1 /* SPDX-License-Identifier: GPL-2.0-only */
2
3 #include <inttypes.h>
4 #include <stdio.h>
5 #include <stdlib.h>
6 #include <string.h>
7
8 #include "elfparsing.h"
9 #include "rmodule.h"
10 #include <commonlib/rmodule-defs.h>
11
12 /*
13 * Architecture specific support operations.
14 */
valid_reloc_386(Elf64_Rela * rel)15 static int valid_reloc_386(Elf64_Rela *rel)
16 {
17 int type;
18
19 type = ELF64_R_TYPE(rel->r_info);
20
21 /* Only these 2 relocations are expected to be found. */
22 return (type == R_386_32 || type == R_386_PC32);
23 }
24
should_emit_386(Elf64_Rela * rel)25 static int should_emit_386(Elf64_Rela *rel)
26 {
27 int type;
28
29 type = ELF64_R_TYPE(rel->r_info);
30
31 /* R_386_32 relocations are absolute. Must emit these. */
32 return (type == R_386_32);
33 }
34
valid_reloc_amd64(Elf64_Rela * rel)35 static int valid_reloc_amd64(Elf64_Rela *rel)
36 {
37 int type;
38
39 type = ELF64_R_TYPE(rel->r_info);
40
41 /*
42 * Relocation R_AMD64_32S is not allowed. It can only be safely used in protected mode,
43 * and when the address pointed to is below 2 GiB in long mode.
44 * Using it in assembly operations will break compilation with error:
45 * E: Invalid reloc type: 11
46 */
47
48 /* Only these 5 relocations are expected to be found. */
49 return (type == R_AMD64_64 ||
50 type == R_AMD64_PC64 ||
51 type == R_AMD64_32 ||
52 type == R_AMD64_PC32 ||
53 /*
54 * binutils 2.31 introduced R_AMD64_PLT32 for non local
55 * functions. As we don't care about procedure linkage
56 * table entries handle it as R_X86_64_PC32.
57 */
58 type == R_AMD64_PLT32);
59 }
60
should_emit_amd64(Elf64_Rela * rel)61 static int should_emit_amd64(Elf64_Rela *rel)
62 {
63 int type;
64
65 type = ELF64_R_TYPE(rel->r_info);
66
67 /* Only emit absolute relocations */
68 return (type == R_AMD64_64 ||
69 type == R_AMD64_32);
70 }
71
valid_reloc_arm(Elf64_Rela * rel)72 static int valid_reloc_arm(Elf64_Rela *rel)
73 {
74 int type;
75
76 type = ELF64_R_TYPE(rel->r_info);
77
78 /* Only these 6 relocations are expected to be found. */
79 return (type == R_ARM_ABS32 || type == R_ARM_THM_PC22 ||
80 type == R_ARM_THM_JUMP24 || type == R_ARM_V4BX ||
81 type == R_ARM_CALL || type == R_ARM_JUMP24);
82 }
83
should_emit_arm(Elf64_Rela * rel)84 static int should_emit_arm(Elf64_Rela *rel)
85 {
86 int type;
87
88 type = ELF64_R_TYPE(rel->r_info);
89
90 /* R_ARM_ABS32 relocations are absolute. Must emit these. */
91 return (type == R_ARM_ABS32);
92 }
93
valid_reloc_aarch64(Elf64_Rela * rel)94 static int valid_reloc_aarch64(Elf64_Rela *rel)
95 {
96 int type;
97
98 type = ELF64_R_TYPE(rel->r_info);
99
100 return (type == R_AARCH64_ADR_PREL_PG_HI21 ||
101 type == R_AARCH64_ADD_ABS_LO12_NC ||
102 type == R_AARCH64_LDST8_ABS_LO12_NC ||
103 type == R_AARCH64_CONDBR19 ||
104 type == R_AARCH64_JUMP26 ||
105 type == R_AARCH64_LDST32_ABS_LO12_NC ||
106 type == R_AARCH64_LDST64_ABS_LO12_NC ||
107 type == R_AARCH64_CALL26 ||
108 type == R_AARCH64_ABS64 ||
109 type == R_AARCH64_LD_PREL_LO19 ||
110 type == R_AARCH64_ADR_PREL_LO21);
111 }
112
should_emit_aarch64(Elf64_Rela * rel)113 static int should_emit_aarch64(Elf64_Rela *rel)
114 {
115 int type;
116
117 type = ELF64_R_TYPE(rel->r_info);
118
119 return (type == R_AARCH64_ABS64);
120 }
121
122 static const struct arch_ops reloc_ops[] = {
123 {
124 .arch = EM_386,
125 .valid_type = valid_reloc_386,
