aboutsummaryrefslogtreecommitdiffstats
path: root/util/cbfstool/elfheaders.c
blob: d217aac0cd05c75f8f70035c0a2f938d27b1ef26 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
/*
 * elf header parsing.
 *
 * Copyright (C) 2013 Google, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "elfparsing.h"
#include "common.h"
#include "cbfs.h"

/*
 * Short form: this is complicated, but we've tried making it simple
 * and we keep hitting problems with our ELF parsing.
 *
 * The ELF parsing situation has always been a bit tricky.  In fact,
 * we (and most others) have been getting it wrong in small ways for
 * years. Recently this has caused real trouble for the ARM V8 build.
 * In this file we attempt to finally get it right for all variations
 * of endian-ness and word size and target architectures and
 * architectures we might get run on. Phew!. To do this we borrow a
 * page from the FreeBSD NFS xdr model (see elf_ehdr and elf_phdr),
 * the Plan 9 endianness functions (see xdr.c), and Go interfaces (see
 * how we use buffer structs in this file). This ends up being a bit
 * wordy at the lowest level, but greatly simplifies the elf parsing
 * code and removes a common source of bugs, namely, forgetting to
 * flip type endianness when referencing a struct member.
 *
 * ELF files can have four combinations of data layout: 32/64, and
 * big/little endian.  Further, to add to the fun, depending on the
 * word size, the size of the ELF structs varies. The coreboot SELF
 * format is simpler in theory: it's supposed to be always BE, and the
 * various struct members allow room for growth: the entry point is
 * always 64 bits, for example, so the size of a SELF struct is
 * constant, regardless of target architecture word size.  Hence, we
 * need to do some transformation of the ELF files.
 *
 * A given architecture, realistically, only supports one of the four
 * combinations at a time as the 'native' format. Hence, our code has
 * been sprinkled with every variation of [nh]to[hn][sll] over the
 * years. We've never quite gotten it all right, however, and a quick
 * pass over this code revealed another bug.  It's all worked because,
 * until now, all the working platforms that had CBFS were 32 LE. Even then,
 * however, bugs crept in: we recently realized that we're not
 * transforming the entry point to big format when we store into the
 * SELF image.
 *
 * The problem is essentially an XDR operation:
 * we have something in a foreign format and need to transform it.
 * It's most like XDR because:
 * 1) the byte order can be wrong
 * 2) the word size can be wrong
 * 3) the size of elements in the stream depends on the value
 *    of other elements in the stream
 * it's not like XDR because:
 * 1) the byte order can be right
 * 2) the word size can be right
 * 3) the struct members are all on a natural alignment
 *
 * Hence, this new approach.  To cover word size issues, we *always*
 * transform the two structs we care about, the file header and
 * program header, into a native struct in the 64 bit format:
 *
 * [32,little] -> [Elf64_Ehdr, Elf64_Phdr]
 * [64,little] -> [Elf64_Ehdr, Elf64_Phdr]
 * [32,big] -> [Elf64_Ehdr, Elf64_Phdr]
 * [64,big] -> [Elf64_Ehdr, Elf64_Phdr]
 * Then we just use those structs, and all the need for inline ntoh* goes away,
 * as well as all the chances for error.
 * This works because all the SELF structs have fields large enough for
 * the largest ELF 64 struct members, and all the Elf64 struct members
 * are at least large enough for all ELF 32 struct members.
 * We end up with one function to do all our ELF parsing, and two functions
 * to transform the headers. For the put case, we also have
 * XDR functions, and hopefully we'll never again spend 5 years with the
 * wrong endian-ness on an output value :-)
 * This should work for all word sizes and endianness we hope to target.
 * I *really* don't want to be here for 128 bit addresses.
 *
 * The parse functions are called with a pointer to an input buffer
 * struct. One might ask: are there enough bytes in the input buffer?
 * We know there need to be at *least* sizeof(Elf32_Ehdr) +
 * sizeof(Elf32_Phdr) bytes. Realistically, there has to be some data
 * too.  If we start to worry, though we have not in the past, we
 * might apply the simple test: the input buffer needs to be at least
 * sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) bytes because, even if it's
 * ELF 32, there's got to be *some* data! This is not theoretically
 * accurate but it is actually good enough in practice. It allows the
 * header transformation code to ignore the possibility of underrun.
 *
 * We also must accomodate different ELF files, and hence formats,
 * in the same cbfs invocation. We might load a 64-bit payload
 * on a 32-bit machine; we might even have a mixed armv7/armv8
 * SOC or even a system with an x86/ARM!
 *
 * A possibly problematic (though unlikely to be so) assumption
 * is that we expect the BIOS to remain in the lowest 32 bits
 * of the physical address space. Since ARMV8 has standardized
 * on that, and x86_64 also has, this seems a safe assumption.
 *
 * To repeat, ELF structs are different sizes because ELF struct
 * members are different sizes, depending on values in the ELF file
 * header. For this we use the functions defined in xdr.c, which
 * consume bytes, convert the endianness, and advance the data pointer
 * in the buffer struct.
 */


