]>
Commit | Line | Data |
---|---|---|
36a8fdfd DL |
1 | # FRR libelf wrapper |
2 | # | |
3 | # Copyright (C) 2020 David Lamparter for NetDEF, Inc. | |
4 | # | |
5 | # This program is free software; you can redistribute it and/or modify it | |
6 | # under the terms of the GNU General Public License as published by the Free | |
7 | # Software Foundation; either version 2 of the License, or (at your option) | |
8 | # any later version. | |
9 | # | |
10 | # This program is distributed in the hope that it will be useful, but WITHOUT | |
11 | # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
12 | # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for | |
13 | # more details. | |
14 | # | |
15 | # You should have received a copy of the GNU General Public License along | |
16 | # with this program; see the file COPYING; if not, write to the Free Software | |
17 | # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA | |
18 | ||
00f0c399 | 19 | """ |
36a8fdfd DL |
20 | Wrapping layer and additional utility around _clippy.ELFFile. |
21 | ||
22 | Essentially, the C bits have the low-level ELF access bits that should be | |
23 | fast while this has the bits that string everything together (and would've | |
24 | been a PITA to do in C.) | |
25 | ||
26 | Surprisingly - or maybe through proper engineering - this actually works | |
27 | across architecture, word size and even endianness boundaries. Both the C | |
28 | module (through GElf_*) and this code (cf. struct.unpack format mangling | |
29 | in ELFDissectStruct) will take appropriate measures to flip and resize | |
30 | fields as needed. | |
00f0c399 | 31 | """ |
36a8fdfd DL |
32 | |
33 | import struct | |
34 | from collections import OrderedDict | |
35 | from weakref import WeakValueDictionary | |
36 | ||
37 | from _clippy import ELFFile, ELFAccessError | |
38 | ||
39 | # | |
40 | # data access | |
41 | # | |
42 | ||
00f0c399 | 43 | |
36a8fdfd | 44 | class ELFNull(object): |
00f0c399 | 45 | """ |
36a8fdfd | 46 | NULL pointer, returned instead of ELFData |
00f0c399 DL |
47 | """ |
48 | ||
36a8fdfd DL |
49 | def __init__(self): |
50 | self.symname = None | |
51 | self._dstsect = None | |
52 | ||
53 | def __repr__(self): | |
00f0c399 | 54 | return "<ptr: NULL>" |
36a8fdfd DL |
55 | |
56 | def __hash__(self): | |
57 | return hash(None) | |
58 | ||
59 | def get_string(self): | |
60 | return None | |
61 | ||
00f0c399 | 62 | |
36a8fdfd | 63 | class ELFUnresolved(object): |
00f0c399 | 64 | """ |
36a8fdfd DL |
65 | Reference to an unresolved external symbol, returned instead of ELFData |
66 | ||
67 | :param symname: name of the referenced symbol | |
68 | :param addend: offset added to the symbol, normally zero | |
00f0c399 DL |
69 | """ |
70 | ||
36a8fdfd DL |
71 | def __init__(self, symname, addend): |
72 | self.addend = addend | |
73 | self.symname = symname | |
74 | self._dstsect = None | |
75 | ||
76 | def __repr__(self): | |
00f0c399 | 77 | return "<unresolved: %s+%d>" % (self.symname, self.addend) |
36a8fdfd DL |
78 | |
79 | def __hash__(self): | |
80 | return hash((self.symname, self.addend)) | |
81 | ||
00f0c399 | 82 | |
36a8fdfd | 83 | class ELFData(object): |
00f0c399 | 84 | """ |
36a8fdfd DL |
85 | Actual data somewhere in the ELF file. |
86 | ||
87 | :type dstsect: ELFSubset | |
