1 /* $NetBSD: elf_update.c,v 1.2 2014/03/09 16:58:04 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2006-2011 Joseph Koshy
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #if HAVE_NBTOOL_CONFIG_H
30 # include "nbtool_config.h"
31 #endif
32
33 #include <sys/param.h>
34 #include <sys/stat.h>
35
36 #include <assert.h>
37 #include <errno.h>
38 #include <gelf.h>
39 #include <libelf.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include <unistd.h>
43
44 #include "_libelf.h"
45
46 #if ELFTC_HAVE_MMAP
47 #include <sys/mman.h>
48 #endif
49
50 __RCSID("$NetBSD: elf_update.c,v 1.2 2014/03/09 16:58:04 christos Exp $");
51 ELFTC_VCSID("Id: elf_update.c 2931 2013-03-23 11:41:07Z jkoshy ");
52
53 /*
54 * Layout strategy:
55 *
56 * - Case 1: ELF_F_LAYOUT is asserted
57 * In this case the application has full control over where the
58 * section header table, program header table, and section data
59 * will reside. The library only perform error checks.
60 *
61 * - Case 2: ELF_F_LAYOUT is not asserted
62 *
63 * The library will do the object layout using the following
64 * ordering:
65 * - The executable header is placed first, are required by the
66 * ELF specification.
67 * - The program header table is placed immediately following the
68 * executable header.
69 * - Section data, if any, is placed after the program header
70 * table, aligned appropriately.
71 * - The section header table, if needed, is placed last.
72 *
73 * There are two sub-cases to be taken care of:
74 *
75 * - Case 2a: e->e_cmd == ELF_C_READ or ELF_C_RDWR
76 *
77 * In this sub-case, the underlying ELF object may already have
78 * content in it, which the application may have modified. The
79 * library will retrieve content from the existing object as
80 * needed.
81 *
82 * - Case 2b: e->e_cmd == ELF_C_WRITE
83 *
84 * The ELF object is being created afresh in this sub-case;
85 * there is no pre-existing content in the underlying ELF
86 * object.
87 */
88
89 /*
90 * The types of extents in an ELF object.
91 */
92 enum elf_extent {
93 ELF_EXTENT_EHDR,
94 ELF_EXTENT_PHDR,
95 ELF_EXTENT_SECTION,
96 ELF_EXTENT_SHDR
97 };
98
99 /*
100 * A extent descriptor, used when laying out an ELF object.
101 */
102 struct _Elf_Extent {
103 SLIST_ENTRY(_Elf_Extent) ex_next;
104 uint64_t ex_start; /* Start of the region. */
105 uint64_t ex_size; /* The size of the region. */
106 enum elf_extent ex_type; /* Type of region. */
107 void *ex_desc; /* Associated descriptor. */
108 };
109
110 SLIST_HEAD(_Elf_Extent_List, _Elf_Extent);
111
112 /*
113 * Compute the extents of a section, by looking at the data
114 * descriptors associated with it. The function returns 1
115 * if successful, or zero if an error was detected.
116 */
117 static int
_libelf_compute_section_extents(Elf * e,Elf_Scn * s,off_t rc)118 _libelf_compute_section_extents(Elf *e, Elf_Scn *s, off_t rc)
119 {
120 int ec;
121 Elf_Data *d;
122 size_t fsz, msz;
123 uint32_t sh_type;
124 uint64_t d_align;
125 Elf32_Shdr *shdr32;
126 Elf64_Shdr *shdr64;
127 unsigned int elftype;
128 struct _Libelf_Data *ld;
129 uint64_t scn_size, scn_alignment;
130 uint64_t sh_align, sh_entsize, sh_offset, sh_size;
131
132 ec = e->e_class;
133
134 shdr32 = &s->s_shdr.s_shdr32;
135 shdr64 = &s->s_shdr.s_shdr64;
136 if (ec == ELFCLASS32) {
137 sh_type = shdr32->sh_type;
138 sh_align = (uint64_t) shdr32->sh_addralign;
139 sh_entsize = (uint64_t) shdr32->sh_entsize;
140 sh_offset = (uint64_t) shdr32->sh_offset;
141 sh_size = (uint64_t) shdr32->sh_size;
142 } else {
143 sh_type = shdr64->sh_type;
144 sh_align = shdr64->sh_addralign;
145 sh_entsize = shdr64->sh_entsize;
146 sh_offset = shdr64->sh_offset;
147 sh_size = shdr64->sh_size;
148 }
149
150 assert(sh_type != SHT_NULL && sh_type != SHT_NOBITS);
151
152 elftype = _libelf_xlate_shtype(sh_type);
153 if (elftype > ELF_T_LAST) {
154 LIBELF_SET_ERROR(SECTION, 0);
155 return (0);
156 }
157
158 if (sh_align == 0)
159 sh_align = _libelf_falign(elftype, ec);
160
161 /*
162 * Compute the section's size and alignment using the data
163 * descriptors associated with the section.
