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