enable pkg/sentry/arch to support arm64 basically

Signed-off-by: Bin Lu <bin.lu@arm.com>
Change-Id: I9cce23db4e5caec82ce42b4970fdb7f7e8c08f1d
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/gvisor/pull/773 from lubinszARM:pr_arch_basic 3fe2fd8e6286766bbe489ef971dce204f924feba
PiperOrigin-RevId: 289795569

11 files changed, 1081 insertions, 231 deletions

diff --git a/pkg/sentry/arch/BUILD b/pkg/sentry/arch/BUILD
index ae3e364cd..65f22af2b 100644
--- a/pkg/sentry/arch/BUILD
+++ b/pkg/sentry/arch/BUILD
@@ -9,17 +9,23 @@ go_library(
     srcs = [
         "aligned.go",
         "arch.go",
+        "arch_aarch64.go",
         "arch_amd64.go",
         "arch_amd64.s",
+        "arch_arm64.go",
+        "arch_state_aarch64.go",
         "arch_state_x86.go",
         "arch_x86.go",
         "auxv.go",
+        "signal.go",
         "signal_act.go",
         "signal_amd64.go",
+        "signal_arm64.go",
         "signal_info.go",
         "signal_stack.go",
         "stack.go",
         "syscalls_amd64.go",
+        "syscalls_arm64.go",
     ],
     importpath = "gvisor.dev/gvisor/pkg/sentry/arch",
     visibility = ["//:sandbox"],
diff --git a/pkg/sentry/arch/arch_aarch64.go b/pkg/sentry/arch/arch_aarch64.go
new file mode 100644
index 000000000..ea4dedbdf
--- /dev/null
+++ b/pkg/sentry/arch/arch_aarch64.go
@@ -0,0 +1,293 @@
+// Copyright 2020 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 arm64
+
+package arch
+
+import (
+	"fmt"
+	"io"
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/cpuid"
+	"gvisor.dev/gvisor/pkg/log"
+	rpb "gvisor.dev/gvisor/pkg/sentry/arch/registers_go_proto"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+const (
+	// SyscallWidth is the width of insturctions.
+	SyscallWidth = 4
+)
+
+// aarch64FPState is aarch64 floating point state.
+type aarch64FPState []byte
+
+// initAarch64FPState (defined in asm files) sets up initial state.
+func initAarch64FPState(data *FloatingPointData) {
+	// TODO(gvisor.dev/issue/1238): floating-point is not supported.
+}
+
+func newAarch64FPStateSlice() []byte {
+	return alignedBytes(4096, 32)[:4096]
+}
+
+// newAarch64FPState returns an initialized floating point state.
+//
+// The returned state is large enough to store all floating point state
+// supported by host, even if the app won't use much of it due to a restricted
+// FeatureSet. Since they may still be able to see state not advertised by
+// CPUID we must ensure it does not contain any sentry state.
+func newAarch64FPState() aarch64FPState {
+	f := aarch64FPState(newAarch64FPStateSlice())
+	initAarch64FPState(f.FloatingPointData())
+	return f
+}
+
+// fork creates and returns an identical copy of the aarch64 floating point state.
+func (f aarch64FPState) fork() aarch64FPState {
+	n := aarch64FPState(newAarch64FPStateSlice())
+	copy(n, f)
+	return n
+}
+
+// FloatingPointData returns the raw data pointer.
+func (f aarch64FPState) FloatingPointData() *FloatingPointData {
+	return (*FloatingPointData)(&f[0])
+}
+
+// NewFloatingPointData returns a new floating point data blob.
+//
+// This is primarily for use in tests.
+func NewFloatingPointData() *FloatingPointData {
+	return (*FloatingPointData)(&(newAarch64FPState()[0]))
+}
+
+// State contains the common architecture bits for aarch64 (the build tag of this
+// file ensures it's only built on aarch64).
+type State struct {
+	// The system registers.
+	Regs syscall.PtraceRegs `state:".(syscallPtraceRegs)"`
+
+	// Our floating point state.
+	aarch64FPState `state:"wait"`
+
+	// FeatureSet is a pointer to the currently active feature set.
+	FeatureSet *cpuid.FeatureSet
+}
+
+// Proto returns a protobuf representation of the system registers in State.
+func (s State) Proto() *rpb.Registers {
+	regs := &rpb.ARM64Registers{
+		R0:     s.Regs.Regs[0],
+		R1:     s.Regs.Regs[1],
+		R2:     s.Regs.Regs[2],
+		R3:     s.Regs.Regs[3],
+		R4:     s.Regs.Regs[4],
+		R5:     s.Regs.Regs[5],
+		R6:     s.Regs.Regs[6],
+		R7:     s.Regs.Regs[7],
+		R8:     s.Regs.Regs[8],
+		R9:     s.Regs.Regs[9],
+		R10:    s.Regs.Regs[10],
+		R11:    s.Regs.Regs[11],
+		R12:    s.Regs.Regs[12],
+		R13:    s.Regs.Regs[13],
+		R14:    s.Regs.Regs[14],
+		R15:    s.Regs.Regs[15],
+		R16:    s.Regs.Regs[16],
+		R17:    s.Regs.Regs[17],
+		R18:    s.Regs.Regs[18],
+		R19:    s.Regs.Regs[19],
+		R20:    s.Regs.Regs[20],
+		R21:    s.Regs.Regs[21],
+		R22:    s.Regs.Regs[22],
+		R23:    s.Regs.Regs[23],
+		R24:    s.Regs.Regs[24],
+		R25:    s.Regs.Regs[25],
+		R26:    s.Regs.Regs[26],
+		R27:    s.Regs.Regs[27],
+		R28:    s.Regs.Regs[28],
+		R29:    s.Regs.Regs[29],
+		R30:    s.Regs.Regs[30],
+		Sp:     s.Regs.Sp,
+		Pc:     s.Regs.Pc,
+		Pstate: s.Regs.Pstate,
+	}
+	return &rpb.Registers{Arch: &rpb.Registers_Arm64{Arm64: regs}}
+}
+
+// Fork creates and returns an identical copy of the state.
+func (s *State) Fork() State {
+	// TODO(gvisor.dev/issue/1238): floating-point is not supported.
