1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * genelf_debug.c
4 * Copyright (C) 2015, Google, Inc
5 *
6 * Contributed by:
7 * Stephane Eranian <eranian@google.com>
8 *
9 * based on GPLv2 source code from Oprofile
10 * @remark Copyright 2007 OProfile authors
11 * @author Philippe Elie
12 */
13 #include <linux/compiler.h>
14 #include <linux/zalloc.h>
15 #include <sys/types.h>
16 #include <stdio.h>
17 #include <getopt.h>
18 #include <stddef.h>
19 #include <libelf.h>
20 #include <string.h>
21 #include <stdlib.h>
22 #include <inttypes.h>
23 #include <limits.h>
24 #include <fcntl.h>
25 #include <err.h>
26 #include <dwarf.h>
27
28 #include "genelf.h"
29 #include "../util/jitdump.h"
30
31 #define BUFFER_EXT_DFL_SIZE (4 * 1024)
32
33 typedef uint32_t uword;
34 typedef uint16_t uhalf;
35 typedef int32_t sword;
36 typedef int16_t shalf;
37 typedef uint8_t ubyte;
38 typedef int8_t sbyte;
39
40 struct buffer_ext {
41 size_t cur_pos;
42 size_t max_sz;
43 void *data;
44 };
45
46 static void
47 buffer_ext_dump(struct buffer_ext *be, const char *msg)
48 {
49 size_t i;
50 warnx("DUMP for %s", msg);
51 for (i = 0 ; i < be->cur_pos; i++)
52 warnx("%4zu 0x%02x", i, (((char *)be->data)[i]) & 0xff);
53 }
54
55 static inline int
56 buffer_ext_add(struct buffer_ext *be, void *addr, size_t sz)
57 {
58 void *tmp;
59 size_t be_sz = be->max_sz;
60
61 retry:
62 if ((be->cur_pos + sz) < be_sz) {
63 memcpy(be->data + be->cur_pos, addr, sz);
64 be->cur_pos += sz;
65 return 0;
66 }
67
68 if (!be_sz)
69 be_sz = BUFFER_EXT_DFL_SIZE;
70 else
71 be_sz <<= 1;
72
73 tmp = realloc(be->data, be_sz);
74 if (!tmp)
75 return -1;
76
77 be->data = tmp;
78 be->max_sz = be_sz;
79
80 goto retry;
81 }
82
83 static void
84 buffer_ext_init(struct buffer_ext *be)
85 {
86 be->data = NULL;
87 be->cur_pos = 0;
88 be->max_sz = 0;
89 }
90
91 static void
92 buffer_ext_exit(struct buffer_ext *be)
93 {
94 zfree(&be->data);
95 }
96
97 static inline size_t
98 buffer_ext_size(struct buffer_ext *be)
99 {
100 return be->cur_pos;
101 }
102
103 static inline void *
104 buffer_ext_addr(struct buffer_ext *be)
105 {
106 return be->data;
107 }
108
109 struct debug_line_header {
110 // Not counting this field
111 uword total_length;
112 // version number (2 currently)
113 uhalf version;
114 // relative offset from next field to
115 // program statement
116 uword prolog_length;
117 ubyte minimum_instruction_length;
118 ubyte default_is_stmt;
119 // line_base - see DWARF 2 specs
120 sbyte line_base;
121 // line_range - see DWARF 2 specs
122 ubyte line_range;
123 // number of opcode + 1
124 ubyte opcode_base;
125 /* follow the array of opcode args nr: ubytes [nr_opcode_base] */
126 /* follow the search directories index, zero terminated string
127 * terminated by an empty string.
128 */
129 /* follow an array of { filename, LEB128, LEB128, LEB128 }, first is
130 * the directory index entry, 0 means current directory, then mtime
131 * and filesize, last entry is followed by en empty string.
132 */
133 /* follow the first program statement */
134 } __packed;
135
136 /* DWARF 2 spec talk only about one possible compilation unit header while
137 * binutils can handle two flavours of dwarf 2, 32 and 64 bits, this is not
138 * related to the used arch, an ELF 32 can hold more than 4 Go of debug
139 * information. For now we handle only DWARF 2 32 bits comp unit. It'll only
140 * become a problem if we generate more than 4GB of debug information.