164 */
165 if (STAILQ_EMPTY(&s->s_data)) {
166 /*
167 * The section's content (if any) has not been read in
168 * yet. If section is not dirty marked dirty, we can
169 * reuse the values in the 'sh_size' and 'sh_offset'
170 * fields of the section header.
171 */
172 if ((s->s_flags & ELF_F_DIRTY) == 0) {
173 /*
174 * If the library is doing the layout, then we
175 * compute the new start offset for the
176 * section based on the current offset and the
177 * section's alignment needs.
178 *
179 * If the application is doing the layout, we
180 * can use the value in the 'sh_offset' field
181 * in the section header directly.
182 */
183 if (e->e_flags & ELF_F_LAYOUT)
184 goto updatedescriptor;
185 else
186 goto computeoffset;
187 }
188
189 /*
190 * Otherwise, we need to bring in the section's data
191 * from the underlying ELF object.
192 */
193 if (e->e_cmd != ELF_C_WRITE && elf_getdata(s, NULL) == NULL)
194 return (0);
195 }
196
197 /*
198 * Loop through the section's data descriptors.
199 */
200 scn_size = 0L;
201 scn_alignment = 0;
202 STAILQ_FOREACH(ld, &s->s_data, d_next) {
203
204 d = &ld->d_data;
205
206 /*
207 * The data buffer's type is known.
208 */
209 if (d->d_type >= ELF_T_NUM) {
210 LIBELF_SET_ERROR(DATA, 0);
211 return (0);
212 }
213
214 /*
215 * The data buffer's version is supported.
216 */
217 if (d->d_version != e->e_version) {
218 LIBELF_SET_ERROR(VERSION, 0);
219 return (0);
220 }
221
222 /*
223 * The buffer's alignment is non-zero and a power of
224 * two.
225 */
226 if ((d_align = d->d_align) == 0 ||
227 (d_align & (d_align - 1))) {
228 LIBELF_SET_ERROR(DATA, 0);
229 return (0);
230 }
231
232 /*
233 * The buffer's size should be a multiple of the
234 * memory size of the underlying type.
235 */
236 msz = _libelf_msize(d->d_type, ec, e->e_version);
237 if (d->d_size % msz) {
238 LIBELF_SET_ERROR(DATA, 0);
239 return (0);
240 }
241
242 /*
243 * If the application is controlling layout, then the
244 * d_offset field should be compatible with the
245 * buffer's specified alignment.
246 */
247 if ((e->e_flags & ELF_F_LAYOUT) &&
248 (d->d_off & (d_align - 1))) {
249 LIBELF_SET_ERROR(LAYOUT, 0);
250 return (0);
251 }
252
253 /*
254 * Compute the section's size.
255 */
256 if (e->e_flags & ELF_F_LAYOUT) {
257 if ((uint64_t) d->d_off + d->d_size > scn_size)
258 scn_size = d->d_off + d->d_size;
259 } else {
260 scn_size = roundup2(scn_size, d->d_align);
261 d->d_off = scn_size;
262 fsz = _libelf_fsize(d->d_type, ec, d->d_version,
263 d->d_size / msz);
264 scn_size += fsz;
265 }
266
267 /*
268 * The section's alignment is the maximum alignment
269 * needed for its data buffers.
270 */
271 if (d_align > scn_alignment)
272 scn_alignment = d_align;
273 }
274
275
276 /*
277 * If the application is requesting full control over the
278 * layout of the section, check the section's specified size,
279 * offsets and alignment for sanity.
280 */
281 if (e->e_flags & ELF_F_LAYOUT) {
282 if (scn_alignment > sh_align || sh_offset % sh_align ||
283 sh_size < scn_size) {
284 LIBELF_SET_ERROR(LAYOUT, 0);
285 return (0);
286 }
287 goto updatedescriptor;
288 }
289
290 /*
291 * Otherwise, compute the values in the section header.
292 *
293 * The section alignment is the maximum alignment for any of
294 * its contained data descriptors.
295 */
296 if (scn_alignment > sh_align)
297 sh_align = scn_alignment;
298
299 /*
300 * If the section entry size is zero, try and fill in an
301 * appropriate entry size. Per the elf(5) manual page
302 * sections without fixed-size entries should have their
303 * 'sh_entsize' field set to zero.
304 */
305 if (sh_entsize == 0 &&
306 (sh_entsize = _libelf_fsize(elftype, ec, e->e_version,
307 (size_t) 1)) == 1)
308 sh_entsize = 0;
309
310 sh_size = scn_size;
311
312 computeoffset:
313 /*
314 * Compute the new offset for the section based on
315 * the section's alignment needs.
316 */
317 sh_offset = roundup(rc, sh_align);
318
319 /*
320 * Update the section header.
