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mirror of https://github.com/golang/go synced 2024-11-22 03:04:41 -07:00

runtime, reflect: avoid allocation in structType.Field common cases

Use assembler to make runtime.staticuint64s into a readonly array
so that the reflect package can safely create a slice without requiring
any allocation.

Fixes #2320
Fixes #68380

Change-Id: If2c97238eca782d0632db265c840581d4ecb9d18
Reviewed-on: https://go-review.googlesource.com/c/go/+/597855
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Ian Lance Taylor 2024-07-11 14:49:43 -07:00 committed by Gopher Robot
parent 8926ca9c5e
commit 493517bb5c
4 changed files with 329 additions and 41 deletions

View File

@ -23,6 +23,7 @@ import (
"reflect/internal/example1"
"reflect/internal/example2"
"runtime"
"runtime/debug"
"slices"
"strconv"
"strings"
@ -3532,6 +3533,14 @@ func TestAllocations(t *testing.T) {
panic("wrong result")
}
})
if runtime.GOOS != "js" && runtime.GOOS != "wasip1" {
typ := TypeFor[struct{ f int }]()
noAlloc(t, 100, func(int) {
if typ.Field(0).Index[0] != 0 {
panic("wrong field index")
}
})
}
}
func TestSmallNegativeInt(t *testing.T) {
@ -6862,6 +6871,25 @@ func TestTypeFieldOutOfRangePanic(t *testing.T) {
}
}
func TestTypeFieldReadOnly(t *testing.T) {
if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
// This is OK because we don't use the optimization
// for js or wasip1.
t.Skip("test does not fault on GOOS=js")
}
// It's important that changing one StructField.Index
// value not affect other StructField.Index values.
// Right now StructField.Index is read-only;
// that saves allocations but is otherwise not important.
typ := TypeFor[struct{ f int }]()
f := typ.Field(0)
defer debug.SetPanicOnFault(debug.SetPanicOnFault(true))
shouldPanic("", func() {
f.Index[0] = 1
})
}
// Issue 9179.
func TestCallGC(t *testing.T) {
f := func(a, b, c, d, e string) {

View File

@ -18,6 +18,7 @@ package reflect
import (
"internal/abi"
"internal/goarch"
"runtime"
"strconv"
"sync"
"unicode"
@ -1114,17 +1115,35 @@ func (t *structType) Field(i int) (f StructField) {
}
f.Offset = p.Offset
// NOTE(rsc): This is the only allocation in the interface
// presented by a reflect.Type. It would be nice to avoid,
// at least in the common cases, but we need to make sure
// that misbehaving clients of reflect cannot affect other
// uses of reflect. One possibility is CL 5371098, but we
// postponed that ugliness until there is a demonstrated
// need for the performance. This is issue 2320.
f.Index = []int{i}
// We can't safely use this optimization on js or wasi,
// which do not appear to support read-only data.
if i < 256 && runtime.GOOS != "js" && runtime.GOOS != "wasip1" {
staticuint64s := getStaticuint64s()
p := unsafe.Pointer(&(*staticuint64s)[i])
if unsafe.Sizeof(int(0)) == 4 && goarch.BigEndian {
p = unsafe.Add(p, 4)
}
f.Index = unsafe.Slice((*int)(p), 1)
} else {
// NOTE(rsc): This is the only allocation in the interface
// presented by a reflect.Type. It would be nice to avoid,
// but we need to make sure that misbehaving clients of
// reflect cannot affect other uses of reflect.
// One possibility is CL 5371098, but we postponed that
// ugliness until there is a demonstrated
// need for the performance. This is issue 2320.
f.Index = []int{i}
}
return
}
// getStaticuint64s returns a pointer to an array of 256 uint64 values,
// defined in the runtime package in read-only memory.
// staticuint64s[0] == 0, staticuint64s[1] == 1, and so forth.
//
//go:linkname getStaticuint64s runtime.getStaticuint64s
func getStaticuint64s() *[256]uint64
// TODO(gri): Should there be an error/bool indicator if the index
// is wrong for FieldByIndex?