88 | :param dstsect: container data area (section or entire file) | |
89 | :param dstoffs: byte offset into dstsect | |
90 | :param dstlen: byte size of object, or None if unknown, open-ended or string | |
00f0c399 DL |
91 | """ |
92 | ||
36a8fdfd DL |
93 | def __init__(self, dstsect, dstoffs, dstlen): |
94 | self._dstsect = dstsect | |
95 | self._dstoffs = dstoffs | |
96 | self._dstlen = dstlen | |
97 | self.symname = None | |
98 | ||
99 | def __repr__(self): | |
00f0c399 DL |
100 | return "<ptr: %s+0x%05x/%d>" % ( |
101 | self._dstsect.name, | |
102 | self._dstoffs, | |
103 | self._dstlen or -1, | |
104 | ) | |
36a8fdfd DL |
105 | |
106 | def __hash__(self): | |
107 | return hash((self._dstsect, self._dstoffs)) | |
108 | ||
109 | def get_string(self): | |
00f0c399 | 110 | """ |
36a8fdfd | 111 | Interpret as C string / null terminated UTF-8 and get the actual text. |
00f0c399 | 112 | """ |
36a8fdfd | 113 | try: |
00f0c399 | 114 | return self._dstsect[self._dstoffs : str].decode("UTF-8") |
36a8fdfd | 115 | except: |
00f0c399 DL |
116 | import pdb |
117 | ||
118 | pdb.set_trace() | |
36a8fdfd DL |
119 | |
120 | def get_data(self, reflen): | |
00f0c399 | 121 | """ |
36a8fdfd DL |
122 | Interpret as some structure (and check vs. expected length) |
123 | ||
124 | :param reflen: expected size of the object, compared against actual | |
125 | size (which is only known in rare cases, mostly when directly | |
126 | accessing a symbol since symbols have their destination object | |
127 | size recorded) | |
00f0c399 | 128 | """ |
36a8fdfd | 129 | if self._dstlen is not None and self._dstlen != reflen: |
00f0c399 DL |
130 | raise ValueError( |
131 | "symbol size mismatch (got %d, expected %d)" % (self._dstlen, reflen) | |
132 | ) | |
133 | return self._dstsect[self._dstoffs : self._dstoffs + reflen] | |
36a8fdfd DL |
134 | |
135 | def offset(self, offs, within_symbol=False): | |
00f0c399 | 136 | """ |
36a8fdfd DL |
137 | Get another ELFData at an offset |
138 | ||
139 | :param offs: byte offset, can be negative (e.g. in container_of) | |
140 | :param within_symbol: retain length information | |
00f0c399 | 141 | """ |
36a8fdfd DL |
142 | if self._dstlen is None or not within_symbol: |
143 | return ELFData(self._dstsect, self._dstoffs + offs, None) | |
144 | else: | |
145 | return ELFData(self._dstsect, self._dstoffs + offs, self._dstlen - offs) | |
146 | ||
00f0c399 | 147 | |
36a8fdfd DL |
148 | # |
149 | # dissection data items | |
150 | # | |
151 | ||
00f0c399 | 152 | |
36a8fdfd | 153 | class ELFDissectData(object): |
00f0c399 | 154 | """ |
36a8fdfd | 155 | Common bits for ELFDissectStruct and ELFDissectUnion |
00f0c399 | 156 | """ |
36a8fdfd DL |
157 | |
158 | def __len__(self): | |
00f0c399 | 159 | """ |
36a8fdfd | 160 | Used for boolean evaluation, e.g. "if struct: ..." |
00f0c399 DL |
161 | """ |
162 | return not ( | |
163 | isinstance(self._data, ELFNull) or isinstance(self._data, ELFUnresolved) | |
164 | ) | |
36a8fdfd DL |
165 | |
166 | def container_of(self, parent, fieldname): | |
00f0c399 | 167 | """ |
36a8fdfd DL |
168 | Assume this struct is embedded in a larger struct and get at the larger |
169 | ||
170 | Python ``self.container_of(a, b)`` = C ``container_of(self, a, b)`` | |
171 | ||
172 | :param parent: class (not instance) of the larger struct | |
