[syserror] Split usermem package

Split usermem package to help remove syserror dependency in go_marshal.
New hostarch package contains code not dependent on syserror.

PiperOrigin-RevId: 365651233

11 files changed, 49 insertions, 884 deletions

diff --git a/pkg/usermem/BUILD b/pkg/usermem/BUILD
index 054269b59..3dba36f12 100644
--- a/pkg/usermem/BUILD
+++ b/pkg/usermem/BUILD
@@ -1,42 +1,22 @@
 load("//tools:defs.bzl", "go_library", "go_test")
-load("//tools/go_generics:defs.bzl", "go_template_instance")
 
 package(licenses = ["notice"])
 
-go_template_instance(
-    name = "addr_range",
-    out = "addr_range.go",
-    package = "usermem",
-    prefix = "Addr",
-    template = "//pkg/segment:generic_range",
-    types = {
-        "T": "Addr",
-    },
-)
-
 go_library(
     name = "usermem",
     srcs = [
-        "access_type.go",
-        "addr.go",
-        "addr_range.go",
-        "addr_range_seq_unsafe.go",
         "bytes_io.go",
         "bytes_io_unsafe.go",
         "usermem.go",
-        "usermem_arm64.go",
-        "usermem_x86.go",
     ],
     visibility = ["//:sandbox"],
     deps = [
         "//pkg/atomicbitops",
-        "//pkg/binary",
         "//pkg/context",
         "//pkg/gohacks",
-        "//pkg/log",
+        "//pkg/hostarch",
         "//pkg/safemem",
         "//pkg/syserror",
-        "@org_golang_x_sys//unix:go_default_library",
     ],
 )
 
