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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.
// +build go1.12
// +build !go1.15
// Check go:linkname function signatures when updating Go version.
package kvm
import (
"fmt"
"math"
"sync/atomic"
"syscall"
"unsafe"
"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) syscall.Errno {
userRegion := userMemoryRegion{
slot: uint32(slot),
flags: uint32(flags),
guestPhysAddr: uint64(physical),
memorySize: uint64(length),
userspaceAddr: uint64(virtual),
}
// Set the region.
_, _, errno := syscall.RawSyscall(
syscall.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 := 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
}
// setUserRegisters sets user registers in the vCPU.
func (c *vCPU) setUserRegisters(uregs *userRegs) error {
if _, _, errno := syscall.RawSyscall(
syscall.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_REGS,
uintptr(unsafe.Pointer(uregs))); errno != 0 {
return fmt.Errorf("error setting user registers: %v", errno)
}
return nil
}
// getUserRegisters reloads user registers in the vCPU.
//
// This is safe to call from a nosplit context.
//
//go:nosplit
func (c *vCPU) getUserRegisters(uregs *userRegs) syscall.Errno {
if _, _, errno := syscall.RawSyscall(
syscall.SYS_IOCTL,
uintptr(c.fd),
_KVM_GET_REGS,
uintptr(unsafe.Pointer(uregs))); errno != 0 {
return errno
}
return 0
}
// setSystemRegisters sets system registers.
func (c *vCPU) setSystemRegisters(sregs *systemRegs) error {
if _, _, errno := syscall.RawSyscall(
syscall.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_SREGS,
uintptr(unsafe.Pointer(sregs))); errno != 0 {
return fmt.Errorf("error setting system registers: %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 := syscall.RawSyscall6(
syscall.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 := syscall.Syscall6(
syscall.SYS_FUTEX,
uintptr(unsafe.Pointer(&c.state)),
linux.FUTEX_WAIT|linux.FUTEX_PRIVATE_FLAG,
uintptr(state),
0, 0, 0)
if errno != 0 && errno != syscall.EINTR && errno != syscall.EAGAIN {
panic("futex wait error")
}
}
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