141 */
142 struct compilation_unit_header {
143 uword total_length;
144 uhalf version;
145 uword debug_abbrev_offset;
146 ubyte pointer_size;
147 } __packed;
148
149 #define DW_LNS_num_opcode (DW_LNS_set_isa + 1)
150
151 /* field filled at run time are marked with -1 */
152 static struct debug_line_header const default_debug_line_header = {
153 .total_length = -1,
154 .version = 2,
155 .prolog_length = -1,
156 .minimum_instruction_length = 1, /* could be better when min instruction size != 1 */
157 .default_is_stmt = 1, /* we don't take care about basic block */
158 .line_base = -5, /* sensible value for line base ... */
159 .line_range = -14, /* ... and line range are guessed statically */
160 .opcode_base = DW_LNS_num_opcode
161 };
162
163 static ubyte standard_opcode_length[] =
164 {
165 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1
166 };
167 #if 0
168 {
169 [DW_LNS_advance_pc] = 1,
170 [DW_LNS_advance_line] = 1,
171 [DW_LNS_set_file] = 1,
172 [DW_LNS_set_column] = 1,
173 [DW_LNS_fixed_advance_pc] = 1,
174 [DW_LNS_set_isa] = 1,
175 };
176 #endif
177
178 /* field filled at run time are marked with -1 */
179 static struct compilation_unit_header default_comp_unit_header = {
180 .total_length = -1,
181 .version = 2,
182 .debug_abbrev_offset = 0, /* we reuse the same abbrev entries for all comp unit */
183 .pointer_size = sizeof(void *)
184 };
185
186 static void emit_uword(struct buffer_ext *be, uword data)
187 {
188 buffer_ext_add(be, &data, sizeof(uword));
189 }
190
191 static void emit_string(struct buffer_ext *be, const char *s)
192 {
193 buffer_ext_add(be, (void *)s, strlen(s) + 1);
194 }
195
196 static void emit_unsigned_LEB128(struct buffer_ext *be,
197 unsigned long data)
198 {
199 do {
200 ubyte cur = data & 0x7F;
201 data >>= 7;
202 if (data)
203 cur |= 0x80;
204 buffer_ext_add(be, &cur, 1);
205 } while (data);
206 }
207
208 static void emit_signed_LEB128(struct buffer_ext *be, long data)
209 {
210 int more = 1;
211 int negative = data < 0;
212 int size = sizeof(long) * CHAR_BIT;
213 while (more) {
214 ubyte cur = data & 0x7F;
215 data >>= 7;
216 if (negative)
217 data |= - (1 << (size - 7));
218 if ((data == 0 && !(cur & 0x40)) ||
219 (data == -1l && (cur & 0x40)))
220 more = 0;
221 else
222 cur |= 0x80;
223 buffer_ext_add(be, &cur, 1);
224 }
225 }
226
227 static void emit_extended_opcode(struct buffer_ext *be, ubyte opcode,
228 void *data, size_t data_len)
229 {
230 buffer_ext_add(be, (char *)"", 1);
231
232 emit_unsigned_LEB128(be, data_len + 1);
233
234 buffer_ext_add(be, &opcode, 1);
235 buffer_ext_add(be, data, data_len);
236 }
237
238 static void emit_opcode(struct buffer_ext *be, ubyte opcode)
239 {
240 buffer_ext_add(be, &opcode, 1);
241 }
242
243 static void emit_opcode_signed(struct buffer_ext *be,
244 ubyte opcode, long data)
245 {
246 buffer_ext_add(be, &opcode, 1);
247 emit_signed_LEB128(be, data);
248 }
249
250 static void emit_opcode_unsigned(struct buffer_ext *be, ubyte opcode,
251 unsigned long data)
252 {
253 buffer_ext_add(be, &opcode, 1);
254 emit_unsigned_LEB128(be, data);
255 }
256
257 static void emit_advance_pc(struct buffer_ext *be, unsigned long delta_pc)
258 {
259 emit_opcode_unsigned(be, DW_LNS_advance_pc, delta_pc);