173 | :param fieldname: fieldname that refers back to this | |
174 | :returns: instance of parent, with fieldname set to this object | |
00f0c399 | 175 | """ |
36a8fdfd | 176 | offset = 0 |
00f0c399 | 177 | if not hasattr(parent, "_efields"): |
36a8fdfd DL |
178 | parent._setup_efields() |
179 | ||
180 | for field in parent._efields[self.elfclass]: | |
181 | if field[0] == fieldname: | |
182 | break | |
b17f302b | 183 | spec = field[1] |
00f0c399 DL |
184 | if spec == "P": |
185 | spec = "I" if self.elfclass == 32 else "Q" | |
b17f302b | 186 | offset += struct.calcsize(spec) |
36a8fdfd | 187 | else: |
00f0c399 DL |
188 | raise AttributeError("%r not found in %r.fields" % (fieldname, parent)) |
189 | ||
190 | return parent(self._data.offset(-offset), replace={fieldname: self}) | |
36a8fdfd | 191 | |
36a8fdfd DL |
192 | |
193 | class ELFDissectStruct(ELFDissectData): | |
00f0c399 | 194 | """ |
36a8fdfd DL |
195 | Decode and provide access to a struct somewhere in the ELF file |
196 | ||
197 | Handles pointers and strings somewhat nicely. Create a subclass for each | |
198 | struct that is to be accessed, and give a field list in a "fields" | |
199 | class-member. | |
200 | ||
201 | :param dataptr: ELFData referring to the data bits to decode. | |
202 | :param parent: where this was instantiated from; only for reference, has | |
203 | no functional impact. | |
204 | :param replace: substitute data values for specific fields. Used by | |
205 | `container_of` to replace the inner struct when creating the outer | |
206 | one. | |
207 | ||
208 | .. attribute:: fields | |
209 | ||
210 | List of tuples describing the struct members. Items can be: | |
211 | - ``('name', ELFDissectData)`` - directly embed another struct | |
212 | - ``('name', 'I')`` - simple data types; second item for struct.unpack | |
213 | - ``('name', 'I', None)`` - field to ignore | |
214 | - ``('name', 'P', str)`` - pointer to string | |
215 | - ``('name', 'P', ELFDissectData)`` - pointer to another struct | |
216 | ||
217 | ``P`` is added as unpack format for pointers (sized appropriately for | |
218 | the ELF file.) | |
219 | ||
220 | Refer to tiabwarfo.py for extracting this from ``pahole``. | |
221 | ||
222 | TBD: replace tuples with a class. | |
223 | ||
224 | .. attribute:: fieldrename | |
225 | ||
226 | Dictionary to rename fields, useful if fields comes from tiabwarfo.py. | |
00f0c399 | 227 | """ |
36a8fdfd DL |
228 | |
229 | class Pointer(object): | |
00f0c399 | 230 | """ |
36a8fdfd DL |
231 | Quick wrapper for pointers to further structs |
232 | ||
233 | This is just here to avoid going into infinite loops when loading | |
234 | structs that have pointers to each other (e.g. struct xref <--> | |
235 | struct xrefdata.) The pointer destination is only instantiated when | |
236 | actually accessed. | |
00f0c399 DL |
237 | """ |
238 | ||
36a8fdfd DL |
239 | def __init__(self, cls, ptr): |
240 | self.cls = cls | |
241 | self.ptr = ptr | |
242 | ||
243 | def __repr__(self): | |
00f0c399 | 244 | return "<Pointer:%s %r>" % (self.cls.__name__, self.ptr) |
36a8fdfd DL |
245 | |
246 | def __call__(self): | |
247 | if isinstance(self.ptr, ELFNull): | |
248 | return None | |
249 | return self.cls(self.ptr) | |
250 | ||