static int iself(const void *input)
{
	const Elf32_Ehdr *ehdr = input;
	return !memcmp(ehdr->e_ident, ELFMAG, 4);
}

/* Get the ident array, so we can figure out
 * endian-ness, word size, and in future other useful
 * parameters
 */
static void
elf_eident(struct buffer *input, Elf64_Ehdr *ehdr)
{
	bgets(input, ehdr->e_ident, sizeof(ehdr->e_ident));
}


static int
check_size(const struct buffer *b, size_t offset, size_t size, const char *desc)
{
	if (size == 0)
		return 0;

	if (offset >= buffer_size(b) || (offset + size) > buffer_size(b)) {
		ERROR("The file is not large enough for the '%s'. "
		      "%ld bytes @ offset %zu, input %zu bytes.\n",
		      desc, size, offset, buffer_size(b));
		return -1;
	}
	return 0;
}

static void
elf_ehdr(struct buffer *input, Elf64_Ehdr *ehdr, struct xdr *xdr, int bit64)
{
	ehdr->e_type = xdr->get16(input);
	ehdr->e_machine = xdr->get16(input);
	ehdr->e_version = xdr->get32(input);
	if (bit64){
		ehdr->e_entry = xdr->get64(input);
		ehdr->e_phoff = xdr->get64(input);
		ehdr->e_shoff = xdr->get64(input);
	} else {
		ehdr->e_entry = xdr->get32(input);
		ehdr->e_phoff = xdr->get32(input);
		ehdr->e_shoff = xdr->get32(input);
	}
	ehdr->e_flags = xdr->get32(input);
	ehdr->e_ehsize = xdr->get16(input);
	ehdr->e_phentsize = xdr->get16(input);
	ehdr->e_phnum = xdr->get16(input);
	ehdr->e_shentsize = xdr->get16(input);
	ehdr->e_shnum = xdr->get16(input);
	ehdr->e_shstrndx = xdr->get16(input);
}

static void
elf_phdr(struct buffer *pinput, Elf64_Phdr *phdr,
	 int entsize, struct xdr *xdr, int bit64)
{
	/*
	 * The entsize need not be sizeof(*phdr).
	 * Hence, it is easier to keep a copy of the input,
	 * as the xdr functions may not advance the input
	 * pointer the full entsize; rather than get tricky
	 * we just advance it below.
	 */
	struct buffer input;
	buffer_clone(&input, pinput);
	if (bit64){
		phdr->p_type = xdr->get32(&input);
		phdr->p_flags = xdr->get32(&input);
		phdr->p_offset = xdr->get64(&input);
		phdr->p_vaddr = xdr->get64(&input);
		phdr->p_paddr = xdr->get64(&input);
		phdr->p_filesz = xdr->get64(&input);
		phdr->p_memsz = xdr->get64(&input);
		phdr->p_align = xdr->get64(&input);
	} else {
		phdr->p_type = xdr->get32(&input);
		phdr->p_offset = xdr->get32(&input);
		phdr->p_vaddr = xdr->get32(&input);
		phdr->p_paddr = xdr->get32(&input);
		phdr->p_filesz = xdr->get32(&input);
		phdr->p_memsz = xdr->get32(&input);
		phdr->p_flags = xdr->get32(&input);
		phdr->p_align = xdr->get32(&input);
	}
	buffer_seek(pinput, entsize);
}

