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1/* Generate assembler source containing symbol information
2 *
3 * Copyright 2002 by Kai Germaschewski
4 *
5 * This software may be used and distributed according to the terms
6 * of the GNU General Public License, incorporated herein by reference.
7 *
8 * Usage: kallsyms [--all-symbols] in.map > out.S
9 *
10 * Table compression uses all the unused char codes on the symbols and
11 * maps these to the most used substrings (tokens). For instance, it might
12 * map char code 0xF7 to represent "write_" and then in every symbol where
13 * "write_" appears it can be replaced by 0xF7, saving 5 bytes.
14 * The used codes themselves are also placed in the table so that the
15 * decompresion can work without "special cases".
16 * Applied to kernel symbols, this usually produces a compression ratio
17 * of about 50%.
18 *
19 */
20
21#include <errno.h>
22#include <getopt.h>
23#include <stdbool.h>
24#include <stdio.h>
25#include <stdlib.h>
26#include <string.h>
27#include <ctype.h>
28#include <limits.h>
29
30#include <xalloc.h>
31
32#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
33
34#define KSYM_NAME_LEN 512
35
36struct sym_entry {
37 unsigned long long addr;
38 unsigned int len;
39 unsigned int seq;
40 unsigned char sym[];
41};
42
43struct addr_range {
44 const char *start_sym, *end_sym;
45 unsigned long long start, end;
46};
47
48static unsigned long long _text;
49static struct addr_range text_ranges[] = {
50 { "_stext", "_etext" },
51 { "_sinittext", "_einittext" },
52};
53#define text_range_text (&text_ranges[0])
54#define text_range_inittext (&text_ranges[1])
55
56static struct sym_entry **table;
57static unsigned int table_size, table_cnt;
58static int all_symbols;
59static int pc_relative;
60
61static int token_profit[0x10000];
62
63/* the table that holds the result of the compression */
64static unsigned char best_table[256][2];
65static unsigned char best_table_len[256];
66
67
68static void usage(void)
69{
70 fprintf(stderr, "Usage: kallsyms [--all-symbols] in.map > out.S\n");
71 exit(1);
72}
73
74static char *sym_name(const struct sym_entry *s)
75{
76 return (char *)s->sym + 1;
77}
78
79static bool is_ignored_symbol(const char *name, char type)
80{
81 if (type == 'u' || type == 'n')
82 return true;
83
84 if (toupper(type) == 'A') {
85 /* Keep these useful absolute symbols */
86 if (strcmp(name, "__kernel_syscall_via_break") &&
87 strcmp(name, "__kernel_syscall_via_epc") &&
88 strcmp(name, "__kernel_sigtramp") &&
89 strcmp(name, "__gp"))
90 return true;
91 }
92
93 return false;
94}
95
96static void check_symbol_range(const char *sym, unsigned long long addr,
97 struct addr_range *ranges, int entries)
98{
99 size_t i;
100 struct addr_range *ar;
101
102 for (i = 0; i < entries; ++i) {
103 ar = &ranges[i];
104
105 if (strcmp(sym, ar->start_sym) == 0) {
106 ar->start = addr;
107 return;
108 } else if (strcmp(sym, ar->end_sym) == 0) {
109 ar->end = addr;
110 return;
111 }
112 }
113}
114
115static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
116{
117 char *name, type, *p;
118 unsigned long long addr;
119 size_t len;
120 ssize_t readlen;
121 struct sym_entry *sym;
122
123 errno = 0;
124 readlen = getline(buf, buf_len, in);
125 if (readlen < 0) {
126 if (errno) {
127 perror("read_symbol");
128 exit(EXIT_FAILURE);
129 }
