1 // elfcpp_file.h -- file access for elfcpp -*- C++ -*-
3 // Copyright 2006, 2007, Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of elfcpp.
8 // This program is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU Library General Public License
10 // as published by the Free Software Foundation; either version 2, or
11 // (at your option) any later version.
13 // In addition to the permissions in the GNU Library General Public
14 // License, the Free Software Foundation gives you unlimited
15 // permission to link the compiled version of this file into
16 // combinations with other programs, and to distribute those
17 // combinations without any restriction coming from the use of this
18 // file. (The Library Public License restrictions do apply in other
19 // respects; for example, they cover modification of the file, and
20 /// distribution when not linked into a combined executable.)
22 // This program is distributed in the hope that it will be useful, but
23 // WITHOUT ANY WARRANTY; without even the implied warranty of
24 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
25 // Library General Public License for more details.
27 // You should have received a copy of the GNU Library General Public
28 // License along with this program; if not, write to the Free Software
29 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
32 // This header file defines the class Elf_file which can be used to
33 // read useful data from an ELF file. The functions here are all
34 // templates which take a file interface object as a parameter. This
35 // type must have a subtype View. This type must support two methods:
36 // View view(off_t file_offset, off_t data_size)
37 // returns a View for the specified part of the file.
38 // void error(const char* printf_format, ...)
39 // prints an error message and does not return. The subtype View must
41 // const unsigned char* data()
42 // which returns a pointer to a buffer containing the requested data.
43 // This general interface is used to read data from the file. Objects
44 // of type View will never survive longer than the elfcpp function.
46 // Some of these functions must return a reference to part of the
47 // file. To use these, the file interface must support a subtype
49 // Location(off_t file_offset, off_t data_size)
50 // To use this in conjunction with the accessors types Shdr, etc., the
51 // file interface should support an overload of view:
52 // View view(Location)
53 // This permits writing
54 // elfcpp::Shdr shdr(file, ef.section_header(n));
65 // This object is used to read an ELF file.
66 // SIZE: The size of file, 32 or 64.
67 // BIG_ENDIAN: Whether the file is in big-endian format.
68 // FILE: A file reading type as described above.
70 template<int size
, bool big_endian
, typename File
>
74 typedef Elf_file
<size
, big_endian
, File
> This
;
77 static const int ehdr_size
= Elf_sizes
<size
>::ehdr_size
;
78 static const int phdr_size
= Elf_sizes
<size
>::phdr_size
;
79 static const int shdr_size
= Elf_sizes
<size
>::shdr_size
;
80 static const int sym_size
= Elf_sizes
<size
>::sym_size
;
81 static const int rel_size
= Elf_sizes
<size
>::rel_size
;
82 static const int rela_size
= Elf_sizes
<size
>::rela_size
;
84 typedef Ehdr
<size
, big_endian
> Ef_ehdr
;
85 typedef Phdr
<size
, big_endian
> Ef_phdr
;
86 typedef Shdr
<size
, big_endian
> Ef_shdr
;
87 typedef Sym
<size
, big_endian
> Ef_sym
;
89 // Construct an Elf_file given an ELF file header.
90 Elf_file(File
* file
, const Ef_ehdr
& ehdr
)
91 { this->construct(file
, ehdr
); }
93 // Construct an ELF file.
97 // Return the file offset to the section headers.
100 { return this->shoff_
; }
102 // Return the number of sections.
106 this->initialize_shnum();
110 // Return the section index of the section name string table.
114 this->initialize_shnum();
115 return this->shstrndx_
;
118 // Return the value to subtract from section indexes >=
119 // SHN_LORESERVE. See the comment in initialize_shnum.
123 this->initialize_shnum();
124 return this->large_shndx_offset_
;
127 // Return the location of the header of section SHNDX.
128 typename
File::Location
129 section_header(unsigned int shndx
)
131 return typename
File::Location(this->section_header_offset(shndx
),
135 // Return the name of section SHNDX.
137 section_name(unsigned int shndx
);
139 // Return the location of the contents of section SHNDX.
140 typename
File::Location
141 section_contents(unsigned int shndx
);
143 // Return the size of section SHNDX.
144 typename Elf_types
<size
>::Elf_WXword
145 section_size(unsigned int shndx
);
147 // Return the flags of section SHNDX.
148 typename Elf_types
<size
>::Elf_WXword
149 section_flags(unsigned int shndx
);
151 // Return the address of section SHNDX.
152 typename Elf_types
<size
>::Elf_Addr
153 section_addr(unsigned int shndx
);
155 // Return the type of section SHNDX.
157 section_type(unsigned int shndx
);
159 // Return the link field of section SHNDX.
161 section_link(unsigned int shndx
);
163 // Return the info field of section SHNDX.
165 section_info(unsigned int shndx
);
167 // Return the addralign field of section SHNDX.
