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91007045 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
9b07e27f SE |
2 | /* |
3 | * genelf.c | |
4 | * Copyright (C) 2014, Google, Inc | |
5 | * | |
6 | * Contributed by: | |
7 | * Stephane Eranian <eranian@gmail.com> | |
9b07e27f SE |
8 | */ |
9 | ||
10 | #include <sys/types.h> | |
11 | #include <stdio.h> | |
12 | #include <getopt.h> | |
13 | #include <stddef.h> | |
14 | #include <libelf.h> | |
15 | #include <string.h> | |
16 | #include <stdlib.h> | |
91854f9a | 17 | #include <unistd.h> |
9b07e27f SE |
18 | #include <inttypes.h> |
19 | #include <limits.h> | |
20 | #include <fcntl.h> | |
21 | #include <err.h> | |
621cb4e7 | 22 | #ifdef HAVE_DWARF_SUPPORT |
9b07e27f | 23 | #include <dwarf.h> |
621cb4e7 | 24 | #endif |
9b07e27f | 25 | |
9b07e27f SE |
26 | #include "genelf.h" |
27 | #include "../util/jitdump.h" | |
91854f9a | 28 | #include <linux/compiler.h> |
9b07e27f | 29 | |
5fef5f3f ACM |
30 | #ifndef NT_GNU_BUILD_ID |
31 | #define NT_GNU_BUILD_ID 3 | |
32 | #endif | |
33 | ||
9b07e27f SE |
34 | #define JVMTI |
35 | ||
36 | #define BUILD_ID_URANDOM /* different uuid for each run */ | |
37 | ||
38 | #ifdef HAVE_LIBCRYPTO | |
39 | ||
40 | #define BUILD_ID_MD5 | |
41 | #undef BUILD_ID_SHA /* does not seem to work well when linked with Java */ | |
42 | #undef BUILD_ID_URANDOM /* different uuid for each run */ | |
43 | ||
44 | #ifdef BUILD_ID_SHA | |
45 | #include <openssl/sha.h> | |
46 | #endif | |
47 | ||
48 | #ifdef BUILD_ID_MD5 | |
49 | #include <openssl/md5.h> | |
50 | #endif | |
51 | #endif | |
52 | ||
53 | ||
54 | typedef struct { | |
55 | unsigned int namesz; /* Size of entry's owner string */ | |
56 | unsigned int descsz; /* Size of the note descriptor */ | |
57 | unsigned int type; /* Interpretation of the descriptor */ | |
58 | char name[0]; /* Start of the name+desc data */ | |
59 | } Elf_Note; | |
60 | ||
61 | struct options { | |
62 | char *output; | |
63 | int fd; | |
64 | }; | |
65 | ||
66 | static char shd_string_table[] = { | |
67 | 0, | |
68 | '.', 't', 'e', 'x', 't', 0, /* 1 */ | |
69 | '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */ | |
70 | '.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */ | |
71 | '.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */ | |
72 | '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */ | |
73 | '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */ | |
74 | '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */ | |
75 | '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */ | |
086f9f3d SS |
76 | '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */ |
77 | '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */ | |
9b07e27f SE |
78 | }; |
79 | ||
80 | static struct buildid_note { | |
81 | Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */ | |
82 | char name[4]; /* GNU\0 */ | |
83 | char build_id[20]; | |
84 | } bnote; | |
85 | ||
86 | static Elf_Sym symtab[]={ | |
87 | /* symbol 0 MUST be the undefined symbol */ | |
88 | { .st_name = 0, /* index in sym_string table */ | |
89 | .st_info = ELF_ST_TYPE(STT_NOTYPE), | |
90 | .st_shndx = 0, /* for now */ | |
91 | .st_value = 0x0, | |
92 | .st_other = ELF_ST_VIS(STV_DEFAULT), | |
93 | .st_size = 0, | |
94 | }, | |
95 | { .st_name = 1, /* index in sym_string table */ | |