130 return NULL;
131 }
132
133 if ((*buf)[readlen - 1] == '\n')
134 (*buf)[readlen - 1] = 0;
135
136 addr = strtoull(*buf, &p, 16);
137
138 if (*buf == p || *p++ != ' ' || !isascii((type = *p++)) || *p++ != ' ') {
139 fprintf(stderr, "line format error\n");
140 exit(EXIT_FAILURE);
141 }
142
143 name = p;
144 len = strlen(name);
145
146 if (len >= KSYM_NAME_LEN) {
147 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
148 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
149 name, len, KSYM_NAME_LEN);
150 return NULL;
151 }
152
153 if (strcmp(name, "_text") == 0)
154 _text = addr;
155
156 /* Ignore most absolute/undefined (?) symbols. */
157 if (is_ignored_symbol(name, type))
158 return NULL;
159
160 check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
161
162 /* include the type field in the symbol name, so that it gets
163 * compressed together */
164 len++;
165
166 sym = xmalloc(sizeof(*sym) + len + 1);
167 sym->addr = addr;
168 sym->len = len;
169 sym->sym[0] = type;
170 strcpy(sym_name(sym), name);
171
172 return sym;
173}
174
175static int symbol_in_range(const struct sym_entry *s,
176 const struct addr_range *ranges, int entries)
177{
178 size_t i;
179 const struct addr_range *ar;
180
181 for (i = 0; i < entries; ++i) {
182 ar = &ranges[i];
183
184 if (s->addr >= ar->start && s->addr <= ar->end)
185 return 1;
186 }
187
188 return 0;
189}
190
191static bool string_starts_with(const char *s, const char *prefix)
192{
193 return strncmp(s, prefix, strlen(prefix)) == 0;
194}
195
196static int symbol_valid(const struct sym_entry *s)
197{
198 const char *name = sym_name(s);
199
200 /* if --all-symbols is not specified, then symbols outside the text
201 * and inittext sections are discarded */
202 if (!all_symbols) {
203 /*
204 * Symbols starting with __start and __stop are used to denote
205 * section boundaries, and should always be included:
206 */
207 if (string_starts_with(name, "__start_") ||
208 string_starts_with(name, "__stop_"))
209 return 1;
210
211 if (symbol_in_range(s, text_ranges,
212 ARRAY_SIZE(text_ranges)) == 0)
213 return 0;
214 /* Corner case. Discard any symbols with the same value as
215 * _etext _einittext; they can move between pass 1 and 2 when
216 * the kallsyms data are added. If these symbols move then
217 * they may get dropped in pass 2, which breaks the kallsyms
218 * rules.
219 */
220 if ((s->addr == text_range_text->end &&
221 strcmp(name, text_range_text->end_sym)) ||
222 (s->addr == text_range_inittext->end &&
223 strcmp(name, text_range_inittext->end_sym)))
224 return 0;
225 }
226
227 return 1;
228}
229
230/* remove all the invalid symbols from the table */
231static void shrink_table(void)
232{
233 unsigned int i, pos;
234
235 pos = 0;
236 for (i = 0; i < table_cnt; i++) {
237 if (symbol_valid(table[i])) {
238 if (pos != i)
239 table[pos] = table[i];
240 pos++;
241 } else {
242 free(table[i]);
243 }
244 }
245 table_cnt = pos;
246}
247
248static void read_map(const char *in)
249{
250 FILE *fp;
251 struct sym_entry *sym;
252 char *buf = NULL;
253 size_t buflen = 0;
254
255 fp = fopen(in, "r");
256 if (!fp) {
257 perror(in);
258 exit(1);
259 }
260
261 while (!feof(fp)) {
262 sym = read_symbol(fp, &buf, &buflen);
263 if (!sym)
264 continue;
265
266 sym->seq = table_cnt;
267
268 if (table_cnt >= table_size) {
269 table_size += 10000;