321 */
322 if (ec == ELFCLASS32) {
323 shdr32->sh_addralign = (uint32_t) sh_align;
324 shdr32->sh_entsize = (uint32_t) sh_entsize;
325 shdr32->sh_offset = (uint32_t) sh_offset;
326 shdr32->sh_size = (uint32_t) sh_size;
327 } else {
328 shdr64->sh_addralign = sh_align;
329 shdr64->sh_entsize = sh_entsize;
330 shdr64->sh_offset = sh_offset;
331 shdr64->sh_size = sh_size;
332 }
333
334 updatedescriptor:
335 /*
336 * Update the section descriptor.
337 */
338 s->s_size = sh_size;
339 s->s_offset = sh_offset;
340
341 return (1);
342 }
343
344 /*
345 * Free a list of extent descriptors.
346 */
347
348 static void
_libelf_release_extents(struct _Elf_Extent_List * extents)349 _libelf_release_extents(struct _Elf_Extent_List *extents)
350 {
351 struct _Elf_Extent *ex;
352
353 while ((ex = SLIST_FIRST(extents)) != NULL) {
354 SLIST_REMOVE_HEAD(extents, ex_next);
355 free(ex);
356 }
357 }
358
359 /*
360 * Check if an extent 's' defined by [start..start+size) is free.
361 * This routine assumes that the given extent list is sorted in order
362 * of ascending extent offsets.
363 */
364
365 static int
_libelf_extent_is_unused(struct _Elf_Extent_List * extents,const uint64_t start,const uint64_t size,struct _Elf_Extent ** prevt)366 _libelf_extent_is_unused(struct _Elf_Extent_List *extents,
367 const uint64_t start, const uint64_t size, struct _Elf_Extent **prevt)
368 {
369 uint64_t tmax, tmin;
370 struct _Elf_Extent *t, *pt;
371 const uint64_t smax = start + size;
372
373 /* First, look for overlaps with existing extents. */
374 pt = NULL;
375 SLIST_FOREACH(t, extents, ex_next) {
376 tmin = t->ex_start;
377 tmax = tmin + t->ex_size;
378
379 if (tmax <= start) {
380 /*
381 * 't' lies entirely before 's': ...| t |...| s |...
382 */
383 pt = t;
384 continue;
385 } else if (smax <= tmin) {
386 /*
387 * 's' lies entirely before 't', and after 'pt':
388 * ...| pt |...| s |...| t |...
389 */
390 assert(pt == NULL ||
391 pt->ex_start + pt->ex_size <= start);
392 break;
393 } else
394 /* 's' and 't' overlap. */
395 return (0);
396 }
397
398 if (prevt)
399 *prevt = pt;
400 return (1);
401 }
402
403 /*
404 * Insert an extent into the list of extents.
405 */
406
407 static int
_libelf_insert_extent(struct _Elf_Extent_List * extents,int type,uint64_t start,uint64_t size,void * desc)408 _libelf_insert_extent(struct _Elf_Extent_List *extents, int type,
409 uint64_t start, uint64_t size, void *desc)
410 {
411 struct _Elf_Extent *ex, *prevt;
412
413 assert(type >= ELF_EXTENT_EHDR && type <= ELF_EXTENT_SHDR);
414
415 prevt = NULL;
416
417 /*
418 * If the requested range overlaps with an existing extent,
419 * signal an error.
420 */
421 if (!_libelf_extent_is_unused(extents, start, size, &prevt)) {
422 LIBELF_SET_ERROR(LAYOUT, 0);
423 return (0);
424 }
425
426 /* Allocate and fill in a new extent descriptor. */
427 if ((ex = malloc(sizeof(struct _Elf_Extent))) == NULL) {
428 LIBELF_SET_ERROR(RESOURCE, errno);
429 return (0);
430 }
431 ex->ex_start = start;
432 ex->ex_size = size;
433 ex->ex_desc = desc;
434 ex->ex_type = type;
435
436 /* Insert the region descriptor into the list. */
437 if (prevt)
438 SLIST_INSERT_AFTER(prevt, ex, ex_next);
439 else
440 SLIST_INSERT_HEAD(extents, ex, ex_next);
441 return (1);
442 }
443
444 /*
445 * Recompute section layout.
446 */
447
448 static off_t
_libelf_resync_sections(Elf * e,off_t rc,struct _Elf_Extent_List * extents)449 _libelf_resync_sections(Elf *e, off_t rc, struct _Elf_Extent_List *extents)
450 {
451 int ec;
452 Elf_Scn *s;
453 size_t sh_type;
454
455 ec = e->e_class;
456
457 /*
458 * Make a pass through sections, computing the extent of each
459 * section.
