github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go

// Copyright 2019 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 arm64

package kvm

import (
	"unsafe"

	"golang.org/x/sys/unix"
	"github.com/SagerNet/gvisor/pkg/ring0"
	"github.com/SagerNet/gvisor/pkg/sentry/arch"
)

// fpsimdPtr returns a fpsimd64 for the given address.
//
//go:nosplit
func fpsimdPtr(addr *byte) *arch.FpsimdContext {
	return (*arch.FpsimdContext)(unsafe.Pointer(addr))
}

// dieArchSetup initialies the state for dieTrampoline.
//
// The arm64 dieTrampoline requires the vCPU to be set in R1, and the last PC
// to be in R0. The trampoline then simulates a call to dieHandler from the
// provided PC.
//
//go:nosplit
func dieArchSetup(c *vCPU, context *arch.SignalContext64, guestRegs *userRegs) {
	// If the vCPU is in user mode, we set the stack to the stored stack
	// value in the vCPU itself. We don't want to unwind the user stack.
	if guestRegs.Regs.Pstate&ring0.PsrModeMask == ring0.UserFlagsSet {
		regs := c.CPU.Registers()
		context.Regs[0] = regs.Regs[0]
		context.Sp = regs.Sp
		context.Regs[29] = regs.Regs[29] // stack base address
	} else {
		context.Regs[0] = guestRegs.Regs.Pc
		context.Sp = guestRegs.Regs.Sp
		context.Regs[29] = guestRegs.Regs.Regs[29]
		context.Pstate = guestRegs.Regs.Pstate
	}
	context.Regs[1] = uint64(uintptr(unsafe.Pointer(c)))
	context.Pc = uint64(dieTrampolineAddr)
}

// bluepillArchFpContext returns the arch-specific fpsimd context.
//
//go:nosplit
func bluepillArchFpContext(context unsafe.Pointer) *arch.FpsimdContext {
	return &((*arch.SignalContext64)(context).Fpsimd64)
}

// getHypercallID returns hypercall ID.
//
// On Arm64, the MMIO address should be 64-bit aligned.
//
//go:nosplit
func getHypercallID(addr uintptr) int {
	if addr < arm64HypercallMMIOBase || addr >= (arm64HypercallMMIOBase+_AARCH64_HYPERCALL_MMIO_SIZE) {
		return _KVM_HYPERCALL_MAX
	} else {
		return int(((addr) - arm64HypercallMMIOBase) >> 3)
	}
}

// bluepillStopGuest is reponsible for injecting sError.
//
//go:nosplit
func bluepillStopGuest(c *vCPU) {
	// vcpuSErrBounce is the event of system error for bouncing KVM.
	vcpuSErrBounce := &kvmVcpuEvents{
		exception: exception{
			sErrPending: 1,
		},
	}

	if _, _, errno := unix.RawSyscall( // escapes: no.
		unix.SYS_IOCTL,
		uintptr(c.fd),
		_KVM_SET_VCPU_EVENTS,
		uintptr(unsafe.Pointer(vcpuSErrBounce))); errno != 0 {
		throw("bounce sErr injection failed")
	}
}

// bluepillSigBus is reponsible for injecting sError to trigger sigbus.
//
//go:nosplit
func bluepillSigBus(c *vCPU) {
	// vcpuSErrNMI is the event of system error to trigger sigbus.
	vcpuSErrNMI := &kvmVcpuEvents{
		exception: exception{
			sErrPending: 1,
			sErrHasEsr:  1,
			sErrEsr:     _ESR_ELx_SERR_NMI,
		},
	}

	// Host must support ARM64_HAS_RAS_EXTN.
	if _, _, errno := unix.RawSyscall( // escapes: no.
		unix.SYS_IOCTL,
		uintptr(c.fd),
		_KVM_SET_VCPU_EVENTS,
		uintptr(unsafe.Pointer(vcpuSErrNMI))); errno != 0 {
		if errno == unix.EINVAL {
			throw("No ARM64_HAS_RAS_EXTN feature in host.")
		}
		throw("nmi sErr injection failed")
	}
}

// bluepillExtDabt is reponsible for injecting external data abort.
//
//go:nosplit
func bluepillExtDabt(c *vCPU) {
	// vcpuExtDabt is the event of ext_dabt.
	vcpuExtDabt := &kvmVcpuEvents{
		exception: exception{
			extDabtPending: 1,
		},
	}

	if _, _, errno := unix.RawSyscall( // escapes: no.
		unix.SYS_IOCTL,
		uintptr(c.fd),
		_KVM_SET_VCPU_EVENTS,
		uintptr(unsafe.Pointer(vcpuExtDabt))); errno != 0 {
		throw("ext_dabt injection failed")
	}
}

// bluepillHandleEnosys is reponsible for handling enosys error.
//
//go:nosplit
func bluepillHandleEnosys(c *vCPU) {
	bluepillExtDabt(c)
}

// bluepillReadyStopGuest checks whether the current vCPU is ready for sError injection.
//
//go:nosplit
func bluepillReadyStopGuest(c *vCPU) bool {
	return true
}

// bluepillArchHandleExit checks architecture specific exitcode.
//
//go:nosplit
func bluepillArchHandleExit(c *vCPU, context unsafe.Pointer) {
	switch c.runData.exitReason {
	case _KVM_EXIT_ARM_NISV:
		bluepillExtDabt(c)
	default:
		c.die(bluepillArchContext(context), "unknown")
	}
}