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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 amd64
// +build amd64
package kvm
import (
"fmt"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
)
// loadSegments copies the current segments.
//
// This may be called from within the signal context and throws on error.
//
//go:nosplit
func (c *vCPU) loadSegments(tid uint64) {
if _, _, errno := unix.RawSyscall(
unix.SYS_ARCH_PRCTL,
linux.ARCH_GET_FS,
uintptr(unsafe.Pointer(&c.CPU.Registers().Fs_base)),
0); errno != 0 {
throw("getting FS segment")
}
if _, _, errno := unix.RawSyscall(
unix.SYS_ARCH_PRCTL,
linux.ARCH_GET_GS,
uintptr(unsafe.Pointer(&c.CPU.Registers().Gs_base)),
0); errno != 0 {
throw("getting GS segment")
}
c.tid.Store(tid)
}
// setCPUID sets the CPUID to be used by the guest.
func (c *vCPU) setCPUID() error {
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_CPUID2,
uintptr(unsafe.Pointer(&cpuidSupported))); errno != 0 {
return fmt.Errorf("error setting CPUID: %v", errno)
}
return nil
}
// getTSCFreq gets the TSC frequency.
//
// If mustSucceed is true, then this function panics on error.
func (c *vCPU) getTSCFreq() (uintptr, error) {
rawFreq, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_GET_TSC_KHZ,
0 /* ignored */)
if errno != 0 {
return 0, errno
}
return rawFreq, nil
}
// setTSCFreq sets the TSC frequency.
func (c *vCPU) setTSCFreq(freq uintptr) error {
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_TSC_KHZ,
freq /* khz */); errno != 0 {
return fmt.Errorf("error setting TSC frequency: %v", errno)
}
return nil
}
// setTSCOffset sets the TSC offset to zero.
func (c *vCPU) setTSCOffset() error {
offset := uint64(0)
da := struct {
flags uint32
group uint32
attr uint64
addr unsafe.Pointer
}{
group: _KVM_VCPU_TSC_CTRL,
attr: _KVM_VCPU_TSC_OFFSET,
addr: unsafe.Pointer(&offset),
}
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_DEVICE_ATTR,
uintptr(unsafe.Pointer(&da))); errno != 0 {
return fmt.Errorf("error setting tsc offset: %v", errno)
}
return nil
}
// setTSC sets the TSC value.
func (c *vCPU) setTSC(value uint64) error {
const _MSR_IA32_TSC = 0x00000010
registers := modelControlRegisters{
nmsrs: 1,
}
registers.entries[0].index = _MSR_IA32_TSC
registers.entries[0].data = value
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_MSRS,
uintptr(unsafe.Pointer(®isters))); errno != 0 {
return fmt.Errorf("error setting tsc: %v", errno)
}
return nil
}
// setUserRegisters sets user registers in the vCPU.
//
//go:nosplit
func (c *vCPU) setUserRegisters(uregs *userRegs) unix.Errno {
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_SET_REGS,
uintptr(unsafe.Pointer(uregs))); errno != 0 {
return errno
}
return 0
}
// getUserRegisters reloads user registers in the vCPU.
//
// This is safe to call from a nosplit context.
//
//go:nosplit
func (c *vCPU) getUserRegisters(uregs *userRegs) unix.Errno {
if _, _, errno := unix.RawSyscall( // escapes: no.
unix.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 := unix.RawSyscall(
unix.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
}
// getSystemRegisters sets system registers.
//
//go:nosplit
func (c *vCPU) getSystemRegisters(sregs *systemRegs) unix.Errno {
if _, _, errno := unix.RawSyscall(
unix.SYS_IOCTL,
uintptr(c.fd),
_KVM_GET_SREGS,
uintptr(unsafe.Pointer(sregs))); errno != 0 {
return errno
}
return 0
}
//go:nosplit
func seccompMmapSyscall(context unsafe.Pointer) (uintptr, uintptr, unix.Errno) {
ctx := bluepillArchContext(context)
// MAP_DENYWRITE is deprecated and ignored by kernel. We use it only for seccomp filters.
addr, _, e := unix.RawSyscall6(uintptr(ctx.Rax), uintptr(ctx.Rdi), uintptr(ctx.Rsi),
uintptr(ctx.Rdx), uintptr(ctx.R10)|unix.MAP_DENYWRITE, uintptr(ctx.R8), uintptr(ctx.R9))
ctx.Rax = uint64(addr)
return addr, uintptr(ctx.Rsi), e
}
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