126 .should_emit = should_emit_386,
127 },
128 {
129 .arch = EM_X86_64,
130 .valid_type = valid_reloc_amd64,
131 .should_emit = should_emit_amd64,
132 },
133 {
134 .arch = EM_ARM,
135 .valid_type = valid_reloc_arm,
136 .should_emit = should_emit_arm,
137 },
138 {
139 .arch = EM_AARCH64,
140 .valid_type = valid_reloc_aarch64,
141 .should_emit = should_emit_aarch64,
142 },
143 };
144
relocation_for_absolute_symbol(struct rmod_context * ctx,Elf64_Rela * r)145 static int relocation_for_absolute_symbol(struct rmod_context *ctx, Elf64_Rela *r)
146 {
147 Elf64_Sym *s = &ctx->pelf.syms[ELF64_R_SYM(r->r_info)];
148
149 if (s->st_shndx == SHN_ABS) {
150 DEBUG("Omitting relocation for absolute symbol: %s\n",
151 &ctx->strtab[s->st_name]);
152 return 1;
153 }
154
155 return 0;
156 }
157
relocation_for_weak_extern_symbols(struct rmod_context * ctx,Elf64_Rela * r)158 static int relocation_for_weak_extern_symbols(struct rmod_context *ctx, Elf64_Rela *r)
159 {
160 Elf64_Sym *s = &ctx->pelf.syms[ELF64_R_SYM(r->r_info)];
161
162 if (ELF64_ST_BIND(s->st_info) == STB_WEAK && ELF64_ST_TYPE(s->st_info) == STT_NOTYPE) {
163 DEBUG("Omitting relocation for undefined extern: %s\n",
164 &ctx->strtab[s->st_name]);
165 return 1;
166 }
167
168 return 0;
169 }
170
relocation_for_undefined_symbol(struct rmod_context * ctx,Elf64_Rela * r)171 static int relocation_for_undefined_symbol(struct rmod_context *ctx, Elf64_Rela *r)
172 {
173 Elf64_Sym *s = &ctx->pelf.syms[ELF64_R_SYM(r->r_info)];
174
175 if (s->st_shndx == SHN_UNDEF) {
176 DEBUG("Omitting relocation for undefined symbol: %s\n",
177 &ctx->strtab[s->st_name]);
178 return 1;
179 }
180
181 return 0;
182 }
183
184 /*
185 * Relocation processing loops.
186 */
187
for_each_reloc(struct rmod_context * ctx,struct reloc_filter * f,int do_emit)188 static int for_each_reloc(struct rmod_context *ctx, struct reloc_filter *f,
189 int do_emit)
190 {
191 Elf64_Half i;
192 struct parsed_elf *pelf = &ctx->pelf;
193
194 for (i = 0; i < pelf->ehdr.e_shnum; i++) {
195 Elf64_Shdr *shdr;
196 Elf64_Rela *relocs;
197 Elf64_Xword nrelocs;
198 Elf64_Xword j;
199
200 relocs = pelf->relocs[i];
201
202 /* No relocations in this section. */
203 if (relocs == NULL)
204 continue;
205
206 shdr = &pelf->shdr[i];
207 nrelocs = shdr->sh_size / shdr->sh_entsize;
208
209 for (j = 0; j < nrelocs; j++) {
210 int filter_emit = 1;
211 Elf64_Rela *r = &relocs[j];
212
213 if (!ctx->ops->valid_type(r)) {
214 ERROR("Invalid reloc type: %u\n",
215 (unsigned int)ELF64_R_TYPE(r->r_info));
216 if ((ctx->ops->arch == EM_X86_64) &&
217 (ELF64_R_TYPE(r->r_info) == R_AMD64_32S))
218 ERROR("Illegal use of 32bit sign extended addressing at offset 0x%x\n",
219 (unsigned int)r->r_offset);
220 return -1;
221 }
222
223 if (relocation_for_absolute_symbol(ctx, r))
224 continue;
225
226 if (relocation_for_weak_extern_symbols(ctx, r))
227 continue;
228
229 if (relocation_for_undefined_symbol(ctx, r))
230 continue;
231
232 /* Allow the provided filter to have precedence. */
233 if (f != NULL) {
234 filter_emit = f->filter(f, r);
235
236 if (filter_emit < 0)
237 return filter_emit;
238 }
239
240 if (filter_emit && ctx->ops->should_emit(r)) {
241 int n = ctx->nrelocs;
242 if (do_emit)
243 ctx->emitted_relocs[n] = r->r_offset;
244 ctx->nrelocs++;
245 }
246 }
247 }
248
249 return 0;
250 }
251
find_program_segment(struct rmod_context * ctx)252 static int find_program_segment(struct rmod_context *ctx)