00f0c399 | 251 | def __new__(cls, dataptr, parent=None, replace=None): |
36a8fdfd DL |
252 | if dataptr._dstsect is None: |
253 | return super().__new__(cls) | |
254 | ||
255 | obj = dataptr._dstsect._pointers.get((cls, dataptr)) | |
256 | if obj is not None: | |
257 | return obj | |
258 | obj = super().__new__(cls) | |
259 | dataptr._dstsect._pointers[(cls, dataptr)] = obj | |
260 | return obj | |
261 | ||
00f0c399 | 262 | replacements = "lLnN" |
36a8fdfd DL |
263 | |
264 | @classmethod | |
265 | def _preproc_structspec(cls, elfclass, spec): | |
266 | elfbits = elfclass | |
267 | ||
00f0c399 DL |
268 | if hasattr(spec, "calcsize"): |
269 | spec = "%ds" % (spec.calcsize(elfclass),) | |
36a8fdfd DL |
270 | |
271 | if elfbits == 32: | |
00f0c399 | 272 | repl = ["i", "I"] |
36a8fdfd | 273 | else: |
00f0c399 | 274 | repl = ["q", "Q"] |
36a8fdfd DL |
275 | for c in cls.replacements: |
276 | spec = spec.replace(c, repl[int(c.isupper())]) | |
277 | return spec | |
278 | ||
279 | @classmethod | |
280 | def _setup_efields(cls): | |
281 | cls._efields = {} | |
282 | cls._esize = {} | |
283 | for elfclass in [32, 64]: | |
284 | cls._efields[elfclass] = [] | |
285 | size = 0 | |
286 | for f in cls.fields: | |
287 | newf = (f[0], cls._preproc_structspec(elfclass, f[1])) + f[2:] | |
288 | cls._efields[elfclass].append(newf) | |
289 | size += struct.calcsize(newf[1]) | |
290 | cls._esize[elfclass] = size | |
291 | ||
00f0c399 DL |
292 | def __init__(self, dataptr, parent=None, replace=None): |
293 | if not hasattr(self.__class__, "_efields"): | |
36a8fdfd DL |
294 | self._setup_efields() |
295 | ||
296 | self._fdata = None | |
297 | self._data = dataptr | |
298 | self._parent = parent | |
299 | self.symname = dataptr.symname | |
300 | if isinstance(dataptr, ELFNull) or isinstance(dataptr, ELFUnresolved): | |
301 | self._fdata = {} | |
302 | return | |
303 | ||
304 | self._elfsect = dataptr._dstsect | |
305 | self.elfclass = self._elfsect._elffile.elfclass | |
306 | self.offset = dataptr._dstoffs | |
307 | ||
308 | pspecl = [f[1] for f in self._efields[self.elfclass]] | |
309 | ||
310 | # need to correlate output from struct.unpack with extra metadata | |
311 | # about the particular fields, so note down byte offsets (in locs) | |
312 | # and tuple indices of pointers (in ptrs) | |
00f0c399 | 313 | pspec = "" |
36a8fdfd DL |
314 | locs = {} |
315 | ptrs = set() | |
316 | ||
317 | for idx, spec in enumerate(pspecl): | |
00f0c399 | 318 | if spec == "P": |
36a8fdfd DL |
319 | ptrs.add(idx) |
320 | spec = self._elfsect.ptrtype | |
321 | ||
322 | locs[idx] = struct.calcsize(pspec) | |
323 | pspec = pspec + spec | |
324 | ||
325 | self._total_size = struct.calcsize(pspec) | |
326 | ||
327 | def replace_ptrs(v): | |
328 | idx, val = v[0], v[1] | |
329 | if idx not in ptrs: | |
330 | return val | |
331 | return self._elfsect.pointer(self.offset + locs[idx]) | |
332 | ||
333 | data = dataptr.get_data(struct.calcsize(pspec)) | |
334 | unpacked = struct.unpack(self._elfsect.endian + pspec, data) | |
335 | unpacked = list(map(replace_ptrs, enumerate(unpacked))) | |
336 | self._fraw = unpacked | |
337 | self._fdata = OrderedDict() | |
338 | replace = replace or {} | |
339 | ||
340 | for i, item in enumerate(unpacked): | |
341 | name = self.fields[i][0] | |
342 | if name is None: | |
343 | continue | |