460 */
461 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) {
462 if (ec == ELFCLASS32)
463 sh_type = s->s_shdr.s_shdr32.sh_type;
464 else
465 sh_type = s->s_shdr.s_shdr64.sh_type;
466
467 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL)
468 continue;
469
470 if (_libelf_compute_section_extents(e, s, rc) == 0)
471 return ((off_t) -1);
472
473 if (s->s_size == 0)
474 continue;
475
476 if (!_libelf_insert_extent(extents, ELF_EXTENT_SECTION,
477 s->s_offset, s->s_size, s))
478 return ((off_t) -1);
479
480 if ((size_t) rc < s->s_offset + s->s_size)
481 rc = s->s_offset + s->s_size;
482 }
483
484 return (rc);
485 }
486
487 /*
488 * Recompute the layout of the ELF object and update the internal data
489 * structures associated with the ELF descriptor.
490 *
491 * Returns the size in bytes the ELF object would occupy in its file
492 * representation.
493 *
494 * After a successful call to this function, the following structures
495 * are updated:
496 *
497 * - The ELF header is updated.
498 * - All extents in the ELF object are sorted in order of ascending
499 * addresses. Sections have their section header table entries
500 * updated. An error is signalled if an overlap was detected among
501 * extents.
502 * - Data descriptors associated with sections are checked for valid
503 * types, offsets and alignment.
504 *
505 * After a resync_elf() successfully returns, the ELF descriptor is
506 * ready for being handed over to _libelf_write_elf().
507 */
508
509 static off_t
_libelf_resync_elf(Elf * e,struct _Elf_Extent_List * extents)510 _libelf_resync_elf(Elf *e, struct _Elf_Extent_List *extents)
511 {
512 int ec, eh_class;
513 unsigned int eh_byteorder, eh_version;
514 size_t align, fsz;
515 size_t phnum, shnum;
516 off_t rc, phoff, shoff;
517 void *ehdr, *phdr;
518 Elf32_Ehdr *eh32;
519 Elf64_Ehdr *eh64;
520
521 rc = 0;
522
523 ec = e->e_class;
524
525 assert(ec == ELFCLASS32 || ec == ELFCLASS64);
526
527 /*
528 * Prepare the EHDR.
529 */
530 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
531 return ((off_t) -1);
532
533 eh32 = ehdr;
534 eh64 = ehdr;
535
536 if (ec == ELFCLASS32) {
537 eh_byteorder = eh32->e_ident[EI_DATA];
538 eh_class = eh32->e_ident[EI_CLASS];
539 phoff = (uint64_t) eh32->e_phoff;
540 shoff = (uint64_t) eh32->e_shoff;
541 eh_version = eh32->e_version;
542 } else {
543 eh_byteorder = eh64->e_ident[EI_DATA];
544 eh_class = eh64->e_ident[EI_CLASS];
545 phoff = eh64->e_phoff;
546 shoff = eh64->e_shoff;
547 eh_version = eh64->e_version;
548 }
549
550 if (eh_version == EV_NONE)
551 eh_version = EV_CURRENT;
552
553 if (eh_version != e->e_version) { /* always EV_CURRENT */
554 LIBELF_SET_ERROR(VERSION, 0);
555 return ((off_t) -1);
556 }
557
558 if (eh_class != e->e_class) {
559 LIBELF_SET_ERROR(CLASS, 0);
560 return ((off_t) -1);
561 }
562
563 if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) {
564 LIBELF_SET_ERROR(HEADER, 0);
565 return ((off_t) -1);
566 }
567
568 shnum = e->e_u.e_elf.e_nscn;
569 phnum = e->e_u.e_elf.e_nphdr;
570
571 e->e_byteorder = eh_byteorder;
572
573 #define INITIALIZE_EHDR(E,EC,V) do { \
574 (E)->e_ident[EI_MAG0] = ELFMAG0; \
575 (E)->e_ident[EI_MAG1] = ELFMAG1; \
576 (E)->e_ident[EI_MAG2] = ELFMAG2; \
577 (E)->e_ident[EI_MAG3] = ELFMAG3; \
578 (E)->e_ident[EI_CLASS] = (EC); \
579 (E)->e_ident[EI_VERSION] = (V); \
580 (E)->e_ehsize = _libelf_fsize(ELF_T_EHDR, (EC), (V), \
581 (size_t) 1); \
582 (E)->e_phentsize = (phnum == 0) ? 0 : _libelf_fsize( \
583 ELF_T_PHDR, (EC), (V), (size_t) 1); \
584 (E)->e_shentsize = _libelf_fsize(ELF_T_SHDR, (EC), (V), \
585 (size_t) 1); \
586 } while (/*CONSTCOND*/0)
587
588 if (ec == ELFCLASS32)
589 INITIALIZE_EHDR(eh32, ec, eh_version);
590 else
591 INITIALIZE_EHDR(eh64, ec, eh_version);
592
593 (void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY);
594
595 rc += _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1);
596
597 if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, rc, ehdr))
598 return ((off_t) -1);
599
600 /*
601 * Compute the layout the program header table, if one is
602 * present. The program header table needs to be aligned to a
603 * `natural' boundary.
