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: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.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 <stdio.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <ctype.h>
25
26 #ifndef ARRAY_SIZE
27 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
28 #endif
29
30 #define KSYM_NAME_LEN 128
31
32 struct sym_entry {
33 unsigned long long addr;
34 unsigned int len;
35 unsigned int start_pos;
36 unsigned char *sym;
37 };
38
39 struct text_range {
40 const char *stext, *etext;
41 unsigned long long start, end;
42 };
43
44 static unsigned long long _text;
45 static struct text_range text_ranges[] = {
46 { "_stext", "_etext" },
47 { "_sinittext", "_einittext" },
48 { "_stext_l1", "_etext_l1" }, /* Blackfin on-chip L1 inst SRAM */
49 { "_stext_l2", "_etext_l2" }, /* Blackfin on-chip L2 SRAM */
50 };
51 #define text_range_text (&text_ranges[0])
52 #define text_range_inittext (&text_ranges[1])
53
54 static struct sym_entry *table;
55 static unsigned int table_size, table_cnt;
56 static int all_symbols = 0;
57 static char symbol_prefix_char = '\0';
58
59 int token_profit[0x10000];
60
61 /* the table that holds the result of the compression */
62 unsigned char best_table[256][2];
63 unsigned char best_table_len[256];
64
65
usage(void)66 static void usage(void)
67 {
68 fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
69 exit(1);
70 }
71
72 /*
73 * This ignores the intensely annoying "mapping symbols" found
74 * in ARM ELF files: $a, $t and $d.
75 */
is_arm_mapping_symbol(const char * str)76 static inline int is_arm_mapping_symbol(const char *str)
77 {
78 return str[0] == '$' && strchr("atd", str[1])
79 && (str[2] == '\0' || str[2] == '.');
80 }
81
read_symbol_tr(const char * sym,unsigned long long addr)82 static int read_symbol_tr(const char *sym, unsigned long long addr)
83 {
84 size_t i;
85 struct text_range *tr;
86
87 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
88 tr = &text_ranges[i];
89
90 if (strcmp(sym, tr->stext) == 0) {
91 tr->start = addr;
92 return 0;
93 } else if (strcmp(sym, tr->etext) == 0) {
94 tr->end = addr;
95 return 0;
96 }
97 }
98
99 return 1;
100 }
101
read_symbol(FILE * in,struct sym_entry * s)102 static int read_symbol(FILE *in, struct sym_entry *s)
103 {
104 char str[500];
105 char *sym, stype;
106 int rc;
107
108 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
109 if (rc != 3) {
110 if (rc != EOF && fgets(str, 500, in) == NULL)
111 fprintf(stderr, "Read error or end of file.\n");
112 return -1;
113 }
114
115 sym = str;
116 /* skip prefix char */
117 if (symbol_prefix_char && str[0] == symbol_prefix_char)
118 sym++;
119
120 /* Ignore most absolute/undefined (?) symbols. */
121 if (strcmp(sym, "_text") == 0)
122 _text = s->addr;
123 else if (read_symbol_tr(sym, s->addr) == 0)
124 /* nothing to do */;
125 else if (toupper(stype) == 'A')
126 {
127 /* Keep these useful absolute symbols */
128 if (strcmp(sym, "__kernel_syscall_via_break") &&
129 strcmp(sym, "__kernel_syscall_via_epc") &&
130 strcmp(sym, "__kernel_sigtramp") &&
131 strcmp(sym, "__gp"))
132 return -1;
133
134 }
135 else if (toupper(stype) == 'U' ||
136 is_arm_mapping_symbol(sym))
137 return -1;
138 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
139 else if (str[0] == '$')
140 return -1;
141 /* exclude debugging symbols */
142 else if (stype == 'N')
143 return -1;
144
145 /* include the type field in the symbol name, so that it gets
146 * compressed together */
147 s->len = strlen(str) + 1;
148 s->sym = malloc(s->len + 1);
149 if (!s->sym) {
150 fprintf(stderr, "kallsyms failure: "
151 "unable to allocate required amount of memory\n");
152 exit(EXIT_FAILURE);
153 }
154 strcpy((char *)s->sym + 1, str);
155 s->sym[0] = stype;
156
157 return 0;
158 }
159
symbol_valid_tr(struct sym_entry * s)160 static int symbol_valid_tr(struct sym_entry *s)
161 {
162 size_t i;
163 struct text_range *tr;
164
165 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
166 tr = &text_ranges[i];
167
168 if (s->addr >= tr->start && s->addr <= tr->end)
169 return 1;
170 }
171
172 return 0;
173 }
174
symbol_valid(struct sym_entry * s)175 static int symbol_valid(struct sym_entry *s)
176 {
177 /* Symbols which vary between passes. Passes 1 and 2 must have
178 * identical symbol lists. The kallsyms_* symbols below are only added
179 * after pass 1, they would be included in pass 2 when --all-symbols is
180 * specified so exclude them to get a stable symbol list.