static void
elf_shdr(struct buffer *pinput, Elf64_Shdr *shdr,
	 int entsize, struct xdr *xdr, int bit64)
{
	/*
	 * The entsize need not be sizeof(*shdr).
	 * Hence, it is easier to keep a copy of the input,
	 * as the xdr functions may not advance the input
	 * pointer the full entsize; rather than get tricky
	 * we just advance it below.
	 */
	struct buffer input = *pinput;
	if (bit64){
		shdr->sh_name = xdr->get32(&input);
		shdr->sh_type = xdr->get32(&input);
		shdr->sh_flags = xdr->get64(&input);
		shdr->sh_addr = xdr->get64(&input);
		shdr->sh_offset = xdr->get64(&input);
		shdr->sh_size= xdr->get64(&input);
		shdr->sh_link = xdr->get32(&input);
		shdr->sh_info = xdr->get32(&input);
		shdr->sh_addralign = xdr->get64(&input);
		shdr->sh_entsize = xdr->get64(&input);
	} else {
		shdr->sh_name = xdr->get32(&input);
		shdr->sh_type = xdr->get32(&input);
		shdr->sh_flags = xdr->get32(&input);
		shdr->sh_addr = xdr->get32(&input);
		shdr->sh_offset = xdr->get32(&input);
		shdr->sh_size = xdr->get32(&input);
		shdr->sh_link = xdr->get32(&input);
		shdr->sh_info = xdr->get32(&input);
		shdr->sh_addralign = xdr->get32(&input);
		shdr->sh_entsize = xdr->get32(&input);
	}
	buffer_seek(pinput, entsize);
}

static int
phdr_read(const struct buffer *in, struct parsed_elf *pelf,
          struct xdr *xdr, int bit64)
{
	struct buffer b;
	Elf64_Phdr *phdr;
	Elf64_Ehdr *ehdr;
	int i;

	ehdr = &pelf->ehdr;
	/* cons up an input buffer for the headers.
	 * Note that the program headers can be anywhere,
	 * per the ELF spec, You'd be surprised how many ELF
	 * readers miss this little detail.
	 */
	buffer_splice(&b, in, ehdr->e_phoff, ehdr->e_phentsize * ehdr->e_phnum);
	if (check_size(in, ehdr->e_phoff, buffer_size(&b), "program headers"))
		return -1;

	/* gather up all the phdrs.
	 * We do them all at once because there is more
	 * than one loop over all the phdrs.
	 */
	phdr = calloc(ehdr->e_phnum, sizeof(*phdr));
	for (i = 0; i < ehdr->e_phnum; i++) {
		DEBUG("Parsing segment %d\n", i);
		elf_phdr(&b, &phdr[i], ehdr->e_phentsize, xdr, bit64);

		/* Ensure the contents are valid within the elf file. */
		if (check_size(in, phdr[i].p_offset, phdr[i].p_filesz,
	                  "segment contents"))
			return -1;
	}

	pelf->phdr = phdr;

	return 0;
}

static int
shdr_read(const struct buffer *in, struct parsed_elf *pelf,
          struct xdr *xdr, int bit64)
{
	struct buffer b;
	Elf64_Shdr *shdr;
	Elf64_Ehdr *ehdr;
	int i;

	ehdr = &pelf->ehdr;

	/* cons up an input buffer for the section headers.
	 * Note that the section headers can be anywhere,
	 * per the ELF spec, You'd be surprised how many ELF
	 * readers miss this little detail.
	 */
	buffer_splice(&b, in, ehdr->e_shoff, ehdr->e_shentsize * ehdr->e_shnum);
	if (check_size(in, ehdr->e_shoff, buffer_size(&b), "section headers"))
		return -1;

	/* gather up all the shdrs. */
	shdr = calloc(ehdr->e_shnum, sizeof(*shdr));
	for (i = 0; i < ehdr->e_shnum; i++) {
		DEBUG("Parsing section %d\n", i);
		elf_shdr(&b, &shdr[i], ehdr->e_shentsize, xdr, bit64);
	}

	pelf->shdr = shdr;

	return 0;
}

static int
reloc_read(const struct buffer *in, struct parsed_elf *pelf,
           struct xdr *xdr, int bit64)
{
	struct buffer b;
	Elf64_Word i;
	Elf64_Ehdr *ehdr;

	ehdr = &pelf->ehdr;
	pelf->relocs = calloc(ehdr->e_shnum, sizeof(Elf64_Rela *));