270 table = xrealloc(table, sizeof(*table) * table_size);
271 }
272
273 table[table_cnt++] = sym;
274 }
275
276 free(buf);
277 fclose(fp);
278}
279
280static void output_label(const char *label)
281{
282 printf(".globl %s\n", label);
283 printf("\t.balign 4\n");
284 printf("%s:\n", label);
285}
286
287/* uncompress a compressed symbol. When this function is called, the best table
288 * might still be compressed itself, so the function needs to be recursive */
289static int expand_symbol(const unsigned char *data, int len, char *result)
290{
291 int c, rlen, total=0;
292
293 while (len) {
294 c = *data;
295 /* if the table holds a single char that is the same as the one
296 * we are looking for, then end the search */
297 if (best_table[c][0]==c && best_table_len[c]==1) {
298 *result++ = c;
299 total++;
300 } else {
301 /* if not, recurse and expand */
302 rlen = expand_symbol(best_table[c], best_table_len[c], result);
303 total += rlen;
304 result += rlen;
305 }
306 data++;
307 len--;
308 }
309 *result=0;
310
311 return total;
312}
313
314static int compare_names(const void *a, const void *b)
315{
316 int ret;
317 const struct sym_entry *sa = *(const struct sym_entry **)a;
318 const struct sym_entry *sb = *(const struct sym_entry **)b;
319
320 ret = strcmp(sym_name(sa), sym_name(sb));
321 if (!ret) {
322 if (sa->addr > sb->addr)
323 return 1;
324 else if (sa->addr < sb->addr)
325 return -1;
326
327 /* keep old order */
328 return (int)(sa->seq - sb->seq);
329 }
330
331 return ret;
332}
333
334static void sort_symbols_by_name(void)
335{
336 qsort(table, table_cnt, sizeof(table[0]), compare_names);
337}
338
339static void write_src(void)
340{
341 unsigned int i, k, off;
342 unsigned int best_idx[256];
343 unsigned int *markers, markers_cnt;
344 char buf[KSYM_NAME_LEN];
345
346 printf("\t.section .rodata, \"a\"\n");
347
348 output_label("kallsyms_num_syms");
349 printf("\t.long\t%u\n", table_cnt);
350 printf("\n");
351
352 /* table of offset markers, that give the offset in the compressed stream
353 * every 256 symbols */
354 markers_cnt = (table_cnt + 255) / 256;
355 markers = xmalloc(sizeof(*markers) * markers_cnt);
356
357 output_label("kallsyms_names");
358 off = 0;
359 for (i = 0; i < table_cnt; i++) {
360 if ((i & 0xFF) == 0)
361 markers[i >> 8] = off;
362 table[i]->seq = i;
363
364 /* There cannot be any symbol of length zero. */
365 if (table[i]->len == 0) {
366 fprintf(stderr, "kallsyms failure: "
367 "unexpected zero symbol length\n");
368 exit(EXIT_FAILURE);
369 }
370
371 /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
372 if (table[i]->len > 0x3FFF) {
373 fprintf(stderr, "kallsyms failure: "
374 "unexpected huge symbol length\n");
375 exit(EXIT_FAILURE);
376 }
377
378 /* Encode length with ULEB128. */
379 if (table[i]->len <= 0x7F) {
380 /* Most symbols use a single byte for the length. */
381 printf("\t.byte 0x%02x", table[i]->len);
382 off += table[i]->len + 1;
383 } else {
384 /* "Big" symbols use two bytes. */
385 printf("\t.byte 0x%02x, 0x%02x",
386 (table[i]->len & 0x7F) | 0x80,
387 (table[i]->len >> 7) & 0x7F);
388 off += table[i]->len + 2;
389 }
390 for (k = 0; k < table[i]->len; k++)
391 printf(", 0x%02x", table[i]->sym[k]);
392
393 /*
394 * Now that we wrote out the compressed symbol name, restore the
395 * original name and print it in the comment.