+	return State{
+		Regs:       s.Regs,
+		FeatureSet: s.FeatureSet,
+	}
+}
+
+// StateData implements Context.StateData.
+func (s *State) StateData() *State {
+	return s
+}
+
+// CPUIDEmulate emulates a cpuid instruction.
+func (s *State) CPUIDEmulate(l log.Logger) {
+	// TODO(gvisor.dev/issue/1255): cpuid is not supported.
+}
+
+// SingleStep implements Context.SingleStep.
+func (s *State) SingleStep() bool {
+	return false
+}
+
+// SetSingleStep enables single stepping.
+func (s *State) SetSingleStep() {
+	// Set the trap flag.
+	// TODO(gvisor.dev/issue/1239): ptrace single-step is not supported.
+}
+
+// ClearSingleStep enables single stepping.
+func (s *State) ClearSingleStep() {
+	// Clear the trap flag.
+	// TODO(gvisor.dev/issue/1239): ptrace single-step is not supported.
+}
+
+// RegisterMap returns a map of all registers.
+func (s *State) RegisterMap() (map[string]uintptr, error) {
+	return map[string]uintptr{
+		"R0":     uintptr(s.Regs.Regs[0]),
+		"R1":     uintptr(s.Regs.Regs[1]),
+		"R2":     uintptr(s.Regs.Regs[2]),
+		"R3":     uintptr(s.Regs.Regs[3]),
+		"R4":     uintptr(s.Regs.Regs[4]),
+		"R5":     uintptr(s.Regs.Regs[5]),
+		"R6":     uintptr(s.Regs.Regs[6]),
+		"R7":     uintptr(s.Regs.Regs[7]),
+		"R8":     uintptr(s.Regs.Regs[8]),
+		"R9":     uintptr(s.Regs.Regs[9]),
+		"R10":    uintptr(s.Regs.Regs[10]),
+		"R11":    uintptr(s.Regs.Regs[11]),
+		"R12":    uintptr(s.Regs.Regs[12]),
+		"R13":    uintptr(s.Regs.Regs[13]),
+		"R14":    uintptr(s.Regs.Regs[14]),
+		"R15":    uintptr(s.Regs.Regs[15]),
+		"R16":    uintptr(s.Regs.Regs[16]),
+		"R17":    uintptr(s.Regs.Regs[17]),
+		"R18":    uintptr(s.Regs.Regs[18]),
+		"R19":    uintptr(s.Regs.Regs[19]),
+		"R20":    uintptr(s.Regs.Regs[20]),
+		"R21":    uintptr(s.Regs.Regs[21]),
+		"R22":    uintptr(s.Regs.Regs[22]),
+		"R23":    uintptr(s.Regs.Regs[23]),
+		"R24":    uintptr(s.Regs.Regs[24]),
+		"R25":    uintptr(s.Regs.Regs[25]),
+		"R26":    uintptr(s.Regs.Regs[26]),
+		"R27":    uintptr(s.Regs.Regs[27]),
+		"R28":    uintptr(s.Regs.Regs[28]),
+		"R29":    uintptr(s.Regs.Regs[29]),
+		"R30":    uintptr(s.Regs.Regs[30]),
+		"Sp":     uintptr(s.Regs.Sp),
+		"Pc":     uintptr(s.Regs.Pc),
+		"Pstate": uintptr(s.Regs.Pstate),
+	}, nil
+}
+
+// PtraceGetRegs implements Context.PtraceGetRegs.
+func (s *State) PtraceGetRegs(dst io.Writer) (int, error) {
+	return dst.Write(binary.Marshal(nil, usermem.ByteOrder, s.ptraceGetRegs()))
+}
+
+func (s *State) ptraceGetRegs() syscall.PtraceRegs {
+	return s.Regs
+}
+
+var ptraceRegsSize = int(binary.Size(syscall.PtraceRegs{}))
+
+// PtraceSetRegs implements Context.PtraceSetRegs.
+func (s *State) PtraceSetRegs(src io.Reader) (int, error) {
+	var regs syscall.PtraceRegs
+	buf := make([]byte, ptraceRegsSize)
+	if _, err := io.ReadFull(src, buf); err != nil {
+		return 0, err
+	}
+	binary.Unmarshal(buf, usermem.ByteOrder, &regs)
+	s.Regs = regs
+	return ptraceRegsSize, nil
+}
+
+// PtraceGetFPRegs implements Context.PtraceGetFPRegs.
+func (s *State) PtraceGetFPRegs(dst io.Writer) (int, error) {
+	// TODO(gvisor.dev/issue/1238): floating-point is not supported.
+	return 0, nil
+}
+
+// PtraceSetFPRegs implements Context.PtraceSetFPRegs.
+func (s *State) PtraceSetFPRegs(src io.Reader) (int, error) {
+	// TODO(gvisor.dev/issue/1238): floating-point is not supported.
+	return 0, nil
+}
+
+// Register sets defined in include/uapi/linux/elf.h.
+const (
+	_NT_PRSTATUS = 1
+	_NT_PRFPREG  = 2
+)
+
+// PtraceGetRegSet implements Context.PtraceGetRegSet.
+func (s *State) PtraceGetRegSet(regset uintptr, dst io.Writer, maxlen int) (int, error) {
+	switch regset {
+	case _NT_PRSTATUS:
+		if maxlen < ptraceRegsSize {
+			return 0, syserror.EFAULT
+		}
+		return s.PtraceGetRegs(dst)
+	default:
+		return 0, syserror.EINVAL
+	}
+}
+
+// PtraceSetRegSet implements Context.PtraceSetRegSet.
+func (s *State) PtraceSetRegSet(regset uintptr, src io.Reader, maxlen int) (int, error) {
+	switch regset {
+	case _NT_PRSTATUS:
+		if maxlen < ptraceRegsSize {
+			return 0, syserror.EFAULT
+		}
+		return s.PtraceSetRegs(src)
+	default:
+		return 0, syserror.EINVAL
+	}
+}
+
+// FullRestore indicates whether a full restore is required.
+func (s *State) FullRestore() bool {
+	return false
+}
+
+// New returns a new architecture context.
