1 /*************************************************************************
2 Copyright (C) 2002,2003,2004,2005 Wei Qin
3 See file COPYING for more information.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14 *************************************************************************/
15
16 #include <stdlib.h>
17 #include <string.h>
18 #include <errno.h>
19 #include <assert.h>
20 #include "read_elf.h"
21
22 #define SwapHalf(a) (((a & 0x00ff) << 8) | ((a & 0xff00) >> 8))
23 #define SwapWord(a) (((a & 0xff000000) >> 24) | ((a & 0x00ff0000) >> 8) | ((a & 0x0000ff00) << 8) | ((a & 0x000000ff) << 24))
24 #define SwapAddr(a) SwapWord(a)
25 #define SwapOff(a) SwapWord(a)
26 #define SwapSection(a) SwapHalf(a)
27
LittleEndian()28 int LittleEndian()
29 {
30 Elf32_Word a = 0x01020304;
31 return *(char *) &a == 0x04;
32 }
33
SwapElfHeader(Elf32_Ehdr * hdr)34 void SwapElfHeader(Elf32_Ehdr *hdr)
35 {
36 hdr->e_type = SwapHalf(hdr->e_type);
37 hdr->e_machine = SwapHalf(hdr->e_machine);
38 hdr->e_version = SwapWord(hdr->e_version);
39 hdr->e_entry = SwapAddr(hdr->e_entry);
40 hdr->e_phoff = SwapOff(hdr->e_phoff);
41 hdr->e_shoff = SwapOff(hdr->e_shoff);
42 hdr->e_flags = SwapWord(hdr->e_flags);
43 hdr->e_ehsize = SwapHalf(hdr->e_ehsize);
44 hdr->e_phentsize = SwapHalf(hdr->e_phentsize);
45 hdr->e_phnum = SwapHalf(hdr->e_phnum);
46 hdr->e_shentsize = SwapHalf(hdr->e_shentsize);
47 hdr->e_shnum = SwapHalf(hdr->e_shnum);
48 hdr->e_shstrndx = SwapHalf(hdr->e_shstrndx);
49 }
50
SwapSectionHeader(Elf32_Shdr * shdr)51 void SwapSectionHeader(Elf32_Shdr *shdr)
52 {
53 shdr->sh_name = SwapWord(shdr->sh_name);
54 shdr->sh_type = SwapWord(shdr->sh_type);
55 shdr->sh_flags = SwapWord(shdr->sh_flags);
56 shdr->sh_addr = SwapAddr(shdr->sh_addr);
57 shdr->sh_offset = SwapOff(shdr->sh_offset);
58 shdr->sh_size = SwapWord(shdr->sh_size);
59 shdr->sh_link = SwapWord(shdr->sh_link);
60 shdr->sh_info = SwapWord(shdr->sh_info);
61 shdr->sh_addralign = SwapWord(shdr->sh_addralign);
62 shdr->sh_entsize = SwapWord(shdr->sh_entsize);
63 }
64
SwapElfSymbol(Elf32_Sym * sym)65 void SwapElfSymbol(Elf32_Sym *sym)
66 {
67 sym->st_name = SwapWord(sym->st_name);
68 sym->st_value = SwapAddr(sym->st_value);
69 sym->st_size = SwapWord(sym->st_size);
70 sym->st_shndx = SwapSection(sym->st_shndx);
71 }
72
AdjustElfHeader(Elf32_Ehdr * hdr)73 void AdjustElfHeader(Elf32_Ehdr *hdr)
74 {
75 switch(hdr->e_ident[EI_DATA])
76 {
77 case ELFDATA2LSB:
78 if (!LittleEndian())
79 SwapElfHeader(hdr);
80 break;
81 case ELFDATA2MSB:
82 if (LittleEndian())
83 SwapElfHeader(hdr);
84 break;
85 }
86 }
87
AdjustSectionHeader(Elf32_Ehdr * hdr,Elf32_Shdr * shdr)88 void AdjustSectionHeader(Elf32_Ehdr *hdr, Elf32_Shdr *shdr)
89 {
90 switch(hdr->e_ident[EI_DATA])
91 {
92 case ELFDATA2LSB:
93 if (!LittleEndian())
94 SwapSectionHeader(shdr);
95 break;
96 case ELFDATA2MSB:
97 if (LittleEndian())
98 SwapSectionHeader(shdr);
99 break;
100 }
101 }
102
AdjustElfSymbols(Elf32_Ehdr * hdr,Elf32_Sym * elf_symbols,int num_entries)103 void AdjustElfSymbols(Elf32_Ehdr *hdr, Elf32_Sym *elf_symbols, int num_entries)