@@ -44,12 +24,12 @@ go_test(
     name = "usermem_test",
     size = "small",
     srcs = [
-        "addr_range_seq_test.go",
         "usermem_test.go",
     ],
     library = ":usermem",
     deps = [
         "//pkg/context",
+        "//pkg/hostarch",
         "//pkg/safemem",
         "//pkg/syserror",
     ],
diff --git a/pkg/usermem/access_type.go b/pkg/usermem/access_type.go
deleted file mode 100644
index 2cfca29af..000000000
--- a/pkg/usermem/access_type.go
+++ /dev/null
@@ -1,126 +0,0 @@
-// 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.
-
-package usermem
-
-import "golang.org/x/sys/unix"
-
-// AccessType specifies memory access types. This is used for
-// setting mapping permissions, as well as communicating faults.
-//
-// +stateify savable
-type AccessType struct {
-	// Read is read access.
-	Read bool
-
-	// Write is write access.
-	Write bool
-
-	// Execute is executable access.
-	Execute bool
-}
-
-// String returns a pretty representation of access. This looks like the
-// familiar r-x, rw-, etc. and can be relied on as such.
-func (a AccessType) String() string {
-	bits := [3]byte{'-', '-', '-'}
-	if a.Read {
-		bits[0] = 'r'
-	}
-	if a.Write {
-		bits[1] = 'w'
-	}
-	if a.Execute {
-		bits[2] = 'x'
-	}
-	return string(bits[:])
-}
-
-// Any returns true iff at least one of Read, Write or Execute is true.
-func (a AccessType) Any() bool {
-	return a.Read || a.Write || a.Execute
-}
-
-// Prot returns the system prot (unix.PROT_READ, etc.) for this access.
-func (a AccessType) Prot() int {
-	var prot int
-	if a.Read {
-		prot |= unix.PROT_READ
-	}
-	if a.Write {
-		prot |= unix.PROT_WRITE
-	}
-	if a.Execute {
-		prot |= unix.PROT_EXEC
-	}
-	return prot
-}
-
-// SupersetOf returns true iff the access types in a are a superset of the
-// access types in other.
-func (a AccessType) SupersetOf(other AccessType) bool {
-	if !a.Read && other.Read {
-		return false
-	}
-	if !a.Write && other.Write {
-		return false
-	}
-	if !a.Execute && other.Execute {
-		return false
-	}
-	return true
-}
-
-// Intersect returns the access types set in both a and other.
-func (a AccessType) Intersect(other AccessType) AccessType {
-	return AccessType{
-		Read:    a.Read && other.Read,
-		Write:   a.Write && other.Write,
-		Execute: a.Execute && other.Execute,
-	}
-}
-
-// Union returns the access types set in either a or other.
-func (a AccessType) Union(other AccessType) AccessType {
-	return AccessType{
-		Read:    a.Read || other.Read,
-		Write:   a.Write || other.Write,
-		Execute: a.Execute || other.Execute,
-	}
-}
-
-// Effective returns the set of effective access types allowed by a, even if
-// some types are not explicitly allowed.
-func (a AccessType) Effective() AccessType {
-	// In Linux, Write and Execute access generally imply Read access. See
-	// mm/mmap.c:protection_map.
-	//
-	// The notable exception is get_user_pages, which only checks against
-	// the original vma flags. That said, most user memory accesses do not
-	// use GUP.
-	if a.Write || a.Execute {
-		a.Read = true
-	}
-	return a
-}
-
-// Convenient access types.
-var (
-	NoAccess  = AccessType{}
-	Read      = AccessType{Read: true}
-	Write     = AccessType{Write: true}
-	Execute   = AccessType{Execute: true}
-	ReadWrite = AccessType{Read: true, Write: true}
-	AnyAccess = AccessType{Read: true, Write: true, Execute: true}
-)
diff --git a/pkg/usermem/addr.go b/pkg/usermem/addr.go
deleted file mode 100644
index c4100481e..000000000
--- a/pkg/usermem/addr.go
+++ /dev/null
@@ -1,125 +0,0 @@
-// 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.
-
-package usermem
-
-import (
-	"fmt"
-)
-
-// Addr represents a generic virtual address.
-//
-// +stateify savable
-type Addr uintptr
-
-// AddLength adds the given length to start and returns the result. ok is true
-// iff adding the length did not overflow the range of Addr.
-//
-// Note: This function is usually used to get the end of an address range
-// defined by its start address and length. Since the resulting end is
-// exclusive, end == 0 is technically valid, and corresponds to a range that
-// extends to the end of the address space, but ok will be false. This isn't
-// expected to ever come up in practice.
-func (v Addr) AddLength(length uint64) (end Addr, ok bool) {
-	end = v + Addr(length)
-	// The second half of the following check is needed in case uintptr is
-	// smaller than 64 bits.
-	ok = end >= v && length <= uint64(^Addr(0))
-	return
-}
-
-// RoundDown returns the address rounded down to the nearest page boundary.
-func (v Addr) RoundDown() Addr {
-	return v & ^Addr(PageSize-1)
-}
-
-// RoundUp returns the address rounded up to the nearest page boundary. ok is
-// true iff rounding up did not wrap around.
-func (v Addr) RoundUp() (addr Addr, ok bool) {
-	addr = Addr(v + PageSize - 1).RoundDown()
-	ok = addr >= v
-	return
-}
-
-// MustRoundUp is equivalent to RoundUp, but panics if rounding up wraps
-// around.
-func (v Addr) MustRoundUp() Addr {
-	addr, ok := v.RoundUp()
-	if !ok {
-		panic(fmt.Sprintf("usermem.Addr(%d).RoundUp() wraps", v))
-	}
-	return addr
-}
-
-// HugeRoundDown returns the address rounded down to the nearest huge page
-// boundary.
-func (v Addr) HugeRoundDown() Addr {
-	return v & ^Addr(HugePageSize-1)
-}
-
-// HugeRoundUp returns the address rounded up to the nearest huge page boundary.
-// ok is true iff rounding up did not wrap around.
-func (v Addr) HugeRoundUp() (addr Addr, ok bool) {
-	addr = Addr(v + HugePageSize - 1).HugeRoundDown()
-	ok = addr >= v
-	return
-}
-
-// PageOffset returns the offset of v into the current page.
-func (v Addr) PageOffset() uint64 {
-	return uint64(v & Addr(PageSize-1))
-}
-
-// IsPageAligned returns true if v.PageOffset() == 0.
-func (v Addr) IsPageAligned() bool {
-	return v.PageOffset() == 0
-}
-
-// AddrRange is a range of Addrs.
-//
-// type AddrRange <generated by go_generics>
-
-// ToRange returns [v, v+length).
-func (v Addr) ToRange(length uint64) (AddrRange, bool) {
-	end, ok := v.AddLength(length)
-	return AddrRange{v, end}, ok
-}
-
-// IsPageAligned returns true if ar.Start.IsPageAligned() and
-// ar.End.IsPageAligned().
-func (ar AddrRange) IsPageAligned() bool {
-	return ar.Start.IsPageAligned() && ar.End.IsPageAligned()
-}
-
-// String implements fmt.Stringer.String.
-func (ar AddrRange) String() string {
-	return fmt.Sprintf("[%#x, %#x)", ar.Start, ar.End)
-}
-
-// PageRoundDown/Up are equivalent to Addr.RoundDown/Up, but without the
-// potentially truncating conversion from uint64 to Addr. This is necessary
-// because there is no way to define generic "PageRoundDown/Up" functions in Go.
-
-// PageRoundDown returns x rounded down to the nearest page boundary.
-func PageRoundDown(x uint64) uint64 {
-	return x &^ (PageSize - 1)
-}
-
-// PageRoundUp returns x rounded up to the nearest page boundary.