+func New(arch Arch, fs *cpuid.FeatureSet) Context {
+	switch arch {
+	case ARM64:
+		return &context64{
+			State{
+				FeatureSet: fs,
+			},
+		}
+	}
+	panic(fmt.Sprintf("unknown architecture %v", arch))
+}
diff --git a/pkg/sentry/arch/arch_arm64.go b/pkg/sentry/arch/arch_arm64.go
new file mode 100644
index 000000000..0d5b7d317
--- /dev/null
+++ b/pkg/sentry/arch/arch_arm64.go
@@ -0,0 +1,266 @@
+// Copyright 2020 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 arch
+
+import (
+	"fmt"
+	"math/rand"
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/cpuid"
+	"gvisor.dev/gvisor/pkg/sentry/limits"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+)
+
+// Host specifies the host architecture.
+const Host = ARM64
+
+// These constants come directly from Linux.
+const (
+	// maxAddr64 is the maximum userspace address. It is TASK_SIZE in Linux
+	// for a 64-bit process.
+	maxAddr64 usermem.Addr = (1 << 48)
+
+	// maxStackRand64 is the maximum randomization to apply to the stack.
+	// It is defined by arch/arm64/mm/mmap.c:(STACK_RND_MASK << PAGE_SHIFT) in Linux.
+	maxStackRand64 = 0x3ffff << 12 // 16 GB
+
+	// maxMmapRand64 is the maximum randomization to apply to the mmap
+	// layout. It is defined by arch/arm64/mm/mmap.c:arch_mmap_rnd in Linux.
+	maxMmapRand64 = (1 << 33) * usermem.PageSize
+
+	// minGap64 is the minimum gap to leave at the top of the address space
+	// for the stack. It is defined by arch/arm64/mm/mmap.c:MIN_GAP in Linux.
+	minGap64 = (128 << 20) + maxStackRand64
+
+	// preferredPIELoadAddr is the standard Linux position-independent
+	// executable base load address. It is ELF_ET_DYN_BASE in Linux.
+	//
+	// The Platform {Min,Max}UserAddress() may preclude loading at this
+	// address. See other preferredFoo comments below.
+	preferredPIELoadAddr usermem.Addr = maxAddr64 / 6 * 5
+)
+
+// These constants are selected as heuristics to help make the Platform's
+// potentially limited address space conform as closely to Linux as possible.
+const (
+	preferredTopDownAllocMin usermem.Addr = 0x7e8000000000
+	preferredAllocationGap                = 128 << 30 // 128 GB
+	preferredTopDownBaseMin               = preferredTopDownAllocMin + preferredAllocationGap
+
+	// minMmapRand64 is the smallest we are willing to make the
+	// randomization to stay above preferredTopDownBaseMin.
+	minMmapRand64 = (1 << 18) * usermem.PageSize
+)
+
+// context64 represents an ARM64 context.
+type context64 struct {
+	State
+}
+
+// Arch implements Context.Arch.
+func (c *context64) Arch() Arch {
+	return ARM64
+}
+
+// Fork returns an exact copy of this context.
+func (c *context64) Fork() Context {
+	return &context64{
+		State: c.State.Fork(),
+	}
+}
+
+// General purpose registers usage on Arm64:
+// R0...R7: parameter/result registers.
+// R8: indirect result location register.
+// R9...R15: temporary rgisters.
+// R16: the first intra-procedure-call scratch register.
+// R17: the second intra-procedure-call scratch register.
+// R18: the platform register.
+// R19...R28: callee-saved registers.
+// R29: the frame pointer.
+// R30: the link register.
+
+// Return returns the current syscall return value.
+func (c *context64) Return() uintptr {
+	return uintptr(c.Regs.Regs[0])
+}
+
+// SetReturn sets the syscall return value.
+func (c *context64) SetReturn(value uintptr) {
+	c.Regs.Regs[0] = uint64(value)
+}
+
+// IP returns the current instruction pointer.
+func (c *context64) IP() uintptr {
+	return uintptr(c.Regs.Pc)
+}
+
+// SetIP sets the current instruction pointer.
+func (c *context64) SetIP(value uintptr) {
+	c.Regs.Pc = uint64(value)
+}
+
+// Stack returns the current stack pointer.
+func (c *context64) Stack() uintptr {
+	return uintptr(c.Regs.Sp)
+}
+
+// SetStack sets the current stack pointer.
+func (c *context64) SetStack(value uintptr) {
+	c.Regs.Sp = uint64(value)
+}
+
+// TLS returns the current TLS pointer.
+func (c *context64) TLS() uintptr {
+	// TODO(gvisor.dev/issue/1238): TLS is not supported.
+	// MRS_TPIDR_EL0
+	return 0
+}
+
+// SetTLS sets the current TLS pointer. Returns false if value is invalid.
+func (c *context64) SetTLS(value uintptr) bool {
+	// TODO(gvisor.dev/issue/1238): TLS is not supported.
+	// MSR_TPIDR_EL0
+	return false
+}
+
+// SetRSEQInterruptedIP implements Context.SetRSEQInterruptedIP.
+func (c *context64) SetRSEQInterruptedIP(value uintptr) {
+	c.Regs.Regs[3] = uint64(value)
+}
+
+// Native returns the native type for the given val.
+func (c *context64) Native(val uintptr) interface{} {
+	v := uint64(val)
+	return &v
+}
+
+// Value returns the generic val for the given native type.
+func (c *context64) Value(val interface{}) uintptr {
+	return uintptr(*val.(*uint64))
+}
+
+// Width returns the byte width of this architecture.
+func (c *context64) Width() uint {
+	return 8
+}
+
+// FeatureSet returns the FeatureSet in use.
+func (c *context64) FeatureSet() *cpuid.FeatureSet {
+	return c.State.FeatureSet
+}
+
+// mmapRand returns a random adjustment for randomizing an mmap layout.
+func mmapRand(max uint64) usermem.Addr {
+	return usermem.Addr(rand.Int63n(int64(max))).RoundDown()
+}
+
+// NewMmapLayout implements Context.NewMmapLayout consistently with Linux.
