forked from google/syzkaller
/
ifuzz.go
308 lines (284 loc) · 7.28 KB
/
ifuzz.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
// Copyright 2017 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
//go:generate bash -c "go run gen/gen.go gen/all-enc-instructions.txt > generated/insns.go"
// Package ifuzz allows to generate and mutate x86 machine code.
package ifuzz
import (
"math/rand"
"sync"
)
const (
ModeLong64 = iota
ModeProt32
ModeProt16
ModeReal16
ModeLast
)
type Insn struct {
Name string
Extension string
Mode int // bitmask of compatible modes
Priv bool // CPL=0
Pseudo bool // pseudo instructions can consist of several real instructions
Opcode []byte
Prefix []byte
Suffix []byte
Modrm bool
Mod int8
Reg int8 // -6 - segment register, -8 - control register
Rm int8
Srm bool // register is embed in the first byte
NoSibDisp bool // no SIB/disp even if modrm says otherwise
Imm int8 // immediate size, -1 - immediate size, -2 - address size, -3 - operand size
Imm2 int8
NoRepPrefix bool
No66Prefix bool
Rexw int8 // 1 must be set, -1 must not be set
Mem32 bool // instruction always references 32-bit memory operand, 0x67 is illegal
Mem16 bool // instruction always references 16-bit memory operand
Vex byte
VexMap byte
VexL int8
VexNoR bool
VexP int8
Avx2Gather bool
generator func(cfg *Config, r *rand.Rand) []byte // for pseudo instructions
}
type Config struct {
Len int // number of instructions to generate
Mode int // one of ModeXXX
Priv bool // generate CPL=0 instructions
Exec bool // generate instructions sequences interesting for execution
MemRegions []MemRegion // generated instructions will reference these regions
}
type MemRegion struct {
Start uint64
Size uint64
}
const (
typeExec = iota
typePriv
typeUser
typeAll
typeLast
)
var modeInsns [ModeLast][typeLast][]*Insn
var (
Insns []*Insn
initOnce sync.Once
)
func initInsns() {
if len(Insns) == 0 {
panic("no instructions")
}
initPseudo()
for mode := 0; mode < ModeLast; mode++ {
for _, insn := range Insns {
if insn.Mode&(1<<uint(mode)) == 0 {
continue
}
if insn.Pseudo {
modeInsns[mode][typeExec] = append(modeInsns[mode][typeExec], insn)
} else if insn.Priv {
modeInsns[mode][typePriv] = append(modeInsns[mode][typePriv], insn)
modeInsns[mode][typeAll] = append(modeInsns[mode][typeAll], insn)
} else {
modeInsns[mode][typeUser] = append(modeInsns[mode][typeUser], insn)
modeInsns[mode][typeAll] = append(modeInsns[mode][typeAll], insn)
}
}
}
}
// ModeInsns returns list of all instructions for the given mode.
func ModeInsns(cfg *Config) []*Insn {
initOnce.Do(initInsns)
if cfg.Mode < 0 || cfg.Mode >= ModeLast {
panic("bad mode")
}
var insns []*Insn
insns = append(insns, modeInsns[cfg.Mode][typeUser]...)
if cfg.Priv {
insns = append(insns, modeInsns[cfg.Mode][typePriv]...)
if cfg.Exec {
insns = append(insns, modeInsns[cfg.Mode][typeExec]...)
}
}
return insns
}
func Generate(cfg *Config, r *rand.Rand) []byte {
initOnce.Do(initInsns)
var text []byte
for i := 0; i < cfg.Len; i++ {
insn := randInsn(cfg, r)
text = append(text, insn.Encode(cfg, r)...)