604 */
605 if (phnum) {
606 fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum);
607 align = _libelf_falign(ELF_T_PHDR, ec);
608
609 if (e->e_flags & ELF_F_LAYOUT) {
610 /*
611 * Check offsets for sanity.
612 */
613 if (rc > phoff) {
614 LIBELF_SET_ERROR(LAYOUT, 0);
615 return ((off_t) -1);
616 }
617
618 if (phoff % align) {
619 LIBELF_SET_ERROR(LAYOUT, 0);
620 return ((off_t) -1);
621 }
622
623 } else
624 phoff = roundup(rc, align);
625
626 rc = phoff + fsz;
627
628 phdr = _libelf_getphdr(e, ec);
629
630 if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR, phoff,
631 fsz, phdr))
632 return ((off_t) -1);
633 } else
634 phoff = 0;
635
636 /*
637 * Compute the layout of the sections associated with the
638 * file.
639 */
640
641 if (e->e_cmd != ELF_C_WRITE &&
642 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
643 _libelf_load_section_headers(e, ehdr) == 0)
644 return ((off_t) -1);
645
646 if ((rc = _libelf_resync_sections(e, rc, extents)) < 0)
647 return ((off_t) -1);
648
649 /*
650 * Compute the space taken up by the section header table, if
651 * one is needed.
652 *
653 * If ELF_F_LAYOUT has been asserted, the application may have
654 * placed the section header table in between existing
655 * sections, so the net size of the file need not increase due
656 * to the presence of the section header table.
657 *
658 * If the library is responsible for laying out the object,
659 * the section header table is placed after section data.
660 */
661 if (shnum) {
662 fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum);
663 align = _libelf_falign(ELF_T_SHDR, ec);
664
665 if (e->e_flags & ELF_F_LAYOUT) {
666 if (shoff % align) {
667 LIBELF_SET_ERROR(LAYOUT, 0);
668 return ((off_t) -1);
669 }
670 } else
671 shoff = roundup(rc, align);
672
673 if (shoff + fsz > (size_t) rc)
674 rc = shoff + fsz;
675
676 if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR, shoff,
677 fsz, NULL))
678 return ((off_t) -1);
679 } else
680 shoff = 0;
681
682 /*
683 * Set the fields of the Executable Header that could potentially use
684 * extended numbering.
685 */
686 _libelf_setphnum(e, ehdr, ec, phnum);
687 _libelf_setshnum(e, ehdr, ec, shnum);
688
689 /*
690 * Update the `e_phoff' and `e_shoff' fields if the library is
691 * doing the layout.
692 */
693 if ((e->e_flags & ELF_F_LAYOUT) == 0) {
694 if (ec == ELFCLASS32) {
695 eh32->e_phoff = (uint32_t) phoff;
696 eh32->e_shoff = (uint32_t) shoff;
697 } else {
698 eh64->e_phoff = (uint64_t) phoff;
699 eh64->e_shoff = (uint64_t) shoff;
700 }
701 }
702
703 return (rc);
704 }
705
706 /*
707 * Write out the contents of an ELF section.
708 */
709
710 static size_t
_libelf_write_scn(Elf * e,char * nf,struct _Elf_Extent * ex)711 _libelf_write_scn(Elf *e, char *nf, struct _Elf_Extent *ex)
712 {
713 int ec;
714 Elf_Scn *s;
715 int elftype;
716 Elf_Data *d, dst;
717 uint32_t sh_type;
718 struct _Libelf_Data *ld;
719 uint64_t sh_off, sh_size;
720 size_t fsz, msz, nobjects, rc;
721
722 assert(ex->ex_type == ELF_EXTENT_SECTION);
723
724 s = ex->ex_desc;
725 rc = ex->ex_start;
726
727 if ((ec = e->e_class) == ELFCLASS32) {
728 sh_type = s->s_shdr.s_shdr32.sh_type;
729 sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size;
730 } else {
731 sh_type = s->s_shdr.s_shdr64.sh_type;
732 sh_size = s->s_shdr.s_shdr64.sh_size;
733 }
734
735 /*
736 * Ignore sections that do not allocate space in the file.
737 */
738 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0)
739 return (rc);
740
741 elftype = _libelf_xlate_shtype(sh_type);
742 assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST);
743
744 sh_off = s->s_offset;
745 assert(sh_off % _libelf_falign(elftype, ec) == 0);
746
747 /*
748 * If the section has a `rawdata' descriptor, and the section
749 * contents have not been modified, use its contents directly.
750 * The `s_rawoff' member contains the offset into the original
751 * file, while `s_offset' contains its new location in the
752 * destination.