+func (c *context64) NewMmapLayout(min, max usermem.Addr, r *limits.LimitSet) (MmapLayout, error) {
+	min, ok := min.RoundUp()
+	if !ok {
+		return MmapLayout{}, syscall.EINVAL
+	}
+	if max > maxAddr64 {
+		max = maxAddr64
+	}
+	max = max.RoundDown()
+
+	if min > max {
+		return MmapLayout{}, syscall.EINVAL
+	}
+
+	stackSize := r.Get(limits.Stack)
+
+	// MAX_GAP in Linux.
+	maxGap := (max / 6) * 5
+	gap := usermem.Addr(stackSize.Cur)
+	if gap < minGap64 {
+		gap = minGap64
+	}
+	if gap > maxGap {
+		gap = maxGap
+	}
+	defaultDir := MmapTopDown
+	if stackSize.Cur == limits.Infinity {
+		defaultDir = MmapBottomUp
+	}
+
+	topDownMin := max - gap - maxMmapRand64
+	maxRand := usermem.Addr(maxMmapRand64)
+	if topDownMin < preferredTopDownBaseMin {
+		// Try to keep TopDownBase above preferredTopDownBaseMin by
+		// shrinking maxRand.
+		maxAdjust := maxRand - minMmapRand64
+		needAdjust := preferredTopDownBaseMin - topDownMin
+		if needAdjust <= maxAdjust {
+			maxRand -= needAdjust
+		}
+	}
+
+	rnd := mmapRand(uint64(maxRand))
+	l := MmapLayout{
+		MinAddr: min,
+		MaxAddr: max,
+		// TASK_UNMAPPED_BASE in Linux.
+		BottomUpBase:     (max/3 + rnd).RoundDown(),
+		TopDownBase:      (max - gap - rnd).RoundDown(),
+		DefaultDirection: defaultDir,
+		// We may have reduced the maximum randomization to keep
+		// TopDownBase above preferredTopDownBaseMin while maintaining
+		// our stack gap. Stack allocations must use that max
+		// randomization to avoiding eating into the gap.
+		MaxStackRand: uint64(maxRand),
+	}
+
+	// Final sanity check on the layout.
+	if !l.Valid() {
+		panic(fmt.Sprintf("Invalid MmapLayout: %+v", l))
+	}
+
+	return l, nil
+}
+
+// PIELoadAddress implements Context.PIELoadAddress.
+func (c *context64) PIELoadAddress(l MmapLayout) usermem.Addr {
+	base := preferredPIELoadAddr
+	max, ok := base.AddLength(maxMmapRand64)
+	if !ok {
+		panic(fmt.Sprintf("preferredPIELoadAddr %#x too large", base))
+	}
+
+	if max > l.MaxAddr {
+		// preferredPIELoadAddr won't fit; fall back to the standard
+		// Linux behavior of 2/3 of TopDownBase. TSAN won't like this.
+		//
+		// Don't bother trying to shrink the randomization for now.
+		base = l.TopDownBase / 3 * 2
+	}
+
+	return base + mmapRand(maxMmapRand64)
+}
+
+// PtracePeekUser implements Context.PtracePeekUser.
+func (c *context64) PtracePeekUser(addr uintptr) (interface{}, error) {
+	// TODO(gvisor.dev/issue/1239): Full ptrace supporting for Arm64.
+	return c.Native(0), nil
+}
+
+// PtracePokeUser implements Context.PtracePokeUser.
+func (c *context64) PtracePokeUser(addr, data uintptr) error {
+	// TODO(gvisor.dev/issue/1239): Full ptrace supporting for Arm64.
+	return nil
+}
diff --git a/pkg/sentry/arch/arch_state_aarch64.go b/pkg/sentry/arch/arch_state_aarch64.go
new file mode 100644
index 000000000..0136a85ad
--- /dev/null
+++ b/pkg/sentry/arch/arch_state_aarch64.go
@@ -0,0 +1,38 @@
+// Copyright 2020 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 arm64
+
+package arch
+
+import (
+	"syscall"
+)
+
+type syscallPtraceRegs struct {
+	Regs   [31]uint64
+	Sp     uint64
+	Pc     uint64
+	Pstate uint64
+}
+
+// saveRegs is invoked by stateify.
+func (s *State) saveRegs() syscallPtraceRegs {
+	return syscallPtraceRegs(s.Regs)
+}
+
+// loadRegs is invoked by stateify.
+func (s *State) loadRegs(r syscallPtraceRegs) {
+	s.Regs = syscall.PtraceRegs(r)
+}
diff --git a/pkg/sentry/arch/arch_state_x86.go b/pkg/sentry/arch/arch_state_x86.go
index 9061fcc86..84f11b0d1 100644
--- a/pkg/sentry/arch/arch_state_x86.go
+++ b/pkg/sentry/arch/arch_state_x86.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build amd64 i386
+
 package arch
 
 import (
diff --git a/pkg/sentry/arch/registers.proto b/pkg/sentry/arch/registers.proto
index 9dc83e241..60c027aab 100644
--- a/pkg/sentry/arch/registers.proto
+++ b/pkg/sentry/arch/registers.proto
@@ -48,8 +48,45 @@ message AMD64Registers {
   uint64 gs_base = 27;
 }
 
+message ARM64Registers {
+  uint64 r0 = 1;
+  uint64 r1 = 2;
+  uint64 r2 = 3;
+  uint64 r3 = 4;
+  uint64 r4 = 5;
+  uint64 r5 = 6;
+  uint64 r6 = 7;
+  uint64 r7 = 8;
+  uint64 r8 = 9;
+  uint64 r9 = 10;
+  uint64 r10 = 11;
+  uint64 r11 = 12;
+  uint64 r12 = 13;
+  uint64 r13 = 14;
+  uint64 r14 = 15;
+  uint64 r15 = 16;
+  uint64 r16 = 17;
+  uint64 r17 = 18;
+  uint64 r18 = 19;
+  uint64 r19 = 20;
+  uint64 r20 = 21;
+  uint64 r21 = 22;
+  uint64 r22 = 23;
+  uint64 r23 = 24;
+  uint64 r24 = 25;
+  uint64 r25 = 26;
+  uint64 r26 = 27;
+  uint64 r27 = 28;
+  uint64 r28 = 29;
+  uint64 r29 = 30;
+  uint64 r30 = 31;
+  uint64 sp = 32;
+  uint64 pc = 33;
+  uint64 pstate = 34;
+}
 message Registers {
   oneof arch {
     AMD64Registers amd64 = 1;
+    ARM64Registers arm64 = 2;
   }
 }
diff --git a/pkg/sentry/arch/signal.go b/pkg/sentry/arch/signal.go
new file mode 100644
index 000000000..402e46025
--- /dev/null
+++ b/pkg/sentry/arch/signal.go
@@ -0,0 +1,250 @@
+// Copyright 2020 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 arch
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+)
+
+// SignalAct represents the action that should be taken when a signal is
+// delivered, and is equivalent to struct sigaction.