344 | ||
345 | if name in replace: | |
346 | self._fdata[name] = replace[name] | |
347 | continue | |
348 | ||
00f0c399 DL |
349 | if isinstance(self.fields[i][1], type) and issubclass( |
350 | self.fields[i][1], ELFDissectData | |
351 | ): | |
36a8fdfd DL |
352 | dataobj = self.fields[i][1](dataptr.offset(locs[i]), self) |
353 | self._fdata[name] = dataobj | |
354 | continue | |
355 | if len(self.fields[i]) == 3: | |
356 | if self.fields[i][2] == str: | |
357 | self._fdata[name] = item.get_string() | |
358 | continue | |
359 | elif self.fields[i][2] is None: | |
360 | pass | |
361 | elif issubclass(self.fields[i][2], ELFDissectData): | |
362 | cls = self.fields[i][2] | |
363 | dataobj = self.Pointer(cls, item) | |
364 | self._fdata[name] = dataobj | |
365 | continue | |
366 | ||
367 | self._fdata[name] = item | |
368 | ||
369 | def __getattr__(self, attrname): | |
370 | if attrname not in self._fdata: | |
371 | raise AttributeError(attrname) | |
372 | if isinstance(self._fdata[attrname], self.Pointer): | |
373 | self._fdata[attrname] = self._fdata[attrname]() | |
374 | return self._fdata[attrname] | |
375 | ||
376 | def __repr__(self): | |
377 | if not isinstance(self._data, ELFData): | |
00f0c399 DL |
378 | return "<%s: %r>" % (self.__class__.__name__, self._data) |
379 | return "<%s: %s>" % ( | |
380 | self.__class__.__name__, | |
381 | ", ".join(["%s=%r" % t for t in self._fdata.items()]), | |
382 | ) | |
36a8fdfd DL |
383 | |
384 | @classmethod | |
385 | def calcsize(cls, elfclass): | |
00f0c399 | 386 | """ |
36a8fdfd DL |
387 | Sum up byte size of this struct |
388 | ||
389 | Wraps struct.calcsize with some extra features. | |
00f0c399 DL |
390 | """ |
391 | if not hasattr(cls, "_efields"): | |
36a8fdfd DL |
392 | cls._setup_efields() |
393 | ||
00f0c399 | 394 | pspec = "".join([f[1] for f in cls._efields[elfclass]]) |
36a8fdfd | 395 | |
00f0c399 DL |
396 | ptrtype = "I" if elfclass == 32 else "Q" |
397 | pspec = pspec.replace("P", ptrtype) | |
36a8fdfd DL |
398 | |
399 | return struct.calcsize(pspec) | |
400 | ||
00f0c399 | 401 | |
36a8fdfd | 402 | class ELFDissectUnion(ELFDissectData): |
00f0c399 | 403 | """ |
36a8fdfd DL |
404 | Decode multiple structs in the same place. |
405 | ||
406 | Not currently used (and hence not tested.) Worked at some point but not | |
407 | needed anymore and may be borked now. Remove this comment when using. | |
00f0c399 DL |
408 | """ |
409 | ||
410 | def __init__(self, dataptr, parent=None): | |
36a8fdfd DL |
411 | self._dataptr = dataptr |
412 | self._parent = parent | |
413 | self.members = [] | |
414 | for name, membercls in self.__class__.members: | |
415 | item = membercls(dataptr, parent) | |
416 | self.members.append(item) | |
417 | setattr(self, name, item) | |
418 | ||
419 | def __repr__(self): | |
00f0c399 DL |
420 | return "<%s: %s>" % ( |
421 | self.__class__.__name__, | |
422 | ", ".join([repr(i) for i in self.members]), | |
423 | ) | |
36a8fdfd DL |
424 | |
425 | @classmethod | |
426 | def calcsize(cls, elfclass): | |
427 | return max([member.calcsize(elfclass) for name, member in cls.members]) | |
428 | ||
00f0c399 | 429 | |
36a8fdfd DL |
430 | # |
431 | # wrappers for spans of ELF data | |
432 | # | |
433 | ||
00f0c399 | 434 | |
36a8fdfd | 435 | class ELFSubset(object): |