260 }
261
262 static void emit_advance_lineno(struct buffer_ext *be, long delta_lineno)
263 {
264 emit_opcode_signed(be, DW_LNS_advance_line, delta_lineno);
265 }
266
267 static void emit_lne_end_of_sequence(struct buffer_ext *be)
268 {
269 emit_extended_opcode(be, DW_LNE_end_sequence, NULL, 0);
270 }
271
272 static void emit_set_file(struct buffer_ext *be, unsigned long idx)
273 {
274 emit_opcode_unsigned(be, DW_LNS_set_file, idx);
275 }
276
277 static void emit_lne_define_filename(struct buffer_ext *be,
278 const char *filename)
279 {
280 buffer_ext_add(be, (void *)"", 1);
281
282 /* LNE field, strlen(filename) + zero termination, 3 bytes for: the dir entry, timestamp, filesize */
283 emit_unsigned_LEB128(be, strlen(filename) + 5);
284 emit_opcode(be, DW_LNE_define_file);
285 emit_string(be, filename);
286 /* directory index 0=do not know */
287 emit_unsigned_LEB128(be, 0);
288 /* last modification date on file 0=do not know */
289 emit_unsigned_LEB128(be, 0);
290 /* filesize 0=do not know */
291 emit_unsigned_LEB128(be, 0);
292 }
293
294 static void emit_lne_set_address(struct buffer_ext *be,
295 void *address)
296 {
297 emit_extended_opcode(be, DW_LNE_set_address, &address, sizeof(unsigned long));
298 }
299
300 static ubyte get_special_opcode(struct debug_entry *ent,
301 unsigned int last_line,
302 unsigned long last_vma)
303 {
304 unsigned int temp;
305 unsigned long delta_addr;
306
307 /*
308 * delta from line_base
309 */
310 temp = (ent->lineno - last_line) - default_debug_line_header.line_base;
311
312 if (temp >= default_debug_line_header.line_range)
313 return 0;
314
315 /*
316 * delta of addresses
317 */
318 delta_addr = (ent->addr - last_vma) / default_debug_line_header.minimum_instruction_length;
319
320 /* This is not sufficient to ensure opcode will be in [0-256] but
321 * sufficient to ensure when summing with the delta lineno we will
322 * not overflow the unsigned long opcode */
323
324 if (delta_addr <= 256 / default_debug_line_header.line_range) {
325 unsigned long opcode = temp +
326 (delta_addr * default_debug_line_header.line_range) +
327 default_debug_line_header.opcode_base;
328
329 return opcode <= 255 ? opcode : 0;
330 }
331 return 0;
332 }
333
334 static void emit_lineno_info(struct buffer_ext *be,
335 struct debug_entry *ent, size_t nr_entry,
336 unsigned long code_addr)
337 {
338 size_t i;
339
340 /* as described in the jitdump format */
341 const char repeated_name_marker[] = {'\xff', '\0'};
342
343 /*
344 * Machine state at start of a statement program
345 * address = 0
346 * file = 1
347 * line = 1
348 * column = 0
349 * is_stmt = default_is_stmt as given in the debug_line_header
350 * basic block = 0
351 * end sequence = 0
352 */
353
354 /* start state of the state machine we take care of */
355 unsigned long last_vma = 0;
356 char const *cur_filename = NULL;
357 unsigned long cur_file_idx = 0;
358 int last_line = 1;
359
360 emit_lne_set_address(be, (void *)code_addr);
361
362 for (i = 0; i < nr_entry; i++, ent = debug_entry_next(ent)) {
363 int need_copy = 0;
364 ubyte special_opcode;
365
366 /*
367 * check if filename changed, if so add it
368 */
369 if ((!cur_filename || strcmp(cur_filename, ent->name)) &&