+//
+// +stateify savable
+type SignalAct struct {
+	Handler  uint64
+	Flags    uint64
+	Restorer uint64 // Only used on amd64.
+	Mask     linux.SignalSet
+}
+
+// SerializeFrom implements NativeSignalAct.SerializeFrom.
+func (s *SignalAct) SerializeFrom(other *SignalAct) {
+	*s = *other
+}
+
+// DeserializeTo implements NativeSignalAct.DeserializeTo.
+func (s *SignalAct) DeserializeTo(other *SignalAct) {
+	*other = *s
+}
+
+// SignalStack represents information about a user stack, and is equivalent to
+// stack_t.
+//
+// +stateify savable
+type SignalStack struct {
+	Addr  uint64
+	Flags uint32
+	_     uint32
+	Size  uint64
+}
+
+// SerializeFrom implements NativeSignalStack.SerializeFrom.
+func (s *SignalStack) SerializeFrom(other *SignalStack) {
+	*s = *other
+}
+
+// DeserializeTo implements NativeSignalStack.DeserializeTo.
+func (s *SignalStack) DeserializeTo(other *SignalStack) {
+	*other = *s
+}
+
+// SignalInfo represents information about a signal being delivered, and is
+// equivalent to struct siginfo in linux kernel(linux/include/uapi/asm-generic/siginfo.h).
+//
+// +stateify savable
+type SignalInfo struct {
+	Signo int32 // Signal number
+	Errno int32 // Errno value
+	Code  int32 // Signal code
+	_     uint32
+
+	// struct siginfo::_sifields is a union. In SignalInfo, fields in the union
+	// are accessed through methods.
+	//
+	// For reference, here is the definition of _sifields: (_sigfault._trapno,
+	// which does not exist on x86, omitted for clarity)
+	//
+	// union {
+	// 	int _pad[SI_PAD_SIZE];
+	//
+	// 	/* kill() */
+	// 	struct {
+	// 		__kernel_pid_t _pid;	/* sender's pid */
+	// 		__ARCH_SI_UID_T _uid;	/* sender's uid */
+	// 	} _kill;
+	//
+	// 	/* POSIX.1b timers */
+	// 	struct {
+	// 		__kernel_timer_t _tid;	/* timer id */
+	// 		int _overrun;		/* overrun count */
+	// 		char _pad[sizeof( __ARCH_SI_UID_T) - sizeof(int)];
+	// 		sigval_t _sigval;	/* same as below */
+	// 		int _sys_private;       /* not to be passed to user */
+	// 	} _timer;
+	//
+	// 	/* POSIX.1b signals */
+	// 	struct {
+	// 		__kernel_pid_t _pid;	/* sender's pid */
+	// 		__ARCH_SI_UID_T _uid;	/* sender's uid */
+	// 		sigval_t _sigval;
+	// 	} _rt;
+	//
+	// 	/* SIGCHLD */
+	// 	struct {
+	// 		__kernel_pid_t _pid;	/* which child */
+	// 		__ARCH_SI_UID_T _uid;	/* sender's uid */
+	// 		int _status;		/* exit code */
+	// 		__ARCH_SI_CLOCK_T _utime;
+	// 		__ARCH_SI_CLOCK_T _stime;
+	// 	} _sigchld;
+	//
+	// 	/* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
+	// 	struct {
+	// 		void *_addr; /* faulting insn/memory ref. */
+	// 		short _addr_lsb; /* LSB of the reported address */
+	// 	} _sigfault;
+	//
+	// 	/* SIGPOLL */
+	// 	struct {
+	// 		__ARCH_SI_BAND_T _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
+	// 		int _fd;
+	// 	} _sigpoll;
+	//
+	// 	/* SIGSYS */
+	// 	struct {
+	// 		void *_call_addr; /* calling user insn */
+	// 		int _syscall;	/* triggering system call number */
+	// 		unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
+	// 	} _sigsys;
+	// } _sifields;
+	//
+	// _sifields is padded so that the size of siginfo is SI_MAX_SIZE = 128
+	// bytes.
+	Fields [128 - 16]byte
+}
+
+// FixSignalCodeForUser fixes up si_code.
+//
+// The si_code we get from Linux may contain the kernel-specific code in the
+// top 16 bits if it's positive (e.g., from ptrace). Linux's
+// copy_siginfo_to_user does
+//     err |= __put_user((short)from->si_code, &to->si_code);
+// to mask out those bits and we need to do the same.
+func (s *SignalInfo) FixSignalCodeForUser() {
+	if s.Code > 0 {
+		s.Code &= 0x0000ffff
+	}
+}
+
+// Pid returns the si_pid field.
+func (s *SignalInfo) Pid() int32 {
+	return int32(usermem.ByteOrder.Uint32(s.Fields[0:4]))
+}
+
+// SetPid mutates the si_pid field.
+func (s *SignalInfo) SetPid(val int32) {
+	usermem.ByteOrder.PutUint32(s.Fields[0:4], uint32(val))
+}
+
+// Uid returns the si_uid field.
+func (s *SignalInfo) Uid() int32 {
+	return int32(usermem.ByteOrder.Uint32(s.Fields[4:8]))
+}
+
+// SetUid mutates the si_uid field.
+func (s *SignalInfo) SetUid(val int32) {
+	usermem.ByteOrder.PutUint32(s.Fields[4:8], uint32(val))
+}
+
+// Sigval returns the sigval field, which is aliased to both si_int and si_ptr.
+func (s *SignalInfo) Sigval() uint64 {
+	return usermem.ByteOrder.Uint64(s.Fields[8:16])
+}
+
+// SetSigval mutates the sigval field.