00f0c399 | 436 | """ |
36a8fdfd | 437 | Common abstract base for section-level and file-level access. |
00f0c399 | 438 | """ |
36a8fdfd DL |
439 | |
440 | def __init__(self): | |
441 | super().__init__() | |
442 | ||
443 | self._pointers = WeakValueDictionary() | |
444 | ||
445 | def __hash__(self): | |
446 | return hash(self.name) | |
447 | ||
448 | def __getitem__(self, k): | |
00f0c399 | 449 | """ |
36a8fdfd DL |
450 | Read data from slice |
451 | ||
452 | Subscript **must** be a slice; a simple index will not return a byte | |
453 | but rather throw an exception. Valid slice syntaxes are defined by | |
454 | the C module: | |
455 | ||
456 | - `this[123:456]` - extract specific range | |
457 | - `this[123:str]` - extract until null byte. The slice stop value is | |
458 | the `str` type (or, technically, `unicode`.) | |
00f0c399 | 459 | """ |
36a8fdfd DL |
460 | return self._obj[k] |
461 | ||
462 | def getreloc(self, offset): | |
00f0c399 | 463 | """ |
36a8fdfd | 464 | Check for a relocation record at the specified offset. |
00f0c399 | 465 | """ |
36a8fdfd DL |
466 | return self._obj.getreloc(offset) |
467 | ||
00f0c399 DL |
468 | def iter_data(self, scls, slice_=slice(None)): |
469 | """ | |
36a8fdfd DL |
470 | Assume an array of structs present at a particular slice and decode |
471 | ||
472 | :param scls: ELFDissectData subclass for the struct | |
473 | :param slice_: optional range specification | |
00f0c399 | 474 | """ |
36a8fdfd DL |
475 | size = scls.calcsize(self._elffile.elfclass) |
476 | ||
477 | offset = slice_.start or 0 | |
478 | stop = slice_.stop or self._obj.len | |
479 | if stop < 0: | |
480 | stop = self._obj.len - stop | |
481 | ||
482 | while offset < stop: | |
483 | yield scls(ELFData(self, offset, size)) | |
484 | offset += size | |
485 | ||
486 | def pointer(self, offset): | |
00f0c399 | 487 | """ |
36a8fdfd DL |
488 | Try to dereference a pointer value |
489 | ||
490 | This checks whether there's a relocation at the given offset and | |
491 | uses that; otherwise (e.g. in a non-PIE executable where the pointer | |
492 | is already resolved by the linker) the data at the location is used. | |
493 | ||
494 | :param offset: byte offset from beginning of section, | |
495 | or virtual address in file | |
496 | :returns: ELFData wrapping pointed-to object | |
00f0c399 | 497 | """ |
36a8fdfd DL |
498 | |
499 | ptrsize = struct.calcsize(self.ptrtype) | |
00f0c399 DL |
500 | data = struct.unpack( |
501 | self.endian + self.ptrtype, self[offset : offset + ptrsize] | |
502 | )[0] | |
36a8fdfd DL |
503 | |
504 | reloc = self.getreloc(offset) | |
505 | dstsect = None | |
506 | if reloc: | |
507 | # section won't be available in whole-file operation | |
508 | dstsect = reloc.getsection(data) | |
509 | addend = reloc.r_addend | |
510 | ||
511 | if reloc.relative: | |
512 | # old-style ELF REL instead of RELA, not well-tested | |
513 | addend += data | |
514 | ||
515 | if reloc.unresolved and reloc.symvalid: | |
516 | return ELFUnresolved(reloc.symname, addend) | |
517 | elif reloc.symvalid: | |
518 | data = addend + reloc.st_value | |
519 | else: | |
520 | data = addend | |
521 | ||
522 | # 0 could technically be a valid pointer for a shared library, | |
523 | # since libraries may use 0 as default virtual start address (it'll | |