-// ok is true iff rounding up did not wrap around.
-func PageRoundUp(x uint64) (addr uint64, ok bool) {
-	addr = PageRoundDown(x + PageSize - 1)
-	ok = addr >= x
-	return
-}
diff --git a/pkg/usermem/addr_range_seq_test.go b/pkg/usermem/addr_range_seq_test.go
deleted file mode 100644
index 82f735026..000000000
--- a/pkg/usermem/addr_range_seq_test.go
+++ /dev/null
@@ -1,197 +0,0 @@
-// 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.
-
-package usermem
-
-import (
-	"testing"
-)
-
-var addrRangeSeqTests = []struct {
-	desc   string
-	ranges []AddrRange
-}{
-	{
-		desc: "Empty sequence",
-	},
-	{
-		desc: "Single empty AddrRange",
-		ranges: []AddrRange{
-			{0x10, 0x10},
-		},
-	},
-	{
-		desc: "Single non-empty AddrRange of length 1",
-		ranges: []AddrRange{
-			{0x10, 0x11},
-		},
-	},
-	{
-		desc: "Single non-empty AddrRange of length 2",
-		ranges: []AddrRange{
-			{0x10, 0x12},
-		},
-	},
-	{
-		desc: "Multiple non-empty AddrRanges",
-		ranges: []AddrRange{
-			{0x10, 0x11},
-			{0x20, 0x22},
-		},
-	},
-	{
-		desc: "Multiple AddrRanges including empty AddrRanges",
-		ranges: []AddrRange{
-			{0x10, 0x10},
-			{0x20, 0x20},
-			{0x30, 0x33},
-			{0x40, 0x44},
-			{0x50, 0x50},
-			{0x60, 0x60},
-			{0x70, 0x77},
-			{0x80, 0x88},
-			{0x90, 0x90},
-			{0xa0, 0xa0},
-		},
-	},
-}
-
-func testAddrRangeSeqEqualityWithTailIteration(t *testing.T, ars AddrRangeSeq, wantRanges []AddrRange) {
-	var wantLen int64
-	for _, ar := range wantRanges {
-		wantLen += int64(ar.Length())
-	}
-
-	var i int
-	for !ars.IsEmpty() {
-		if gotLen := ars.NumBytes(); gotLen != wantLen {
-			t.Errorf("Iteration %d: %v.NumBytes(): got %d, wanted %d", i, ars, gotLen, wantLen)
-		}
-		if gotN, wantN := ars.NumRanges(), len(wantRanges)-i; gotN != wantN {
-			t.Errorf("Iteration %d: %v.NumRanges(): got %d, wanted %d", i, ars, gotN, wantN)
-		}
-		got := ars.Head()
-		if i >= len(wantRanges) {
-			t.Errorf("Iteration %d: %v.Head(): got %s, wanted <end of sequence>", i, ars, got)
-		} else if want := wantRanges[i]; got != want {
-			t.Errorf("Iteration %d: %v.Head(): got %s, wanted %s", i, ars, got, want)
-		}
-		ars = ars.Tail()
-		wantLen -= int64(got.Length())
-		i++
-	}
-	if gotLen := ars.NumBytes(); gotLen != 0 || wantLen != 0 {
-		t.Errorf("Iteration %d: %v.NumBytes(): got %d, wanted %d (which should be 0)", i, ars, gotLen, wantLen)
-	}
-	if gotN := ars.NumRanges(); gotN != 0 {
-		t.Errorf("Iteration %d: %v.NumRanges(): got %d, wanted 0", i, ars, gotN)
-	}
-}
-
-func TestAddrRangeSeqTailIteration(t *testing.T) {
-	for _, test := range addrRangeSeqTests {
-		t.Run(test.desc, func(t *testing.T) {
-			testAddrRangeSeqEqualityWithTailIteration(t, AddrRangeSeqFromSlice(test.ranges), test.ranges)
-		})
-	}
-}
-
-func TestAddrRangeSeqDropFirstEmpty(t *testing.T) {
-	var ars AddrRangeSeq
-	if got, want := ars.DropFirst(1), ars; got != want {
-		t.Errorf("%v.DropFirst(1): got %v, wanted %v", ars, got, want)
-	}
-}
-
-func TestAddrRangeSeqDropSingleByteIteration(t *testing.T) {
-	// Tests AddrRangeSeq iteration using Head/DropFirst, simulating
-	// I/O-per-AddrRange.
-	for _, test := range addrRangeSeqTests {
-		t.Run(test.desc, func(t *testing.T) {
-			// Figure out what AddrRanges we expect to see.
-			var wantLen int64
-			var wantRanges []AddrRange
-			for _, ar := range test.ranges {
-				wantLen += int64(ar.Length())
-				wantRanges = append(wantRanges, ar)
-				if ar.Length() == 0 {
-					// We "do" 0 bytes of I/O and then call DropFirst(0),
-					// advancing to the next AddrRange.
-					continue
-				}
-				// Otherwise we "do" 1 byte of I/O and then call DropFirst(1),
-				// advancing the AddrRange by 1 byte, or to the next AddrRange
-				// if this one is exhausted.
-				for ar.Start++; ar.Length() != 0; ar.Start++ {
-					wantRanges = append(wantRanges, ar)
-				}
-			}
-			t.Logf("Expected AddrRanges: %s (%d bytes)", wantRanges, wantLen)
-
-			ars := AddrRangeSeqFromSlice(test.ranges)
-			var i int
-			for !ars.IsEmpty() {
-				if gotLen := ars.NumBytes(); gotLen != wantLen {
-					t.Errorf("Iteration %d: %v.NumBytes(): got %d, wanted %d", i, ars, gotLen, wantLen)
-				}
-				got := ars.Head()
-				if i >= len(wantRanges) {
-					t.Errorf("Iteration %d: %v.Head(): got %s, wanted <end of sequence>", i, ars, got)
-				} else if want := wantRanges[i]; got != want {
-					t.Errorf("Iteration %d: %v.Head(): got %s, wanted %s", i, ars, got, want)
-				}
-				if got.Length() == 0 {
-					ars = ars.DropFirst(0)
-				} else {
-					ars = ars.DropFirst(1)
-					wantLen--
-				}
-				i++
-			}
-			if gotLen := ars.NumBytes(); gotLen != 0 || wantLen != 0 {
-				t.Errorf("Iteration %d: %v.NumBytes(): got %d, wanted %d (which should be 0)", i, ars, gotLen, wantLen)
-			}
-		})
-	}
-}
-
-func TestAddrRangeSeqTakeFirstEmpty(t *testing.T) {
-	var ars AddrRangeSeq
-	if got, want := ars.TakeFirst(1), ars; got != want {
-		t.Errorf("%v.TakeFirst(1): got %v, wanted %v", ars, got, want)
-	}
-}
-
-func TestAddrRangeSeqTakeFirst(t *testing.T) {
-	ranges := []AddrRange{
-		{0x10, 0x11},
-		{0x20, 0x22},
-		{0x30, 0x30},
-		{0x40, 0x44},
-		{0x50, 0x55},
-		{0x60, 0x60},
-		{0x70, 0x77},
-	}
-	ars := AddrRangeSeqFromSlice(ranges).TakeFirst(5)
-	want := []AddrRange{
-		{0x10, 0x11}, // +1 byte (total 1 byte), not truncated
-		{0x20, 0x22}, // +2 bytes (total 3 bytes), not truncated
-		{0x30, 0x30}, // +0 bytes (total 3 bytes), no change
-		{0x40, 0x42}, // +2 bytes (total 5 bytes), partially truncated
-		{0x50, 0x50}, // +0 bytes (total 5 bytes), fully truncated
-		{0x60, 0x60}, // +0 bytes (total 5 bytes), "fully truncated" (no change)
-		{0x70, 0x70}, // +0 bytes (total 5 bytes), fully truncated
-	}
-	testAddrRangeSeqEqualityWithTailIteration(t, ars, want)
-}
diff --git a/pkg/usermem/addr_range_seq_unsafe.go b/pkg/usermem/addr_range_seq_unsafe.go
deleted file mode 100644
index c9a1415a0..000000000
--- a/pkg/usermem/addr_range_seq_unsafe.go
+++ /dev/null
@@ -1,280 +0,0 @@
-// 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.
-
-package usermem
-
-import (
-	"bytes"
-	"fmt"
-	"unsafe"
-
-	"gvisor.dev/gvisor/pkg/gohacks"
-)
-
-// An AddrRangeSeq represents a sequence of AddrRanges.
-//
-// AddrRangeSeqs are immutable and may be copied by value. The zero value of
-// AddrRangeSeq represents an empty sequence.
-//
-// An AddrRangeSeq may contain AddrRanges with a length of 0. This is necessary
-// since zero-length AddrRanges are significant to MM bounds checks.
-type AddrRangeSeq struct {
-	// If length is 0, then the AddrRangeSeq represents no AddrRanges.
-	// Invariants: data == 0; offset == 0; limit == 0.
-	//
-	// If length is 1, then the AddrRangeSeq represents the single
-	// AddrRange{offset, offset+limit}. Invariants: data == 0.
-	//
-	// Otherwise, length >= 2, and the AddrRangeSeq represents the `length`
