1 // elfcpp_file.h -- file access for elfcpp -*- C++ -*-
3 // This header file defines the class Elf_file which can be used to
4 // read useful data from an ELF file. The functions here are all
5 // templates which take a file interface object as a parameter. This
6 // type must have a subtype View. This type must support two methods:
7 // View view(off_t file_offset, off_t data_size)
8 // returns a View for the specified part of the file.
9 // void error(const char* printf_format, ...)
10 // prints an error message and does not return. The subtype View must
12 // const unsigned char* data()
13 // which returns a pointer to a buffer containing the requested data.
14 // This general interface is used to read data from the file. Objects
15 // of type View will never survive longer than the elfcpp function.
17 // Some of these functions must return a reference to part of the
18 // file. To use these, the file interface must support a subtype
20 // Location(off_t file_offset, off_t data_size)
21 // To use this in conjunction with the accessors types Shdr, etc., the
22 // file interface should support an overload of view:
23 // View view(Location)
24 // This permits writing
25 // elfcpp::Shdr shdr(file, ef.section_header(n));
36 // This object is used to read an ELF file.
37 // SIZE: The size of file, 32 or 64.
38 // BIG_ENDIAN: Whether the file is in big-endian format.
39 // FILE: A file reading type as described above.
41 template<int size
, bool big_endian
, typename File
>
45 typedef Elf_file
<size
, big_endian
, File
> This
;
48 static const int ehdr_size
= Elf_sizes
<size
>::ehdr_size
;
49 static const int phdr_size
= Elf_sizes
<size
>::phdr_size
;
50 static const int shdr_size
= Elf_sizes
<size
>::shdr_size
;
51 static const int sym_size
= Elf_sizes
<size
>::sym_size
;
52 static const int rel_size
= Elf_sizes
<size
>::rel_size
;
53 static const int rela_size
= Elf_sizes
<size
>::rela_size
;
55 typedef Ehdr
<size
, big_endian
> Ef_ehdr
;
56 typedef Phdr
<size
, big_endian
> Ef_phdr
;
57 typedef Shdr
<size
, big_endian
> Ef_shdr
;
58 typedef Sym
<size
, big_endian
> Ef_sym
;
60 // Construct an Elf_file given an ELF file header.
61 Elf_file(File
* file
, const Ef_ehdr
& ehdr
)
62 { this->construct(file
, ehdr
); }
64 // Construct an ELF file.
68 // Return the file offset to the section headers.
71 { return this->shoff_
; }
73 // Return the number of sections.
77 this->initialize_shnum();
81 // Return the section index of the section name string table.
85 this->initialize_shnum();
86 return this->shstrndx_
;
89 // Return the location of the header of section SHNDX.
90 typename
File::Location
91 section_header(unsigned int shndx
)
93 return typename
File::Location(this->section_header_offset(shndx
),
97 // Return the name of section SHNDX.
99 section_name(unsigned int shndx
);
101 // Return the location of the contents of section SHNDX.
102 typename
File::Location
103 section_contents(unsigned int shndx
);
105 // Return the flags of section SHNDX.
106 typename Elf_types
<size
>::Elf_WXword
107 section_flags(unsigned int shndx
);
109 // Return the type of section SHNDX.
111 section_type(unsigned int shndx
);
114 // Shared constructor code.
116 construct(File
* file
, const Ef_ehdr
& ehdr
);
118 // Initialize shnum_ and shstrndx_.
122 // Return the file offset of the header of section SHNDX.
124 section_header_offset(unsigned int shndx
);
126 // The file we are reading.
128 // The file offset to the section headers.
130 // The number of sections.
132 // The section index of the section name string table.
133 unsigned int shstrndx_
;
136 // Template function definitions.
138 // Construct an Elf_file given an ELF file header.
140 template<int size
, bool big_endian
, typename File
>
142 Elf_file
<size
, big_endian
, File
>::construct(File
* file
, const Ef_ehdr
& ehdr
)
145 this->shoff_
= ehdr
.get_e_shoff();
146 this->shnum_
= ehdr
.get_e_shnum();
147 this->shstrndx_
= ehdr
.get_e_shstrndx();
148 if (ehdr
.get_e_ehsize() != This::ehdr_size
)
149 file
->error(_("bad e_ehsize (%d != %d)"),
150 ehdr
.get_e_ehsize(), This::ehdr_size
);
151 if (ehdr
.get_e_shentsize() != This::shdr_size
)
152 file
->error(_("bad e_shentsize (%d != %d)"),
153 ehdr
.get_e_shentsize(), This::shdr_size
);
156 // Construct an ELF file.