370 strcmp(repeated_name_marker, ent->name)) {
371 emit_lne_define_filename(be, ent->name);
372 cur_filename = ent->name;
373 emit_set_file(be, ++cur_file_idx);
374 need_copy = 1;
375 }
376
377 special_opcode = get_special_opcode(ent, last_line, last_vma);
378 if (special_opcode != 0) {
379 last_line = ent->lineno;
380 last_vma = ent->addr;
381 emit_opcode(be, special_opcode);
382 } else {
383 /*
384 * lines differ, emit line delta
385 */
386 if (last_line != ent->lineno) {
387 emit_advance_lineno(be, ent->lineno - last_line);
388 last_line = ent->lineno;
389 need_copy = 1;
390 }
391 /*
392 * addresses differ, emit address delta
393 */
394 if (last_vma != ent->addr) {
395 emit_advance_pc(be, ent->addr - last_vma);
396 last_vma = ent->addr;
397 need_copy = 1;
398 }
399 /*
400 * add new row to matrix
401 */
402 if (need_copy)
403 emit_opcode(be, DW_LNS_copy);
404 }
405 }
406 }
407
408 static void add_debug_line(struct buffer_ext *be,
409 struct debug_entry *ent, size_t nr_entry,
410 unsigned long code_addr)
411 {
412 struct debug_line_header * dbg_header;
413 size_t old_size;
414
415 old_size = buffer_ext_size(be);
416
417 buffer_ext_add(be, (void *)&default_debug_line_header,
418 sizeof(default_debug_line_header));
419
420 buffer_ext_add(be, &standard_opcode_length, sizeof(standard_opcode_length));
421
422 // empty directory entry
423 buffer_ext_add(be, (void *)"", 1);
424
425 // empty filename directory
426 buffer_ext_add(be, (void *)"", 1);
427
428 dbg_header = buffer_ext_addr(be) + old_size;
429 dbg_header->prolog_length = (buffer_ext_size(be) - old_size) -
430 offsetof(struct debug_line_header, minimum_instruction_length);
431
432 emit_lineno_info(be, ent, nr_entry, code_addr);
433
434 emit_lne_end_of_sequence(be);
435
436 dbg_header = buffer_ext_addr(be) + old_size;
437 dbg_header->total_length = (buffer_ext_size(be) - old_size) -
438 offsetof(struct debug_line_header, version);
439 }
440
441 static void
442 add_debug_abbrev(struct buffer_ext *be)
443 {
444 emit_unsigned_LEB128(be, 1);
445 emit_unsigned_LEB128(be, DW_TAG_compile_unit);
446 emit_unsigned_LEB128(be, DW_CHILDREN_yes);
447 emit_unsigned_LEB128(be, DW_AT_stmt_list);
448 emit_unsigned_LEB128(be, DW_FORM_data4);
449 emit_unsigned_LEB128(be, 0);
450 emit_unsigned_LEB128(be, 0);
451 emit_unsigned_LEB128(be, 0);
452 }
453
454 static void
455 add_compilation_unit(struct buffer_ext *be,
456 size_t offset_debug_line)
457 {
458 struct compilation_unit_header *comp_unit_header;
459 size_t old_size = buffer_ext_size(be);
460
461 buffer_ext_add(be, &default_comp_unit_header,
462 sizeof(default_comp_unit_header));
463
464 emit_unsigned_LEB128(be, 1);
465 emit_uword(be, offset_debug_line);
466
467 comp_unit_header = buffer_ext_addr(be) + old_size;
468 comp_unit_header->total_length = (buffer_ext_size(be) - old_size) -
469 offsetof(struct compilation_unit_header, version);
470 }
471
472 static int
473 jit_process_debug_info(uint64_t code_addr,
474 void *debug, int nr_debug_entries,
475 struct buffer_ext *dl,
476 struct buffer_ext *da,
477 struct buffer_ext *di)
478 {
479 struct debug_entry *ent = debug;
480 int i;
481
482 for (i = 0; i < nr_debug_entries; i++) {
483 ent->addr = ent->addr - code_addr;