181 */
182 static char *special_symbols[] = {
183 "kallsyms_addresses",
184 "kallsyms_num_syms",
185 "kallsyms_names",
186 "kallsyms_markers",
187 "kallsyms_token_table",
188 "kallsyms_token_index",
189
190 /* Exclude linker generated symbols which vary between passes */
191 "_SDA_BASE_", /* ppc */
192 "_SDA2_BASE_", /* ppc */
193 NULL };
194 int i;
195 int offset = 1;
196
197 /* skip prefix char */
198 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
199 offset++;
200
201 /* if --all-symbols is not specified, then symbols outside the text
202 * and inittext sections are discarded */
203 if (!all_symbols) {
204 if (symbol_valid_tr(s) == 0)
205 return 0;
206 /* Corner case. Discard any symbols with the same value as
207 * _etext _einittext; they can move between pass 1 and 2 when
208 * the kallsyms data are added. If these symbols move then
209 * they may get dropped in pass 2, which breaks the kallsyms
210 * rules.
211 */
212 if ((s->addr == text_range_text->end &&
213 strcmp((char *)s->sym + offset, text_range_text->etext)) ||
214 (s->addr == text_range_inittext->end &&
215 strcmp((char *)s->sym + offset, text_range_inittext->etext)))
216 return 0;
217 }
218
219 /* Exclude symbols which vary between passes. */
220 if (strstr((char *)s->sym + offset, "_compiled."))
221 return 0;
222
223 for (i = 0; special_symbols[i]; i++)
224 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
225 return 0;
226
227 return 1;
228 }
229
read_map(FILE * in)230 static void read_map(FILE *in)
231 {
232 while (!feof(in)) {
233 if (table_cnt >= table_size) {
234 table_size += 10000;
235 table = realloc(table, sizeof(*table) * table_size);
236 if (!table) {
237 fprintf(stderr, "out of memory\n");
238 exit (1);
239 }
240 }
241 if (read_symbol(in, &table[table_cnt]) == 0) {
242 table[table_cnt].start_pos = table_cnt;
243 table_cnt++;
244 }
245 }
246 }
247
output_label(char * label)248 static void output_label(char *label)
249 {
250 if (symbol_prefix_char)
251 printf(".globl %c%s\n", symbol_prefix_char, label);
252 else
253 printf(".globl %s\n", label);
254 printf("\tALGN\n");
255 if (symbol_prefix_char)
256 printf("%c%s:\n", symbol_prefix_char, label);
257 else
258 printf("%s:\n", label);
259 }
260
261 /* uncompress a compressed symbol. When this function is called, the best table
262 * might still be compressed itself, so the function needs to be recursive */
expand_symbol(unsigned char * data,int len,char * result)263 static int expand_symbol(unsigned char *data, int len, char *result)
264 {
265 int c, rlen, total=0;
266
267 while (len) {
268 c = *data;
269 /* if the table holds a single char that is the same as the one
270 * we are looking for, then end the search */
271 if (best_table[c][0]==c && best_table_len[c]==1) {
272 *result++ = c;
273 total++;
274 } else {
275 /* if not, recurse and expand */
276 rlen = expand_symbol(best_table[c], best_table_len[c], result);
277 total += rlen;
278 result += rlen;
279 }
280 data++;
281 len--;
282 }
283 *result=0;
284
285 return total;
286 }
287
write_src(void)288 static void write_src(void)
289 {
290 unsigned int i, k, off;
291 unsigned int best_idx[256];
292 unsigned int *markers;
293 char buf[KSYM_NAME_LEN];
294
295 printf("#include <asm/types.h>\n");
296 printf("#if BITS_PER_LONG == 64\n");
297 printf("#define PTR .quad\n");
298 printf("#define ALGN .align 8\n");
299 printf("#else\n");
300 printf("#define PTR .long\n");
301 printf("#define ALGN .align 4\n");
302 printf("#endif\n");
303
304 printf("\t.section .rodata, \"a\"\n");
305
306 /* Provide proper symbols relocatability by their '_text'
307 * relativeness. The symbol names cannot be used to construct
308 * normal symbol references as the list of symbols contains
309 * symbols that are declared static and are private to their
310 * .o files. This prevents .tmp_kallsyms.o or any other
311 * object from referencing them.
