables.Translater.TranslateToPhysical.
func (m *machine) TranslateToPhysical(ptes *pagetables.PTEs) uintptr {
// The length doesn't matter because all these translations require
// only a single page, which is guaranteed to be satisfied.
physical, _, ok := TranslateToPhysical(uintptr(unsafe.Pointer(ptes)))
if !ok {
panic("unable to translate pagetables.Node to physical address")
}
return physical
}
// mapRunData maps the vCPU run data.
func mapRunData(fd int) (*runData, error) {
r, _, errno := syscall.RawSyscall6(
syscall.SYS_MMAP,
0,
uintptr(runDataSize),
syscall.PROT_READ|syscall.PROT_WRITE,
syscall.MAP_SHARED,
uintptr(fd),
0)
if errno != 0 {
return nil, fmt.Errorf("error mapping runData: %v", errno)
}
return (*runData)(unsafe.Pointer(r)), nil
}
// unmapRunData unmaps the vCPU run data.
func unmapRunData(r *runData) error {
if _, _, errno := syscall.RawSyscall(
syscall.SYS_MUNMAP,
uintptr(unsafe.Pointer(r)),
uintptr(runDataSize),
0); errno != 0 {
return fmt.Errorf("error unmapping runData: %v", errno)
}
return nil
}
// notify notifies that the vCPU has returned to host mode.
//
// This may be called by a signal handler and therefore throws on error.
//
//go:nosplit
func (c *vCPU) notify() {
_, _, errno := syscall.RawSyscall6(
syscall.SYS_FUTEX,
uintptr(unsafe.Pointer(&c.state)),
linux.FUTEX_WAKE,
^uintptr(0), // Number of waiters.
0, 0, 0)
if errno != 0 {
throw("futex wake error")
}
}
// wait waits for the vCPU to return to host mode.
//
// This panics on error.
func (c *vCPU) wait() {
if !atomic.CompareAndSwapUintptr(&c.state, vCPUGuest, vCPUWaiter) {
return // Nothing to wait for.
}
for {
_, _, errno := syscall.Syscall6(
syscall.SYS_FUTEX,
uintptr(unsafe.Pointer(&c.state)),
linux.FUTEX_WAIT,
uintptr(vCPUWaiter), // Expected value.
0, 0, 0)
if errno == syscall.EINTR {
continue
} else if errno == syscall.EAGAIN {
break
} else if errno != 0 {
panic("futex wait error")
}
break
}
}
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