-	// AddrRanges in the array of AddrRanges starting at address `data`,
-	// starting at `offset` bytes into the first AddrRange and limited to the
-	// following `limit` bytes. (AddrRanges after `limit` are still iterated,
-	// but are truncated to a length of 0.) Invariants: data != 0; offset <=
-	// data[0].Length(); limit > 0; offset+limit <= the combined length of all
-	// AddrRanges in the array.
-	data   unsafe.Pointer
-	length int
-	offset Addr
-	limit  Addr
-}
-
-// AddrRangeSeqOf returns an AddrRangeSeq representing the single AddrRange ar.
-func AddrRangeSeqOf(ar AddrRange) AddrRangeSeq {
-	return AddrRangeSeq{
-		length: 1,
-		offset: ar.Start,
-		limit:  ar.Length(),
-	}
-}
-
-// AddrRangeSeqFromSlice returns an AddrRangeSeq representing all AddrRanges in
-// slice.
-//
-// Whether the returned AddrRangeSeq shares memory with slice is unspecified;
-// clients should avoid mutating slices passed to AddrRangeSeqFromSlice.
-//
-// Preconditions: The combined length of all AddrRanges in slice <=
-// math.MaxInt64.
-func AddrRangeSeqFromSlice(slice []AddrRange) AddrRangeSeq {
-	var limit int64
-	for _, ar := range slice {
-		len64 := int64(ar.Length())
-		if len64 < 0 {
-			panic(fmt.Sprintf("Length of AddrRange %v overflows int64", ar))
-		}
-		sum := limit + len64
-		if sum < limit {
-			panic(fmt.Sprintf("Total length of AddrRanges %v overflows int64", slice))
-		}
-		limit = sum
-	}
-	return addrRangeSeqFromSliceLimited(slice, limit)
-}
-
-// Preconditions:
-// * The combined length of all AddrRanges in slice <= limit.
-// * limit >= 0.
-// * If len(slice) != 0, then limit > 0.
-func addrRangeSeqFromSliceLimited(slice []AddrRange, limit int64) AddrRangeSeq {
-	switch len(slice) {
-	case 0:
-		return AddrRangeSeq{}
-	case 1:
-		return AddrRangeSeq{
-			length: 1,
-			offset: slice[0].Start,
-			limit:  Addr(limit),
-		}
-	default:
-		return AddrRangeSeq{
-			data:   unsafe.Pointer(&slice[0]),
-			length: len(slice),
-			limit:  Addr(limit),
-		}
-	}
-}
-
-// IsEmpty returns true if ars.NumRanges() == 0.
-//
-// Note that since AddrRangeSeq may contain AddrRanges with a length of zero,
-// an AddrRange representing 0 bytes (AddrRangeSeq.NumBytes() == 0) is not
-// necessarily empty.
-func (ars AddrRangeSeq) IsEmpty() bool {
-	return ars.length == 0
-}
-
-// NumRanges returns the number of AddrRanges in ars.
-func (ars AddrRangeSeq) NumRanges() int {
-	return ars.length
-}
-
-// NumBytes returns the number of bytes represented by ars.
-func (ars AddrRangeSeq) NumBytes() int64 {
-	return int64(ars.limit)
-}
-
-// Head returns the first AddrRange in ars.
-//
-// Preconditions: !ars.IsEmpty().
-func (ars AddrRangeSeq) Head() AddrRange {
-	if ars.length == 0 {
-		panic("empty AddrRangeSeq")
-	}
-	if ars.length == 1 {
-		return AddrRange{ars.offset, ars.offset + ars.limit}
-	}
-	ar := *(*AddrRange)(ars.data)
-	ar.Start += ars.offset
-	if ar.Length() > ars.limit {
-		ar.End = ar.Start + ars.limit
-	}
-	return ar
-}
-
-// Tail returns an AddrRangeSeq consisting of all AddrRanges in ars after the
-// first.
-//
-// Preconditions: !ars.IsEmpty().
-func (ars AddrRangeSeq) Tail() AddrRangeSeq {
-	if ars.length == 0 {
-		panic("empty AddrRangeSeq")
-	}
-	if ars.length == 1 {
-		return AddrRangeSeq{}
-	}
-	return ars.externalTail()
-}
-
-// Preconditions: ars.length >= 2.
-func (ars AddrRangeSeq) externalTail() AddrRangeSeq {
-	headLen := (*AddrRange)(ars.data).Length() - ars.offset
-	var tailLimit int64
-	if ars.limit > headLen {
-		tailLimit = int64(ars.limit - headLen)
-	}
-	var extSlice []AddrRange
-	extSliceHdr := (*gohacks.SliceHeader)(unsafe.Pointer(&extSlice))
-	extSliceHdr.Data = ars.data
-	extSliceHdr.Len = ars.length
-	extSliceHdr.Cap = ars.length
-	return addrRangeSeqFromSliceLimited(extSlice[1:], tailLimit)
-}
-
-// DropFirst returns an AddrRangeSeq equivalent to ars, but with the first n
-// bytes omitted. If n > ars.NumBytes(), DropFirst returns an empty
-// AddrRangeSeq.
-//
-// If !ars.IsEmpty() and ars.Head().Length() == 0, DropFirst will always omit
-// at least ars.Head(), even if n == 0. This guarantees that the basic pattern
-// of:
-//
-//     for !ars.IsEmpty() {
-//       n, err = doIOWith(ars.Head())
-//       if err != nil {
-//         return err
-//       }
-//       ars = ars.DropFirst(n)
-//     }
-//
-// works even in the presence of zero-length AddrRanges.
-//
-// Preconditions: n >= 0.
-func (ars AddrRangeSeq) DropFirst(n int) AddrRangeSeq {
-	if n < 0 {
-		panic(fmt.Sprintf("invalid n: %d", n))
-	}
-	return ars.DropFirst64(int64(n))
-}
-
-// DropFirst64 is equivalent to DropFirst but takes an int64.
-func (ars AddrRangeSeq) DropFirst64(n int64) AddrRangeSeq {
-	if n < 0 {
-		panic(fmt.Sprintf("invalid n: %d", n))
-	}
-	if Addr(n) > ars.limit {
-		return AddrRangeSeq{}
-	}
-	// Handle initial empty AddrRange.
-	switch ars.length {
-	case 0:
-		return AddrRangeSeq{}
-	case 1:
-		if ars.limit == 0 {
-			return AddrRangeSeq{}
-		}
-	default:
-		if rawHeadLen := (*AddrRange)(ars.data).Length(); ars.offset == rawHeadLen {
-			ars = ars.externalTail()
-		}
-	}
-	for n != 0 {
-		// Calling ars.Head() here is surprisingly expensive, so inline getting
-		// the head's length.
-		var headLen Addr
-		if ars.length == 1 {
-			headLen = ars.limit
-		} else {
-			headLen = (*AddrRange)(ars.data).Length() - ars.offset
-		}
-		if Addr(n) < headLen {
-			// Dropping ends partway through the head AddrRange.
-			ars.offset += Addr(n)
-			ars.limit -= Addr(n)
-			return ars
-		}
-		n -= int64(headLen)
-		ars = ars.Tail()
-	}
-	return ars
-}
-
-// TakeFirst returns an AddrRangeSeq equivalent to ars, but iterating at most n
-// bytes. TakeFirst never removes AddrRanges from ars; AddrRanges beyond the
-// first n bytes are reduced to a length of zero, but will still be iterated.
-//
-// Preconditions: n >= 0.
-func (ars AddrRangeSeq) TakeFirst(n int) AddrRangeSeq {
-	if n < 0 {
-		panic(fmt.Sprintf("invalid n: %d", n))
-	}
-	return ars.TakeFirst64(int64(n))
-}
-
-// TakeFirst64 is equivalent to TakeFirst but takes an int64.
-func (ars AddrRangeSeq) TakeFirst64(n int64) AddrRangeSeq {
-	if n < 0 {
-		panic(fmt.Sprintf("invalid n: %d", n))
-	}
-	if ars.limit > Addr(n) {
-		ars.limit = Addr(n)
-	}
-	return ars
-}
-
-// String implements fmt.Stringer.String.
-func (ars AddrRangeSeq) String() string {
-	// This is deliberately chosen to be the same as fmt's automatic stringer
-	// for []AddrRange.
-	var buf bytes.Buffer
-	buf.WriteByte('[')
-	var sep string
-	for !ars.IsEmpty() {
-		buf.WriteString(sep)
-		sep = " "
-		buf.WriteString(ars.Head().String())
-		ars = ars.Tail()
-	}
-	buf.WriteByte(']')
-	return buf.String()
-}
diff --git a/pkg/usermem/bytes_io.go b/pkg/usermem/bytes_io.go
index e177d30eb..3da3c0294 100644
--- a/pkg/usermem/bytes_io.go
+++ b/pkg/usermem/bytes_io.go
@@ -16,6 +16,7 @@ package usermem
 
