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
|
// Copyright 2018 Google Inc. 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.
// Verifies a host bionic executable with an embedded linker, then injects
// the address of the _start function for the linker_wrapper to use.
package main
import (
"debug/elf"
"flag"
"fmt"
"io"
"os"
"android/soong/symbol_inject"
)
func main() {
var inputFile, linkerFile, outputFile string
flag.StringVar(&inputFile, "i", "", "Input file")
flag.StringVar(&linkerFile, "l", "", "Linker file")
flag.StringVar(&outputFile, "o", "", "Output file")
flag.Parse()
if inputFile == "" || linkerFile == "" || outputFile == "" || flag.NArg() != 0 {
flag.Usage()
os.Exit(1)
}
r, err := os.Open(inputFile)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(2)
}
defer r.Close()
file, err := symbol_inject.OpenFile(r)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(3)
}
linker, err := elf.Open(linkerFile)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(4)
}
start_addr, err := parseElf(r, linker)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(5)
}
w, err := os.OpenFile(outputFile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0777)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(6)
}
defer w.Close()
err = symbol_inject.InjectUint64Symbol(file, w, "__dlwrap_original_start", start_addr)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(7)
}
}
// Check the ELF file, and return the address to the _start function
func parseElf(r io.ReaderAt, linker *elf.File) (uint64, error) {
file, err := elf.NewFile(r)
if err != nil {
return 0, err
}
symbols, err := file.Symbols()
if err != nil {
return 0, err
}
for _, prog := range file.Progs {
if prog.Type == elf.PT_INTERP {
return 0, fmt.Errorf("File should not have a PT_INTERP header")
}
}
if dlwrap_start, err := findSymbol(symbols, "__dlwrap__start"); err != nil {
return 0, err
} else if dlwrap_start.Value != file.Entry {
return 0, fmt.Errorf("Expected file entry(0x%x) to point to __dlwrap_start(0x%x)",
file.Entry, dlwrap_start.Value)
}
err = checkLinker(file, linker, symbols)
if err != nil {
return 0, fmt.Errorf("Linker executable failed verification against app embedded linker: %s\n"+
"linker might not be in sync with crtbegin_dynamic.o.",
err)
}
start, err := findSymbol(symbols, "_start")
if err != nil {
return 0, fmt.Errorf("Failed to find _start symbol")
}
return start.Value, nil
}
func findSymbol(symbols []elf.Symbol, name string) (elf.Symbol, error) {
for _, sym := range symbols {
if sym.Name == name {
return sym, nil
}
}
return elf.Symbol{}, fmt.Errorf("Failed to find symbol %q", name)
}
// Check that all of the PT_LOAD segments have been embedded properly
func checkLinker(file, linker *elf.File, fileSyms []elf.Symbol) error {
dlwrap_linker_offset, err := findSymbol(fileSyms, "__dlwrap_linker_offset")
if err != nil {
return err
}
for i, lprog := range linker.Progs {
if lprog.Type != elf.PT_LOAD {
continue
}
laddr := lprog.Vaddr + dlwrap_linker_offset.Value
found := false
for _, prog := range file.Progs {
if prog.Type != elf.PT_LOAD {
continue
}
if laddr < prog.Vaddr || laddr > prog.Vaddr+prog.Memsz {
continue
}
found = true
if lprog.Flags != prog.Flags {
return fmt.Errorf("Linker prog %d (0x%x) flags (%s) do not match (%s)",
i, lprog.Vaddr, lprog.Flags, prog.Flags)
}
if laddr+lprog.Memsz > prog.Vaddr+prog.Filesz {
return fmt.Errorf("Linker prog %d (0x%x) not fully present (0x%x > 0x%x)",
i, lprog.Vaddr, laddr+lprog.Memsz, prog.Vaddr+prog.Filesz)
}
}
if !found {
return fmt.Errorf("Linker prog %d (0x%x) not found at offset 0x%x",
i, lprog.Vaddr, dlwrap_linker_offset.Value)
}
}
return nil
}
|