104 {
105 if (hdr->e_ident[EI_DATA] == ELFDATA2LSB && LittleEndian())
106 return;
107 if (hdr->e_ident[EI_DATA] == ELFDATA2MSB && !LittleEndian())
108 return;
109 for (int ii = 0; ii < num_entries; ++ii) {
110 SwapElfSymbol(&elf_symbols[ii]);
111 }
112 }
113
ReadElfHeader(FILE * fobj)114 Elf32_Ehdr *ReadElfHeader(FILE *fobj)
115 {
116 Elf32_Ehdr *hdr = new Elf32_Ehdr;
117 int rval = fread(hdr, sizeof(Elf32_Ehdr), 1, fobj);
118 if (rval != 1) {
119 delete hdr;
120 return NULL;
121 }
122 if (hdr->e_ident[EI_MAG0] != 0x7f || hdr->e_ident[EI_MAG1] != 'E' ||
123 hdr->e_ident[EI_MAG2] != 'L' || hdr->e_ident[EI_MAG3] != 'F') {
124 delete hdr;
125 return NULL;
126 }
127 AdjustElfHeader(hdr);
128 return hdr;
129 }
130
ReadSectionHeaders(Elf32_Ehdr * hdr,FILE * f)131 Elf32_Shdr *ReadSectionHeaders(Elf32_Ehdr *hdr, FILE *f)
132 {
133 int i;
134 unsigned long sz = hdr->e_shnum * hdr->e_shentsize;
135 assert(sizeof(Elf32_Shdr) == hdr->e_shentsize);
136 Elf32_Shdr *shdr = new Elf32_Shdr[hdr->e_shnum];
137
138 if (fseek(f, hdr->e_shoff, SEEK_SET) != 0)
139 {
140 delete[] shdr;
141 return NULL;
142 }
143 if (fread(shdr, sz, 1, f) != 1)
144 {
145 delete[] shdr;
146 return NULL;
147 }
148
149 for(i = 0; i < hdr->e_shnum; i++)
150 AdjustSectionHeader(hdr, shdr + i);
151
152 return shdr;
153 }
154
155
ReadStringTable(Elf32_Ehdr * hdr,Elf32_Shdr * shdr_table,FILE * f)156 char *ReadStringTable(Elf32_Ehdr *hdr, Elf32_Shdr *shdr_table, FILE *f)
157 {
158 Elf32_Shdr *shdr = shdr_table + hdr->e_shstrndx;
159 char *string_table;
160
161 string_table = new char[shdr->sh_size];
162 fseek(f, shdr->sh_offset, SEEK_SET);
163 fread(string_table, shdr->sh_size, 1, f);
164
165 return string_table;
166 }
167
ReadSection(Elf32_Shdr * shdr,void * buffer,FILE * f)168 int ReadSection(Elf32_Shdr *shdr, void *buffer, FILE *f)
169 {
170 if (fseek(f, shdr->sh_offset, SEEK_SET) != 0)
171 return -1;
172 if (fread(buffer, shdr->sh_size, 1, f) != 1)
173 return -1;
174 return 0;
175 }
176
GetSymbolName(Elf32_Half index,char * string_table)177 char *GetSymbolName(Elf32_Half index, char *string_table)
178 {
179 return string_table + index;
180 }
181
FindSymbolTableSection(Elf32_Ehdr * hdr,Elf32_Shdr * shdr,char * string_table)182 Elf32_Shdr *FindSymbolTableSection(Elf32_Ehdr *hdr,
183 Elf32_Shdr *shdr,
184 char *string_table)
185 {
186 for(int ii = 0; ii < hdr->e_shnum; ii++) {
187 if (shdr[ii].sh_type == SHT_SYMTAB &&
188 strcmp(GetSymbolName(shdr[ii].sh_name, string_table),
189 ".symtab") == 0)
190 {
191 return &shdr[ii];
192 }
193 }
194 return NULL;
195 }
196
FindSymbolStringTableSection(Elf32_Ehdr * hdr,Elf32_Shdr * shdr,char * string_table)197 Elf32_Shdr *FindSymbolStringTableSection(Elf32_Ehdr *hdr,
198 Elf32_Shdr *shdr,
199 char *string_table)
200 {
201 for(int ii = 0; ii < hdr->e_shnum; ii++) {
202 if (shdr[ii].sh_type == SHT_STRTAB &&
203 strcmp(GetSymbolName(shdr[ii].sh_name, string_table),
204 ".strtab") == 0)
205 {
206 return &shdr[ii];
207 }
208 }
209 return NULL;
210 }
211