396 */
397 expand_symbol(table[i]->sym, table[i]->len, buf);
398 strcpy((char *)table[i]->sym, buf);
399 printf("\t/* %s */\n", table[i]->sym);
400 }
401 printf(".size kallsyms_names, . - kallsyms_names\n");
402 printf("\n");
403
404 output_label("kallsyms_markers");
405 for (i = 0; i < markers_cnt; i++)
406 printf("\t.long\t%u\n", markers[i]);
407 printf(".size kallsyms_markers, . - kallsyms_markers\n");
408 printf("\n");
409
410 free(markers);
411
412 output_label("kallsyms_token_table");
413 off = 0;
414 for (i = 0; i < 256; i++) {
415 best_idx[i] = off;
416 expand_symbol(best_table[i], best_table_len[i], buf);
417 printf("\t.asciz\t\"%s\"\n", buf);
418 off += strlen(buf) + 1;
419 }
420 printf(".size kallsyms_token_table, . - kallsyms_token_table\n");
421 printf("\n");
422
423 output_label("kallsyms_token_index");
424 for (i = 0; i < 256; i++)
425 printf("\t.short\t%d\n", best_idx[i]);
426 printf("\n");
427
428 output_label("kallsyms_offsets");
429
430 for (i = 0; i < table_cnt; i++) {
431 if (pc_relative) {
432 long long offset = table[i]->addr - _text;
433
434 if (offset < INT_MIN || offset > INT_MAX) {
435 fprintf(stderr, "kallsyms failure: "
436 "relative symbol value %#llx out of range\n",
437 table[i]->addr);
438 exit(EXIT_FAILURE);
439 }
440 printf("\t.long\t_text - . + (%d)\t/* %s */\n",
441 (int)offset, table[i]->sym);
442 } else {
443 printf("\t.long\t%#x\t/* %s */\n",
444 (unsigned int)table[i]->addr, table[i]->sym);
445 }
446 }
447 printf(".size kallsyms_offsets, . - kallsyms_offsets\n");
448 printf("\n");
449
450 sort_symbols_by_name();
451 output_label("kallsyms_seqs_of_names");
452 for (i = 0; i < table_cnt; i++)
453 printf("\t.byte 0x%02x, 0x%02x, 0x%02x\t/* %s */\n",
454 (unsigned char)(table[i]->seq >> 16),
455 (unsigned char)(table[i]->seq >> 8),
456 (unsigned char)(table[i]->seq >> 0),
457 table[i]->sym);
458 printf("\n");
459}
460
461
462/* table lookup compression functions */
463
464/* count all the possible tokens in a symbol */
465static void learn_symbol(const unsigned char *symbol, int len)
466{
467 int i;
468
469 for (i = 0; i < len - 1; i++)
470 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
471}
472
473/* decrease the count for all the possible tokens in a symbol */
474static void forget_symbol(const unsigned char *symbol, int len)
475{
476 int i;
477
478 for (i = 0; i < len - 1; i++)
479 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
480}
481
482/* do the initial token count */
483static void build_initial_token_table(void)
484{
485 unsigned int i;
486
487 for (i = 0; i < table_cnt; i++)
488 learn_symbol(table[i]->sym, table[i]->len);
489}
490
491static unsigned char *find_token(unsigned char *str, int len,
492 const unsigned char *token)
493{
494 int i;
495
496 for (i = 0; i < len - 1; i++) {
497 if (str[i] == token[0] && str[i+1] == token[1])
498 return &str[i];
499 }
500 return NULL;
501}
502
503/* replace a given token in all the valid symbols. Use the sampled symbols
504 * to update the counts */
505static void compress_symbols(const unsigned char *str, int idx)
506{
507 unsigned int i, len, size;
508 unsigned char *p1, *p2;
509
510 for (i = 0; i < table_cnt; i++) {
511
512 len = table[i]->len;
513 p1 = table[i]->sym;
514
515 /* find the token on the symbol */
516 p2 = find_token(p1, len, str);
517 if (!p2) continue;
518
519 /* decrease the counts for this symbol's tokens */
520 forget_symbol(table[i]->sym, len);
521
522 size = len;
523
524 do {
525 *p2 = idx;
526 p2++;
527 size -= (p2 - p1);
528 memmove(p2, p2 + 1, size);
529 p1 = p2;
530 len--;
531
532 if (size < 2) break;
533
534 /* find the token on the symbol */
535 p2 = find_token(p1, size, str);
536
537 } while (p2);
538
539 table[i]->len = len;
540
541 /* increase the counts for this symbol's new tokens */
542 learn_symbol(table[i]->sym, len);
543 }
544}
545
546/* search the token with the maximum profit */
547static int find_best_token(void)
