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// 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.
//go:build arm64
// +build arm64
package systrap
import (
"fmt"
"strings"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/seccomp"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/platform/systrap/sysmsg"
)
const (
// initRegsRipAdjustment is the size of the svc instruction.
initRegsRipAdjustment = 4
)
// resetSysemuRegs sets up emulation registers.
//
// This should be called prior to calling sysemu.
func (s *subprocess) resetSysemuRegs(regs *arch.Registers) {
}
// createSyscallRegs sets up syscall registers.
//
// This should be called to generate registers for a system call.
func createSyscallRegs(initRegs *arch.Registers, sysno uintptr, args ...arch.SyscallArgument) arch.Registers {
// Copy initial registers (Pc, Sp, etc.).
regs := *initRegs
// Set our syscall number.
// r8 for the syscall number.
// r0-r6 is used to store the parameters.
regs.Regs[8] = uint64(sysno)
if len(args) >= 1 {
regs.Regs[0] = args[0].Uint64()
}
if len(args) >= 2 {
regs.Regs[1] = args[1].Uint64()
}
if len(args) >= 3 {
regs.Regs[2] = args[2].Uint64()
}
if len(args) >= 4 {
regs.Regs[3] = args[3].Uint64()
}
if len(args) >= 5 {
regs.Regs[4] = args[4].Uint64()
}
if len(args) >= 6 {
regs.Regs[5] = args[5].Uint64()
}
return regs
}
// updateSyscallRegs updates registers after finishing sysemu.
func updateSyscallRegs(regs *arch.Registers) {
// No special work is necessary.
return
}
// syscallReturnValue extracts a sensible return from registers.
func syscallReturnValue(regs *arch.Registers) (uintptr, error) {
rval := int64(regs.Regs[0])
if rval < 0 {
return 0, unix.Errno(-rval)
}
return uintptr(rval), nil
}
func dumpRegs(regs *arch.Registers) string {
var m strings.Builder
fmt.Fprintf(&m, "Registers:\n")
for i := 0; i < 31; i++ {
fmt.Fprintf(&m, "\tRegs[%d]\t = %016x\n", i, regs.Regs[i])
}
fmt.Fprintf(&m, "\tSp\t = %016x\n", regs.Sp)
fmt.Fprintf(&m, "\tPc\t = %016x\n", regs.Pc)
fmt.Fprintf(&m, "\tPstate\t = %016x\n", regs.Pstate)
return m.String()
}
// adjustInitregsRip adjust the current register RIP value to
// be just before the system call instruction execution.
func (t *thread) adjustInitRegsRip() {
t.initRegs.Pc -= initRegsRipAdjustment
}
// Pass the expected PPID to the child via X7 when creating stub process
func initChildProcessPPID(initregs *arch.Registers, ppid int32) {
// R9 has to be set to 1 when creating stub process.
initregs.Regs[9] = _NEW_STUB
}
func maybePatchSignalInfo(regs *arch.Registers, signalInfo *linux.SignalInfo) (patched bool) {
// vsyscall emulation is not supported on ARM64. No need to patch anything.
return false
}
// Noop on arm64.
//
//go:nosplit
func enableCpuidFault() {
}
// appendArchSeccompRules append architecture specific seccomp rules when creating BPF program.
// Ref attachedThread() for more detail.
func appendArchSeccompRules(rules []seccomp.RuleSet) []seccomp.RuleSet {
return rules
}
// probeSeccomp returns true if seccomp is run after ptrace notifications,
// which is generally the case for kernel version >= 4.8.
//
// On arm64, the support of PTRACE_SYSEMU was added in the 5.3 kernel, so
// probeSeccomp can always return true.
func probeSeccomp() bool {
return true
}
func (s *subprocess) arm64SyscallWorkaround(t *thread, regs *arch.Registers) {
// On ARM64, when ptrace stops on a system call, it uses the x7
// register to indicate whether the stop has been signalled from
// syscall entry or syscall exit. This means that we can't get a value
// of this register and we can't change it. More details are in the
// comment for tracehook_report_syscall in arch/arm64/kernel/ptrace.c.
//
// This happens only if we stop on a system call, so let's queue a
// signal, resume a stub thread and catch it on a signal handling.
t.NotifyInterrupt()
for {
if _, _, errno := unix.RawSyscall6(
unix.SYS_PTRACE,
unix.PTRACE_SYSEMU,
uintptr(t.tid), 0, 0, 0, 0); errno != 0 {
panic(fmt.Sprintf("ptrace sysemu failed: %v", errno))
}
// Wait for the syscall-enter stop.
sig := t.wait(stopped)
if sig == unix.SIGSTOP {
// SIGSTOP was delivered to another thread in the same thread
// group, which initiated another group stop. Just ignore it.
continue
}
if sig == (syscallEvent | unix.SIGTRAP) {
t.dumpAndPanic(fmt.Sprintf("unexpected syscall event"))
}
break
}
if err := t.getRegs(regs); err != nil {
panic(fmt.Sprintf("ptrace get regs failed: %v", err))
}
}
func restoreArchSpecificState(ctx *sysmsg.ThreadContext, ac *arch.Context64) {
ctx.TLS = uint64(ac.TLS())
}
func setArchSpecificRegs(sysThread *sysmsgThread, regs *arch.Registers) {
}
func retrieveArchSpecificState(ctx *sysmsg.ThreadContext, ac *arch.Context64) {
if !ac.SetTLS(uintptr(ctx.TLS)) {
panic(fmt.Sprintf("ac.SetTLS(%+v) failed", ctx.TLS))
}
}
func archSpecificSysmsgThreadInit(sysThread *sysmsgThread) {
// Send a fake event to stop the BPF process so that it enters the sighandler.
if _, _, e := unix.RawSyscall(unix.SYS_TGKILL, uintptr(sysThread.thread.tgid), uintptr(sysThread.thread.tid), uintptr(unix.SIGSEGV)); e != 0 {
panic(fmt.Sprintf("tkill failed: %v", e))
}
}
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