	/* Allocate array for each section that contains relocation entries. */
	for (i = 0; i < ehdr->e_shnum; i++) {
		Elf64_Shdr *shdr;
		Elf64_Rela *rela;
		Elf64_Xword j;
		Elf64_Xword nrelocs;
		int is_rela;

		shdr = &pelf->shdr[i];

		/* Only process REL and RELA sections. */
		if (shdr->sh_type != SHT_REL && shdr->sh_type != SHT_RELA)
			continue;

		DEBUG("Checking relocation section %u\n", i);

		/* Ensure the section that relocations apply is a valid. */
		if (shdr->sh_info >= ehdr->e_shnum ||
		    shdr->sh_info == SHN_UNDEF) {
			ERROR("Relocations apply to an invalid section: %u\n",
			      shdr[i].sh_info);
			return -1;
		}

		is_rela = shdr->sh_type == SHT_RELA;

		/* Determine the number relocations in this section. */
		nrelocs = shdr->sh_size / shdr->sh_entsize;

		pelf->relocs[i] = calloc(nrelocs, sizeof(Elf64_Rela));

		buffer_splice(&b, in, shdr->sh_offset, shdr->sh_size);
		if (check_size(in, shdr->sh_offset, buffer_size(&b),
		               "relocation section")) {
			ERROR("Relocation section %u failed.\n", i);
			return -1;
		}

		rela = pelf->relocs[i];
		for (j = 0; j < nrelocs; j++) {
			if (bit64) {
				rela->r_offset = xdr->get64(&b);
				rela->r_info = xdr->get64(&b);
				if (is_rela)
					rela->r_addend = xdr->get64(&b);
			} else {
				uint32_t r_info;

				rela->r_offset = xdr->get32(&b);
				r_info = xdr->get32(&b);
				rela->r_info = ELF64_R_INFO(ELF32_R_SYM(r_info),
				                          ELF32_R_TYPE(r_info));
				if (is_rela)
					rela->r_addend = xdr->get32(&b);
			}
			rela++;
		}
	}

	return 0;
}

static int strtab_read(const struct buffer *in, struct parsed_elf *pelf)
{
	Elf64_Ehdr *ehdr;
	Elf64_Word i;

	ehdr = &pelf->ehdr;

	if (ehdr->e_shstrndx >= ehdr->e_shnum) {
		ERROR("Section header string table index out of range: %d\n",
		      ehdr->e_shstrndx);
		return -1;
	}

	/* For each section of type SHT_STRTAB create a symtab buffer. */
	pelf->strtabs = calloc(ehdr->e_shnum, sizeof(struct buffer *));

	for (i = 0; i < ehdr->e_shnum; i++) {
		struct buffer *b;
		Elf64_Shdr *shdr = &pelf->shdr[i];

		if (shdr->sh_type != SHT_STRTAB)
			continue;

		b = calloc(1, sizeof(*b));
		buffer_splice(b, in, shdr->sh_offset, shdr->sh_size);
		if (check_size(in, shdr->sh_offset, buffer_size(b), "strtab")) {
			ERROR("STRTAB section not within bounds: %d\n", i);
			return -1;
		}
		pelf->strtabs[i] = b;
	}

	return 0;
}

static int
symtab_read(const struct buffer *in, struct parsed_elf *pelf,
            struct xdr *xdr, int bit64)
{
	Elf64_Ehdr *ehdr;
	Elf64_Shdr *shdr;
	Elf64_Half i;
	Elf64_Xword nsyms;
	Elf64_Sym *sym;
	struct buffer b;

	ehdr = &pelf->ehdr;

	shdr = NULL;
	for (i = 0; i < ehdr->e_shnum; i++) {
		if (pelf->shdr[i].sh_type != SHT_SYMTAB)
			continue;

		if (shdr != NULL) {
			ERROR("Multiple symbol sections found. %u and %u\n",
			      (unsigned int)(shdr - pelf->shdr), i);
			return -1;
		}

		shdr = &pelf->shdr[i];
	}

	if (shdr == NULL) {
		ERROR("No symbol table found.\n");
		return -1;
	}

	buffer_splice(&b, in, shdr->sh_offset, shdr->sh_size);
	if (check_size(in, shdr->sh_offset, buffer_size(&b), "symtab"))
		return -1;

	nsyms = shdr->sh_size / shdr->sh_entsize;

	pelf->syms = calloc(nsyms, sizeof(Elf64_Sym));

