105 lines
2.7 KiB
Go
105 lines
2.7 KiB
Go
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build amd64
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package ptrace
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import (
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"syscall"
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"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
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)
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const (
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// maximumUserAddress is the largest possible user address.
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maximumUserAddress = 0x7ffffffff000
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// initRegsRipAdjustment is the size of the syscall instruction.
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initRegsRipAdjustment = 2
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)
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// Linux kernel errnos which "should never be seen by user programs", but will
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// be revealed to ptrace syscall exit tracing.
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//
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// These constants are used in subprocess.go.
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const (
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ERESTARTSYS = syscall.Errno(512)
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ERESTARTNOINTR = syscall.Errno(513)
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ERESTARTNOHAND = syscall.Errno(514)
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)
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// resetSysemuRegs sets up emulation registers.
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//
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// This should be called prior to calling sysemu.
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func (t *thread) resetSysemuRegs(regs *syscall.PtraceRegs) {
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regs.Cs = t.initRegs.Cs
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regs.Ss = t.initRegs.Ss
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regs.Ds = t.initRegs.Ds
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regs.Es = t.initRegs.Es
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regs.Fs = t.initRegs.Fs
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regs.Gs = t.initRegs.Gs
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}
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// createSyscallRegs sets up syscall registers.
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//
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// This should be called to generate registers for a system call.
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func createSyscallRegs(initRegs *syscall.PtraceRegs, sysno uintptr, args ...arch.SyscallArgument) syscall.PtraceRegs {
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// Copy initial registers.
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regs := *initRegs
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// Set our syscall number.
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regs.Rax = uint64(sysno)
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if len(args) >= 1 {
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regs.Rdi = args[0].Uint64()
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}
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if len(args) >= 2 {
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regs.Rsi = args[1].Uint64()
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}
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if len(args) >= 3 {
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regs.Rdx = args[2].Uint64()
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}
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if len(args) >= 4 {
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regs.R10 = args[3].Uint64()
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}
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if len(args) >= 5 {
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regs.R8 = args[4].Uint64()
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}
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if len(args) >= 6 {
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regs.R9 = args[5].Uint64()
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}
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return regs
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}
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// isSingleStepping determines if the registers indicate single-stepping.
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func isSingleStepping(regs *syscall.PtraceRegs) bool {
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return (regs.Eflags & arch.X86TrapFlag) != 0
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}
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// updateSyscallRegs updates registers after finishing sysemu.
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func updateSyscallRegs(regs *syscall.PtraceRegs) {
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// Ptrace puts -ENOSYS in rax on syscall-enter-stop.
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regs.Rax = regs.Orig_rax
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}
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// syscallReturnValue extracts a sensible return from registers.
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func syscallReturnValue(regs *syscall.PtraceRegs) (uintptr, error) {
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rval := int64(regs.Rax)
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if rval < 0 {
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return 0, syscall.Errno(-rval)
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}
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return uintptr(rval), nil
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}
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