753 */
754
755 if (STAILQ_EMPTY(&s->s_data)) {
756
757 if ((d = elf_rawdata(s, NULL)) == NULL)
758 return ((off_t) -1);
759
760 STAILQ_FOREACH(ld, &s->s_rawdata, d_next) {
761
762 d = &ld->d_data;
763
764 if ((uint64_t) rc < sh_off + d->d_off)
765 (void) memset(nf + rc,
766 LIBELF_PRIVATE(fillchar), sh_off +
767 d->d_off - rc);
768 rc = sh_off + d->d_off;
769
770 assert(d->d_buf != NULL);
771 assert(d->d_type == ELF_T_BYTE);
772 assert(d->d_version == e->e_version);
773
774 (void) memcpy(nf + rc,
775 e->e_rawfile + s->s_rawoff + d->d_off, d->d_size);
776
777 rc += d->d_size;
778 }
779
780 return (rc);
781 }
782
783 /*
784 * Iterate over the set of data descriptors for this section.
785 * The prior call to _libelf_resync_elf() would have setup the
786 * descriptors for this step.
787 */
788
789 dst.d_version = e->e_version;
790
791 STAILQ_FOREACH(ld, &s->s_data, d_next) {
792
793 d = &ld->d_data;
794
795 msz = _libelf_msize(d->d_type, ec, e->e_version);
796
797 if ((uint64_t) rc < sh_off + d->d_off)
798 (void) memset(nf + rc,
799 LIBELF_PRIVATE(fillchar), sh_off + d->d_off - rc);
800
801 rc = sh_off + d->d_off;
802
803 assert(d->d_buf != NULL);
804 assert(d->d_version == e->e_version);
805 assert(d->d_size % msz == 0);
806
807 nobjects = d->d_size / msz;
808
809 fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects);
810
811 dst.d_buf = nf + rc;
812 dst.d_size = fsz;
813
814 if (_libelf_xlate(&dst, d, e->e_byteorder, ec, ELF_TOFILE) ==
815 NULL)
816 return ((off_t) -1);
817
818 rc += fsz;
819 }
820
821 return ((off_t) rc);
822 }
823
824 /*
825 * Write out an ELF Executable Header.
826 */
827
828 static off_t
_libelf_write_ehdr(Elf * e,char * nf,struct _Elf_Extent * ex)829 _libelf_write_ehdr(Elf *e, char *nf, struct _Elf_Extent *ex)
830 {
831 int ec;
832 void *ehdr;
833 size_t fsz, msz;
834 Elf_Data dst, src;
835
836 assert(ex->ex_type == ELF_EXTENT_EHDR);
837 assert(ex->ex_start == 0); /* Ehdr always comes first. */
838
839 ec = e->e_class;
840
841 ehdr = _libelf_ehdr(e, ec, 0);
842 assert(ehdr != NULL);
843
844 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
845 msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version);
846
847 (void) memset(&dst, 0, sizeof(dst));
848 (void) memset(&src, 0, sizeof(src));
849
850 src.d_buf = ehdr;
851 src.d_size = msz;
852 src.d_type = ELF_T_EHDR;
853 src.d_version = dst.d_version = e->e_version;
854
855 dst.d_buf = nf;
856 dst.d_size = fsz;
857
858 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) ==
859 NULL)
860 return ((off_t) -1);
861
862 return ((off_t) fsz);
863 }
864
865 /*
866 * Write out an ELF program header table.
867 */
868
869 static off_t
_libelf_write_phdr(Elf * e,char * nf,struct _Elf_Extent * ex)870 _libelf_write_phdr(Elf *e, char *nf, struct _Elf_Extent *ex)
871 {
872 int ec;
873 void *ehdr;
874 Elf32_Ehdr *eh32;
875 Elf64_Ehdr *eh64;
876 Elf_Data dst, src;
877 size_t fsz, phnum;
878 uint64_t phoff;
879
880 assert(ex->ex_type == ELF_EXTENT_PHDR);
881
882 ec = e->e_class;
883 ehdr = _libelf_ehdr(e, ec, 0);
884 phnum = e->e_u.e_elf.e_nphdr;
885
886 assert(phnum > 0);
887
888 if (ec == ELFCLASS32) {
889 eh32 = (Elf32_Ehdr *) ehdr;
890 phoff = (uint64_t) eh32->e_phoff;
891 } else {
892 eh64 = (Elf64_Ehdr *) ehdr;
893 phoff = eh64->e_phoff;
894 }
895
896 assert(phoff > 0);
897 assert(ex->ex_start == phoff);
898 assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0);
899
900 (void) memset(&dst, 0, sizeof(dst));
901 (void) memset(&src, 0, sizeof(src));
902
903 fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum);
904 assert(fsz > 0);
905
906 src.d_buf = _libelf_getphdr(e, ec);
907 src.d_version = dst.d_version = e->e_version;
908 src.d_type = ELF_T_PHDR;
909 src.d_size = phnum * _libelf_msize(ELF_T_PHDR, ec,
910 e->e_version);
911
912 dst.d_size = fsz;
913 dst.d_buf = nf + ex->ex_start;
914
915 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) ==
916 NULL)
917 return ((off_t) -1);
918
919 return (phoff + fsz);
920 }
921
922 /*
923 * Write out an ELF section header table.