158 template<int size
, bool big_endian
, typename File
>
160 Elf_file
<size
, big_endian
, File
>::Elf_file(File
* file
)
162 typename
File::View
v(file
->view(file_header_offset
, This::ehdr_size
));
163 this->construct(file
, Ef_ehdr(v
.data()));
166 // Initialize the shnum_ and shstrndx_ fields, handling overflow.
168 template<int size
, bool big_endian
, typename File
>
170 Elf_file
<size
, big_endian
, File
>::initialize_shnum()
172 if ((this->shnum_
== 0 || this->shstrndx_
== SHN_XINDEX
)
173 && this->shoff_
!= 0)
175 typename
File::View
v(this->file_
->view(this->shoff_
, This::shdr_size
));
176 Ef_shdr
shdr(v
.data());
177 if (this->shnum_
== 0)
178 this->shnum_
= shdr
.get_sh_size();
179 if (this->shstrndx_
== SHN_XINDEX
)
180 this->shstrndx_
= shdr
.get_sh_link();
184 // Return the file offset of the section header of section SHNDX.
186 template<int size
, bool big_endian
, typename File
>
188 Elf_file
<size
, big_endian
, File
>::section_header_offset(unsigned int shndx
)
190 if (shndx
>= this->shnum())
191 this->file_
->error(_("section_header_offset: bad shndx %u >= %u"),
192 shndx
, this->shnum());
193 return this->shoff_
+ This::shdr_size
* shndx
;
196 // Return the name of section SHNDX.
198 template<int size
, bool big_endian
, typename File
>
200 Elf_file
<size
, big_endian
, File
>::section_name(unsigned int shndx
)
202 File
* const file
= this->file_
;
204 // Get the section name offset.
205 unsigned int sh_name
;
207 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
209 Ef_shdr
shdr(v
.data());
210 sh_name
= shdr
.get_sh_name();
213 // Get the file offset for the section name string table data.
217 const unsigned int shstrndx
= this->shstrndx_
;
218 typename
File::View
v(file
->view(this->section_header_offset(shstrndx
),
220 Ef_shdr
shstr_shdr(v
.data());
221 shstr_off
= shstr_shdr
.get_sh_offset();
222 shstr_size
= shstr_shdr
.get_sh_size();
225 if (sh_name
>= shstr_size
)
226 file
->error(_("bad section name offset for section %u: %u"),
229 typename
File::View
v(file
->view(shstr_off
, shstr_size
));
231 const unsigned char* datau
= v
.data();
232 const char* data
= reinterpret_cast<const char*>(datau
);
233 const void* p
= ::memchr(data
+ sh_name
, '\0', shstr_size
- sh_name
);
235 file
->error(_("missing null terminator for name of section %u"),
238 size_t len
= static_cast<const char*>(p
) - (data
+ sh_name
);
240 return std::string(data
+ sh_name
, len
);
243 // Return the contents of section SHNDX.
245 template<int size
, bool big_endian
, typename File
>
246 typename
File::Location
247 Elf_file
<size
, big_endian
, File
>::section_contents(unsigned int shndx
)
249 File
* const file
= this->file_
;
251 if (shndx
>= this->shnum())
252 file
->error(_("section_contents: bad shndx %u >= %u"),
253 shndx
, this->shnum());
255 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
257 Ef_shdr
shdr(v
.data());
258 return typename
File::Location(shdr
.get_sh_offset(), shdr
.get_sh_size());
261 // Return the section flags of section SHNDX.
263 template<int size
, bool big_endian
, typename File
>
264 typename Elf_types
<size
>::Elf_WXword
265 Elf_file
<size
, big_endian
, File
>::section_flags(unsigned int shndx
)
267 File
* const file
= this->file_
;
269 if (shndx
>= this->shnum())
270 file
->error(_("section_flags: bad shndx %u >= %u"),
271 shndx
, this->shnum());
273 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
276 Ef_shdr
shdr(v
.data());
277 return shdr
.get_sh_flags();
280 // Return the type of section SHNDX.
282 template<int size
, bool big_endian
, typename File
>
284 Elf_file
<size
, big_endian
, File
>::section_type(unsigned int shndx
)
286 File
* const file
= this->file_
;
288 if (shndx
>= this->shnum())
289 file
->error(_("section_type: bad shndx %u >= %u"),
290 shndx
, this->shnum());
292 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
295 Ef_shdr
shdr(v
.data());
296 return shdr
.get_sh_type();
299 } // End namespace elfcpp.
301 #endif // !defined(ELFCPP_FILE_H)