96 | .st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC), | |
97 | .st_shndx = 1, | |
98 | .st_value = 0, /* for now */ | |
99 | .st_other = ELF_ST_VIS(STV_DEFAULT), | |
100 | .st_size = 0, /* for now */ | |
101 | } | |
102 | }; | |
103 | ||
104 | #ifdef BUILD_ID_URANDOM | |
105 | static void | |
106 | gen_build_id(struct buildid_note *note, | |
107 | unsigned long load_addr __maybe_unused, | |
108 | const void *code __maybe_unused, | |
109 | size_t csize __maybe_unused) | |
110 | { | |
111 | int fd; | |
112 | size_t sz = sizeof(note->build_id); | |
113 | ssize_t sret; | |
114 | ||
115 | fd = open("/dev/urandom", O_RDONLY); | |
116 | if (fd == -1) | |
24690761 | 117 | err(1, "cannot access /dev/urandom for buildid"); |
9b07e27f SE |
118 | |
119 | sret = read(fd, note->build_id, sz); | |
120 | ||
121 | close(fd); | |
122 | ||
123 | if (sret != (ssize_t)sz) | |
124 | memset(note->build_id, 0, sz); | |
125 | } | |
126 | #endif | |
127 | ||
128 | #ifdef BUILD_ID_SHA | |
129 | static void | |
130 | gen_build_id(struct buildid_note *note, | |
131 | unsigned long load_addr __maybe_unused, | |
132 | const void *code, | |
133 | size_t csize) | |
134 | { | |
135 | if (sizeof(note->build_id) < SHA_DIGEST_LENGTH) | |
136 | errx(1, "build_id too small for SHA1"); | |
137 | ||
138 | SHA1(code, csize, (unsigned char *)note->build_id); | |
139 | } | |
140 | #endif | |
141 | ||
142 | #ifdef BUILD_ID_MD5 | |
143 | static void | |
144 | gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize) | |
145 | { | |
146 | MD5_CTX context; | |
147 | ||
148 | if (sizeof(note->build_id) < 16) | |
149 | errx(1, "build_id too small for MD5"); | |
150 | ||
151 | MD5_Init(&context); | |
152 | MD5_Update(&context, &load_addr, sizeof(load_addr)); | |
153 | MD5_Update(&context, code, csize); | |
154 | MD5_Final((unsigned char *)note->build_id, &context); | |
155 | } | |
156 | #endif | |
157 | ||
086f9f3d SS |
158 | static int |
159 | jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size, | |
160 | uint64_t unwinding_size, uint64_t base_offset) | |
161 | { | |
162 | Elf_Data *d; | |
163 | Elf_Scn *scn; | |
164 | Elf_Shdr *shdr; | |
165 | uint64_t unwinding_table_size = unwinding_size - unwinding_header_size; | |
166 | ||
167 | /* | |
168 | * setup eh_frame section | |
169 | */ | |
170 | scn = elf_newscn(e); | |
171 | if (!scn) { | |
172 | warnx("cannot create section"); | |
173 | return -1; | |
174 | } | |
175 | ||
176 | d = elf_newdata(scn); | |
177 | if (!d) { | |
178 | warnx("cannot get new data"); | |
179 | return -1; | |
180 | } | |
181 | ||
182 | d->d_align = 8; | |
183 | d->d_off = 0LL; | |
184 | d->d_buf = unwinding; | |
185 | d->d_type = ELF_T_BYTE; | |
186 | d->d_size = unwinding_table_size; | |
187 | d->d_version = EV_CURRENT; | |
188 | ||
189 | shdr = elf_getshdr(scn); | |
190 | if (!shdr) { | |
191 | warnx("cannot get section header"); | |
192 | return -1; | |
193 | } | |
194 | ||
195 | shdr->sh_name = 104; | |
196 | shdr->sh_type = SHT_PROGBITS; | |
197 | shdr->sh_addr = base_offset; | |
198 | shdr->sh_flags = SHF_ALLOC; | |
199 | shdr->sh_entsize = 0; | |
200 | ||
201 | /* | |
202 | * setup eh_frame_hdr section | |
203 | */ | |
204 | scn = elf_newscn(e); | |
205 | if (!scn) { | |
206 | warnx("cannot create section"); | |
207 | return -1; | |