	for (i = 0; i < nsyms; i++) {
		sym = &pelf->syms[i];

		if (bit64) {
			sym->st_name = xdr->get32(&b);
			sym->st_info = xdr->get8(&b);
			sym->st_other = xdr->get8(&b);
			sym->st_shndx = xdr->get16(&b);
			sym->st_value = xdr->get64(&b);
			sym->st_size = xdr->get64(&b);
		} else {
			sym->st_name = xdr->get32(&b);
			sym->st_value = xdr->get32(&b);
			sym->st_size = xdr->get32(&b);
			sym->st_info = xdr->get8(&b);
			sym->st_other = xdr->get8(&b);
			sym->st_shndx = xdr->get16(&b);
		}
	}

	return 0;
}

int parse_elf(const struct buffer *pinput, struct parsed_elf *pelf, int flags)
{
	struct xdr *xdr = &xdr_le;
	int bit64 = 0;
	struct buffer input;
	Elf64_Ehdr *ehdr;

	/* Zero out the parsed elf structure. */
	memset(pelf, 0, sizeof(*pelf));

	if (!iself(buffer_get(pinput))) {
		ERROR("The stage file is not in ELF format!\n");
		return -1;
	}

	buffer_clone(&input, pinput);
	ehdr = &pelf->ehdr;
	elf_eident(&input, ehdr);
	bit64 = ehdr->e_ident[EI_CLASS] == ELFCLASS64;
	/* Assume LE unless we are sure otherwise.
	 * We're not going to take on the task of
	 * fully validating the ELF file. That way
	 * lies madness.
	 */
	if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
		xdr = &xdr_be;

	elf_ehdr(&input, ehdr, xdr, bit64);

	/* Relocation processing requires section header parsing. */
	if (flags & ELF_PARSE_RELOC)
		flags |= ELF_PARSE_SHDR;

	/* String table processing requires section header parsing. */
	if (flags & ELF_PARSE_STRTAB)
		flags |= ELF_PARSE_SHDR;

	/* Symbole table processing requires section header parsing. */
	if (flags & ELF_PARSE_SYMTAB)
		flags |= ELF_PARSE_SHDR;

	if ((flags & ELF_PARSE_PHDR) && phdr_read(pinput, pelf, xdr, bit64))
		goto fail;

	if ((flags & ELF_PARSE_SHDR) && shdr_read(pinput, pelf, xdr, bit64))
		goto fail;

	if ((flags & ELF_PARSE_RELOC) && reloc_read(pinput, pelf, xdr, bit64))
		goto fail;

	if ((flags & ELF_PARSE_STRTAB) && strtab_read(pinput, pelf))
		goto fail;

	if ((flags & ELF_PARSE_SYMTAB) && symtab_read(pinput, pelf, xdr, bit64))
		goto fail;

	return 0;

fail:
	parsed_elf_destroy(pelf);
	return -1;
}

void parsed_elf_destroy(struct parsed_elf *pelf)
{
	Elf64_Half i;

	free(pelf->phdr);
	free(pelf->shdr);
	if (pelf->relocs != NULL) {
		for (i = 0; i < pelf->ehdr.e_shnum; i++)
			free(pelf->relocs[i]);
	}
	free(pelf->relocs);

	if (pelf->strtabs != NULL) {
		for (i = 0; i < pelf->ehdr.e_shnum; i++)
			free(pelf->strtabs[i]);
	}
	free(pelf->strtabs);
	free(pelf->syms);
}

/* Get the headers from the buffer.
 * Return -1 in the event of an error.
 * The section headers are optional; if NULL
 * is passed in for pshdr they won't be parsed.
 * We don't (yet) make payload parsing optional
 * because we've never seen a use case.
 */
int
elf_headers(const struct buffer *pinput,
	    uint32_t arch,
	    Elf64_Ehdr *ehdr,
	    Elf64_Phdr **pphdr,
	    Elf64_Shdr **pshdr)
{

	struct parsed_elf pelf;
	int flags;

	flags = ELF_PARSE_PHDR;

	if (pshdr != NULL)
		flags |= ELF_PARSE_SHDR;

	if (parse_elf(pinput, &pelf, flags))
		return -1;

	/* Copy out the parsed elf header. */
	memcpy(ehdr, &pelf.ehdr, sizeof(*ehdr));

