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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 ptrace
import (
"fmt"
"strings"
"syscall"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/seccomp"
"gvisor.dev/gvisor/pkg/sentry/arch"
)
const (
// maximumUserAddress is the largest possible user address.
maximumUserAddress = 0x7ffffffff000
// stubInitAddress is the initial attempt link address for the stub.
stubInitAddress = 0x7fffffff0000
// initRegsRipAdjustment is the size of the syscall instruction.
initRegsRipAdjustment = 2
)
// resetSysemuRegs sets up emulation registers.
//
// This should be called prior to calling sysemu.
func (t *thread) resetSysemuRegs(regs *syscall.PtraceRegs) {
regs.Cs = t.initRegs.Cs
regs.Ss = t.initRegs.Ss
regs.Ds = t.initRegs.Ds
regs.Es = t.initRegs.Es
regs.Fs = t.initRegs.Fs
regs.Gs = t.initRegs.Gs
}
// createSyscallRegs sets up syscall registers.
//
// This should be called to generate registers for a system call.
func createSyscallRegs(initRegs *syscall.PtraceRegs, sysno uintptr, args ...arch.SyscallArgument) syscall.PtraceRegs {
// Copy initial registers.
regs := *initRegs
// Set our syscall number.
regs.Rax = uint64(sysno)
if len(args) >= 1 {
regs.Rdi = args[0].Uint64()
}
if len(args) >= 2 {
regs.Rsi = args[1].Uint64()
}
if len(args) >= 3 {
regs.Rdx = args[2].Uint64()
}
if len(args) >= 4 {
regs.R10 = args[3].Uint64()
}
if len(args) >= 5 {
regs.R8 = args[4].Uint64()
}
if len(args) >= 6 {
regs.R9 = args[5].Uint64()
}
return regs
}
// isSingleStepping determines if the registers indicate single-stepping.
func isSingleStepping(regs *syscall.PtraceRegs) bool {
return (regs.Eflags & arch.X86TrapFlag) != 0
}
// updateSyscallRegs updates registers after finishing sysemu.
func updateSyscallRegs(regs *syscall.PtraceRegs) {
// Ptrace puts -ENOSYS in rax on syscall-enter-stop.
regs.Rax = regs.Orig_rax
}
// syscallReturnValue extracts a sensible return from registers.
func syscallReturnValue(regs *syscall.PtraceRegs) (uintptr, error) {
rval := int64(regs.Rax)
if rval < 0 {
return 0, syscall.Errno(-rval)
}
return uintptr(rval), nil
}
func dumpRegs(regs *syscall.PtraceRegs) string {
var m strings.Builder
fmt.Fprintf(&m, "Registers:\n")
fmt.Fprintf(&m, "\tR15\t = %016x\n", regs.R15)
fmt.Fprintf(&m, "\tR14\t = %016x\n", regs.R14)
fmt.Fprintf(&m, "\tR13\t = %016x\n", regs.R13)
fmt.Fprintf(&m, "\tR12\t = %016x\n", regs.R12)
fmt.Fprintf(&m, "\tRbp\t = %016x\n", regs.Rbp)
fmt.Fprintf(&m, "\tRbx\t = %016x\n", regs.Rbx)
fmt.Fprintf(&m, "\tR11\t = %016x\n", regs.R11)
fmt.Fprintf(&m, "\tR10\t = %016x\n", regs.R10)
fmt.Fprintf(&m, "\tR9\t = %016x\n", regs.R9)
fmt.Fprintf(&m, "\tR8\t = %016x\n", regs.R8)
fmt.Fprintf(&m, "\tRax\t = %016x\n", regs.Rax)
fmt.Fprintf(&m, "\tRcx\t = %016x\n", regs.Rcx)
fmt.Fprintf(&m, "\tRdx\t = %016x\n", regs.Rdx)
fmt.Fprintf(&m, "\tRsi\t = %016x\n", regs.Rsi)
fmt.Fprintf(&m, "\tRdi\t = %016x\n", regs.Rdi)
fmt.Fprintf(&m, "\tOrig_rax = %016x\n", regs.Orig_rax)
fmt.Fprintf(&m, "\tRip\t = %016x\n", regs.Rip)
fmt.Fprintf(&m, "\tCs\t = %016x\n", regs.Cs)
fmt.Fprintf(&m, "\tEflags\t = %016x\n", regs.Eflags)
fmt.Fprintf(&m, "\tRsp\t = %016x\n", regs.Rsp)
fmt.Fprintf(&m, "\tSs\t = %016x\n", regs.Ss)
fmt.Fprintf(&m, "\tFs_base\t = %016x\n", regs.Fs_base)
fmt.Fprintf(&m, "\tGs_base\t = %016x\n", regs.Gs_base)
fmt.Fprintf(&m, "\tDs\t = %016x\n", regs.Ds)
fmt.Fprintf(&m, "\tEs\t = %016x\n", regs.Es)
fmt.Fprintf(&m, "\tFs\t = %016x\n", regs.Fs)
fmt.Fprintf(&m, "\tGs\t = %016x\n", regs.Gs)
return m.String()
}
// adjustInitregsRip adjust the current register RIP value to
// be just before the system call instruction excution
func (t *thread) adjustInitRegsRip() {
t.initRegs.Rip -= initRegsRipAdjustment
}
// Pass the expected PPID to the child via R15 when creating stub process.
func initChildProcessPPID(initregs *syscall.PtraceRegs, ppid int32) {
initregs.R15 = uint64(ppid)
// Rbx has to be set to 1 when creating stub process.
initregs.Rbx = 1
}
// patchSignalInfo patches the signal info to account for hitting the seccomp
// filters from vsyscall emulation, specified below. We allow for SIGSYS as a
// synchronous trap, but patch the structure to appear like a SIGSEGV with the
// Rip as the faulting address.
//
// Note that this should only be called after verifying that the signalInfo has
// been generated by the kernel.
func patchSignalInfo(regs *syscall.PtraceRegs, signalInfo *arch.SignalInfo) {
if linux.Signal(signalInfo.Signo) == linux.SIGSYS {
signalInfo.Signo = int32(linux.SIGSEGV)
// Unwind the kernel emulation, if any has occurred. A SIGSYS is delivered
// with the si_call_addr field pointing to the current RIP. This field
// aligns with the si_addr field for a SIGSEGV, so we don't need to touch
// anything there. We do need to unwind emulation however, so we set the
// instruction pointer to the faulting value, and "unpop" the stack.
regs.Rip = signalInfo.Addr()
regs.Rsp -= 8
}
}
// enableCpuidFault enables cpuid-faulting.
//
// This may fail on older kernels or hardware, so we just disregard the result.
// Host CPUID will be enabled.
//
// This is safe to call in an afterFork context.
//
//go:nosplit
func enableCpuidFault() {
syscall.RawSyscall6(syscall.SYS_ARCH_PRCTL, linux.ARCH_SET_CPUID, 0, 0, 0, 0, 0)
}
// appendArchSeccompRules append architecture specific seccomp rules when creating BPF program.
// Ref attachedThread() for more detail.
func appendArchSeccompRules(rules []seccomp.RuleSet) []seccomp.RuleSet {
return append(rules, seccomp.RuleSet{
Rules: seccomp.SyscallRules{
syscall.SYS_ARCH_PRCTL: []seccomp.Rule{
{seccomp.AllowValue(linux.ARCH_SET_CPUID), seccomp.AllowValue(0)},
},
},
Action: linux.SECCOMP_RET_ALLOW,
})
}
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