208 | } | |
209 | ||
210 | d = elf_newdata(scn); | |
211 | if (!d) { | |
212 | warnx("cannot get new data"); | |
213 | return -1; | |
214 | } | |
215 | ||
216 | d->d_align = 4; | |
217 | d->d_off = 0LL; | |
218 | d->d_buf = unwinding + unwinding_table_size; | |
219 | d->d_type = ELF_T_BYTE; | |
220 | d->d_size = unwinding_header_size; | |
221 | d->d_version = EV_CURRENT; | |
222 | ||
223 | shdr = elf_getshdr(scn); | |
224 | if (!shdr) { | |
225 | warnx("cannot get section header"); | |
226 | return -1; | |
227 | } | |
228 | ||
229 | shdr->sh_name = 90; | |
230 | shdr->sh_type = SHT_PROGBITS; | |
231 | shdr->sh_addr = base_offset + unwinding_table_size; | |
232 | shdr->sh_flags = SHF_ALLOC; | |
233 | shdr->sh_entsize = 0; | |
234 | ||
235 | return 0; | |
236 | } | |
237 | ||
9b07e27f SE |
238 | /* |
239 | * fd: file descriptor open for writing for the output file | |
240 | * load_addr: code load address (could be zero, just used for buildid) | |
241 | * sym: function name (for native code - used as the symbol) | |
242 | * code: the native code | |
243 | * csize: the code size in bytes | |
244 | */ | |
245 | int | |
246 | jit_write_elf(int fd, uint64_t load_addr, const char *sym, | |
598b7c69 | 247 | const void *code, int csize, |
086f9f3d SS |
248 | void *debug __maybe_unused, int nr_debug_entries __maybe_unused, |
249 | void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size) | |
9b07e27f SE |
250 | { |
251 | Elf *e; | |
252 | Elf_Data *d; | |
253 | Elf_Scn *scn; | |
254 | Elf_Ehdr *ehdr; | |
255 | Elf_Shdr *shdr; | |
086f9f3d | 256 | uint64_t eh_frame_base_offset; |
9b07e27f SE |
257 | char *strsym = NULL; |
258 | int symlen; | |
259 | int retval = -1; | |
260 | ||
261 | if (elf_version(EV_CURRENT) == EV_NONE) { | |
262 | warnx("ELF initialization failed"); | |
263 | return -1; | |
264 | } | |
265 | ||
266 | e = elf_begin(fd, ELF_C_WRITE, NULL); | |
267 | if (!e) { | |
268 | warnx("elf_begin failed"); | |
269 | goto error; | |
270 | } | |
271 | ||
272 | /* | |
273 | * setup ELF header | |
274 | */ | |
275 | ehdr = elf_newehdr(e); | |
276 | if (!ehdr) { | |
277 | warnx("cannot get ehdr"); | |
278 | goto error; | |
279 | } | |
280 | ||
281 | ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN; | |
282 | ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS; | |
283 | ehdr->e_machine = GEN_ELF_ARCH; | |
284 | ehdr->e_type = ET_DYN; | |
285 | ehdr->e_entry = GEN_ELF_TEXT_OFFSET; | |
286 | ehdr->e_version = EV_CURRENT; | |
086f9f3d | 287 | ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */ |
9b07e27f SE |
288 | |
289 | /* | |
290 | * setup text section | |
291 | */ | |
292 | scn = elf_newscn(e); | |
293 | if (!scn) { | |
294 | warnx("cannot create section"); | |
295 | goto error; | |
296 | } | |
297 | ||
298 | d = elf_newdata(scn); | |
299 | if (!d) { | |
300 | warnx("cannot get new data"); | |
301 | goto error; | |
302 | } | |
303 | ||
304 | d->d_align = 16; | |
305 | d->d_off = 0LL; | |
306 | d->d_buf = (void *)code; | |
307 | d->d_type = ELF_T_BYTE; | |
308 | d->d_size = csize; | |
309 | d->d_version = EV_CURRENT; | |
310 | ||
311 | shdr = elf_getshdr(scn); | |
312 | if (!shdr) { | |
313 | warnx("cannot get section header"); | |
314 | goto error; | |
315 | } | |
316 | ||
317 | shdr->sh_name = 1; | |
318 | shdr->sh_type = SHT_PROGBITS; | |