253 {
254 int i;
255 int nsegments;
256 struct parsed_elf *pelf;
257 Elf64_Phdr *phdr = NULL;
258
259 pelf = &ctx->pelf;
260
261 /* There should only be a single loadable segment. */
262 nsegments = 0;
263 for (i = 0; i < pelf->ehdr.e_phnum; i++) {
264 if (pelf->phdr[i].p_type != PT_LOAD)
265 continue;
266 if (!phdr)
267 phdr = &pelf->phdr[i];
268 nsegments++;
269 }
270
271 if (nsegments == 0) {
272 ERROR("No loadable segment found.\n");
273 return -1;
274 }
275
276 INFO("Segment at 0x%0llx, file size 0x%0llx, mem size 0x%0llx.\n",
277 (long long)phdr->p_vaddr, (long long)phdr->p_filesz,
278 (long long)phdr->p_memsz);
279
280 ctx->phdr = phdr;
281 ctx->nsegments = nsegments;
282
283 return 0;
284 }
285
286 static int
filter_relocation_sections(struct rmod_context * ctx)287 filter_relocation_sections(struct rmod_context *ctx)
288 {
289 int i, j;
290 const char *shstrtab;
291 struct parsed_elf *pelf;
292 const Elf64_Phdr *phdr;
293
294 pelf = &ctx->pelf;
295 shstrtab = buffer_get(pelf->strtabs[pelf->ehdr.e_shstrndx]);
296
297 /*
298 * Find all relocation sections that contain relocation entries
299 * for sections that fall within the bounds of the segments. For
300 * easier processing the pointer to the relocation array for the
301 * sections that don't fall within the loadable program are NULL'd
302 * out.
303 */
304 for (i = 0; i < pelf->ehdr.e_shnum; i++) {
305 Elf64_Shdr *shdr;
306 Elf64_Word sh_info;
307 const char *section_name;
308
309 shdr = &pelf->shdr[i];
310
311 /* Ignore non-relocation sections. */
312 if (shdr->sh_type != SHT_RELA && shdr->sh_type != SHT_REL)
313 continue;
314
315 /* Obtain section which relocations apply. */
316 sh_info = shdr->sh_info;
317 shdr = &pelf->shdr[sh_info];
318
319 section_name = &shstrtab[shdr->sh_name];
320 DEBUG("Relocation section found for '%s' section.\n",
321 section_name);
322
323 /* Do not process relocations for debug sections. */
324 if (strstr(section_name, ".debug") != NULL) {
325 pelf->relocs[i] = NULL;
326 continue;
327 }
328
329 /*
330 * If relocations apply to a non program section ignore the
331 * relocations for future processing.
332 */
333 if (shdr->sh_type != SHT_PROGBITS) {
334 pelf->relocs[i] = NULL;
335 continue;
336 }
337
338 for (j = 0; j < pelf->ehdr.e_phnum; j++) {
339 phdr = &pelf->phdr[j];
340 if (phdr->p_type == PT_LOAD &&
341 shdr->sh_addr >= phdr->p_vaddr &&
342 ((shdr->sh_addr + shdr->sh_size) <=
343 (phdr->p_vaddr + phdr->p_memsz)))
344 break;
345 }
346 if (j == pelf->ehdr.e_phnum) {
347 ERROR("Relocations being applied to section %d not "
348 "within segments region.\n", sh_info);
349 pelf->relocs[i] = NULL;
350 return -1;
351 }
352 }
353
354 return 0;
355 }
356
vaddr_cmp(const void * a,const void * b)357 static int vaddr_cmp(const void *a, const void *b)
358 {
359 const Elf64_Addr *pa = a;
360 const Elf64_Addr *pb = b;
361
362 if (*pa < *pb)
363 return -1;
364 if (*pa > *pb)
365 return 1;
366 return 0;
367 }
368
rmodule_collect_relocations(struct rmod_context * ctx,struct reloc_filter * f)369 int rmodule_collect_relocations(struct rmod_context *ctx,
370 struct reloc_filter *f)
371 {
372 Elf64_Xword nrelocs;
373
374 /*
375 * The relocs array in the pelf should only contain relocations that
376 * apply to the program. Count the number relocations. Then collect
377 * them into the allocated buffer.