View File

@ -692,39 +692,16 @@ func iterate_itabs(fn func(*itab)) {
}
// staticuint64s is used to avoid allocating in convTx for small integer values.
var staticuint64s = [...]uint64{
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
// staticuint64s[0] == 0, staticuint64s[1] == 1, and so forth.
// It is defined in assembler code so that it is read-only.
var staticuint64s [256]uint64
// getStaticuint64s is called by the reflect package to get a pointer
// to the read-only array.
//
//go:linkname getStaticuint64s
func getStaticuint64s() *[256]uint64 {
return &staticuint64s
}
// The linker redirects a reference of a method that it determined

264
src/runtime/ints.s Normal file
View File

@ -0,0 +1,264 @@
// Copyright 2024 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
DATA ·staticuint64s+0x000(SB)/8, $0
DATA ·staticuint64s+0x008(SB)/8, $1
DATA ·staticuint64s+0x010(SB)/8, $2
DATA ·staticuint64s+0x018(SB)/8, $3
DATA ·staticuint64s+0x020(SB)/8, $4
DATA ·staticuint64s+0x028(SB)/8, $5
DATA ·staticuint64s+0x030(SB)/8, $6
DATA ·staticuint64s+0x038(SB)/8, $7
DATA ·staticuint64s+0x040(SB)/8, $8
DATA ·staticuint64s+0x048(SB)/8, $9
DATA ·staticuint64s+0x050(SB)/8, $10
DATA ·staticuint64s+0x058(SB)/8, $11
DATA ·staticuint64s+0x060(SB)/8, $12
DATA ·staticuint64s+0x068(SB)/8, $13
DATA ·staticuint64s+0x070(SB)/8, $14
DATA ·staticuint64s+0x078(SB)/8, $15
DATA ·staticuint64s+0x080(SB)/8, $16
DATA ·staticuint64s+0x088(SB)/8, $17
DATA ·staticuint64s+0x090(SB)/8, $18
DATA ·staticuint64s+0x098(SB)/8, $19
DATA ·staticuint64s+0x0a0(SB)/8, $20
DATA ·staticuint64s+0x0a8(SB)/8, $21
DATA ·staticuint64s+0x0b0(SB)/8, $22
DATA ·staticuint64s+0x0b8(SB)/8, $23
DATA ·staticuint64s+0x0c0(SB)/8, $24
DATA ·staticuint64s+0x0c8(SB)/8, $25
DATA ·staticuint64s+0x0d0(SB)/8, $26
DATA ·staticuint64s+0x0d8(SB)/8, $27
DATA ·staticuint64s+0x0e0(SB)/8, $28
DATA ·staticuint64s+0x0e8(SB)/8, $29
DATA ·staticuint64s+0x0f0(SB)/8, $30
DATA ·staticuint64s+0x0f8(SB)/8, $31
DATA ·staticuint64s+0x100(SB)/8, $32
DATA ·staticuint64s+0x108(SB)/8, $33
DATA ·staticuint64s+0x110(SB)/8, $34
DATA ·staticuint64s+0x118(SB)/8, $35
DATA ·staticuint64s+0x120(SB)/8, $36
DATA ·staticuint64s+0x128(SB)/8, $37
DATA ·staticuint64s+0x130(SB)/8, $38
DATA ·staticuint64s+0x138(SB)/8, $39
DATA ·staticuint64s+0x140(SB)/8, $40
DATA ·staticuint64s+0x148(SB)/8, $41
DATA ·staticuint64s+0x150(SB)/8, $42
DATA ·staticuint64s+0x158(SB)/8, $43
DATA ·staticuint64s+0x160(SB)/8, $44
DATA ·staticuint64s+0x168(SB)/8, $45
DATA ·staticuint64s+0x170(SB)/8, $46
DATA ·staticuint64s+0x178(SB)/8, $47
DATA ·staticuint64s+0x180(SB)/8, $48
DATA ·staticuint64s+0x188(SB)/8, $49
