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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.
package kvm
import (
"fmt"
"reflect"
"syscall"
"gvisor.dev/gvisor/pkg/safecopy"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/platform/ring0"
)
// bluepill enters guest mode.
func bluepill(*vCPU)
// sighandler is the signal entry point.
func sighandler()
// dieTrampoline is the assembly trampoline. This calls dieHandler.
//
// This uses an architecture-specific calling convention, documented in
// dieArchSetup and the assembly implementation for dieTrampoline.
func dieTrampoline()
var (
// bounceSignal is the signal used for bouncing KVM.
//
// We use SIGCHLD because it is not masked by the runtime, and
// it will be ignored properly by other parts of the kernel.
bounceSignal = syscall.SIGCHLD
// bounceSignalMask has only bounceSignal set.
bounceSignalMask = uint64(1 << (uint64(bounceSignal) - 1))
// otherSignalsMask includes all other signals that will be cause the
// vCPU to exit during execution.
//
// Currently, this includes the preemption signal and the profiling
// signal. In general, these should be signals whose delivery actually
// influences the way the program executes as the switch can be costly.
otherSignalsMask = uint64(1<<(uint64(syscall.SIGURG)-1)) | uint64(1<<(uint64(syscall.SIGPROF)-1))
// bounce is the interrupt vector used to return to the kernel.
bounce = uint32(ring0.VirtualizationException)
// savedHandler is a pointer to the previous handler.
//
// This is called by bluepillHandler.
savedHandler uintptr
// dieTrampolineAddr is the address of dieTrampoline.
dieTrampolineAddr uintptr
)
// redpill invokes a syscall with -1.
//
//go:nosplit
func redpill() {
syscall.RawSyscall(^uintptr(0), 0, 0, 0)
}
// dieHandler is called by dieTrampoline.
//
//go:nosplit
func dieHandler(c *vCPU) {
throw(c.dieState.message)
}
// die is called to set the vCPU up to panic.
//
// This loads vCPU state, and sets up a call for the trampoline.
//
//go:nosplit
func (c *vCPU) die(context *arch.SignalContext64, msg string) {
// Save the death message, which will be thrown.
c.dieState.message = msg
// Setup the trampoline.
dieArchSetup(c, context, &c.dieState.guestRegs)
}
func init() {
// Install the handler, masking all signals.
if err := safecopy.ReplaceSignalHandler(bluepillSignal, reflect.ValueOf(sighandler).Pointer(), &savedHandler, ^uint64(0)); err != nil {
panic(fmt.Sprintf("Unable to set handler for signal %d: %v", bluepillSignal, err))
}
// Extract the address for the trampoline.
dieTrampolineAddr = reflect.ValueOf(dieTrampoline).Pointer()
}
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