+func (s *SignalInfo) SetSigval(val uint64) {
+	usermem.ByteOrder.PutUint64(s.Fields[8:16], val)
+}
+
+// TimerID returns the si_timerid field.
+func (s *SignalInfo) TimerID() linux.TimerID {
+	return linux.TimerID(usermem.ByteOrder.Uint32(s.Fields[0:4]))
+}
+
+// SetTimerID sets the si_timerid field.
+func (s *SignalInfo) SetTimerID(val linux.TimerID) {
+	usermem.ByteOrder.PutUint32(s.Fields[0:4], uint32(val))
+}
+
+// Overrun returns the si_overrun field.
+func (s *SignalInfo) Overrun() int32 {
+	return int32(usermem.ByteOrder.Uint32(s.Fields[4:8]))
+}
+
+// SetOverrun sets the si_overrun field.
+func (s *SignalInfo) SetOverrun(val int32) {
+	usermem.ByteOrder.PutUint32(s.Fields[4:8], uint32(val))
+}
+
+// Addr returns the si_addr field.
+func (s *SignalInfo) Addr() uint64 {
+	return usermem.ByteOrder.Uint64(s.Fields[0:8])
+}
+
+// SetAddr sets the si_addr field.
+func (s *SignalInfo) SetAddr(val uint64) {
+	usermem.ByteOrder.PutUint64(s.Fields[0:8], val)
+}
+
+// Status returns the si_status field.
+func (s *SignalInfo) Status() int32 {
+	return int32(usermem.ByteOrder.Uint32(s.Fields[8:12]))
+}
+
+// SetStatus mutates the si_status field.
+func (s *SignalInfo) SetStatus(val int32) {
+	usermem.ByteOrder.PutUint32(s.Fields[8:12], uint32(val))
+}
+
+// CallAddr returns the si_call_addr field.
+func (s *SignalInfo) CallAddr() uint64 {
+	return usermem.ByteOrder.Uint64(s.Fields[0:8])
+}
+
+// SetCallAddr mutates the si_call_addr field.
+func (s *SignalInfo) SetCallAddr(val uint64) {
+	usermem.ByteOrder.PutUint64(s.Fields[0:8], val)
+}
+
+// Syscall returns the si_syscall field.
+func (s *SignalInfo) Syscall() int32 {
+	return int32(usermem.ByteOrder.Uint32(s.Fields[8:12]))
+}
+
+// SetSyscall mutates the si_syscall field.
+func (s *SignalInfo) SetSyscall(val int32) {
+	usermem.ByteOrder.PutUint32(s.Fields[8:12], uint32(val))
+}
+
+// Arch returns the si_arch field.
+func (s *SignalInfo) Arch() uint32 {
+	return usermem.ByteOrder.Uint32(s.Fields[12:16])
+}
+
+// SetArch mutates the si_arch field.
+func (s *SignalInfo) SetArch(val uint32) {
+	usermem.ByteOrder.PutUint32(s.Fields[12:16], val)
+}
diff --git a/pkg/sentry/arch/signal_amd64.go b/pkg/sentry/arch/signal_amd64.go
index febd6f9b9..1e4f9c3c2 100644
--- a/pkg/sentry/arch/signal_amd64.go
+++ b/pkg/sentry/arch/signal_amd64.go
@@ -26,236 +26,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
-// SignalAct represents the action that should be taken when a signal is
-// delivered, and is equivalent to struct sigaction on 64-bit x86.
-//
-// +stateify savable
-type SignalAct struct {
-	Handler  uint64
-	Flags    uint64
-	Restorer uint64
-	Mask     linux.SignalSet
-}
-
-// SerializeFrom implements NativeSignalAct.SerializeFrom.
-func (s *SignalAct) SerializeFrom(other *SignalAct) {
-	*s = *other
-}
-
-// DeserializeTo implements NativeSignalAct.DeserializeTo.
-func (s *SignalAct) DeserializeTo(other *SignalAct) {
-	*other = *s
-}
-
-// SignalStack represents information about a user stack, and is equivalent to
-// stack_t on 64-bit x86.
-//
-// +stateify savable
-type SignalStack struct {
-	Addr  uint64
-	Flags uint32
-	_     uint32
-	Size  uint64
-}
-
-// SerializeFrom implements NativeSignalStack.SerializeFrom.
-func (s *SignalStack) SerializeFrom(other *SignalStack) {
-	*s = *other
-}
-
-// DeserializeTo implements NativeSignalStack.DeserializeTo.
-func (s *SignalStack) DeserializeTo(other *SignalStack) {
-	*other = *s
-}
-
-// SignalInfo represents information about a signal being delivered, and is
-// equivalent to struct siginfo on 64-bit x86.
-//
-// +stateify savable
-type SignalInfo struct {
-	Signo int32 // Signal number
-	Errno int32 // Errno value
-	Code  int32 // Signal code
-	_     uint32
-
-	// struct siginfo::_sifields is a union. In SignalInfo, fields in the union
-	// are accessed through methods.
-	//
-	// For reference, here is the definition of _sifields: (_sigfault._trapno,
-	// which does not exist on x86, omitted for clarity)
-	//
-	// union {
-	// 	int _pad[SI_PAD_SIZE];
-	//
-	// 	/* kill() */
-	// 	struct {
-	// 		__kernel_pid_t _pid;	/* sender's pid */
-	// 		__ARCH_SI_UID_T _uid;	/* sender's uid */
-	// 	} _kill;
-	//
-	// 	/* POSIX.1b timers */
-	// 	struct {
-	// 		__kernel_timer_t _tid;	/* timer id */
-	// 		int _overrun;		/* overrun count */
-	// 		char _pad[sizeof( __ARCH_SI_UID_T) - sizeof(int)];
-	// 		sigval_t _sigval;	/* same as below */
-	// 		int _sys_private;       /* not to be passed to user */
-	// 	} _timer;
-	//
-	// 	/* POSIX.1b signals */
-	// 	struct {
-	// 		__kernel_pid_t _pid;	/* sender's pid */
-	// 		__ARCH_SI_UID_T _uid;	/* sender's uid */
-	// 		sigval_t _sigval;
-	// 	} _rt;
-	//
-	// 	/* SIGCHLD */
-	// 	struct {
-	// 		__kernel_pid_t _pid;	/* which child */
-	// 		__ARCH_SI_UID_T _uid;	/* sender's uid */
-	// 		int _status;		/* exit code */
-	// 		__ARCH_SI_CLOCK_T _utime;
-	// 		__ARCH_SI_CLOCK_T _stime;
-	// 	} _sigchld;
-	//
-	// 	/* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
-	// 	struct {
-	// 		void *_addr; /* faulting insn/memory ref. */
-	// 		short _addr_lsb; /* LSB of the reported address */
-	// 	} _sigfault;
-	//
-	// 	/* SIGPOLL */
-	// 	struct {
-	// 		__ARCH_SI_BAND_T _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
-	// 		int _fd;
-	// 	} _sigpoll;
-	//
-	// 	/* SIGSYS */
-	// 	struct {
-	// 		void *_call_addr; /* calling user insn */
-	// 		int _syscall;	/* triggering system call number */
-	// 		unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
-	// 	} _sigsys;
-	// } _sifields;
-	//
-	// _sifields is padded so that the size of siginfo is SI_MAX_SIZE = 128
-	// bytes.