378 */
379 if (for_each_reloc(ctx, f, 0))
380 return -1;
381
382 nrelocs = ctx->nrelocs;
383 INFO("%" PRIu64 " relocations to be emitted.\n", nrelocs);
384 if (!nrelocs)
385 return 0;
386
387 /* Reset the counter for indexing into the array. */
388 ctx->nrelocs = 0;
389 ctx->emitted_relocs = calloc(nrelocs, sizeof(Elf64_Addr));
390 /* Write out the relocations into the emitted_relocs array. */
391 if (for_each_reloc(ctx, f, 1))
392 return -1;
393
394 if (ctx->nrelocs != nrelocs) {
395 ERROR("Mismatch counted and emitted relocations: %zu vs %zu.\n",
396 (size_t)nrelocs, (size_t)ctx->nrelocs);
397 return -1;
398 }
399
400 /* Sort the relocations by their address. */
401 qsort(ctx->emitted_relocs, nrelocs, sizeof(Elf64_Addr), vaddr_cmp);
402
403 return 0;
404 }
405
406 static int
populate_sym(struct rmod_context * ctx,const char * sym_name,Elf64_Addr * addr,int nsyms,int optional)407 populate_sym(struct rmod_context *ctx, const char *sym_name, Elf64_Addr *addr,
408 int nsyms, int optional)
409 {
410 int i;
411 Elf64_Sym *syms;
412
413 syms = ctx->pelf.syms;
414
415 for (i = 0; i < nsyms; i++) {
416 if (syms[i].st_name == 0)
417 continue;
418 if (strcmp(sym_name, &ctx->strtab[syms[i].st_name]))
419 continue;
420 DEBUG("%s -> 0x%llx\n", sym_name, (long long)syms[i].st_value);
421 *addr = syms[i].st_value;
422 return 0;
423 }
424
425 if (optional) {
426 DEBUG("optional symbol '%s' not found.\n", sym_name);
427 *addr = 0;
428 return 0;
429 }
430
431 ERROR("symbol '%s' not found.\n", sym_name);
432 return -1;
433 }
434
populate_rmodule_info(struct rmod_context * ctx)435 static int populate_rmodule_info(struct rmod_context *ctx)
436 {
437 int i;
438 struct parsed_elf *pelf;
439 Elf64_Ehdr *ehdr;
440 int nsyms;
441
442 pelf = &ctx->pelf;
443 ehdr = &pelf->ehdr;
444
445 /* Determine number of symbols. */
446 nsyms = 0;
447 for (i = 0; i < ehdr->e_shnum; i++) {
448 if (pelf->shdr[i].sh_type != SHT_SYMTAB)
449 continue;
450
451 nsyms = pelf->shdr[i].sh_size / pelf->shdr[i].sh_entsize;
452 break;
453 }
454
455 if (populate_sym(ctx, "_rmodule_params", &ctx->parameters_begin, nsyms, 1))
456 return -1;
457
458 if (populate_sym(ctx, "_ermodule_params", &ctx->parameters_end, nsyms, 1))
459 return -1;
460
461 if (populate_sym(ctx, "_bss", &ctx->bss_begin, nsyms, 0))
462 return -1;
463
464 if (populate_sym(ctx, "_ebss", &ctx->bss_end, nsyms, 0))
465 return -1;
466
467 return 0;
468 }
469
470 static int
add_section(struct elf_writer * ew,struct buffer * data,const char * name,Elf64_Addr addr,Elf64_Word size)471 add_section(struct elf_writer *ew, struct buffer *data, const char *name,
472 Elf64_Addr addr, Elf64_Word size)
473 {
474 Elf64_Shdr shdr;
475 int ret;
476
477 memset(&shdr, 0, sizeof(shdr));
478 if (data != NULL) {
479 shdr.sh_type = SHT_PROGBITS;
480 shdr.sh_flags = SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR;
481 } else {
482 shdr.sh_type = SHT_NOBITS;
483 shdr.sh_flags = SHF_ALLOC;
484 }
485 shdr.sh_addr = addr;
486 shdr.sh_offset = addr;
487 shdr.sh_size = size;
488
489 ret = elf_writer_add_section(ew, &shdr, data, name);
490
491 if (ret)
492 ERROR("Could not add '%s' section.\n", name);
493
494 return ret;
495 }
496
497 static int
write_elf(const struct rmod_context * ctx,const struct buffer * in,struct buffer * out)498 write_elf(const struct rmod_context *ctx, const struct buffer *in,
499 struct buffer *out)
500 {
501 int ret;
502 int bit64;
503 size_t loc;
504 size_t rmod_data_size;
505 struct elf_writer *ew;
506 struct buffer rmod_data;
507 struct buffer rmod_header;
508 struct buffer program;
509 struct buffer relocs;
