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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 (
"unsafe"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/platform/ring0"
)
// 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)
}
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