168 typename Elf_types
<size
>::Elf_WXword
169 section_addralign(unsigned int shndx
);
172 // Shared constructor code.
174 construct(File
* file
, const Ef_ehdr
& ehdr
);
176 // Initialize shnum_ and shstrndx_.
180 // Return the file offset of the header of section SHNDX.
182 section_header_offset(unsigned int shndx
);
184 // The file we are reading.
186 // The file offset to the section headers.
188 // The number of sections.
190 // The section index of the section name string table.
191 unsigned int shstrndx_
;
192 // Offset to add to sections larger than SHN_LORESERVE.
193 int large_shndx_offset_
;
196 // Template function definitions.
198 // Construct an Elf_file given an ELF file header.
200 template<int size
, bool big_endian
, typename File
>
202 Elf_file
<size
, big_endian
, File
>::construct(File
* file
, const Ef_ehdr
& ehdr
)
205 this->shoff_
= ehdr
.get_e_shoff();
206 this->shnum_
= ehdr
.get_e_shnum();
207 this->shstrndx_
= ehdr
.get_e_shstrndx();
208 this->large_shndx_offset_
= 0;
209 if (ehdr
.get_e_ehsize() != This::ehdr_size
)
210 file
->error(_("bad e_ehsize (%d != %d)"),
211 ehdr
.get_e_ehsize(), This::ehdr_size
);
212 if (ehdr
.get_e_shentsize() != This::shdr_size
)
213 file
->error(_("bad e_shentsize (%d != %d)"),
214 ehdr
.get_e_shentsize(), This::shdr_size
);
217 // Construct an ELF file.
219 template<int size
, bool big_endian
, typename File
>
221 Elf_file
<size
, big_endian
, File
>::Elf_file(File
* file
)
223 typename
File::View
v(file
->view(file_header_offset
, This::ehdr_size
));
224 this->construct(file
, Ef_ehdr(v
.data()));
227 // Initialize the shnum_ and shstrndx_ fields, handling overflow.
229 template<int size
, bool big_endian
, typename File
>
231 Elf_file
<size
, big_endian
, File
>::initialize_shnum()
233 if ((this->shnum_
== 0 || this->shstrndx_
== SHN_XINDEX
)
234 && this->shoff_
!= 0)
236 typename
File::View
v(this->file_
->view(this->shoff_
, This::shdr_size
));
237 Ef_shdr
shdr(v
.data());
239 if (this->shnum_
== 0)
240 this->shnum_
= shdr
.get_sh_size();
242 if (this->shstrndx_
== SHN_XINDEX
)
244 this->shstrndx_
= shdr
.get_sh_link();
246 // Versions of the GNU binutils between 2.12 and 2.18 did
247 // not handle objects with more than SHN_LORESERVE sections
248 // correctly. All large section indexes were offset by
249 // 0x100. Some information can be found here:
250 // http://sourceware.org/bugzilla/show_bug.cgi?id=5900 .
251 // Fortunately these object files are easy to detect, as the
252 // GNU binutils always put the section header string table
253 // near the end of the list of sections. Thus if the
254 // section header string table index is larger than the
255 // number of sections, then we know we have to subtract
256 // 0x100 to get the real section index.
257 if (this->shstrndx_
>= this->shnum_
)
259 if (this->shstrndx_
>= elfcpp::SHN_LORESERVE
+ 0x100)
261 this->large_shndx_offset_
= - 0x100;
262 this->shstrndx_
-= 0x100;
264 if (this->shstrndx_
>= this->shnum_
)
265 this->file_
->error(_("bad shstrndx: %u >= %u"),
266 this->shstrndx_
, this->shnum_
);
272 // Return the file offset of the section header of section SHNDX.
274 template<int size
, bool big_endian
, typename File
>
276 Elf_file
<size
, big_endian
, File
>::section_header_offset(unsigned int shndx
)
278 if (shndx
>= this->shnum())
279 this->file_
->error(_("section_header_offset: bad shndx %u >= %u"),
280 shndx
, this->shnum());
281 return this->shoff_
+ This::shdr_size
* shndx
;
284 // Return the name of section SHNDX.
286 template<int size
, bool big_endian
, typename File
>
288 Elf_file
<size
, big_endian
, File
>::section_name(unsigned int shndx
)
290 File
* const file
= this->file_
;
292 // Get the section name offset.
293 unsigned int sh_name
;
295 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
297 Ef_shdr
shdr(v
.data());
298 sh_name
= shdr
.get_sh_name();
301 // Get the file offset for the section name string table data.