 import (
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/hostarch"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -30,7 +31,7 @@ type BytesIO struct {
 }
 
 // CopyOut implements IO.CopyOut.
-func (b *BytesIO) CopyOut(ctx context.Context, addr Addr, src []byte, opts IOOpts) (int, error) {
+func (b *BytesIO) CopyOut(ctx context.Context, addr hostarch.Addr, src []byte, opts IOOpts) (int, error) {
 	rngN, rngErr := b.rangeCheck(addr, len(src))
 	if rngN == 0 {
 		return 0, rngErr
@@ -39,7 +40,7 @@ func (b *BytesIO) CopyOut(ctx context.Context, addr Addr, src []byte, opts IOOpt
 }
 
 // CopyIn implements IO.CopyIn.
-func (b *BytesIO) CopyIn(ctx context.Context, addr Addr, dst []byte, opts IOOpts) (int, error) {
+func (b *BytesIO) CopyIn(ctx context.Context, addr hostarch.Addr, dst []byte, opts IOOpts) (int, error) {
 	rngN, rngErr := b.rangeCheck(addr, len(dst))
 	if rngN == 0 {
 		return 0, rngErr
@@ -48,7 +49,7 @@ func (b *BytesIO) CopyIn(ctx context.Context, addr Addr, dst []byte, opts IOOpts
 }
 
 // ZeroOut implements IO.ZeroOut.
-func (b *BytesIO) ZeroOut(ctx context.Context, addr Addr, toZero int64, opts IOOpts) (int64, error) {
+func (b *BytesIO) ZeroOut(ctx context.Context, addr hostarch.Addr, toZero int64, opts IOOpts) (int64, error) {
 	if toZero > int64(maxInt) {
 		return 0, syserror.EINVAL
 	}
@@ -64,7 +65,7 @@ func (b *BytesIO) ZeroOut(ctx context.Context, addr Addr, toZero int64, opts IOO
 }
 
 // CopyOutFrom implements IO.CopyOutFrom.
-func (b *BytesIO) CopyOutFrom(ctx context.Context, ars AddrRangeSeq, src safemem.Reader, opts IOOpts) (int64, error) {
+func (b *BytesIO) CopyOutFrom(ctx context.Context, ars hostarch.AddrRangeSeq, src safemem.Reader, opts IOOpts) (int64, error) {
 	dsts, rngErr := b.blocksFromAddrRanges(ars)
 	n, err := src.ReadToBlocks(dsts)
 	if err != nil {
@@ -74,7 +75,7 @@ func (b *BytesIO) CopyOutFrom(ctx context.Context, ars AddrRangeSeq, src safemem
 }
 
 // CopyInTo implements IO.CopyInTo.
-func (b *BytesIO) CopyInTo(ctx context.Context, ars AddrRangeSeq, dst safemem.Writer, opts IOOpts) (int64, error) {
+func (b *BytesIO) CopyInTo(ctx context.Context, ars hostarch.AddrRangeSeq, dst safemem.Writer, opts IOOpts) (int64, error) {
 	srcs, rngErr := b.blocksFromAddrRanges(ars)
 	n, err := dst.WriteFromBlocks(srcs)
 	if err != nil {
@@ -83,14 +84,14 @@ func (b *BytesIO) CopyInTo(ctx context.Context, ars AddrRangeSeq, dst safemem.Wr
 	return int64(n), rngErr
 }
 
-func (b *BytesIO) rangeCheck(addr Addr, length int) (int, error) {
+func (b *BytesIO) rangeCheck(addr hostarch.Addr, length int) (int, error) {
 	if length == 0 {
 		return 0, nil
 	}
 	if length < 0 {
 		return 0, syserror.EINVAL
 	}
-	max := Addr(len(b.Bytes))
+	max := hostarch.Addr(len(b.Bytes))
 	if addr >= max {
 		return 0, syserror.EFAULT
 	}
@@ -101,7 +102,7 @@ func (b *BytesIO) rangeCheck(addr Addr, length int) (int, error) {
 	return length, nil
 }
 
-func (b *BytesIO) blocksFromAddrRanges(ars AddrRangeSeq) (safemem.BlockSeq, error) {
+func (b *BytesIO) blocksFromAddrRanges(ars hostarch.AddrRangeSeq) (safemem.BlockSeq, error) {
 	switch ars.NumRanges() {
 	case 0:
 		return safemem.BlockSeq{}, nil
@@ -124,7 +125,7 @@ func (b *BytesIO) blocksFromAddrRanges(ars AddrRangeSeq) (safemem.BlockSeq, erro
 	}
 }
 
-func (b *BytesIO) blockFromAddrRange(ar AddrRange) (safemem.Block, error) {
+func (b *BytesIO) blockFromAddrRange(ar hostarch.AddrRange) (safemem.Block, error) {
 	n, err := b.rangeCheck(ar.Start, int(ar.Length()))
 	if n == 0 {
 		return safemem.Block{}, err
@@ -136,6 +137,6 @@ func (b *BytesIO) blockFromAddrRange(ar AddrRange) (safemem.Block, error) {
 func BytesIOSequence(buf []byte) IOSequence {
 	return IOSequence{
 		IO:    &BytesIO{buf},
-		Addrs: AddrRangeSeqOf(AddrRange{0, Addr(len(buf))}),
+		Addrs: hostarch.AddrRangeSeqOf(hostarch.AddrRange{0, hostarch.Addr(len(buf))}),
 	}
 }
diff --git a/pkg/usermem/bytes_io_unsafe.go b/pkg/usermem/bytes_io_unsafe.go
index 20de5037d..dcd5c81d1 100644
--- a/pkg/usermem/bytes_io_unsafe.go
+++ b/pkg/usermem/bytes_io_unsafe.go
@@ -20,10 +20,11 @@ import (
 