924 */
925
926 static off_t
_libelf_write_shdr(Elf * e,char * nf,struct _Elf_Extent * ex)927 _libelf_write_shdr(Elf *e, char *nf, struct _Elf_Extent *ex)
928 {
929 int ec;
930 void *ehdr;
931 Elf_Scn *scn;
932 uint64_t shoff;
933 Elf32_Ehdr *eh32;
934 Elf64_Ehdr *eh64;
935 size_t fsz, nscn;
936 Elf_Data dst, src;
937
938 assert(ex->ex_type == ELF_EXTENT_SHDR);
939
940 ec = e->e_class;
941 ehdr = _libelf_ehdr(e, ec, 0);
942 nscn = e->e_u.e_elf.e_nscn;
943
944 if (ec == ELFCLASS32) {
945 eh32 = (Elf32_Ehdr *) ehdr;
946 shoff = (uint64_t) eh32->e_shoff;
947 } else {
948 eh64 = (Elf64_Ehdr *) ehdr;
949 shoff = eh64->e_shoff;
950 }
951
952 assert(nscn > 0);
953 assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0);
954 assert(ex->ex_start == shoff);
955
956 (void) memset(&dst, 0, sizeof(dst));
957 (void) memset(&src, 0, sizeof(src));
958
959 src.d_type = ELF_T_SHDR;
960 src.d_size = _libelf_msize(ELF_T_SHDR, ec, e->e_version);
961 src.d_version = dst.d_version = e->e_version;
962
963 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
964
965 STAILQ_FOREACH(scn, &e->e_u.e_elf.e_scn, s_next) {
966 if (ec == ELFCLASS32)
967 src.d_buf = &scn->s_shdr.s_shdr32;
968 else
969 src.d_buf = &scn->s_shdr.s_shdr64;
970
971 dst.d_size = fsz;
972 dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz;
973
974 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec,
975 ELF_TOFILE) == NULL)
976 return ((off_t) -1);
977 }
978
979 return (ex->ex_start + nscn * fsz);
980 }
981
982 /*
983 * Write out the file image.
984 *
985 * The original file could have been mapped in with an ELF_C_RDWR
986 * command and the application could have added new content or
987 * re-arranged its sections before calling elf_update(). Consequently
988 * its not safe to work `in place' on the original file. So we
989 * malloc() the required space for the updated ELF object and build
990 * the object there and write it out to the underlying file at the
991 * end. Note that the application may have opened the underlying file
992 * in ELF_C_RDWR and only retrieved/modified a few sections. We take
993 * care to avoid translating file sections unnecessarily.
994 *
995 * Gaps in the coverage of the file by the file's sections will be
996 * filled with the fill character set by elf_fill(3).
997 */
998
999 static off_t
_libelf_write_elf(Elf * e,off_t newsize,struct _Elf_Extent_List * extents)1000 _libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents)
1001 {
1002 off_t nrc, rc;
1003 char *newfile;
1004 Elf_Scn *scn, *tscn;
1005 struct _Elf_Extent *ex;
1006
1007 assert(e->e_kind == ELF_K_ELF);
1008 assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE);
1009 assert(e->e_fd >= 0);
1010
1011 if ((newfile = malloc((size_t) newsize)) == NULL) {
1012 LIBELF_SET_ERROR(RESOURCE, errno);
1013 return ((off_t) -1);
1014 }
1015
1016 nrc = rc = 0;
1017 SLIST_FOREACH(ex, extents, ex_next) {
1018
1019 /* Fill inter-extent gaps. */
1020 if (ex->ex_start > (size_t) rc)
1021 (void) memset(newfile + rc, LIBELF_PRIVATE(fillchar),
1022 ex->ex_start - rc);
1023
1024 switch (ex->ex_type) {
1025 case ELF_EXTENT_EHDR:
1026 if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0)
1027 goto error;
1028 break;
1029
1030 case ELF_EXTENT_PHDR:
1031 if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0)
1032 goto error;
1033 break;
1034
1035 case ELF_EXTENT_SECTION:
1036 if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0)
1037 goto error;
1038 break;
1039
1040 case ELF_EXTENT_SHDR:
1041 if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0)
1042 goto error;
1043 break;
1044
1045 default:
1046 assert(0);
1047 break;
1048 }
1049
1050 assert(ex->ex_start + ex->ex_size == (size_t) nrc);
1051 assert(rc < nrc);
1052
1053 rc = nrc;
1054 }
1055
1056 assert(rc == newsize);
1057
1058 /*
1059 * For regular files, throw away existing file content and
1060 * unmap any existing mappings.
