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// 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.
//go:build go1.12
// +build go1.12
// //go:linkname directives type-checked by checklinkname. Any other
// non-linkname assumptions outside the Go 1 compatibility guarantee should
// have an accompanied vet check or version guard build tag.
package kvm
import (
"fmt"
"math"
"sync/atomic"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
)
//go:linkname entersyscall runtime.entersyscall
func entersyscall()
//go:linkname exitsyscall runtime.exitsyscall
func exitsyscall()
// setMemoryRegion initializes a region.
//
// This may be called from bluepillHandler, and therefore returns an errno
// directly (instead of wrapping in an error) to avoid allocations.
//
//go:nosplit
func (m *machine) setMemoryRegion(slot int, physical, length, virtual uintptr, flags uint32) unix.Errno {
userRegion := userMemoryRegion{
slot: uint32(slot),
flags: uint32(flags),
guestPhysAddr: uint64(physical),
memorySize: uint64(length),
userspaceAddr: uint64(virtual),
}
// Set the region.
_, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(m.fd),
_KVM_SET_USER_MEMORY_REGION,
uintptr(unsafe.Pointer(&userRegion)))
return errno
}
// mapRunData maps the vCPU run data.
func mapRunData(fd int) (*runData, error) {
r, _, errno := unix.RawSyscall6(
unix.SYS_MMAP,
0,
uintptr(runDataSize),
unix.PROT_READ|unix.PROT_WRITE,
unix.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 := unix.RawSyscall(
unix.SYS_MUNMAP,
uintptr(unsafe.Pointer(r)),
uintptr(runDataSize),
0); errno != 0 {
return fmt.Errorf("error unmapping runData: %v", errno)
}
return nil
}
// atomicAddressSpace is an atomic address space pointer.
type atomicAddressSpace struct {
pointer unsafe.Pointer
}
// set sets the address space value.
//
//go:nosplit
func (a *atomicAddressSpace) set(as *addressSpace) {
atomic.StorePointer(&a.pointer, unsafe.Pointer(as))
}
// get gets the address space value.
//
// Note that this should be considered best-effort, and may have changed by the
// time this function returns.
//
//go:nosplit
func (a *atomicAddressSpace) get() *addressSpace {
return (*addressSpace)(atomic.LoadPointer(&a.pointer))
}
// notify notifies that the vCPU has transitioned modes.
//
// This may be called by a signal handler and therefore throws on error.
//
//go:nosplit
func (c *vCPU) notify() {
_, _, errno := unix.RawSyscall6( // escapes: no.
unix.SYS_FUTEX,
uintptr(unsafe.Pointer(&c.state)),
linux.FUTEX_WAKE|linux.FUTEX_PRIVATE_FLAG,
math.MaxInt32, // Number of waiters.
0, 0, 0)
if errno != 0 {
throw("futex wake error")
}
}
// waitUntilNot waits for the vCPU to transition modes.
//
// The state should have been previously set to vCPUWaiter after performing an
// appropriate action to cause a transition (e.g. interrupt injection).
//
// This panics on error.
func (c *vCPU) waitUntilNot(state uint32) {
_, _, errno := unix.Syscall6(
unix.SYS_FUTEX,
uintptr(unsafe.Pointer(&c.state)),
linux.FUTEX_WAIT|linux.FUTEX_PRIVATE_FLAG,
uintptr(state),
0, 0, 0)
if errno != 0 && errno != unix.EINTR && errno != unix.EAGAIN {
panic("futex wait error")
}
}
// setSignalMask sets the vCPU signal mask.
//
// This must be called prior to running the vCPU.
func (c *vCPU) setSignalMask() error {
// The layout of this structure implies that it will not necessarily be
// the same layout chosen by the Go compiler. It gets fudged here.
var data struct {
length uint32
mask1 uint32
mask2 uint32
_ uint32
}
data.length = 8 // Fixed sigset size.
data.mask1 = ^uint32(bounceSignalMask & 0xffffffff)
data.mask2 = ^uint32(bounceSignalMask >> 32)
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_SIGNAL_MASK,
uintptr(unsafe.Pointer(&data))); errno != 0 {
return fmt.Errorf("error setting signal mask: %v", errno)
}
return nil
}
// seccompMmapHandler is a signal handler for runtime mmap system calls
// that are trapped by seccomp.
//
// It executes the mmap syscall with specified arguments and maps a new region
// to the guest.
//
//go:nosplit
func seccompMmapHandler(context unsafe.Pointer) {
addr, length, errno := seccompMmapSyscall(context)
if errno != 0 {
return
}
for i := uint32(0); i < atomic.LoadUint32(&machinePoolLen); i++ {
m := machinePool[i].Load()
if m == nil {
continue
}
// Map the new region to the guest.
vr := region{
virtual: addr,
length: length,
}
for virtual := vr.virtual; virtual < vr.virtual+vr.length; {
physical, length, ok := translateToPhysical(virtual)
if !ok {
// This must be an invalid region that was
// knocked out by creation of the physical map.
return
}
if virtual+length > vr.virtual+vr.length {
// Cap the length to the end of the area.
length = vr.virtual + vr.length - virtual
}
// Ensure the physical range is mapped.
m.mapPhysical(physical, length, physicalRegions, _KVM_MEM_FLAGS_NONE)
virtual += length
}
}
}
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