548{
549 int i, best, bestprofit;
550
551 bestprofit=-10000;
552 best = 0;
553
554 for (i = 0; i < 0x10000; i++) {
555 if (token_profit[i] > bestprofit) {
556 best = i;
557 bestprofit = token_profit[i];
558 }
559 }
560 return best;
561}
562
563/* this is the core of the algorithm: calculate the "best" table */
564static void optimize_result(void)
565{
566 int i, best;
567
568 /* using the '\0' symbol last allows compress_symbols to use standard
569 * fast string functions */
570 for (i = 255; i >= 0; i--) {
571
572 /* if this table slot is empty (it is not used by an actual
573 * original char code */
574 if (!best_table_len[i]) {
575
576 /* find the token with the best profit value */
577 best = find_best_token();
578 if (token_profit[best] == 0)
579 break;
580
581 /* place it in the "best" table */
582 best_table_len[i] = 2;
583 best_table[i][0] = best & 0xFF;
584 best_table[i][1] = (best >> 8) & 0xFF;
585
586 /* replace this token in all the valid symbols */
587 compress_symbols(best_table[i], i);
588 }
589 }
590}
591
592/* start by placing the symbols that are actually used on the table */
593static void insert_real_symbols_in_table(void)
594{
595 unsigned int i, j, c;
596
597 for (i = 0; i < table_cnt; i++) {
598 for (j = 0; j < table[i]->len; j++) {
599 c = table[i]->sym[j];
600 best_table[c][0]=c;
601 best_table_len[c]=1;
602 }
603 }
604}
605
606static void optimize_token_table(void)
607{
608 build_initial_token_table();
609
610 insert_real_symbols_in_table();
611
612 optimize_result();
613}
614
615/* guess for "linker script provide" symbol */
616static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
617{
618 const char *symbol = sym_name(se);
619 int len = se->len - 1;
620
621 if (len < 8)
622 return 0;
623
624 if (symbol[0] != '_' || symbol[1] != '_')
625 return 0;
626
627 /* __start_XXXXX */
628 if (!memcmp(symbol + 2, "start_", 6))
629 return 1;
630
631 /* __stop_XXXXX */
632 if (!memcmp(symbol + 2, "stop_", 5))
633 return 1;
634
635 /* __end_XXXXX */
636 if (!memcmp(symbol + 2, "end_", 4))
637 return 1;
638
639 /* __XXXXX_start */
640 if (!memcmp(symbol + len - 6, "_start", 6))
641 return 1;
642
643 /* __XXXXX_end */
644 if (!memcmp(symbol + len - 4, "_end", 4))
645 return 1;
646
647 return 0;
648}
649
650static int compare_symbols(const void *a, const void *b)
651{
652 const struct sym_entry *sa = *(const struct sym_entry **)a;
653 const struct sym_entry *sb = *(const struct sym_entry **)b;
654 int wa, wb;
655
656 /* sort by address first */
657 if (sa->addr > sb->addr)
658 return 1;
659 if (sa->addr < sb->addr)
660 return -1;
661
662 /* sort by "weakness" type */
663 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
664 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
665 if (wa != wb)
666 return wa - wb;
667
668 /* sort by "linker script provide" type */
669 wa = may_be_linker_script_provide_symbol(sa);
670 wb = may_be_linker_script_provide_symbol(sb);
671 if (wa != wb)
672 return wa - wb;
673
674 /* sort by the number of prefix underscores */
675 wa = strspn(sym_name(sa), "_");
676 wb = strspn(sym_name(sb), "_");
677 if (wa != wb)
678 return wa - wb;
679
680 /* sort by initial order, so that other symbols are left undisturbed */
681 return sa->seq - sb->seq;
682}
683
684static void sort_symbols(void)
685{
686 qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
687}
688
689int main(int argc, char **argv)
690{
691 while (1) {
692 static const struct option long_options[] = {
693 {"all-symbols", no_argument, &all_symbols, 1},
694 {"pc-relative", no_argument, &pc_relative, 1},
695 {},
696 };
697
698 int c = getopt_long(argc, argv, "", long_options, NULL);
699
700 if (c == -1)
701 break;
702 if (c != 0)
703 usage();
704 }
705
706 if (optind >= argc)
707 usage();
708
709 read_map(argv[optind]);
710 shrink_table();
711 sort_symbols();
712 optimize_token_table();
713 write_src();
714
715 return 0;
716}