DATA ·staticuint64s+0x190(SB)/8, $50
DATA ·staticuint64s+0x198(SB)/8, $51
DATA ·staticuint64s+0x1a0(SB)/8, $52
DATA ·staticuint64s+0x1a8(SB)/8, $53
DATA ·staticuint64s+0x1b0(SB)/8, $54
DATA ·staticuint64s+0x1b8(SB)/8, $55
DATA ·staticuint64s+0x1c0(SB)/8, $56
DATA ·staticuint64s+0x1c8(SB)/8, $57
DATA ·staticuint64s+0x1d0(SB)/8, $58
DATA ·staticuint64s+0x1d8(SB)/8, $59
DATA ·staticuint64s+0x1e0(SB)/8, $60
DATA ·staticuint64s+0x1e8(SB)/8, $61
DATA ·staticuint64s+0x1f0(SB)/8, $62
DATA ·staticuint64s+0x1f8(SB)/8, $63
DATA ·staticuint64s+0x200(SB)/8, $64
DATA ·staticuint64s+0x208(SB)/8, $65
DATA ·staticuint64s+0x210(SB)/8, $66
DATA ·staticuint64s+0x218(SB)/8, $67
DATA ·staticuint64s+0x220(SB)/8, $68
DATA ·staticuint64s+0x228(SB)/8, $69
DATA ·staticuint64s+0x230(SB)/8, $70
DATA ·staticuint64s+0x238(SB)/8, $71
DATA ·staticuint64s+0x240(SB)/8, $72
DATA ·staticuint64s+0x248(SB)/8, $73
DATA ·staticuint64s+0x250(SB)/8, $74
DATA ·staticuint64s+0x258(SB)/8, $75
DATA ·staticuint64s+0x260(SB)/8, $76
DATA ·staticuint64s+0x268(SB)/8, $77
DATA ·staticuint64s+0x270(SB)/8, $78
DATA ·staticuint64s+0x278(SB)/8, $79
DATA ·staticuint64s+0x280(SB)/8, $80
DATA ·staticuint64s+0x288(SB)/8, $81
DATA ·staticuint64s+0x290(SB)/8, $82
DATA ·staticuint64s+0x298(SB)/8, $83
DATA ·staticuint64s+0x2a0(SB)/8, $84
DATA ·staticuint64s+0x2a8(SB)/8, $85
DATA ·staticuint64s+0x2b0(SB)/8, $86
DATA ·staticuint64s+0x2b8(SB)/8, $87
DATA ·staticuint64s+0x2c0(SB)/8, $88
DATA ·staticuint64s+0x2c8(SB)/8, $89
DATA ·staticuint64s+0x2d0(SB)/8, $90
DATA ·staticuint64s+0x2d8(SB)/8, $91
DATA ·staticuint64s+0x2e0(SB)/8, $92
DATA ·staticuint64s+0x2e8(SB)/8, $93
DATA ·staticuint64s+0x2f0(SB)/8, $94
DATA ·staticuint64s+0x2f8(SB)/8, $95
DATA ·staticuint64s+0x300(SB)/8, $96
DATA ·staticuint64s+0x308(SB)/8, $97
DATA ·staticuint64s+0x310(SB)/8, $98
DATA ·staticuint64s+0x318(SB)/8, $99
DATA ·staticuint64s+0x320(SB)/8, $100
DATA ·staticuint64s+0x328(SB)/8, $101
DATA ·staticuint64s+0x330(SB)/8, $102
DATA ·staticuint64s+0x338(SB)/8, $103
DATA ·staticuint64s+0x340(SB)/8, $104
DATA ·staticuint64s+0x348(SB)/8, $105
DATA ·staticuint64s+0x350(SB)/8, $106
DATA ·staticuint64s+0x358(SB)/8, $107
DATA ·staticuint64s+0x360(SB)/8, $108
DATA ·staticuint64s+0x368(SB)/8, $109
DATA ·staticuint64s+0x370(SB)/8, $110
DATA ·staticuint64s+0x378(SB)/8, $111
DATA ·staticuint64s+0x380(SB)/8, $112
DATA ·staticuint64s+0x388(SB)/8, $113
DATA ·staticuint64s+0x390(SB)/8, $114
DATA ·staticuint64s+0x398(SB)/8, $115
DATA ·staticuint64s+0x3a0(SB)/8, $116
DATA ·staticuint64s+0x3a8(SB)/8, $117
DATA ·staticuint64s+0x3b0(SB)/8, $118
DATA ·staticuint64s+0x3b8(SB)/8, $119