-	Fields [128 - 16]byte
-}
-
-// FixSignalCodeForUser fixes up si_code.
-//
-// The si_code we get from Linux may contain the kernel-specific code in the
-// top 16 bits if it's positive (e.g., from ptrace). Linux's
-// copy_siginfo_to_user does
-//     err |= __put_user((short)from->si_code, &to->si_code);
-// to mask out those bits and we need to do the same.
-func (s *SignalInfo) FixSignalCodeForUser() {
-	if s.Code > 0 {
-		s.Code &= 0x0000ffff
-	}
-}
-
-// Pid returns the si_pid field.
-func (s *SignalInfo) Pid() int32 {
-	return int32(usermem.ByteOrder.Uint32(s.Fields[0:4]))
-}
-
-// SetPid mutates the si_pid field.
-func (s *SignalInfo) SetPid(val int32) {
-	usermem.ByteOrder.PutUint32(s.Fields[0:4], uint32(val))
-}
-
-// Uid returns the si_uid field.
-func (s *SignalInfo) Uid() int32 {
-	return int32(usermem.ByteOrder.Uint32(s.Fields[4:8]))
-}
-
-// SetUid mutates the si_uid field.
-func (s *SignalInfo) SetUid(val int32) {
-	usermem.ByteOrder.PutUint32(s.Fields[4:8], uint32(val))
-}
-
-// Sigval returns the sigval field, which is aliased to both si_int and si_ptr.
-func (s *SignalInfo) Sigval() uint64 {
-	return usermem.ByteOrder.Uint64(s.Fields[8:16])
-}
-
-// SetSigval mutates the sigval field.
-func (s *SignalInfo) SetSigval(val uint64) {
-	usermem.ByteOrder.PutUint64(s.Fields[8:16], val)
-}
-
-// TimerID returns the si_timerid field.
-func (s *SignalInfo) TimerID() linux.TimerID {
-	return linux.TimerID(usermem.ByteOrder.Uint32(s.Fields[0:4]))
-}
-
-// SetTimerID sets the si_timerid field.
-func (s *SignalInfo) SetTimerID(val linux.TimerID) {
-	usermem.ByteOrder.PutUint32(s.Fields[0:4], uint32(val))
-}
-
-// Overrun returns the si_overrun field.
-func (s *SignalInfo) Overrun() int32 {
-	return int32(usermem.ByteOrder.Uint32(s.Fields[4:8]))
-}
-
-// SetOverrun sets the si_overrun field.
-func (s *SignalInfo) SetOverrun(val int32) {
-	usermem.ByteOrder.PutUint32(s.Fields[4:8], uint32(val))
-}
-
-// Addr returns the si_addr field.
-func (s *SignalInfo) Addr() uint64 {
-	return usermem.ByteOrder.Uint64(s.Fields[0:8])
-}
-
-// SetAddr sets the si_addr field.
-func (s *SignalInfo) SetAddr(val uint64) {
-	usermem.ByteOrder.PutUint64(s.Fields[0:8], val)
-}
-
-// Status returns the si_status field.
-func (s *SignalInfo) Status() int32 {
-	return int32(usermem.ByteOrder.Uint32(s.Fields[8:12]))
-}
-
-// SetStatus mutates the si_status field.
-func (s *SignalInfo) SetStatus(val int32) {
-	usermem.ByteOrder.PutUint32(s.Fields[8:12], uint32(val))
-}
-
-// CallAddr returns the si_call_addr field.
-func (s *SignalInfo) CallAddr() uint64 {
-	return usermem.ByteOrder.Uint64(s.Fields[0:8])
-}
-
-// SetCallAddr mutates the si_call_addr field.
-func (s *SignalInfo) SetCallAddr(val uint64) {
-	usermem.ByteOrder.PutUint64(s.Fields[0:8], val)
-}
-
-// Syscall returns the si_syscall field.
-func (s *SignalInfo) Syscall() int32 {
-	return int32(usermem.ByteOrder.Uint32(s.Fields[8:12]))
-}
-
-// SetSyscall mutates the si_syscall field.
-func (s *SignalInfo) SetSyscall(val int32) {
-	usermem.ByteOrder.PutUint32(s.Fields[8:12], uint32(val))
-}
-
-// Arch returns the si_arch field.
-func (s *SignalInfo) Arch() uint32 {
-	return usermem.ByteOrder.Uint32(s.Fields[12:16])
-}
-
-// SetArch mutates the si_arch field.
-func (s *SignalInfo) SetArch(val uint32) {
-	usermem.ByteOrder.PutUint32(s.Fields[12:16], val)
-}
-
 // SignalContext64 is equivalent to struct sigcontext, the type passed as the
 // second argument to signal handlers set by signal(2).
 type SignalContext64 struct {
diff --git a/pkg/sentry/arch/signal_arm64.go b/pkg/sentry/arch/signal_arm64.go
new file mode 100644
index 000000000..7d0e98935
--- /dev/null
+++ b/pkg/sentry/arch/signal_arm64.go
@@ -0,0 +1,126 @@
+// Copyright 2020 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 arch
+
+import (
+	"encoding/binary"
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+)
+
+// SignalContext64 is equivalent to struct sigcontext, the type passed as the
+// second argument to signal handlers set by signal(2).