510 Elf64_Xword total_size;
511 Elf64_Addr addr;
512 Elf64_Ehdr ehdr;
513
514 if (ctx->nsegments != 1) {
515 ERROR("Multiple loadable segments is not supported.\n");
516 return -1;
517 }
518
519 bit64 = ctx->pelf.ehdr.e_ident[EI_CLASS] == ELFCLASS64;
520
521 /*
522 * 3 sections will be added to the ELF file.
523 * +------------------+
524 * | rmodule header |
525 * +------------------+
526 * | program |
527 * +------------------+
528 * | relocations |
529 * +------------------+
530 */
531
532 /* Create buffer for header and relocations. */
533 rmod_data_size = sizeof(struct rmodule_header);
534 if (bit64)
535 rmod_data_size += ctx->nrelocs * sizeof(Elf64_Addr);
536 else
537 rmod_data_size += ctx->nrelocs * sizeof(Elf32_Addr);
538
539 if (buffer_create(&rmod_data, rmod_data_size, "rmod"))
540 return -1;
541
542 buffer_splice(&rmod_header, &rmod_data,
543 0, sizeof(struct rmodule_header));
544 buffer_clone(&relocs, &rmod_data);
545 buffer_seek(&relocs, sizeof(struct rmodule_header));
546
547 /* Reset current location. */
548 buffer_set_size(&rmod_header, 0);
549 buffer_set_size(&relocs, 0);
550
551 /* Program contents. */
552 buffer_splice(&program, in, ctx->phdr->p_offset, ctx->phdr->p_filesz);
553
554 /* Create ELF writer. Set entry point to 0 to match section offsets. */
555 memcpy(&ehdr, &ctx->pelf.ehdr, sizeof(ehdr));
556 ehdr.e_entry = 0;
557 ew = elf_writer_init(&ehdr);
558
559 if (ew == NULL) {
560 ERROR("Failed to create ELF writer.\n");
561 buffer_delete(&rmod_data);
562 return -1;
563 }
564
565 /* Write out rmodule_header. */
566 ctx->xdr->put16(&rmod_header, RMODULE_MAGIC);
567 ctx->xdr->put8(&rmod_header, RMODULE_VERSION_1);
568 ctx->xdr->put8(&rmod_header, 0);
569 /* payload_begin_offset */
570 loc = sizeof(struct rmodule_header);
571 ctx->xdr->put32(&rmod_header, loc);
572 /* payload_end_offset */
573 loc += ctx->phdr->p_filesz;
574 ctx->xdr->put32(&rmod_header, loc);
575 /* relocations_begin_offset */
576 ctx->xdr->put32(&rmod_header, loc);
577 /* relocations_end_offset */
578 if (bit64)
579 loc += ctx->nrelocs * sizeof(Elf64_Addr);
580 else
581 loc += ctx->nrelocs * sizeof(Elf32_Addr);
582 ctx->xdr->put32(&rmod_header, loc);
583 /* module_link_start_address */
584 ctx->xdr->put32(&rmod_header, ctx->phdr->p_vaddr);
585 /* module_program_size */
586 ctx->xdr->put32(&rmod_header, ctx->phdr->p_memsz);
587 /* module_entry_point */
588 ctx->xdr->put32(&rmod_header, ctx->pelf.ehdr.e_entry);
589 /* parameters_begin */
590 ctx->xdr->put32(&rmod_header, ctx->parameters_begin);
591 /* parameters_end */
592 ctx->xdr->put32(&rmod_header, ctx->parameters_end);
593 /* bss_begin */
594 ctx->xdr->put32(&rmod_header, ctx->bss_begin);
595 /* bss_end */
596 ctx->xdr->put32(&rmod_header, ctx->bss_end);
597 /* padding[4] */
598 ctx->xdr->put32(&rmod_header, 0);
599 ctx->xdr->put32(&rmod_header, 0);
600 ctx->xdr->put32(&rmod_header, 0);
601 ctx->xdr->put32(&rmod_header, 0);
602
603 /* Write the relocations. */
604 for (unsigned i = 0; i < ctx->nrelocs; i++) {
605 if (bit64)
606 ctx->xdr->put64(&relocs, ctx->emitted_relocs[i]);
607 else
608 ctx->xdr->put32(&relocs, ctx->emitted_relocs[i]);
609 }
610
611 total_size = 0;
612 addr = 0;
613
614 /*
615 * There are 2 cases to deal with. The program has a large NOBITS
616 * section and the relocations can fit entirely within occupied memory
617 * region for the program. The other is that the relocations increase
618 * the memory footprint of the program if it was loaded directly into
619 * the region it would run. The rmodule header is a fixed cost that
620 * is considered a part of the program.