 	"gvisor.dev/gvisor/pkg/atomicbitops"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/hostarch"
 )
 
 // SwapUint32 implements IO.SwapUint32.
-func (b *BytesIO) SwapUint32(ctx context.Context, addr Addr, new uint32, opts IOOpts) (uint32, error) {
+func (b *BytesIO) SwapUint32(ctx context.Context, addr hostarch.Addr, new uint32, opts IOOpts) (uint32, error) {
 	if _, rngErr := b.rangeCheck(addr, 4); rngErr != nil {
 		return 0, rngErr
 	}
@@ -31,7 +32,7 @@ func (b *BytesIO) SwapUint32(ctx context.Context, addr Addr, new uint32, opts IO
 }
 
 // CompareAndSwapUint32 implements IO.CompareAndSwapUint32.
-func (b *BytesIO) CompareAndSwapUint32(ctx context.Context, addr Addr, old, new uint32, opts IOOpts) (uint32, error) {
+func (b *BytesIO) CompareAndSwapUint32(ctx context.Context, addr hostarch.Addr, old, new uint32, opts IOOpts) (uint32, error) {
 	if _, rngErr := b.rangeCheck(addr, 4); rngErr != nil {
 		return 0, rngErr
 	}
@@ -39,7 +40,7 @@ func (b *BytesIO) CompareAndSwapUint32(ctx context.Context, addr Addr, old, new
 }
 
 // LoadUint32 implements IO.LoadUint32.
-func (b *BytesIO) LoadUint32(ctx context.Context, addr Addr, opts IOOpts) (uint32, error) {
+func (b *BytesIO) LoadUint32(ctx context.Context, addr hostarch.Addr, opts IOOpts) (uint32, error) {
 	if _, err := b.rangeCheck(addr, 4); err != nil {
 		return 0, err
 	}
diff --git a/pkg/usermem/usermem.go b/pkg/usermem/usermem.go
index dc2571154..0d6d25e50 100644
--- a/pkg/usermem/usermem.go
+++ b/pkg/usermem/usermem.go
@@ -25,6 +25,8 @@ import (
 	"gvisor.dev/gvisor/pkg/gohacks"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/syserror"
+
+	"gvisor.dev/gvisor/pkg/hostarch"
 )
 
 // IO provides access to the contents of a virtual memory space.
@@ -37,7 +39,7 @@ type IO interface {
 	// any following locks in the lock order.
 	//
 	// Postconditions: CopyOut does not retain src.
-	CopyOut(ctx context.Context, addr Addr, src []byte, opts IOOpts) (int, error)
+	CopyOut(ctx context.Context, addr hostarch.Addr, src []byte, opts IOOpts) (int, error)
 
 	// CopyIn copies len(dst) bytes from the memory mapped at addr to dst.
 	// It returns the number of bytes copied. If the number of bytes copied is
@@ -47,7 +49,7 @@ type IO interface {
 	// any following locks in the lock order.
 	//
 	// Postconditions: CopyIn does not retain dst.
-	CopyIn(ctx context.Context, addr Addr, dst []byte, opts IOOpts) (int, error)
+	CopyIn(ctx context.Context, addr hostarch.Addr, dst []byte, opts IOOpts) (int, error)
 
 	// ZeroOut sets toZero bytes to 0, starting at addr. It returns the number
 	// of bytes zeroed. If the number of bytes zeroed is < toZero, it returns a
@@ -57,7 +59,7 @@ type IO interface {
 	// * The caller must not hold mm.MemoryManager.mappingMu or any
 	//   following locks in the lock order.
 	// * toZero >= 0.
-	ZeroOut(ctx context.Context, addr Addr, toZero int64, opts IOOpts) (int64, error)
+	ZeroOut(ctx context.Context, addr hostarch.Addr, toZero int64, opts IOOpts) (int64, error)
 
 	// CopyOutFrom copies ars.NumBytes() bytes from src to the memory mapped at
 	// ars. It returns the number of bytes copied, which may be less than the
@@ -72,7 +74,7 @@ type IO interface {
 	//   following locks in the lock order.
 	// * src.ReadToBlocks must not block on mm.MemoryManager.activeMu or
 	//   any preceding locks in the lock order.
-	CopyOutFrom(ctx context.Context, ars AddrRangeSeq, src safemem.Reader, opts IOOpts) (int64, error)
+	CopyOutFrom(ctx context.Context, ars hostarch.AddrRangeSeq, src safemem.Reader, opts IOOpts) (int64, error)
 
 	// CopyInTo copies ars.NumBytes() bytes from the memory mapped at ars to
 	// dst. It returns the number of bytes copied. CopyInTo may return a
@@ -86,7 +88,7 @@ type IO interface {
 	//   following locks in the lock order.
 	// * dst.WriteFromBlocks must not block on mm.MemoryManager.activeMu or
 	//   any preceding locks in the lock order.
-	CopyInTo(ctx context.Context, ars AddrRangeSeq, dst safemem.Writer, opts IOOpts) (int64, error)
+	CopyInTo(ctx context.Context, ars hostarch.AddrRangeSeq, dst safemem.Writer, opts IOOpts) (int64, error)
 
 	// TODO(jamieliu): The requirement that CopyOutFrom/CopyInTo call src/dst
 	// at most once, which is unnecessary in most cases, forces implementations
@@ -101,7 +103,7 @@ type IO interface {
 	// * The caller must not hold mm.MemoryManager.mappingMu or any
 	//   following locks in the lock order.
 	// * addr must be aligned to a 4-byte boundary.
-	SwapUint32(ctx context.Context, addr Addr, new uint32, opts IOOpts) (uint32, error)
+	SwapUint32(ctx context.Context, addr hostarch.Addr, new uint32, opts IOOpts) (uint32, error)
 
 	// CompareAndSwapUint32 atomically compares the uint32 value at addr to
 	// old; if they are equal, the value in memory is replaced by new. In
@@ -111,7 +113,7 @@ type IO interface {
 	// * The caller must not hold mm.MemoryManager.mappingMu or any
 	//   following locks in the lock order.
 	// * addr must be aligned to a 4-byte boundary.
-	CompareAndSwapUint32(ctx context.Context, addr Addr, old, new uint32, opts IOOpts) (uint32, error)
+	CompareAndSwapUint32(ctx context.Context, addr hostarch.Addr, old, new uint32, opts IOOpts) (uint32, error)
 