+type SignalContext64 struct {
+	FaultAddr uint64
+	Regs      [31]uint64
+	Sp        uint64
+	Pc        uint64
+	Pstate    uint64
+	_pad      [8]byte // __attribute__((__aligned__(16)))
+	Reserved  [4096]uint8
+}
+
+// UContext64 is equivalent to ucontext on arm64(arch/arm64/include/uapi/asm/ucontext.h).
+type UContext64 struct {
+	Flags  uint64
+	Link   *UContext64
+	Stack  SignalStack
+	Sigset linux.SignalSet
+	// glibc uses a 1024-bit sigset_t
+	_pad [(1024 - 64) / 8]byte
+	// sigcontext must be aligned to 16-byte
+	_pad2 [8]byte
+	// last for future expansion
+	MContext SignalContext64
+}
+
+// NewSignalAct implements Context.NewSignalAct.
+func (c *context64) NewSignalAct() NativeSignalAct {
+	return &SignalAct{}
+}
+
+// NewSignalStack implements Context.NewSignalStack.
+func (c *context64) NewSignalStack() NativeSignalStack {
+	return &SignalStack{}
+}
+
+// SignalSetup implements Context.SignalSetup.
+func (c *context64) SignalSetup(st *Stack, act *SignalAct, info *SignalInfo, alt *SignalStack, sigset linux.SignalSet) error {
+	sp := st.Bottom
+
+	if !(alt.IsEnabled() && sp == alt.Top()) {
+		sp -= 128
+	}
+
+	// Construct the UContext64 now since we need its size.
+	uc := &UContext64{
+		Flags: 0,
+		Stack: *alt,
+		MContext: SignalContext64{
+			Regs:   c.Regs.Regs,
+			Sp:     c.Regs.Sp,
+			Pc:     c.Regs.Pc,
+			Pstate: c.Regs.Pstate,
+		},
+		Sigset: sigset,
+	}
+
+	ucSize := binary.Size(uc)
+	if ucSize < 0 {
+		panic("can't get size of UContext64")
+	}
+	// st.Arch.Width() is for the restorer address. sizeof(siginfo) == 128.
+	frameSize := int(st.Arch.Width()) + ucSize + 128
+	frameBottom := (sp-usermem.Addr(frameSize)) & ^usermem.Addr(15) - 8
+	sp = frameBottom + usermem.Addr(frameSize)
+	st.Bottom = sp
+
+	// Prior to proceeding, figure out if the frame will exhaust the range
+	// for the signal stack. This is not allowed, and should immediately
+	// force signal delivery (reverting to the default handler).
+	if act.IsOnStack() && alt.IsEnabled() && !alt.Contains(frameBottom) {
+		return syscall.EFAULT
+	}
+
+	// Adjust the code.
+	info.FixSignalCodeForUser()
+
+	// Set up the stack frame.
+	infoAddr, err := st.Push(info)
+	if err != nil {
+		return err
+	}
+	ucAddr, err := st.Push(uc)
+	if err != nil {
+		return err
+	}
+
+	// Set up registers.
+	c.Regs.Sp = uint64(st.Bottom)
+	c.Regs.Pc = act.Handler
+	c.Regs.Regs[0] = uint64(info.Signo)
+	c.Regs.Regs[1] = uint64(infoAddr)
+	c.Regs.Regs[2] = uint64(ucAddr)
+
+	return nil
+}
+
+// SignalRestore implements Context.SignalRestore.
+// Only used on intel.
+func (c *context64) SignalRestore(st *Stack, rt bool) (linux.SignalSet, SignalStack, error) {
+	return 0, SignalStack{}, nil
+}
diff --git a/pkg/sentry/arch/signal_stack.go b/pkg/sentry/arch/signal_stack.go
index 5a3228113..d324da705 100644
--- a/pkg/sentry/arch/signal_stack.go
+++ b/pkg/sentry/arch/signal_stack.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build i386 amd64
+// +build i386 amd64 arm64
 
 package arch
 
diff --git a/pkg/sentry/arch/syscalls_arm64.go b/pkg/sentry/arch/syscalls_arm64.go
new file mode 100644
index 000000000..00d5ef461
--- /dev/null
+++ b/pkg/sentry/arch/syscalls_arm64.go
@@ -0,0 +1,62 @@
+// Copyright 2020 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 arm64
+
+package arch
+
+const restartSyscallNr = uintptr(128)
+
+// SyscallNo returns the syscall number according to the 64-bit convention.
+func (c *context64) SyscallNo() uintptr {
+	return uintptr(c.Regs.Regs[8])
+}
+
+// SyscallArgs provides syscall arguments according to the 64-bit convention.
+//
+// Due to the way addresses are mapped for the sentry this binary *must* be
+// built in 64-bit mode. So we can just assume the syscall numbers that come
+// back match the expected host system call numbers.
+// General purpose registers usage on Arm64:
+// R0...R7: parameter/result registers.
+// R8: indirect result location register.
+// R9...R15: temporary registers.
+// R16: the first intra-procedure-call scratch register.
+// R17: the second intra-procedure-call scratch register.
+// R18: the platform register.
+// R19...R28: callee-saved registers.
+// R29: the frame pointer.
+// R30: the link register.
+func (c *context64) SyscallArgs() SyscallArguments {
+	return SyscallArguments{
+		SyscallArgument{Value: uintptr(c.Regs.Regs[0])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[1])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[2])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[3])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[4])},
+		SyscallArgument{Value: uintptr(c.Regs.Regs[5])},
+	}
+}
+
+// RestartSyscall implements Context.RestartSyscall.
+func (c *context64) RestartSyscall() {
+	c.Regs.Pc -= SyscallWidth
+	c.Regs.Regs[8] = uint64(restartSyscallNr)
+}
+
+// RestartSyscallWithRestartBlock implements Context.RestartSyscallWithRestartBlock.
+func (c *context64) RestartSyscallWithRestartBlock() {
+	c.Regs.Pc -= SyscallWidth
+	c.Regs.Regs[8] = uint64(restartSyscallNr)
+}