621 */
622 total_size += buffer_size(&rmod_header);
623 if (buffer_size(&relocs) + ctx->phdr->p_filesz > ctx->phdr->p_memsz) {
624 total_size += buffer_size(&relocs);
625 total_size += ctx->phdr->p_filesz;
626 } else {
627 total_size += ctx->phdr->p_memsz;
628 }
629
630 ret = add_section(ew, &rmod_header, ".header", addr,
631 buffer_size(&rmod_header));
632 if (ret < 0)
633 goto out;
634 addr += buffer_size(&rmod_header);
635
636 ret = add_section(ew, &program, ".program", addr, ctx->phdr->p_filesz);
637 if (ret < 0)
638 goto out;
639 addr += ctx->phdr->p_filesz;
640
641 if (ctx->nrelocs) {
642 ret = add_section(ew, &relocs, ".relocs", addr,
643 buffer_size(&relocs));
644 if (ret < 0)
645 goto out;
646 addr += buffer_size(&relocs);
647 }
648
649 if (total_size != addr) {
650 ret = add_section(ew, NULL, ".empty", addr, total_size - addr);
651 if (ret < 0)
652 goto out;
653 }
654
655 /*
656 * Ensure last section has a memory usage that meets the required
657 * total size of the program in memory.
658 */
659
660 ret = elf_writer_serialize(ew, out);
661 if (ret < 0)
662 ERROR("Failed to serialize ELF to buffer.\n");
663
664 out:
665 buffer_delete(&rmod_data);
666 elf_writer_destroy(ew);
667
668 return ret;
669 }
670
rmodule_init(struct rmod_context * ctx,const struct buffer * elfin)671 int rmodule_init(struct rmod_context *ctx, const struct buffer *elfin)
672 {
673 struct parsed_elf *pelf;
674 size_t i;
675 int ret;
676
677 ret = -1;
678 memset(ctx, 0, sizeof(*ctx));
679 pelf = &ctx->pelf;
680
681 if (parse_elf(elfin, pelf, ELF_PARSE_ALL)) {
682 ERROR("Couldn't parse ELF!\n");
683 return -1;
684 }
685
686 /* Only allow executables to be turned into rmodules. */
687 if (pelf->ehdr.e_type != ET_EXEC) {
688 ERROR("ELF is not an executable: %u.\n", pelf->ehdr.e_type);
689 goto out;
690 }
691
692 /* Determine if architecture is supported. */
693 for (i = 0; i < ARRAY_SIZE(reloc_ops); i++) {
694 if (reloc_ops[i].arch == pelf->ehdr.e_machine) {
695 ctx->ops = &reloc_ops[i];
696 break;
697 }
698 }
699
700 if (ctx->ops == NULL) {
701 ERROR("ELF is unsupported arch: %u.\n", pelf->ehdr.e_machine);
702 goto out;
703 }
704
705 /* Set the endian ops. */
706 if (ctx->pelf.ehdr.e_ident[EI_DATA] == ELFDATA2MSB)
707 ctx->xdr = &xdr_be;
708 else
709 ctx->xdr = &xdr_le;
710
711 /* Obtain the string table. */
712 for (i = 0; i < pelf->ehdr.e_shnum; i++) {
713 if (pelf->strtabs[i] == NULL)
714 continue;
715 /* Don't use the section headers' string table. */
716 if (i == pelf->ehdr.e_shstrndx)
717 continue;
718 ctx->strtab = buffer_get(pelf->strtabs[i]);
719 break;
720 }
721
722 if (ctx->strtab == NULL) {
723 ERROR("No string table found.\n");
724 return -1;
725 }
726
727 if (find_program_segment(ctx))
728 goto out;
729
730 if (filter_relocation_sections(ctx))
731 goto out;
732
733 ret = 0;
734
735 out:
736 return ret;
737 }
738
rmodule_cleanup(struct rmod_context * ctx)739 void rmodule_cleanup(struct rmod_context *ctx)
740 {
741 free(ctx->emitted_relocs);