 	// LoadUint32 atomically loads the uint32 value at addr and returns it.
 	//
@@ -119,7 +121,7 @@ type IO interface {
 	// * The caller must not hold mm.MemoryManager.mappingMu or any
 	//   following locks in the lock order.
 	// * addr must be aligned to a 4-byte boundary.
-	LoadUint32(ctx context.Context, addr Addr, opts IOOpts) (uint32, error)
+	LoadUint32(ctx context.Context, addr hostarch.Addr, opts IOOpts) (uint32, error)
 }
 
 // IOOpts contains options applicable to all IO methods.
@@ -142,7 +144,7 @@ type IOOpts struct {
 type IOReadWriter struct {
 	Ctx  context.Context
 	IO   IO
-	Addr Addr
+	Addr hostarch.Addr
 	Opts IOOpts
 }
 
@@ -159,7 +161,7 @@ func (rw *IOReadWriter) Read(dst []byte) (int, error) {
 		rw.Addr = end
 	} else {
 		// Disallow wraparound.
-		rw.Addr = ^Addr(0)
+		rw.Addr = ^hostarch.Addr(0)
 		if err != nil {
 			err = syserror.EFAULT
 		}
@@ -175,7 +177,7 @@ func (rw *IOReadWriter) Write(src []byte) (int, error) {
 		rw.Addr = end
 	} else {
 		// Disallow wraparound.
-		rw.Addr = ^Addr(0)
+		rw.Addr = ^hostarch.Addr(0)
 		if err != nil {
 			err = syserror.EFAULT
 		}
@@ -197,7 +199,7 @@ const (
 //
 // Preconditions: Same as IO.CopyFromUser, plus:
 // * maxlen >= 0.
-func CopyStringIn(ctx context.Context, uio IO, addr Addr, maxlen int, opts IOOpts) (string, error) {
+func CopyStringIn(ctx context.Context, uio IO, addr hostarch.Addr, maxlen int, opts IOOpts) (string, error) {
 	initLen := maxlen
 	if initLen > copyStringMaxInitBufLen {
 		initLen = copyStringMaxInitBufLen
@@ -251,12 +253,12 @@ func CopyStringIn(ctx context.Context, uio IO, addr Addr, maxlen int, opts IOOpt
 // the maximum, it returns a non-nil error explaining why.
 //
 // Preconditions: Same as IO.CopyOut.
-func CopyOutVec(ctx context.Context, uio IO, ars AddrRangeSeq, src []byte, opts IOOpts) (int, error) {
+func CopyOutVec(ctx context.Context, uio IO, ars hostarch.AddrRangeSeq, src []byte, opts IOOpts) (int, error) {
 	var done int
 	for !ars.IsEmpty() && done < len(src) {
 		ar := ars.Head()
 		cplen := len(src) - done
-		if Addr(cplen) >= ar.Length() {
+		if hostarch.Addr(cplen) >= ar.Length() {
 			cplen = int(ar.Length())
 		}
 		n, err := uio.CopyOut(ctx, ar.Start, src[done:done+cplen], opts)
@@ -275,12 +277,12 @@ func CopyOutVec(ctx context.Context, uio IO, ars AddrRangeSeq, src []byte, opts
 // maximum, it returns a non-nil error explaining why.
 //
 // Preconditions: Same as IO.CopyIn.
-func CopyInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dst []byte, opts IOOpts) (int, error) {
+func CopyInVec(ctx context.Context, uio IO, ars hostarch.AddrRangeSeq, dst []byte, opts IOOpts) (int, error) {
 	var done int
 	for !ars.IsEmpty() && done < len(dst) {
 		ar := ars.Head()
 		cplen := len(dst) - done
-		if Addr(cplen) >= ar.Length() {
+		if hostarch.Addr(cplen) >= ar.Length() {
 			cplen = int(ar.Length())
 		}
 		n, err := uio.CopyIn(ctx, ar.Start, dst[done:done+cplen], opts)
@@ -299,12 +301,12 @@ func CopyInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dst []byte, opts I
 // maximum, it returns a non-nil error explaining why.
 //
 // Preconditions: Same as IO.ZeroOut.
-func ZeroOutVec(ctx context.Context, uio IO, ars AddrRangeSeq, toZero int64, opts IOOpts) (int64, error) {
+func ZeroOutVec(ctx context.Context, uio IO, ars hostarch.AddrRangeSeq, toZero int64, opts IOOpts) (int64, error) {
 	var done int64
 	for !ars.IsEmpty() && done < toZero {
 		ar := ars.Head()
 		cplen := toZero - done
-		if Addr(cplen) >= ar.Length() {
+		if hostarch.Addr(cplen) >= ar.Length() {
 			cplen = int64(ar.Length())
 		}
 		n, err := uio.ZeroOut(ctx, ar.Start, cplen, opts)
@@ -352,7 +354,7 @@ func isASCIIWhitespace(b byte) bool {
 // - CopyInt32StringsInVec returns EINVAL if ars.NumBytes() == 0.
 //
 // Preconditions: Same as CopyInVec.
-func CopyInt32StringsInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dsts []int32, opts IOOpts) (int64, error) {
+func CopyInt32StringsInVec(ctx context.Context, uio IO, ars hostarch.AddrRangeSeq, dsts []int32, opts IOOpts) (int64, error) {
 	if len(dsts) == 0 {
 		return 0, nil
 	}
@@ -403,7 +405,7 @@ func CopyInt32StringsInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dsts [
 
 // CopyInt32StringInVec is equivalent to CopyInt32StringsInVec, but copies at
 // most one int32.
-func CopyInt32StringInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dst *int32, opts IOOpts) (int64, error) {
+func CopyInt32StringInVec(ctx context.Context, uio IO, ars hostarch.AddrRangeSeq, dst *int32, opts IOOpts) (int64, error) {
 	dsts := [1]int32{*dst}
 	n, err := CopyInt32StringsInVec(ctx, uio, ars, dsts[:], opts)
 	*dst = dsts[0]
@@ -413,7 +415,7 @@ func CopyInt32StringInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dst *in
 // IOSequence holds arguments to IO methods.
 type IOSequence struct {
 	IO    IO
-	Addrs AddrRangeSeq
+	Addrs hostarch.AddrRangeSeq
 	Opts  IOOpts
 }
 
@@ -444,28 +446,28 @@ func (s IOSequence) NumBytes() int64 {
 
 // DropFirst returns a copy of s with s.Addrs.DropFirst(n).
 //
-// Preconditions: Same as AddrRangeSeq.DropFirst.
+// Preconditions: Same as hostarch.AddrRangeSeq.DropFirst.
 func (s IOSequence) DropFirst(n int) IOSequence {
 	return IOSequence{s.IO, s.Addrs.DropFirst(n), s.Opts}
 }
 
