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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 amd64
package kvm
import (
"syscall"
"unsafe"
"gvisor.dev/gvisor/pkg/ring0"
"gvisor.dev/gvisor/pkg/sentry/arch"
)
// dieArchSetup initializes the state for dieTrampoline.
//
// The amd64 dieTrampoline requires the vCPU to be set in BX, and the last RIP
// to be in AX. The trampoline then simulates a call to dieHandler from the
// provided RIP.
//
//go:nosplit
func dieArchSetup(c *vCPU, context *arch.SignalContext64, guestRegs *userRegs) {
// Reload all registers to have an accurate stack trace when we return
// to host mode. This means that the stack should be unwound correctly.
if errno := c.getUserRegisters(&c.dieState.guestRegs); errno != 0 {
throw(c.dieState.message)
}
// 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.RFLAGS&ring0.UserFlagsSet == ring0.UserFlagsSet {
regs := c.CPU.Registers()
context.Rax = regs.Rax
context.Rsp = regs.Rsp
context.Rbp = regs.Rbp
} else {
context.Rax = guestRegs.RIP
context.Rsp = guestRegs.RSP
context.Rbp = guestRegs.RBP
context.Eflags = guestRegs.RFLAGS
}
context.Rbx = uint64(uintptr(unsafe.Pointer(c)))
context.Rip = uint64(dieTrampolineAddr)
}
// getHypercallID returns hypercall ID.
//
//go:nosplit
func getHypercallID(addr uintptr) int {
return _KVM_HYPERCALL_MAX
}
// bluepillStopGuest is reponsible for injecting interrupt.
//
//go:nosplit
func bluepillStopGuest(c *vCPU) {
// Interrupt: we must have requested an interrupt
// window; set the interrupt line.
if _, _, errno := syscall.RawSyscall(
syscall.SYS_IOCTL,
uintptr(c.fd),
_KVM_INTERRUPT,
uintptr(unsafe.Pointer(&bounce))); errno != 0 {
throw("interrupt injection failed")
}
// Clear previous injection request.
c.runData.requestInterruptWindow = 0
}
// bluepillSigBus is reponsible for injecting NMI to trigger sigbus.
//
//go:nosplit
func bluepillSigBus(c *vCPU) {
if _, _, errno := syscall.RawSyscall( // escapes: no.
syscall.SYS_IOCTL,
uintptr(c.fd),
_KVM_NMI, 0); errno != 0 {
throw("NMI injection failed")
}
}
// bluepillHandleEnosys is reponsible for handling enosys error.
//
//go:nosplit
func bluepillHandleEnosys(c *vCPU) {
throw("run failed: ENOSYS")
}
// bluepillReadyStopGuest checks whether the current vCPU is ready for interrupt injection.
//
//go:nosplit
func bluepillReadyStopGuest(c *vCPU) bool {
if c.runData.readyForInterruptInjection == 0 {
return false
}
if c.runData.ifFlag == 0 {
// This is impossible if readyForInterruptInjection is 1.
throw("interrupts are disabled")
}
// Disable interrupts if we are in the kernel space.
//
// When the Sentry switches into the kernel mode, it disables
// interrupts. But when goruntime switches on a goroutine which has
// been saved in the host mode, it restores flags and this enables
// interrupts. See the comment of UserFlagsSet for more details.
uregs := userRegs{}
err := c.getUserRegisters(&uregs)
if err != 0 {
throw("failed to get user registers")
}
if ring0.IsKernelFlags(uregs.RFLAGS) {
uregs.RFLAGS &^= ring0.KernelFlagsClear
err = c.setUserRegisters(&uregs)
if err != 0 {
throw("failed to set user registers")
}
return false
}
return true
}
// bluepillArchHandleExit checks architecture specific exitcode.
//
//go:nosplit
func bluepillArchHandleExit(c *vCPU, context unsafe.Pointer) {
c.die(bluepillArchContext(context), "unknown")
}
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