319 | shdr->sh_addr = GEN_ELF_TEXT_OFFSET; | |
320 | shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; | |
321 | shdr->sh_entsize = 0; | |
322 | ||
086f9f3d SS |
323 | /* |
324 | * Setup .eh_frame_hdr and .eh_frame | |
325 | */ | |
326 | if (unwinding) { | |
327 | eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize); | |
328 | retval = jit_add_eh_frame_info(e, unwinding, | |
329 | unwinding_header_size, unwinding_size, | |
330 | eh_frame_base_offset); | |
331 | if (retval) | |
332 | goto error; | |
333 | } | |
334 | ||
9b07e27f SE |
335 | /* |
336 | * setup section headers string table | |
337 | */ | |
338 | scn = elf_newscn(e); | |
339 | if (!scn) { | |
340 | warnx("cannot create section"); | |
341 | goto error; | |
342 | } | |
343 | ||
344 | d = elf_newdata(scn); | |
345 | if (!d) { | |
346 | warnx("cannot get new data"); | |
347 | goto error; | |
348 | } | |
349 | ||
350 | d->d_align = 1; | |
351 | d->d_off = 0LL; | |
352 | d->d_buf = shd_string_table; | |
353 | d->d_type = ELF_T_BYTE; | |
354 | d->d_size = sizeof(shd_string_table); | |
355 | d->d_version = EV_CURRENT; | |
356 | ||
357 | shdr = elf_getshdr(scn); | |
358 | if (!shdr) { | |
359 | warnx("cannot get section header"); | |
360 | goto error; | |
361 | } | |
362 | ||
363 | shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */ | |
364 | shdr->sh_type = SHT_STRTAB; | |
365 | shdr->sh_flags = 0; | |
366 | shdr->sh_entsize = 0; | |
367 | ||
368 | /* | |
369 | * setup symtab section | |
370 | */ | |
371 | symtab[1].st_size = csize; | |
372 | symtab[1].st_value = GEN_ELF_TEXT_OFFSET; | |
373 | ||
374 | scn = elf_newscn(e); | |
375 | if (!scn) { | |
376 | warnx("cannot create section"); | |
377 | goto error; | |
378 | } | |
379 | ||
380 | d = elf_newdata(scn); | |
381 | if (!d) { | |
382 | warnx("cannot get new data"); | |
383 | goto error; | |
384 | } | |
385 | ||
386 | d->d_align = 8; | |
387 | d->d_off = 0LL; | |
388 | d->d_buf = symtab; | |
389 | d->d_type = ELF_T_SYM; | |
390 | d->d_size = sizeof(symtab); | |
391 | d->d_version = EV_CURRENT; | |
392 | ||
393 | shdr = elf_getshdr(scn); | |
394 | if (!shdr) { | |
395 | warnx("cannot get section header"); | |
396 | goto error; | |
397 | } | |
398 | ||
399 | shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */ | |
400 | shdr->sh_type = SHT_SYMTAB; | |
401 | shdr->sh_flags = 0; | |
402 | shdr->sh_entsize = sizeof(Elf_Sym); | |
086f9f3d | 403 | shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */ |
9b07e27f SE |
404 | |
405 | /* | |
406 | * setup symbols string table | |
407 | * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry | |
408 | */ | |
409 | symlen = 2 + strlen(sym); | |
410 | strsym = calloc(1, symlen); | |
411 | if (!strsym) { | |
412 | warnx("cannot allocate strsym"); | |
413 | goto error; | |
414 | } | |
415 | strcpy(strsym + 1, sym); | |
416 | ||
417 | scn = elf_newscn(e); | |
418 | if (!scn) { | |
419 | warnx("cannot create section"); | |
420 | goto error; | |
421 | } | |
422 | ||
423 | d = elf_newdata(scn); | |
424 | if (!d) { | |
425 | warnx("cannot get new data"); | |
426 | goto error; | |
427 | } | |
428 | ||
429 | d->d_align = 1; | |
430 | d->d_off = 0LL; | |
431 | d->d_buf = strsym; | |
432 | d->d_type = ELF_T_BYTE; | |
433 | d->d_size = symlen; | |
434 | d->d_version = EV_CURRENT; | |