524 | # be adjusted on loading) | |
525 | # That said, if the library starts at 0, that's where the ELF header | |
526 | # would be so it's still an invalid pointer. | |
527 | if data == 0 and dstsect == None: | |
528 | return ELFNull() | |
529 | ||
530 | # wrap_data is different between file & section | |
531 | return self._wrap_data(data, dstsect) | |
532 | ||
00f0c399 | 533 | |
36a8fdfd | 534 | class ELFDissectSection(ELFSubset): |
00f0c399 | 535 | """ |
36a8fdfd DL |
536 | Access the contents of an ELF section like ``.text`` or ``.data`` |
537 | ||
538 | :param elfwrap: ELFDissectFile wrapper for the file | |
539 | :param idx: section index in section header table | |
540 | :param section: section object from C module | |
00f0c399 | 541 | """ |
36a8fdfd DL |
542 | |
543 | def __init__(self, elfwrap, idx, section): | |
544 | super().__init__() | |
545 | ||
546 | self._elfwrap = elfwrap | |
547 | self._elffile = elfwrap._elffile | |
548 | self._idx = idx | |
549 | self._section = self._obj = section | |
550 | self.name = section.name | |
551 | self.ptrtype = elfwrap.ptrtype | |
552 | self.endian = elfwrap.endian | |
553 | ||
554 | def _wrap_data(self, data, dstsect): | |
555 | if dstsect is None: | |
556 | dstsect = self._elfwrap._elffile.get_section_addr(data) | |
557 | offs = data - dstsect.sh_addr | |
558 | dstsect = self._elfwrap.get_section(dstsect.idx) | |
559 | return ELFData(dstsect, offs, None) | |
560 | ||
00f0c399 | 561 | |
36a8fdfd | 562 | class ELFDissectFile(ELFSubset): |
00f0c399 | 563 | """ |
36a8fdfd DL |
564 | Access the contents of an ELF file. |
565 | ||
566 | Note that offsets for array subscript and relocation/pointer access are | |
567 | based on the file's virtual address space and are NOT offsets to the | |
568 | start of the file on disk! | |
569 | ||
570 | (Shared libraries frequently have a virtual address space starting at 0, | |
571 | but non-PIE executables have an architecture specific default loading | |
572 | address like 0x400000 on x86. | |
573 | ||
574 | :param filename: ELF file to open | |
00f0c399 | 575 | """ |
36a8fdfd DL |
576 | |
577 | def __init__(self, filename): | |
578 | super().__init__() | |
579 | ||
580 | self.name = filename | |
581 | self._elffile = self._obj = ELFFile(filename) | |
582 | self._sections = {} | |
583 | ||
00f0c399 DL |
584 | self.ptrtype = "I" if self._elffile.elfclass == 32 else "Q" |
585 | self.endian = ">" if self._elffile.bigendian else "<" | |
36a8fdfd DL |
586 | |
587 | @property | |
588 | def _elfwrap(self): | |
589 | return self | |
590 | ||
591 | def _wrap_data(self, data, dstsect): | |
592 | return ELFData(self, data, None) | |
593 | ||
594 | def get_section(self, secname): | |
00f0c399 | 595 | """ |
36a8fdfd | 596 | Look up section by name or index |
00f0c399 | 597 | """ |
36a8fdfd DL |
598 | if isinstance(secname, int): |
599 | sh_idx = secname | |
600 | section = self._elffile.get_section_idx(secname) | |
601 | else: | |
602 | section = self._elffile.get_section(secname) | |
603 | ||
604 | if section is None: | |
605 | return None | |
606 | ||
607 | sh_idx = section.idx | |
608 | ||
609 | if sh_idx not in self._sections: | |
610 | self._sections[sh_idx] = ELFDissectSection(self, sh_idx, section) | |
611 | ||
612 | return self._sections[sh_idx] |