1061 */
1062 if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) {
1063 if (ftruncate(e->e_fd, (off_t) 0) < 0 ||
1064 lseek(e->e_fd, (off_t) 0, SEEK_SET)) {
1065 LIBELF_SET_ERROR(IO, errno);
1066 goto error;
1067 }
1068 #if ELFTC_HAVE_MMAP
1069 if (e->e_flags & LIBELF_F_RAWFILE_MMAP) {
1070 assert(e->e_rawfile != NULL);
1071 assert(e->e_cmd == ELF_C_RDWR);
1072 if (munmap(e->e_rawfile, e->e_rawsize) < 0) {
1073 LIBELF_SET_ERROR(IO, errno);
1074 goto error;
1075 }
1076 }
1077 #endif
1078 }
1079
1080 /*
1081 * Write out the new contents.
1082 */
1083 if (write(e->e_fd, newfile, (size_t) newsize) != newsize) {
1084 LIBELF_SET_ERROR(IO, errno);
1085 goto error;
1086 }
1087
1088 /*
1089 * For files opened in ELF_C_RDWR mode, set up the new 'raw'
1090 * contents.
1091 */
1092 if (e->e_cmd == ELF_C_RDWR) {
1093 assert(e->e_rawfile != NULL);
1094 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) ||
1095 (e->e_flags & LIBELF_F_RAWFILE_MMAP));
1096 if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) {
1097 free(e->e_rawfile);
1098 e->e_rawfile = newfile;
1099 newfile = NULL;
1100 }
1101 #if ELFTC_HAVE_MMAP
1102 else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) {
1103 if ((e->e_rawfile = mmap(NULL, (size_t) newsize,
1104 PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) ==
1105 MAP_FAILED) {
1106 LIBELF_SET_ERROR(IO, errno);
1107 goto error;
1108 }
1109 }
1110 #endif /* ELFTC_HAVE_MMAP */
1111
1112 /* Record the new size of the file. */
1113 e->e_rawsize = newsize;
1114 } else {
1115 /* File opened in ELF_C_WRITE mode. */
1116 assert(e->e_rawfile == NULL);
1117 }
1118
1119 /*
1120 * Reset flags, remove existing section descriptors and
1121 * {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr()
1122 * and elf_getscn() will function correctly.
1123 */
1124
1125 e->e_flags &= ~ELF_F_DIRTY;
1126
1127 STAILQ_FOREACH_SAFE(scn, &e->e_u.e_elf.e_scn, s_next, tscn)
1128 _libelf_release_scn(scn);
1129
1130 if (e->e_class == ELFCLASS32) {
1131 free(e->e_u.e_elf.e_ehdr.e_ehdr32);
1132 if (e->e_u.e_elf.e_phdr.e_phdr32)
1133 free(e->e_u.e_elf.e_phdr.e_phdr32);
1134
1135 e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL;
1136 e->e_u.e_elf.e_phdr.e_phdr32 = NULL;
1137 } else {
1138 free(e->e_u.e_elf.e_ehdr.e_ehdr64);
1139 if (e->e_u.e_elf.e_phdr.e_phdr64)
1140 free(e->e_u.e_elf.e_phdr.e_phdr64);
1141
1142 e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL;
1143 e->e_u.e_elf.e_phdr.e_phdr64 = NULL;
1144 }
1145
1146 /* Free the temporary buffer. */
1147 if (newfile)
1148 free(newfile);
1149
1150 return (rc);
1151
1152 error:
1153 free(newfile);
1154
1155 return ((off_t) -1);
1156 }
1157
1158 /*
1159 * Update an ELF object.
1160 */
1161
1162 off_t
elf_update(Elf * e,Elf_Cmd c)1163 elf_update(Elf *e, Elf_Cmd c)
1164 {
1165 int ec;
1166 off_t rc;
1167 struct _Elf_Extent_List extents;
1168
1169 rc = (off_t) -1;
1170
1171 if (e == NULL || e->e_kind != ELF_K_ELF ||
1172 (c != ELF_C_NULL && c != ELF_C_WRITE)) {
1173 LIBELF_SET_ERROR(ARGUMENT, 0);
1174 return (rc);
1175 }
1176
1177 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
1178 LIBELF_SET_ERROR(CLASS, 0);
1179 return (rc);
1180 }
1181
1182 if (e->e_version == EV_NONE)
1183 e->e_version = EV_CURRENT;
1184
1185 if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) {
1186 LIBELF_SET_ERROR(MODE, 0);
1187 return (rc);
1188 }
1189
1190 SLIST_INIT(&extents);
1191
1192 if ((rc = _libelf_resync_elf(e, &extents)) < 0)
1193 goto done;
1194
1195 if (c == ELF_C_NULL)
1196 goto done;
1197
1198 if (e->e_fd < 0) {
1199 rc = (off_t) -1;
1200 LIBELF_SET_ERROR(SEQUENCE, 0);
1201 goto done;
1202 }
1203
1204 rc = _libelf_write_elf(e, rc, &extents);
1205
1206 done:
1207 _libelf_release_extents(&extents);
1208 return (rc);
1209 }
1210