484 ent = debug_entry_next(ent);
485 }
486 add_compilation_unit(di, buffer_ext_size(dl));
487 add_debug_line(dl, debug, nr_debug_entries, GEN_ELF_TEXT_OFFSET);
488 add_debug_abbrev(da);
489 if (0) buffer_ext_dump(da, "abbrev");
490
491 return 0;
492 }
493
494 int
495 jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries)
496 {
497 Elf_Data *d;
498 Elf_Scn *scn;
499 Elf_Shdr *shdr;
500 struct buffer_ext dl, di, da;
501 int ret = -1;
502
503 buffer_ext_init(&dl);
504 buffer_ext_init(&di);
505 buffer_ext_init(&da);
506
507 if (jit_process_debug_info(code_addr, debug, nr_debug_entries, &dl, &da, &di))
508 goto out;
509
510 /*
511 * setup .debug_line section
512 */
513 scn = elf_newscn(e);
514 if (!scn) {
515 warnx("cannot create section");
516 goto out;
517 }
518
519 d = elf_newdata(scn);
520 if (!d) {
521 warnx("cannot get new data");
522 goto out;
523 }
524
525 d->d_align = 1;
526 d->d_off = 0LL;
527 d->d_buf = buffer_ext_addr(&dl);
528 d->d_type = ELF_T_BYTE;
529 d->d_size = buffer_ext_size(&dl);
530 d->d_version = EV_CURRENT;
531
532 shdr = elf_getshdr(scn);
533 if (!shdr) {
534 warnx("cannot get section header");
535 goto out;
536 }
537
538 shdr->sh_name = 52; /* .debug_line */
539 shdr->sh_type = SHT_PROGBITS;
540 shdr->sh_addr = 0; /* must be zero or == sh_offset -> dynamic object */
541 shdr->sh_flags = 0;
542 shdr->sh_entsize = 0;
543
544 /*
545 * setup .debug_info section
546 */
547 scn = elf_newscn(e);
548 if (!scn) {
549 warnx("cannot create section");
550 goto out;
551 }
552
553 d = elf_newdata(scn);
554 if (!d) {
555 warnx("cannot get new data");
556 goto out;
557 }
558
559 d->d_align = 1;
560 d->d_off = 0LL;
561 d->d_buf = buffer_ext_addr(&di);
562 d->d_type = ELF_T_BYTE;
563 d->d_size = buffer_ext_size(&di);
564 d->d_version = EV_CURRENT;
565
566 shdr = elf_getshdr(scn);
567 if (!shdr) {
568 warnx("cannot get section header");
569 goto out;
570 }
571
572 shdr->sh_name = 64; /* .debug_info */
573 shdr->sh_type = SHT_PROGBITS;
574 shdr->sh_addr = 0; /* must be zero or == sh_offset -> dynamic object */
575 shdr->sh_flags = 0;
576 shdr->sh_entsize = 0;
577
578 /*
579 * setup .debug_abbrev section
580 */
581 scn = elf_newscn(e);
582 if (!scn) {
583 warnx("cannot create section");
584 goto out;
585 }
586
587 d = elf_newdata(scn);
588 if (!d) {
589 warnx("cannot get new data");
590 goto out;
591 }
592
593 d->d_align = 1;
594 d->d_off = 0LL;
595 d->d_buf = buffer_ext_addr(&da);
596 d->d_type = ELF_T_BYTE;
597 d->d_size = buffer_ext_size(&da);
598 d->d_version = EV_CURRENT;
599
600 shdr = elf_getshdr(scn);
601 if (!shdr) {
602 warnx("cannot get section header");
603 goto out;
604 }
605
606 shdr->sh_name = 76; /* .debug_info */
607 shdr->sh_type = SHT_PROGBITS;
608 shdr->sh_addr = 0; /* must be zero or == sh_offset -> dynamic object */
609 shdr->sh_flags = 0;
610 shdr->sh_entsize = 0;
611
612 /*
613 * now we update the ELF image with all the sections
614 */
615 if (elf_update(e, ELF_C_WRITE) < 0)
616 warnx("elf_update debug failed");
617 else
618 ret = 0;
619
620 out:
621 buffer_ext_exit(&dl);
622 buffer_ext_exit(&di);
623 buffer_ext_exit(&da);
624 return ret;
625 }
626
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