	// The tool may work in architecture-independent way.
	if (arch != CBFS_ARCHITECTURE_UNKNOWN &&
	    !((ehdr->e_machine == EM_ARM) && (arch == CBFS_ARCHITECTURE_ARMV7)) &&
	    !((ehdr->e_machine == EM_386) && (arch == CBFS_ARCHITECTURE_X86))) {
		ERROR("The stage file has the wrong architecture\n");
		return -1;
	}

	*pphdr = calloc(ehdr->e_phnum, sizeof(Elf64_Phdr));
	memcpy(*pphdr, pelf.phdr, ehdr->e_phnum * sizeof(Elf64_Phdr));

	if (pshdr != NULL) {
		*pshdr = calloc(ehdr->e_shnum, sizeof(Elf64_Shdr));
		memcpy(*pshdr, pelf.shdr, ehdr->e_shnum * sizeof(Elf64_Shdr));
	}

	parsed_elf_destroy(&pelf);

	return 0;
}

/* ELF Writing  Support
 *
 * The ELF file is written according to the following layout:
 * +------------------+
 * |    ELF Header    |
 * +------------------+
 * | Section  Headers |
 * +------------------+
 * | Program  Headers |
 * +------------------+
 * |   String table   |
 * +------------------+ <- 4KiB Aligned
 * |     Code/Data    |
 * +------------------+
 */

/* Arbitray maximum number of sections. */
#define MAX_SECTIONS 16
struct elf_writer_section {
	Elf64_Shdr shdr;
	struct buffer content;
	const char *name;
};

struct elf_writer
{
	Elf64_Ehdr ehdr;
	struct xdr *xdr;
	size_t num_secs;
	struct elf_writer_section sections[MAX_SECTIONS];
	Elf64_Phdr *phdrs;
	struct elf_writer_section *shstrtab;
	int bit64;
};

struct elf_writer *elf_writer_init(const Elf64_Ehdr *ehdr)
{
	struct elf_writer *ew;
	Elf64_Shdr shdr;
	struct buffer empty_buffer;

	if (!iself(ehdr))
		return NULL;

	ew = calloc(1, sizeof(*ew));

	memcpy(&ew->ehdr, ehdr, sizeof(ew->ehdr));

	ew->bit64 = ew->ehdr.e_ident[EI_CLASS] == ELFCLASS64;

	/* Set the endinan ops. */
	if (ew->ehdr.e_ident[EI_DATA] == ELFDATA2MSB)
		ew->xdr = &xdr_be;
	else
		ew->xdr = &xdr_le;

	/* Reset count and offsets */
	ew->ehdr.e_phoff = 0;
	ew->ehdr.e_shoff = 0;
	ew->ehdr.e_shnum = 0;
	ew->ehdr.e_phnum = 0;

	memset(&empty_buffer, 0, sizeof(empty_buffer));
	memset(&shdr, 0, sizeof(shdr));

	/* Add SHT_NULL section header. */
	shdr.sh_type = SHT_NULL;
	elf_writer_add_section(ew, &shdr, &empty_buffer, NULL);

	/* Add section header string table and maintain reference to it.  */
	shdr.sh_type = SHT_STRTAB;
	elf_writer_add_section(ew, &shdr, &empty_buffer, ".shstrtab");
	ew->ehdr.e_shstrndx = ew->num_secs - 1;
	ew->shstrtab = &ew->sections[ew->ehdr.e_shstrndx];

	return ew;
}

/*
 * Clean up any internal state represented by ew. Aftewards the elf_writer
 * is invalid.
 */
void elf_writer_destroy(struct elf_writer *ew)
{
	if (ew->phdrs != NULL)
		free(ew->phdrs);
	free(ew);
}

/*
 * Add a section to the ELF file. Section type, flags, and memsize are
 * maintained from the passed in Elf64_Shdr. The buffer represents the
 * content of the section while the name is the name of section itself.
 * Returns < 0 on error, 0 on success.
 */
int elf_writer_add_section(struct elf_writer *ew, const Elf64_Shdr *shdr,
                           struct buffer *contents, const char *name)
{
	struct elf_writer_section *newsh;

	if (ew->num_secs == MAX_SECTIONS)
		return -1;

	newsh = &ew->sections[ew->num_secs];
	ew->num_secs++;

	memcpy(&newsh->shdr, shdr, sizeof(newsh->shdr));
	newsh->shdr.sh_offset = 0;