312 */
313 output_label("kallsyms_addresses");
314 for (i = 0; i < table_cnt; i++) {
315 if (toupper(table[i].sym[0]) != 'A') {
316 if (_text <= table[i].addr)
317 printf("\tPTR\t_text + %#llx\n",
318 table[i].addr - _text);
319 else
320 printf("\tPTR\t_text - %#llx\n",
321 _text - table[i].addr);
322 } else {
323 printf("\tPTR\t%#llx\n", table[i].addr);
324 }
325 }
326 printf("\n");
327
328 output_label("kallsyms_num_syms");
329 printf("\tPTR\t%d\n", table_cnt);
330 printf("\n");
331
332 /* table of offset markers, that give the offset in the compressed stream
333 * every 256 symbols */
334 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
335 if (!markers) {
336 fprintf(stderr, "kallsyms failure: "
337 "unable to allocate required memory\n");
338 exit(EXIT_FAILURE);
339 }
340
341 output_label("kallsyms_names");
342 off = 0;
343 for (i = 0; i < table_cnt; i++) {
344 if ((i & 0xFF) == 0)
345 markers[i >> 8] = off;
346
347 printf("\t.byte 0x%02x", table[i].len);
348 for (k = 0; k < table[i].len; k++)
349 printf(", 0x%02x", table[i].sym[k]);
350 printf("\n");
351
352 off += table[i].len + 1;
353 }
354 printf("\n");
355
356 output_label("kallsyms_markers");
357 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
358 printf("\tPTR\t%d\n", markers[i]);
359 printf("\n");
360
361 free(markers);
362
363 output_label("kallsyms_token_table");
364 off = 0;
365 for (i = 0; i < 256; i++) {
366 best_idx[i] = off;
367 expand_symbol(best_table[i], best_table_len[i], buf);
368 printf("\t.asciz\t\"%s\"\n", buf);
369 off += strlen(buf) + 1;
370 }
371 printf("\n");
372
373 output_label("kallsyms_token_index");
374 for (i = 0; i < 256; i++)
375 printf("\t.short\t%d\n", best_idx[i]);
376 printf("\n");
377 }
378
379
380 /* table lookup compression functions */
381
382 /* count all the possible tokens in a symbol */
learn_symbol(unsigned char * symbol,int len)383 static void learn_symbol(unsigned char *symbol, int len)
384 {
385 int i;
386
387 for (i = 0; i < len - 1; i++)
388 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
389 }
390
391 /* decrease the count for all the possible tokens in a symbol */
forget_symbol(unsigned char * symbol,int len)392 static void forget_symbol(unsigned char *symbol, int len)
393 {
394 int i;
395
396 for (i = 0; i < len - 1; i++)
397 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
398 }
399
400 /* remove all the invalid symbols from the table and do the initial token count */
build_initial_tok_table(void)401 static void build_initial_tok_table(void)
402 {
403 unsigned int i, pos;
404
405 pos = 0;
406 for (i = 0; i < table_cnt; i++) {
407 if ( symbol_valid(&table[i]) ) {
408 if (pos != i)
409 table[pos] = table[i];
410 learn_symbol(table[pos].sym, table[pos].len);
411 pos++;
412 }
413 }
414 table_cnt = pos;
415 }
416
find_token(unsigned char * str,int len,unsigned char * token)417 static void *find_token(unsigned char *str, int len, unsigned char *token)
418 {
419 int i;
420
421 for (i = 0; i < len - 1; i++) {
422 if (str[i] == token[0] && str[i+1] == token[1])
423 return &str[i];
424 }
425 return NULL;
426 }
427
428 /* replace a given token in all the valid symbols. Use the sampled symbols
429 * to update the counts */
compress_symbols(unsigned char * str,int idx)430 static void compress_symbols(unsigned char *str, int idx)
431 {
432 unsigned int i, len, size;
433 unsigned char *p1, *p2;
434
435 for (i = 0; i < table_cnt; i++) {
436
437 len = table[i].len;
438 p1 = table[i].sym;
439
440 /* find the token on the symbol */
441 p2 = find_token(p1, len, str);
442 if (!p2) continue;
443
444 /* decrease the counts for this symbol's tokens */
445 forget_symbol(table[i].sym, len);
446
447 size = len;
448
449 do {
450 *p2 = idx;
451 p2++;
452 size -= (p2 - p1);
453 memmove(p2, p2 + 1, size);
454 p1 = p2;
455 len--;
456
457 if (size < 2) break;
458
459 /* find the token on the symbol */
460 p2 = find_token(p1, size, str);
461
462 } while (p2);
463
464 table[i].len = len;
465
466 /* increase the counts for this symbol's new tokens */
467 learn_symbol(table[i].sym, len);
468 }
469 }
470
471 /* search the token with the maximum profit */
find_best_token(void)472 static int find_best_token(void)
473 {
474 int i, best, bestprofit;
475
476 bestprofit=-10000;
477 best = 0;
478
479 for (i = 0; i < 0x10000; i++) {
480 if (token_profit[i] > bestprofit) {
481 best = i;
482 bestprofit = token_profit[i];
483 }
484 }
485 return best;
486 }
487