}
return text
}
func Mutate(cfg *Config, r *rand.Rand, text []byte) []byte {
initOnce.Do(initInsns)
insns := split(cfg, text)
retry := false
for stop := false; !stop || retry || len(insns) == 0; stop = r.Intn(2) == 0 {
retry = false
switch x := r.Intn(100); {
case x < 10 && len(insns) != 0:
// delete instruction
i := r.Intn(len(insns))
copy(insns[i:], insns[i+1:])
insns = insns[:len(insns)-1]
case x < 40 && len(insns) != 0:
// replace instruction with another
insn := randInsn(cfg, r)
text1 := insn.Encode(cfg, r)
i := r.Intn(len(insns))
insns[i] = text1
case x < 70 && len(insns) != 0:
// mutate instruction
i := r.Intn(len(insns))
text1 := insns[i]
for stop := false; !stop || len(text1) == 0; stop = r.Intn(2) == 0 {
switch x := r.Intn(100); {
case x < 5 && len(text1) != 0:
// delete byte
pos := r.Intn(len(text1))
copy(text1[pos:], text1[pos+1:])
text1 = text1[:len(text1)-1]
case x < 40 && len(text1) != 0:
// replace a byte
pos := r.Intn(len(text1))
text1[pos] = byte(r.Intn(256))
case x < 70 && len(text1) != 0:
// flip a bit
pos := r.Intn(len(text1))
text1[pos] ^= 1 << byte(r.Intn(8))
default:
// insert a byte
pos := r.Intn(len(text1) + 1)
text1 = append(text1, 0)
copy(text1[pos+1:], text1[pos:])
text1[pos] = byte(r.Intn(256))
}
}
insns[i] = text1
case len(insns) < cfg.Len:
// insert a new instruction
insn := randInsn(cfg, r)
text1 := insn.Encode(cfg, r)
i := r.Intn(len(insns) + 1)
insns = append(insns, nil)
copy(insns[i+1:], insns[i:])
insns[i] = text1
default:
retry = true
}
}
text = nil
for _, insn := range insns {
text = append(text, insn...)
}
return text
}
func randInsn(cfg *Config, r *rand.Rand) *Insn {
var insns []*Insn
if cfg.Priv && cfg.Exec {
insns = modeInsns[cfg.Mode][r.Intn(3)]
} else if cfg.Priv {
insns = modeInsns[cfg.Mode][r.Intn(2)]
} else {
insns = modeInsns[cfg.Mode][typeUser]
}
return insns[r.Intn(len(insns))]
}
func split(cfg *Config, text []byte) [][]byte {
text = append([]byte{}, text...)
var insns [][]byte
var bad []byte
for len(text) != 0 {
n, err := Decode(cfg.Mode, text)
if err != nil || n == 0 {
bad = append(bad, text[0])
text = text[1:]
continue
}
if bad != nil {
insns = append(insns, bad)
bad = nil
}
insns = append(insns, text[:n])
text = text[n:]
}
if bad != nil {
insns = append(insns, bad)
}
return insns
}
func generateArg(cfg *Config, r *rand.Rand, size int) []byte {
v := generateInt(cfg, r, size)
arg := make([]byte, size)
for i := 0; i < size; i++ {
arg[i] = byte(v)
v >>= 8
}
return arg
}
func (insn *Insn) isCompatible(cfg *Config) bool {
if cfg.Mode < 0 || cfg.Mode >= ModeLast {
panic("bad mode")
}
if insn.Priv && !cfg.Priv {
return false
}
if insn.Pseudo && !cfg.Exec {
return false
}
if insn.Mode&(1<<uint(cfg.Mode)) == 0 {
return false
}
return true
}
func generateInt(cfg *Config, r *rand.Rand, size int) uint64 {
if size != 1 && size != 2 && size != 4 && size != 8 {
panic("bad arg size")
}
var v uint64
switch x := r.Intn(60); {
case x < 10:
v = uint64(r.Intn(1 << 4))
case x < 20:
v = uint64(r.Intn(1 << 16))
case x < 25:
v = uint64(r.Int63()) % (1 << 32)
case x < 30:
v = uint64(r.Int63())
case x < 40:
v = specialNumbers[r.Intn(len(specialNumbers))]
if r.Intn(5) == 0 {
v += uint64(r.Intn(33)) - 16
}
case x < 50 && len(cfg.MemRegions) != 0:
mem := cfg.MemRegions[r.Intn(len(cfg.MemRegions))]
switch x := r.Intn(100); {
case x < 25:
v = mem.Start
case x < 50:
v = mem.Start + mem.Size
case x < 75:
v = mem.Start + mem.Size/2
default:
v = mem.Start + uint64(r.Int63())%mem.Size
}
if r.Intn(10) == 0 {
v += uint64(r.Intn(33)) - 16
}
default:
v = uint64(r.Intn(1 << 8))
}
if r.Intn(50) == 0 {
v = uint64(-int64(v))
}
if r.Intn(50) == 0 && size != 1 {
v &^= 1<<12 - 1
}
return v
}
var specialNumbers = []uint64{0, 1 << 15, 1 << 16, 1 << 31, 1 << 32, 1 << 47, 1 << 47, 1 << 63}