742 parsed_elf_destroy(&ctx->pelf);
743 }
744
rmodule_create(const struct buffer * elfin,struct buffer * elfout)745 int rmodule_create(const struct buffer *elfin, struct buffer *elfout)
746 {
747 struct rmod_context ctx;
748 int ret = -1;
749
750 if (rmodule_init(&ctx, elfin))
751 goto out;
752
753 if (rmodule_collect_relocations(&ctx, NULL))
754 goto out;
755
756 if (populate_rmodule_info(&ctx))
757 goto out;
758
759 if (write_elf(&ctx, elfin, elfout))
760 goto out;
761
762 ret = 0;
763
764 out:
765 rmodule_cleanup(&ctx);
766 return ret;
767 }
768
rmod_deserialize(struct rmodule_header * rmod,struct buffer * buff,struct xdr * xdr)769 static void rmod_deserialize(struct rmodule_header *rmod, struct buffer *buff,
770 struct xdr *xdr)
771 {
772 rmod->magic = xdr->get16(buff);
773 rmod->version = xdr->get8(buff);
774 rmod->type = xdr->get8(buff);
775 rmod->payload_begin_offset = xdr->get32(buff);
776 rmod->payload_end_offset = xdr->get32(buff);
777 rmod->relocations_begin_offset = xdr->get32(buff);
778 rmod->relocations_end_offset = xdr->get32(buff);
779 rmod->module_link_start_address = xdr->get32(buff);
780 rmod->module_program_size = xdr->get32(buff);
781 rmod->module_entry_point = xdr->get32(buff);
782 rmod->parameters_begin = xdr->get32(buff);
783 rmod->parameters_end = xdr->get32(buff);
784 rmod->bss_begin = xdr->get32(buff);
785 rmod->bss_end = xdr->get32(buff);
786 rmod->padding[0] = xdr->get32(buff);
787 rmod->padding[1] = xdr->get32(buff);
788 rmod->padding[2] = xdr->get32(buff);
789 rmod->padding[3] = xdr->get32(buff);
790 }
791
rmodule_stage_to_elf(Elf64_Ehdr * ehdr,struct buffer * buff)792 int rmodule_stage_to_elf(Elf64_Ehdr *ehdr, struct buffer *buff)
793 {
794 struct buffer reader;
795 struct buffer elf_out;
796 struct rmodule_header rmod;
797 struct xdr *xdr;
798 struct elf_writer *ew;
799 Elf64_Shdr shdr;
800 int bit64;
801 size_t payload_sz;
802 const char *section_name = ".program";
803 const size_t input_sz = buffer_size(buff);
804
805 buffer_clone(&reader, buff);
806
807 xdr = (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) ? &xdr_be : &xdr_le;
808 bit64 = ehdr->e_ident[EI_CLASS] == ELFCLASS64;
809
810 rmod_deserialize(&rmod, &reader, xdr);
811
812 /* Indicate that file is not an rmodule if initial checks fail. */
813 if (rmod.magic != RMODULE_MAGIC)
814 return 1;
815 if (rmod.version != RMODULE_VERSION_1)
816 return 1;
817
818 if (rmod.payload_begin_offset > input_sz ||
819 rmod.payload_end_offset > input_sz ||
820 rmod.relocations_begin_offset > input_sz ||
821 rmod.relocations_end_offset > input_sz) {
822 ERROR("Rmodule fields out of bounds.\n");
823 return -1;
824 }
825
826 ehdr->e_entry = rmod.module_entry_point;
827 ew = elf_writer_init(ehdr);
828
829 if (ew == NULL)
830 return -1;
831
832 payload_sz = rmod.payload_end_offset - rmod.payload_begin_offset;
833 memset(&shdr, 0, sizeof(shdr));
834 shdr.sh_type = SHT_PROGBITS;
835 shdr.sh_flags = SHF_WRITE | SHF_ALLOC | SHF_EXECINSTR;