488 /* this is the core of the algorithm: calculate the "best" table */
optimize_result(void)489 static void optimize_result(void)
490 {
491 int i, best;
492
493 /* using the '\0' symbol last allows compress_symbols to use standard
494 * fast string functions */
495 for (i = 255; i >= 0; i--) {
496
497 /* if this table slot is empty (it is not used by an actual
498 * original char code */
499 if (!best_table_len[i]) {
500
501 /* find the token with the breates profit value */
502 best = find_best_token();
503 if (token_profit[best] == 0)
504 break;
505
506 /* place it in the "best" table */
507 best_table_len[i] = 2;
508 best_table[i][0] = best & 0xFF;
509 best_table[i][1] = (best >> 8) & 0xFF;
510
511 /* replace this token in all the valid symbols */
512 compress_symbols(best_table[i], i);
513 }
514 }
515 }
516
517 /* start by placing the symbols that are actually used on the table */
insert_real_symbols_in_table(void)518 static void insert_real_symbols_in_table(void)
519 {
520 unsigned int i, j, c;
521
522 memset(best_table, 0, sizeof(best_table));
523 memset(best_table_len, 0, sizeof(best_table_len));
524
525 for (i = 0; i < table_cnt; i++) {
526 for (j = 0; j < table[i].len; j++) {
527 c = table[i].sym[j];
528 best_table[c][0]=c;
529 best_table_len[c]=1;
530 }
531 }
532 }
533
optimize_token_table(void)534 static void optimize_token_table(void)
535 {
536 build_initial_tok_table();
537
538 insert_real_symbols_in_table();
539
540 /* When valid symbol is not registered, exit to error */
541 if (!table_cnt) {
542 fprintf(stderr, "No valid symbol.\n");
543 exit(1);
544 }
545
546 optimize_result();
547 }
548
549 /* guess for "linker script provide" symbol */
may_be_linker_script_provide_symbol(const struct sym_entry * se)550 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
551 {
552 const char *symbol = (char *)se->sym + 1;
553 int len = se->len - 1;
554
555 if (len < 8)
556 return 0;
557
558 if (symbol[0] != '_' || symbol[1] != '_')
559 return 0;
560
561 /* __start_XXXXX */
562 if (!memcmp(symbol + 2, "start_", 6))
563 return 1;
564
565 /* __stop_XXXXX */
566 if (!memcmp(symbol + 2, "stop_", 5))
567 return 1;
568
569 /* __end_XXXXX */
570 if (!memcmp(symbol + 2, "end_", 4))
571 return 1;
572
573 /* __XXXXX_start */
574 if (!memcmp(symbol + len - 6, "_start", 6))
575 return 1;
576
577 /* __XXXXX_end */
578 if (!memcmp(symbol + len - 4, "_end", 4))
579 return 1;
580
581 return 0;
582 }
583
prefix_underscores_count(const char * str)584 static int prefix_underscores_count(const char *str)
585 {
586 const char *tail = str;
587
588 while (*tail == '_')
589 tail++;
590
591 return tail - str;
592 }
593
compare_symbols(const void * a,const void * b)594 static int compare_symbols(const void *a, const void *b)
595 {
596 const struct sym_entry *sa;
597 const struct sym_entry *sb;
598 int wa, wb;
599
600 sa = a;
601 sb = b;
602
603 /* sort by address first */
604 if (sa->addr > sb->addr)
605 return 1;
606 if (sa->addr < sb->addr)
607 return -1;
608
609 /* sort by "weakness" type */
610 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
611 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
612 if (wa != wb)
613 return wa - wb;
614
615 /* sort by "linker script provide" type */
616 wa = may_be_linker_script_provide_symbol(sa);
617 wb = may_be_linker_script_provide_symbol(sb);
618 if (wa != wb)
619 return wa - wb;
620
621 /* sort by the number of prefix underscores */
622 wa = prefix_underscores_count((const char *)sa->sym + 1);
623 wb = prefix_underscores_count((const char *)sb->sym + 1);
624 if (wa != wb)
625 return wa - wb;
626
627 /* sort by initial order, so that other symbols are left undisturbed */
628 return sa->start_pos - sb->start_pos;
629 }
630
sort_symbols(void)631 static void sort_symbols(void)
632 {
633 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
634 }
635
main(int argc,char ** argv)636 int main(int argc, char **argv)
637 {
638 if (argc >= 2) {
639 int i;
640 for (i = 1; i < argc; i++) {
641 if(strcmp(argv[i], "--all-symbols") == 0)
642 all_symbols = 1;
643 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
644 char *p = &argv[i][16];
645 /* skip quote */
646 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
647 p++;
648 symbol_prefix_char = *p;
649 } else
650 usage();
651 }
652 } else if (argc != 1)
653 usage();
654
655 read_map(stdin);
656 sort_symbols();
657 optimize_token_table();
658 write_src();
659
660 return 0;
661 }
662