DATA ·staticuint64s+0x3c0(SB)/8, $120
DATA ·staticuint64s+0x3c8(SB)/8, $121
DATA ·staticuint64s+0x3d0(SB)/8, $122
DATA ·staticuint64s+0x3d8(SB)/8, $123
DATA ·staticuint64s+0x3e0(SB)/8, $124
DATA ·staticuint64s+0x3e8(SB)/8, $125
DATA ·staticuint64s+0x3f0(SB)/8, $126
DATA ·staticuint64s+0x3f8(SB)/8, $127
DATA ·staticuint64s+0x400(SB)/8, $128
DATA ·staticuint64s+0x408(SB)/8, $129
DATA ·staticuint64s+0x410(SB)/8, $130
DATA ·staticuint64s+0x418(SB)/8, $131
DATA ·staticuint64s+0x420(SB)/8, $132
DATA ·staticuint64s+0x428(SB)/8, $133
DATA ·staticuint64s+0x430(SB)/8, $134
DATA ·staticuint64s+0x438(SB)/8, $135
DATA ·staticuint64s+0x440(SB)/8, $136
DATA ·staticuint64s+0x448(SB)/8, $137
DATA ·staticuint64s+0x450(SB)/8, $138
DATA ·staticuint64s+0x458(SB)/8, $139
DATA ·staticuint64s+0x460(SB)/8, $140
DATA ·staticuint64s+0x468(SB)/8, $141
DATA ·staticuint64s+0x470(SB)/8, $142
DATA ·staticuint64s+0x478(SB)/8, $143
DATA ·staticuint64s+0x480(SB)/8, $144
DATA ·staticuint64s+0x488(SB)/8, $145
DATA ·staticuint64s+0x490(SB)/8, $146
DATA ·staticuint64s+0x498(SB)/8, $147
DATA ·staticuint64s+0x4a0(SB)/8, $148
DATA ·staticuint64s+0x4a8(SB)/8, $149
DATA ·staticuint64s+0x4b0(SB)/8, $150
DATA ·staticuint64s+0x4b8(SB)/8, $151
DATA ·staticuint64s+0x4c0(SB)/8, $152
DATA ·staticuint64s+0x4c8(SB)/8, $153
DATA ·staticuint64s+0x4d0(SB)/8, $154
DATA ·staticuint64s+0x4d8(SB)/8, $155
DATA ·staticuint64s+0x4e0(SB)/8, $156
DATA ·staticuint64s+0x4e8(SB)/8, $157
DATA ·staticuint64s+0x4f0(SB)/8, $158
DATA ·staticuint64s+0x4f8(SB)/8, $159
DATA ·staticuint64s+0x500(SB)/8, $160
DATA ·staticuint64s+0x508(SB)/8, $161
DATA ·staticuint64s+0x510(SB)/8, $162
DATA ·staticuint64s+0x518(SB)/8, $163
DATA ·staticuint64s+0x520(SB)/8, $164
DATA ·staticuint64s+0x528(SB)/8, $165
DATA ·staticuint64s+0x530(SB)/8, $166
DATA ·staticuint64s+0x538(SB)/8, $167
DATA ·staticuint64s+0x540(SB)/8, $168
DATA ·staticuint64s+0x548(SB)/8, $169
DATA ·staticuint64s+0x550(SB)/8, $170
DATA ·staticuint64s+0x558(SB)/8, $171
DATA ·staticuint64s+0x560(SB)/8, $172
DATA ·staticuint64s+0x568(SB)/8, $173
DATA ·staticuint64s+0x570(SB)/8, $174
DATA ·staticuint64s+0x578(SB)/8, $175
DATA ·staticuint64s+0x580(SB)/8, $176
DATA ·staticuint64s+0x588(SB)/8, $177
DATA ·staticuint64s+0x590(SB)/8, $178
DATA ·staticuint64s+0x598(SB)/8, $179
DATA ·staticuint64s+0x5a0(SB)/8, $180
DATA ·staticuint64s+0x5a8(SB)/8, $181
DATA ·staticuint64s+0x5b0(SB)/8, $182
DATA ·staticuint64s+0x5b8(SB)/8, $183
DATA ·staticuint64s+0x5c0(SB)/8, $184
DATA ·staticuint64s+0x5c8(SB)/8, $185
DATA ·staticuint64s+0x5d0(SB)/8, $186
DATA ·staticuint64s+0x5d8(SB)/8, $187
