/
ldcache.go
317 lines (270 loc) · 7.15 KB
/
ldcache.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
309
310
311
312
313
314
315
316
317
/*
# Copyright (c) 2021-2022, NVIDIA CORPORATION. All rights reserved.
#
# 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.
*/
// Adapted from https://github.com/rai-project/ldcache
package ldcache
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"os"
"path/filepath"
"strings"
"syscall"
"unsafe"
"github.com/NVIDIA/nvidia-container-toolkit/internal/logger"
"github.com/NVIDIA/nvidia-container-toolkit/internal/lookup/symlinks"
)
const ldcachePath = "/etc/ld.so.cache"
const (
magicString1 = "ld.so-1.7.0"
magicString2 = "glibc-ld.so.cache"
magicVersion = "1.1"
)
const (
flagTypeMask = 0x00ff
flagTypeELF = 0x0001
flagArchMask = 0xff00
flagArchI386 = 0x0000
flagArchX8664 = 0x0300
flagArchX32 = 0x0800
flagArchPpc64le = 0x0500
)
var errInvalidCache = errors.New("invalid ld.so.cache file")
type header1 struct {
Magic [len(magicString1) + 1]byte // include null delimiter
NLibs uint32
}
type entry1 struct {
Flags int32
Key, Value uint32
}
type header2 struct {
Magic [len(magicString2)]byte
Version [len(magicVersion)]byte
NLibs uint32
TableSize uint32
_ [3]uint32 // unused
_ uint64 // force 8 byte alignment
}
type entry2 struct {
Flags int32
Key, Value uint32
OSVersion uint32
HWCap uint64
}
// LDCache represents the interface for performing lookups into the LDCache
type LDCache interface {
List() ([]string, []string)
Lookup(...string) ([]string, []string)
}
type ldcache struct {
*bytes.Reader
data, libs []byte
header header2
entries []entry2
root string
logger logger.Interface
}
// New creates a new LDCache with the specified logger and root.
func New(logger logger.Interface, root string) (LDCache, error) {
path := filepath.Join(root, ldcachePath)
logger.Debugf("Opening ld.conf at %v", path)
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
fi, err := f.Stat()
if err != nil {
return nil, err
}
d, err := syscall.Mmap(int(f.Fd()), 0, int(fi.Size()),
syscall.PROT_READ, syscall.MAP_PRIVATE)
if err != nil {
return nil, err
}
cache := &ldcache{
data: d,
Reader: bytes.NewReader(d),
root: root,
logger: logger,
}
return cache, cache.parse()
}
func (c *ldcache) Close() error {
return syscall.Munmap(c.data)
}
func (c *ldcache) Magic() string {
return string(c.header.Magic[:])
}
func (c *ldcache) Version() string {
return string(c.header.Version[:])
}
func strn(b []byte, n int) string {
return string(b[:n])
}
func (c *ldcache) parse() error {
var header header1
// Check for the old format (< glibc-2.2)
if c.Len() <= int(unsafe.Sizeof(header)) {
return errInvalidCache
}
if strn(c.data, len(magicString1)) == magicString1 {
if err := binary.Read(c, binary.LittleEndian, &header); err != nil {
return err
}
n := int64(header.NLibs) * int64(unsafe.Sizeof(entry1{}))
offset, err := c.Seek(n, 1) // skip old entries
if err != nil {
return err
}
n = (-offset) & int64(unsafe.Alignof(c.header)-1)
_, err = c.Seek(n, 1) // skip padding
if err != nil {
return err
}
}
c.libs = c.data[c.Size()-int64(c.Len()):] // kv offsets start here
if err := binary.Read(c, binary.LittleEndian, &c.header); err != nil {
return err
}
if c.Magic() != magicString2 || c.Version() != magicVersion {
return errInvalidCache
}
c.entries = make([]entry2, c.header.NLibs)
if err := binary.Read(c, binary.LittleEndian, &c.entries); err != nil {
return err
}
return nil
}
type entry struct {
libname string
bits int
value string
}
// getEntries returns the entires of the ldcache in a go-friendly struct.
func (c *ldcache) getEntries(selected func(string) bool) []entry {
var entries []entry
for _, e := range c.entries {
bits := 0
if ((e.Flags & flagTypeMask) & flagTypeELF) == 0 {
continue
}
switch e.Flags & flagArchMask {
case flagArchX8664:
fallthrough
case flagArchPpc64le:
bits = 64
case flagArchX32:
fallthrough
case flagArchI386:
bits = 32
default:
continue
}
if e.Key > uint32(len(c.libs)) || e.Value > uint32(len(c.libs)) {
continue
}
lib := bytesToString(c.libs[e.Key:])
if lib == "" {
c.logger.Debugf("Skipping invalid lib")
continue
}
if !selected(lib) {
continue
}
value := bytesToString(c.libs[e.Value:])
if value == "" {
c.logger.Debugf("Skipping invalid value for lib %v", lib)
continue
}
e := entry{
libname: lib,
bits: bits,
value: value,
}
entries = append(entries, e)
}
return entries
}
// List creates a list of libraries in the ldcache.
// The 32-bit and 64-bit libraries are returned separately.
func (c *ldcache) List() ([]string, []string) {
all := func(s string) bool { return true }
return c.resolveSelected(all)
}
// Lookup searches the ldcache for the specified prefixes.
// The 32-bit and 64-bit libraries matching the prefixes are returned.
func (c *ldcache) Lookup(libPrefixes ...string) ([]string, []string) {
c.logger.Debugf("Looking up %v in cache", libPrefixes)
// We define a functor to check whether a given library name matches any of the prefixes
matchesAnyPrefix := func(s string) bool {
for _, p := range libPrefixes {
if strings.HasPrefix(s, p) {
return true
}
}
return false
}
return c.resolveSelected(matchesAnyPrefix)
}
// resolveSelected process the entries in the LDCach based on the supplied filter and returns the resolved paths.
// The paths are separated by bittage.
func (c *ldcache) resolveSelected(selected func(string) bool) ([]string, []string) {
paths := make(map[int][]string)
processed := make(map[string]bool)
for _, e := range c.getEntries(selected) {
path, err := c.resolve(e.value)
if err != nil {
c.logger.Debugf("Could not resolve entry: %v", err)
continue
}
if processed[path] {
continue
}
paths[e.bits] = append(paths[e.bits], path)
processed[path] = true
}
return paths[32], paths[64]
}
// resolve resolves the specified ldcache entry based on the value being processed.
// The input is the name of the entry in the cache.
func (c *ldcache) resolve(target string) (string, error) {
name := filepath.Join(c.root, target)
c.logger.Debugf("checking %v", name)
link, err := symlinks.Resolve(name)
if err != nil {
return "", fmt.Errorf("failed to resolve symlink: %v", err)
}
if link == name {
return name, nil
}
// We return absolute paths for all targets
if !filepath.IsAbs(link) || strings.HasPrefix(link, ".") {
link = filepath.Join(filepath.Dir(target), link)
}
return c.resolve(link)
}
// bytesToString converts a byte slice to a string.
// This assumes that the byte slice is null-terminated
func bytesToString(value []byte) string {
n := bytes.IndexByte(value, 0)
if n < 0 {
return ""
}
return strn(value, n)
}