836 shdr.sh_addr = rmod.module_link_start_address;
837 shdr.sh_size = payload_sz;
838 buffer_splice(&reader, buff, rmod.payload_begin_offset, payload_sz);
839
840 if (elf_writer_add_section(ew, &shdr, &reader, section_name)) {
841 ERROR("Unable to add ELF section: %s\n", section_name);
842 elf_writer_destroy(ew);
843 return -1;
844 }
845
846 if (payload_sz != rmod.module_program_size) {
847 struct buffer b;
848
849 buffer_init(&b, NULL, NULL, 0);
850 memset(&shdr, 0, sizeof(shdr));
851 shdr.sh_type = SHT_NOBITS;
852 shdr.sh_flags = SHF_WRITE | SHF_ALLOC;
853 shdr.sh_addr = rmod.module_link_start_address + payload_sz;
854 shdr.sh_size = rmod.module_program_size - payload_sz;
855 if (elf_writer_add_section(ew, &shdr, &b, ".empty")) {
856 ERROR("Unable to add ELF section: .empty\n");
857 elf_writer_destroy(ew);
858 return -1;
859 }
860 }
861
862 /* Provide a section symbol so the relcoations can reference that. */
863 if (elf_writer_add_symbol(ew, section_name, section_name, shdr.sh_addr,
864 0, STB_LOCAL, STT_SECTION)) {
865 ERROR("Unable to add section symbol to ELF.\n");
866 elf_writer_destroy(ew);
867 return -1;
868 }
869
870 /* Add symbols for the parameters if they are non-zero. */
871 if (rmod.parameters_begin != rmod.parameters_end) {
872 int ret = 0;
873
874 ret |= elf_writer_add_symbol(ew, "_rmodule_params",
875 section_name,
876 rmod.parameters_begin, 0,
877 STB_GLOBAL, STT_NOTYPE);
878 ret |= elf_writer_add_symbol(ew, "_ermodule_params",
879 section_name,
880 rmod.parameters_end, 0,
881 STB_GLOBAL, STT_NOTYPE);
882
883 if (ret != 0) {
884 ERROR("Unable to add module params symbols to ELF\n");
885 elf_writer_destroy(ew);
886 return -1;
887 }
888 }
889
890 if (elf_writer_add_symbol(ew, "_bss", section_name, rmod.bss_begin, 0,
891 STB_GLOBAL, STT_NOTYPE) ||
892 elf_writer_add_symbol(ew, "_ebss", section_name, rmod.bss_end, 0,
893 STB_GLOBAL, STT_NOTYPE)) {
894 ERROR("Unable to add bss symbols to ELF\n");
895 elf_writer_destroy(ew);
896 return -1;
897 }
898
899 ssize_t relocs_sz = rmod.relocations_end_offset;
900 relocs_sz -= rmod.relocations_begin_offset;
901 buffer_splice(&reader, buff, rmod.relocations_begin_offset, relocs_sz);
902 while (relocs_sz > 0) {
903 Elf64_Addr addr;
904
905 if (bit64) {
906 relocs_sz -= sizeof(Elf64_Addr);
907 addr = xdr->get64(&reader);
908 } else {
909 relocs_sz -= sizeof(Elf32_Addr);
910 addr = xdr->get32(&reader);
911 }
912
913 /* Skip any relocations that are below the link address. */
914 if (addr < rmod.module_link_start_address)
915 continue;
916
917 if (elf_writer_add_rel(ew, section_name, addr)) {
918 ERROR("Relocation addition failure.\n");
919 elf_writer_destroy(ew);
920 return -1;
921 }
922 }
923
924 if (elf_writer_serialize(ew, &elf_out)) {
925 ERROR("ELF writer serialize failure.\n");
926 elf_writer_destroy(ew);
927 return -1;
928 }
929
930 elf_writer_destroy(ew);
931
932 /* Flip buffer with the created ELF one. */
933 buffer_delete(buff);
934 *buff = elf_out;
935
936 return 0;
937 }
938