	newsh->name = name;
	if (contents != NULL)
		buffer_clone(&newsh->content, contents);

	return 0;
}

static void ehdr_write(struct elf_writer *ew, struct buffer *m)
{
	int i;

	for (i = 0; i < EI_NIDENT; i++)
		ew->xdr->put8(m, ew->ehdr.e_ident[i]);
	ew->xdr->put16(m, ew->ehdr.e_type);
	ew->xdr->put16(m, ew->ehdr.e_machine);
	ew->xdr->put32(m, ew->ehdr.e_version);
	if (ew->bit64) {
		ew->xdr->put64(m, ew->ehdr.e_entry);
		ew->xdr->put64(m, ew->ehdr.e_phoff);
		ew->xdr->put64(m, ew->ehdr.e_shoff);
	} else {
		ew->xdr->put32(m, ew->ehdr.e_entry);
		ew->xdr->put32(m, ew->ehdr.e_phoff);
		ew->xdr->put32(m, ew->ehdr.e_shoff);
	}
	ew->xdr->put32(m, ew->ehdr.e_flags);
	ew->xdr->put16(m, ew->ehdr.e_ehsize);
	ew->xdr->put16(m, ew->ehdr.e_phentsize);
	ew->xdr->put16(m, ew->ehdr.e_phnum);
	ew->xdr->put16(m, ew->ehdr.e_shentsize);
	ew->xdr->put16(m, ew->ehdr.e_shnum);
	ew->xdr->put16(m, ew->ehdr.e_shstrndx);
}

static void shdr_write(struct elf_writer *ew, size_t n, struct buffer *m)
{
	struct xdr *xdr = ew->xdr;
	int bit64 = ew->bit64;
	struct elf_writer_section *sec = &ew->sections[n];
	Elf64_Shdr *shdr = &sec->shdr;

	xdr->put32(m, shdr->sh_name);
	xdr->put32(m, shdr->sh_type);
	xdr->put32(m, shdr->sh_flags);
	if (bit64) {
		xdr->put64(m, shdr->sh_addr);
		xdr->put64(m, shdr->sh_offset);
		xdr->put64(m, shdr->sh_size);
		xdr->put32(m, shdr->sh_link);
		xdr->put32(m, shdr->sh_info);
		xdr->put64(m, shdr->sh_addralign);
		xdr->put64(m, shdr->sh_entsize);
	} else {
		xdr->put32(m, shdr->sh_addr);
		xdr->put32(m, shdr->sh_offset);
		xdr->put32(m, shdr->sh_size);
		xdr->put32(m, shdr->sh_link);
		xdr->put32(m, shdr->sh_info);
		xdr->put32(m, shdr->sh_addralign);
		xdr->put32(m, shdr->sh_entsize);
	}
}

static void
phdr_write(struct elf_writer *ew, struct buffer *m, Elf64_Phdr *phdr)
{
	if (ew->bit64) {
		ew->xdr->put32(m, phdr->p_type);
		ew->xdr->put32(m, phdr->p_flags);
		ew->xdr->put64(m, phdr->p_offset);
		ew->xdr->put64(m, phdr->p_vaddr);
		ew->xdr->put64(m, phdr->p_paddr);
		ew->xdr->put64(m, phdr->p_filesz);
		ew->xdr->put64(m, phdr->p_memsz);
		ew->xdr->put64(m, phdr->p_align);
	} else {
		ew->xdr->put32(m, phdr->p_type);
		ew->xdr->put32(m, phdr->p_offset);
		ew->xdr->put32(m, phdr->p_vaddr);
		ew->xdr->put32(m, phdr->p_paddr);
		ew->xdr->put32(m, phdr->p_filesz);
		ew->xdr->put32(m, phdr->p_memsz);
		ew->xdr->put32(m, phdr->p_flags);
		ew->xdr->put32(m, phdr->p_align);
	}

}

/*
 * Serialize the ELF file to the output buffer. Return < 0 on error,
 * 0 on success.
 */
int elf_writer_serialize(struct elf_writer *ew, struct buffer *out)
{
	Elf64_Half i;
	Elf64_Xword metadata_size;
	Elf64_Xword program_size;
	Elf64_Off shstroffset;
	size_t shstrlen;
	struct buffer metadata;
	struct buffer phdrs;
	struct buffer data;
	struct buffer *strtab;