 // DropFirst64 returns a copy of s with s.Addrs.DropFirst64(n).
 //
-// Preconditions: Same as AddrRangeSeq.DropFirst64.
+// Preconditions: Same as hostarch.AddrRangeSeq.DropFirst64.
 func (s IOSequence) DropFirst64(n int64) IOSequence {
 	return IOSequence{s.IO, s.Addrs.DropFirst64(n), s.Opts}
 }
 
 // TakeFirst returns a copy of s with s.Addrs.TakeFirst(n).
 //
-// Preconditions: Same as AddrRangeSeq.TakeFirst.
+// Preconditions: Same as hostarch.AddrRangeSeq.TakeFirst.
 func (s IOSequence) TakeFirst(n int) IOSequence {
 	return IOSequence{s.IO, s.Addrs.TakeFirst(n), s.Opts}
 }
 
 // TakeFirst64 returns a copy of s with s.Addrs.TakeFirst64(n).
 //
-// Preconditions: Same as AddrRangeSeq.TakeFirst64.
+// Preconditions: Same as hostarch.AddrRangeSeq.TakeFirst64.
 func (s IOSequence) TakeFirst64(n int64) IOSequence {
 	return IOSequence{s.IO, s.Addrs.TakeFirst64(n), s.Opts}
 }
diff --git a/pkg/usermem/usermem_arm64.go b/pkg/usermem/usermem_arm64.go
deleted file mode 100644
index 7e7529585..000000000
--- a/pkg/usermem/usermem_arm64.go
+++ /dev/null
@@ -1,54 +0,0 @@
-// 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.
-
-// +build arm64
-
-package usermem
-
-import (
-	"encoding/binary"
-
-	"golang.org/x/sys/unix"
-)
-
-const (
-	// PageSize is the system page size.
-	// arm64 support 4K/16K/64K page size,
-	// which can be get by unix.Getpagesize().
-	// Currently, only 4K page size is supported.
-	PageSize = 1 << PageShift
-
-	// HugePageSize is the system huge page size.
-	HugePageSize = 1 << HugePageShift
-
-	// PageShift is the binary log of the system page size.
-	PageShift = 12
-
-	// HugePageShift is the binary log of the system huge page size.
-	// Should be calculated by "PageShift + (PageShift - 3)"
-	// when multiple page size support is ready.
-	HugePageShift = 21
-)
-
-var (
-	// ByteOrder is the native byte order (little endian).
-	ByteOrder = binary.LittleEndian
-)
-
-func init() {
-	// Make sure the page size is 4K on arm64 platform.
-	if size := unix.Getpagesize(); size != PageSize {
-		panic("Only 4K page size is supported on arm64!")
-	}
-}
diff --git a/pkg/usermem/usermem_test.go b/pkg/usermem/usermem_test.go
index da60b0cc7..9b697b593 100644
--- a/pkg/usermem/usermem_test.go
+++ b/pkg/usermem/usermem_test.go
@@ -22,6 +22,7 @@ import (
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/hostarch"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -106,7 +107,7 @@ func TestBytesIOZeroOutFailure(t *testing.T) {
 
 func TestBytesIOCopyOutFromSuccess(t *testing.T) {
 	b := newBytesIOString("ABCDEFGH")
-	n, err := b.CopyOutFrom(newContext(), AddrRangeSeqFromSlice([]AddrRange{
+	n, err := b.CopyOutFrom(newContext(), hostarch.AddrRangeSeqFromSlice([]hostarch.AddrRange{
 		{Start: 4, End: 7},
 		{Start: 1, End: 4},
 	}), safemem.FromIOReader{bytes.NewBufferString("barfoo")}, IOOpts{})
@@ -120,7 +121,7 @@ func TestBytesIOCopyOutFromSuccess(t *testing.T) {
 
 func TestBytesIOCopyOutFromFailure(t *testing.T) {
 	b := newBytesIOString("ABCDE")
-	n, err := b.CopyOutFrom(newContext(), AddrRangeSeqFromSlice([]AddrRange{
+	n, err := b.CopyOutFrom(newContext(), hostarch.AddrRangeSeqFromSlice([]hostarch.AddrRange{
 		{Start: 1, End: 4},
 		{Start: 4, End: 7},
 	}), safemem.FromIOReader{bytes.NewBufferString("foobar")}, IOOpts{})
@@ -135,7 +136,7 @@ func TestBytesIOCopyOutFromFailure(t *testing.T) {
 func TestBytesIOCopyInToSuccess(t *testing.T) {
 	b := newBytesIOString("AfoobarH")
 	var dst bytes.Buffer
-	n, err := b.CopyInTo(newContext(), AddrRangeSeqFromSlice([]AddrRange{
+	n, err := b.CopyInTo(newContext(), hostarch.AddrRangeSeqFromSlice([]hostarch.AddrRange{
 		{Start: 4, End: 7},
 		{Start: 1, End: 4},
 	}), safemem.FromIOWriter{&dst}, IOOpts{})
@@ -150,7 +151,7 @@ func TestBytesIOCopyInToSuccess(t *testing.T) {
 func TestBytesIOCopyInToFailure(t *testing.T) {
 	b := newBytesIOString("Afoob")
 	var dst bytes.Buffer
-	n, err := b.CopyInTo(newContext(), AddrRangeSeqFromSlice([]AddrRange{
+	n, err := b.CopyInTo(newContext(), hostarch.AddrRangeSeqFromSlice([]hostarch.AddrRange{
 		{Start: 1, End: 4},
 		{Start: 4, End: 7},
 	}), safemem.FromIOWriter{&dst}, IOOpts{})
diff --git a/pkg/usermem/usermem_x86.go b/pkg/usermem/usermem_x86.go
deleted file mode 100644
index d96f829fb..000000000
--- a/pkg/usermem/usermem_x86.go
+++ /dev/null
@@ -1,38 +0,0 @@
-// 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 386
-
-package usermem
-
-import "encoding/binary"
-
-const (
-	// PageSize is the system page size.
-	PageSize = 1 << PageShift
-
-	// HugePageSize is the system huge page size.
-	HugePageSize = 1 << HugePageShift
-
-	// PageShift is the binary log of the system page size.
-	PageShift = 12
-
-	// HugePageShift is the binary log of the system huge page size.
-	HugePageShift = 21
-)
-
-var (
-	// ByteOrder is the native byte order (little endian).
-	ByteOrder = binary.LittleEndian
-)