305 const unsigned int shstrndx
= this->shstrndx_
;
306 typename
File::View
v(file
->view(this->section_header_offset(shstrndx
),
308 Ef_shdr
shstr_shdr(v
.data());
309 shstr_off
= shstr_shdr
.get_sh_offset();
310 shstr_size
= shstr_shdr
.get_sh_size();
313 if (sh_name
>= shstr_size
)
314 file
->error(_("bad section name offset for section %u: %u"),
317 typename
File::View
v(file
->view(shstr_off
, shstr_size
));
319 const unsigned char* datau
= v
.data();
320 const char* data
= reinterpret_cast<const char*>(datau
);
321 const void* p
= ::memchr(data
+ sh_name
, '\0', shstr_size
- sh_name
);
323 file
->error(_("missing null terminator for name of section %u"),
326 size_t len
= static_cast<const char*>(p
) - (data
+ sh_name
);
328 return std::string(data
+ sh_name
, len
);
331 // Return the contents of section SHNDX.
333 template<int size
, bool big_endian
, typename File
>
334 typename
File::Location
335 Elf_file
<size
, big_endian
, File
>::section_contents(unsigned int shndx
)
337 File
* const file
= this->file_
;
339 if (shndx
>= this->shnum())
340 file
->error(_("section_contents: bad shndx %u >= %u"),
341 shndx
, this->shnum());
343 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
345 Ef_shdr
shdr(v
.data());
346 return typename
File::Location(shdr
.get_sh_offset(), shdr
.get_sh_size());
349 // Get the size of section SHNDX.
351 template<int size
, bool big_endian
, typename File
>
352 typename Elf_types
<size
>::Elf_WXword
353 Elf_file
<size
, big_endian
, File
>::section_size(unsigned int shndx
)
355 File
* const file
= this->file_
;
357 if (shndx
>= this->shnum())
358 file
->error(_("section_size: bad shndx %u >= %u"),
359 shndx
, this->shnum());
361 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
364 Ef_shdr
shdr(v
.data());
365 return shdr
.get_sh_size();
368 // Return the section flags of section SHNDX.
370 template<int size
, bool big_endian
, typename File
>
371 typename Elf_types
<size
>::Elf_WXword
372 Elf_file
<size
, big_endian
, File
>::section_flags(unsigned int shndx
)
374 File
* const file
= this->file_
;
376 if (shndx
>= this->shnum())
377 file
->error(_("section_flags: bad shndx %u >= %u"),
378 shndx
, this->shnum());
380 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
383 Ef_shdr
shdr(v
.data());
384 return shdr
.get_sh_flags();
387 // Return the address of section SHNDX.
389 template<int size
, bool big_endian
, typename File
>
390 typename Elf_types
<size
>::Elf_Addr
391 Elf_file
<size
, big_endian
, File
>::section_addr(unsigned int shndx
)
393 File
* const file
= this->file_
;
395 if (shndx
>= this->shnum())
396 file
->error(_("section_flags: bad shndx %u >= %u"),
397 shndx
, this->shnum());
399 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
402 Ef_shdr
shdr(v
.data());
403 return shdr
.get_sh_addr();
406 // Return the type of section SHNDX.
408 template<int size
, bool big_endian
, typename File
>
410 Elf_file
<size
, big_endian
, File
>::section_type(unsigned int shndx
)
412 File
* const file
= this->file_
;
414 if (shndx
>= this->shnum())
415 file
->error(_("section_type: bad shndx %u >= %u"),
416 shndx
, this->shnum());
418 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
421 Ef_shdr
shdr(v
.data());
422 return shdr
.get_sh_type();
425 // Return the sh_link field of section SHNDX.
427 template<int size
, bool big_endian
, typename File
>
429 Elf_file
<size
, big_endian
, File
>::section_link(unsigned int shndx
)
431 File
* const file
= this->file_
;
433 if (shndx
>= this->shnum())
434 file
->error(_("section_link: bad shndx %u >= %u"),
435 shndx
, this->shnum());
437 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
440 Ef_shdr
shdr(v
.data());
441 return shdr
.get_sh_link();
444 // Return the sh_info field of section SHNDX.
446 template<int size
, bool big_endian
, typename File
>
448 Elf_file
<size
, big_endian
, File
>::section_info(unsigned int shndx
)
450 File
* const file
= this->file_
;
452 if (shndx
>= this->shnum())
453 file
->error(_("section_info: bad shndx %u >= %u"),
454 shndx
, this->shnum());
456 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
459 Ef_shdr
shdr(v
.data());
460 return shdr
.get_sh_info();
463 // Return the sh_addralign field of section SHNDX.
465 template<int size
, bool big_endian
, typename File
>
466 typename Elf_types
<size
>::Elf_WXword
467 Elf_file
<size
, big_endian
, File
>::section_addralign(unsigned int shndx
)
469 File
* const file
= this->file_
;
471 if (shndx
>= this->shnum())
472 file
->error(_("section_addralign: bad shndx %u >= %u"),
473 shndx
, this->shnum());
475 typename
File::View
v(file
->view(this->section_header_offset(shndx
),
478 Ef_shdr
shdr(v
.data());
479 return shdr
.get_sh_addralign();
482 } // End namespace elfcpp.
484 #endif // !defined(ELFCPP_FILE_H)
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