	INFO("Writing %zu sections.\n", ew->num_secs);

	/* Determine size of sections to be written. */
	program_size = 0;
	/* Start with 1 byte for first byte of section header string table. */
	shstrlen = 1;
	for (i = 0; i < ew->num_secs; i++) {
		struct elf_writer_section *sec = &ew->sections[i];

		if (sec->shdr.sh_flags & SHF_ALLOC)
			ew->ehdr.e_phnum++;

		program_size += buffer_size(&sec->content);

		/* Keep track of the length sections' names. */
		if (sec->name != NULL) {
			sec->shdr.sh_name = shstrlen;
			shstrlen += strlen(sec->name) + 1;
		}
	}
	ew->ehdr.e_shnum = ew->num_secs;
	metadata_size = 0;
	metadata_size += ew->ehdr.e_ehsize;
	metadata_size += ew->ehdr.e_shnum * ew->ehdr.e_shentsize;
	metadata_size += ew->ehdr.e_phnum * ew->ehdr.e_phentsize;
	shstroffset = metadata_size;
	/* Align up section header string size and metadata size to 4KiB */
	metadata_size = ALIGN(metadata_size + shstrlen, 4096);

	if (buffer_create(out, metadata_size + program_size, "elfout")) {
		ERROR("Could not create output buffer for ELF.\n");
		return -1;
	}

	INFO("Created %zu output buffer for ELF file.\n", buffer_size(out));

	/*
	 * Write out ELF header. Section headers come right after ELF header
	 * followed by the program headers. Buffers need to be created first
	 * to do the writing.
	 */
	ew->ehdr.e_shoff = ew->ehdr.e_ehsize;
	ew->ehdr.e_phoff = ew->ehdr.e_shoff +
	                   ew->ehdr.e_shnum * ew->ehdr.e_shentsize;

	buffer_splice(&metadata, out, 0, metadata_size);
	buffer_splice(&phdrs, out, ew->ehdr.e_phoff,
	              ew->ehdr.e_phnum * ew->ehdr.e_phentsize);
	buffer_splice(&data, out, metadata_size, program_size);
	/* Set up the section header string table contents. */
	strtab = &ew->shstrtab->content;
	buffer_splice(strtab, out, shstroffset, shstrlen);
	ew->shstrtab->shdr.sh_size = shstrlen;

	/* Reset current locations. */
	buffer_set_size(&metadata, 0);
	buffer_set_size(&data, 0);
	buffer_set_size(&phdrs, 0);
	buffer_set_size(strtab, 0);

	/* ELF Header */
	ehdr_write(ew, &metadata);

	/* Write out section headers, section strings, section content, and
	 * program headers. */
	ew->xdr->put8(strtab, 0);
	for (i = 0; i < ew->num_secs; i++) {
		Elf64_Phdr phdr;
		struct elf_writer_section *sec = &ew->sections[i];

		/* Update section offsets. Be sure to not update SHT_NULL. */
		if (sec == ew->shstrtab)
			sec->shdr.sh_offset = shstroffset;
		else if (i != 0)
			sec->shdr.sh_offset = buffer_size(&data) +
			                      metadata_size;
		shdr_write(ew, i, &metadata);

		/* Add section name to string table. */
		if (sec->name != NULL)
			bputs(strtab, sec->name, strlen(sec->name) + 1);

		if (!(sec->shdr.sh_flags & SHF_ALLOC))
			continue;

		bputs(&data, buffer_get(&sec->content),
		      buffer_size(&sec->content));

		phdr.p_type = PT_LOAD;
		phdr.p_offset = sec->shdr.sh_offset;
		phdr.p_vaddr = sec->shdr.sh_addr;
		phdr.p_paddr = sec->shdr.sh_addr;
		phdr.p_filesz = buffer_size(&sec->content);
		phdr.p_memsz = sec->shdr.sh_size;
		phdr.p_flags = 0;
		if (sec->shdr.sh_flags & SHF_EXECINSTR)
			phdr.p_flags |= PF_X | PF_R;
		if (sec->shdr.sh_flags & SHF_WRITE)
			phdr.p_flags |= PF_W;
		phdr.p_align = sec->shdr.sh_addralign;
		phdr_write(ew, &phdrs, &phdr);
	}

	return 0;
}