435 | ||
436 | shdr = elf_getshdr(scn); | |
437 | if (!shdr) { | |
438 | warnx("cannot get section header"); | |
439 | goto error; | |
440 | } | |
441 | ||
442 | shdr->sh_name = 25; /* offset in shd_string_table */ | |
443 | shdr->sh_type = SHT_STRTAB; | |
444 | shdr->sh_flags = 0; | |
445 | shdr->sh_entsize = 0; | |
446 | ||
447 | /* | |
448 | * setup build-id section | |
449 | */ | |
450 | scn = elf_newscn(e); | |
451 | if (!scn) { | |
452 | warnx("cannot create section"); | |
453 | goto error; | |
454 | } | |
455 | ||
456 | d = elf_newdata(scn); | |
457 | if (!d) { | |
458 | warnx("cannot get new data"); | |
459 | goto error; | |
460 | } | |
461 | ||
462 | /* | |
463 | * build-id generation | |
464 | */ | |
465 | gen_build_id(&bnote, load_addr, code, csize); | |
466 | bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */ | |
467 | bnote.desc.descsz = sizeof(bnote.build_id); | |
468 | bnote.desc.type = NT_GNU_BUILD_ID; | |
469 | strcpy(bnote.name, "GNU"); | |
470 | ||
471 | d->d_align = 4; | |
472 | d->d_off = 0LL; | |
473 | d->d_buf = &bnote; | |
474 | d->d_type = ELF_T_BYTE; | |
475 | d->d_size = sizeof(bnote); | |
476 | d->d_version = EV_CURRENT; | |
477 | ||
478 | shdr = elf_getshdr(scn); | |
479 | if (!shdr) { | |
480 | warnx("cannot get section header"); | |
481 | goto error; | |
482 | } | |
483 | ||
484 | shdr->sh_name = 33; /* offset in shd_string_table */ | |
485 | shdr->sh_type = SHT_NOTE; | |
486 | shdr->sh_addr = 0x0; | |
487 | shdr->sh_flags = SHF_ALLOC; | |
488 | shdr->sh_size = sizeof(bnote); | |
489 | shdr->sh_entsize = 0; | |
490 | ||
621cb4e7 | 491 | #ifdef HAVE_DWARF_SUPPORT |
598b7c69 SE |
492 | if (debug && nr_debug_entries) { |
493 | retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries); | |
494 | if (retval) | |
495 | goto error; | |
621cb4e7 MD |
496 | } else |
497 | #endif | |
498 | { | |
598b7c69 SE |
499 | if (elf_update(e, ELF_C_WRITE) < 0) { |
500 | warnx("elf_update 4 failed"); | |
501 | goto error; | |
502 | } | |
9b07e27f SE |
503 | } |
504 | ||
505 | retval = 0; | |
506 | error: | |
507 | (void)elf_end(e); | |
508 | ||
509 | free(strsym); | |
510 | ||
511 | ||
512 | return retval; | |
513 | } | |
514 | ||
515 | #ifndef JVMTI | |
516 | ||
517 | static unsigned char x86_code[] = { | |
518 | 0xBB, 0x2A, 0x00, 0x00, 0x00, /* movl $42, %ebx */ | |
519 | 0xB8, 0x01, 0x00, 0x00, 0x00, /* movl $1, %eax */ | |
520 | 0xCD, 0x80 /* int $0x80 */ | |
521 | }; | |
522 | ||
523 | static struct options options; | |
524 | ||
525 | int main(int argc, char **argv) | |
526 | { | |
527 | int c, fd, ret; | |
528 | ||
529 | while ((c = getopt(argc, argv, "o:h")) != -1) { | |
530 | switch (c) { | |
531 | case 'o': | |
532 | options.output = optarg; | |
533 | break; | |
534 | case 'h': | |
535 | printf("Usage: genelf -o output_file [-h]\n"); | |
536 | return 0; | |
537 | default: | |
538 | errx(1, "unknown option"); | |
539 | } | |
540 | } | |
541 | ||
542 | fd = open(options.output, O_CREAT|O_TRUNC|O_RDWR, 0666); | |
543 | if (fd == -1) | |
544 | err(1, "cannot create file %s", options.output); | |
545 | ||
546 | ret = jit_write_elf(fd, "main", x86_code, sizeof(x86_code)); | |
547 | close(fd); | |
548 | ||
549 | if (ret != 0) | |
550 | unlink(options.output); | |
551 | ||
552 | return ret; | |
553 | } | |
554 | #endif |