DATA ·staticuint64s+0x5e0(SB)/8, $188
DATA ·staticuint64s+0x5e8(SB)/8, $189
DATA ·staticuint64s+0x5f0(SB)/8, $190
DATA ·staticuint64s+0x5f8(SB)/8, $191
DATA ·staticuint64s+0x600(SB)/8, $192
DATA ·staticuint64s+0x608(SB)/8, $193
DATA ·staticuint64s+0x610(SB)/8, $194
DATA ·staticuint64s+0x618(SB)/8, $195
DATA ·staticuint64s+0x620(SB)/8, $196
DATA ·staticuint64s+0x628(SB)/8, $197
DATA ·staticuint64s+0x630(SB)/8, $198
DATA ·staticuint64s+0x638(SB)/8, $199
DATA ·staticuint64s+0x640(SB)/8, $200
DATA ·staticuint64s+0x648(SB)/8, $201
DATA ·staticuint64s+0x650(SB)/8, $202
DATA ·staticuint64s+0x658(SB)/8, $203
DATA ·staticuint64s+0x660(SB)/8, $204
DATA ·staticuint64s+0x668(SB)/8, $205
DATA ·staticuint64s+0x670(SB)/8, $206
DATA ·staticuint64s+0x678(SB)/8, $207
DATA ·staticuint64s+0x680(SB)/8, $208
DATA ·staticuint64s+0x688(SB)/8, $209
DATA ·staticuint64s+0x690(SB)/8, $210
DATA ·staticuint64s+0x698(SB)/8, $211
DATA ·staticuint64s+0x6a0(SB)/8, $212
DATA ·staticuint64s+0x6a8(SB)/8, $213
DATA ·staticuint64s+0x6b0(SB)/8, $214
DATA ·staticuint64s+0x6b8(SB)/8, $215
DATA ·staticuint64s+0x6c0(SB)/8, $216
DATA ·staticuint64s+0x6c8(SB)/8, $217
DATA ·staticuint64s+0x6d0(SB)/8, $218
DATA ·staticuint64s+0x6d8(SB)/8, $219
DATA ·staticuint64s+0x6e0(SB)/8, $220
DATA ·staticuint64s+0x6e8(SB)/8, $221
DATA ·staticuint64s+0x6f0(SB)/8, $222
DATA ·staticuint64s+0x6f8(SB)/8, $223
DATA ·staticuint64s+0x700(SB)/8, $224
DATA ·staticuint64s+0x708(SB)/8, $225
DATA ·staticuint64s+0x710(SB)/8, $226
DATA ·staticuint64s+0x718(SB)/8, $227
DATA ·staticuint64s+0x720(SB)/8, $228
DATA ·staticuint64s+0x728(SB)/8, $229
DATA ·staticuint64s+0x730(SB)/8, $230
DATA ·staticuint64s+0x738(SB)/8, $231
DATA ·staticuint64s+0x740(SB)/8, $232
DATA ·staticuint64s+0x748(SB)/8, $233
DATA ·staticuint64s+0x750(SB)/8, $234
DATA ·staticuint64s+0x758(SB)/8, $235
DATA ·staticuint64s+0x760(SB)/8, $236
DATA ·staticuint64s+0x768(SB)/8, $237
DATA ·staticuint64s+0x770(SB)/8, $238
DATA ·staticuint64s+0x778(SB)/8, $239
DATA ·staticuint64s+0x780(SB)/8, $240
DATA ·staticuint64s+0x788(SB)/8, $241
DATA ·staticuint64s+0x790(SB)/8, $242
DATA ·staticuint64s+0x798(SB)/8, $243
DATA ·staticuint64s+0x7a0(SB)/8, $244
DATA ·staticuint64s+0x7a8(SB)/8, $245
DATA ·staticuint64s+0x7b0(SB)/8, $246
DATA ·staticuint64s+0x7b8(SB)/8, $247
DATA ·staticuint64s+0x7c0(SB)/8, $248
DATA ·staticuint64s+0x7c8(SB)/8, $249
DATA ·staticuint64s+0x7d0(SB)/8, $250
DATA ·staticuint64s+0x7d8(SB)/8, $251
DATA ·staticuint64s+0x7e0(SB)/8, $252
DATA ·staticuint64s+0x7e8(SB)/8, $253
DATA ·staticuint64s+0x7f0(SB)/8, $254
DATA ·staticuint64s+0x7f8(SB)/8, $255
GLOBL ·staticuint64s(SB), RODATA, $0x800