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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: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S | |
9 | * | |
10 | * ChangeLog: | |
11 | * | |
12 | * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com> | |
13 | * Changed the compression method from stem compression to "table lookup" | |
14 | * compression | |
15 | * | |
16 | * Table compression uses all the unused char codes on the symbols and | |
17 | * maps these to the most used substrings (tokens). For instance, it might | |
18 | * map char code 0xF7 to represent "write_" and then in every symbol where | |
19 | * "write_" appears it can be replaced by 0xF7, saving 5 bytes. | |
20 | * The used codes themselves are also placed in the table so that the | |
21 | * decompresion can work without "special cases". | |
22 | * Applied to kernel symbols, this usually produces a compression ratio | |
23 | * of about 50%. | |
24 | * | |
25 | */ | |
26 | ||
27 | #define _GNU_SOURCE | |
28 | ||
29 | #include <stdio.h> | |
30 | #include <stdlib.h> | |
31 | #include <string.h> | |
32 | #include <ctype.h> | |
33 | ||
34 | #define KSYM_NAME_LEN 127 | |
35 | ||
36 | ||
37 | struct sym_entry { | |
38 | unsigned long long addr; | |
39 | unsigned int len; | |
40 | unsigned char *sym; | |
41 | }; | |
42 | ||
43 | ||
44 | static struct sym_entry *table; | |
45 | static unsigned int table_size, table_cnt; | |
46 | static unsigned long long _text, _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext; | |
47 | static int all_symbols = 0; | |
48 | static char symbol_prefix_char = '\0'; | |
49 | ||
50 | int token_profit[0x10000]; | |
51 | ||
52 | /* the table that holds the result of the compression */ | |
53 | unsigned char best_table[256][2]; | |
54 | unsigned char best_table_len[256]; | |
55 | ||
56 | ||
57 | static void usage(void) | |
58 | { | |
59 | fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n"); | |
60 | exit(1); | |
61 | } | |
62 | ||
63 | /* | |
64 | * This ignores the intensely annoying "mapping symbols" found | |
65 | * in ARM ELF files: $a, $t and $d. | |
66 | */ | |
67 | static inline int is_arm_mapping_symbol(const char *str) | |
68 | { | |
69 | return str[0] == '$' && strchr("atd", str[1]) | |
70 | && (str[2] == '\0' || str[2] == '.'); | |
71 | } | |
72 | ||
73 | static int read_symbol(FILE *in, struct sym_entry *s) | |
74 | { | |
75 | char str[500]; | |
76 | char *sym, stype; | |
77 | int rc; | |
78 | ||
79 | rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); | |
80 | if (rc != 3) { | |
81 | if (rc != EOF) { | |
82 | /* skip line */ | |
83 | fgets(str, 500, in); | |
84 | } | |
85 | return -1; | |
86 | } | |
87 | ||
88 | sym = str; | |
89 | /* skip prefix char */ | |
90 | if (symbol_prefix_char && str[0] == symbol_prefix_char) | |
91 | sym++; | |
92 | ||
93 | /* Ignore most absolute/undefined (?) symbols. */ | |
94 | if (strcmp(sym, "_text") == 0) | |
95 | _text = s->addr; | |
96 | else if (strcmp(sym, "_stext") == 0) | |
97 | _stext = s->addr; | |
98 | else if (strcmp(sym, "_etext") == 0) | |
99 | _etext = s->addr; | |
100 | else if (strcmp(sym, "_sinittext") == 0) | |
101 | _sinittext = s->addr; | |
102 | else if (strcmp(sym, "_einittext") == 0) | |
103 | _einittext = s->addr; | |
104 | else if (strcmp(sym, "_sextratext") == 0) | |
105 | _sextratext = s->addr; | |
106 | else if (strcmp(sym, "_eextratext") == 0) | |
107 | _eextratext = s->addr; | |
108 | else if (toupper(stype) == 'A') | |
109 | { | |
110 | /* Keep these useful absolute symbols */ | |
111 | if (strcmp(sym, "__kernel_syscall_via_break") && | |
112 | strcmp(sym, "__kernel_syscall_via_epc") && | |
113 | strcmp(sym, "__kernel_sigtramp") && | |
114 | strcmp(sym, "__gp")) | |
115 | return -1; | |
116 | ||
117 | } | |
118 | else if (toupper(stype) == 'U' || | |
119 | is_arm_mapping_symbol(sym)) | |
120 | return -1; | |
121 | /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ | |
122 | else if (str[0] == '$') | |
123 | return -1; | |
124 | ||
125 | /* include the type field in the symbol name, so that it gets | |
126 | * compressed together */ | |
127 | s->len = strlen(str) + 1; | |
128 | s->sym = malloc(s->len + 1); | |
129 | if (!s->sym) { | |
130 | fprintf(stderr, "kallsyms failure: " | |
131 | "unable to allocate required amount of memory\n"); | |
132 | exit(EXIT_FAILURE); | |
133 | } | |
134 | strcpy((char *)s->sym + 1, str); | |
135 | s->sym[0] = stype; | |
136 | ||
137 | return 0; | |
138 | } | |
139 | ||
140 | static int symbol_valid(struct sym_entry *s) | |
141 | { | |
142 | /* Symbols which vary between passes. Passes 1 and 2 must have | |
143 | * identical symbol lists. The kallsyms_* symbols below are only added | |
144 | * after pass 1, they would be included in pass 2 when --all-symbols is | |
145 | * specified so exclude them to get a stable symbol list. | |
146 | */ | |
147 | static char *special_symbols[] = { | |
148 | "kallsyms_addresses", | |
149 | "kallsyms_num_syms", | |
150 | "kallsyms_names", | |
151 | "kallsyms_markers", | |
152 | "kallsyms_token_table", | |
153 | "kallsyms_token_index", | |
154 | ||
155 | /* Exclude linker generated symbols which vary between passes */ | |
156 | "_SDA_BASE_", /* ppc */ | |
157 | "_SDA2_BASE_", /* ppc */ | |
158 | NULL }; | |
159 | int i; | |
160 | int offset = 1; | |
161 | ||
162 | /* skip prefix char */ | |
163 | if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) | |
164 | offset++; | |
165 | ||
166 | /* if --all-symbols is not specified, then symbols outside the text | |
167 | * and inittext sections are discarded */ | |
168 | if (!all_symbols) { | |
169 | if ((s->addr < _stext || s->addr > _etext) | |
170 | && (s->addr < _sinittext || s->addr > _einittext) | |
171 | && (s->addr < _sextratext || s->addr > _eextratext)) | |
172 | return 0; | |
173 | /* Corner case. Discard any symbols with the same value as | |
174 | * _etext _einittext or _eextratext; they can move between pass | |
175 | * 1 and 2 when the kallsyms data are added. If these symbols | |
176 | * move then they may get dropped in pass 2, which breaks the | |
177 | * kallsyms rules. | |
178 | */ | |
179 | if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) || | |
180 | (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) || | |
181 | (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext"))) | |
182 | return 0; | |
183 | } | |
184 | ||
185 | /* Exclude symbols which vary between passes. */ | |
186 | if (strstr((char *)s->sym + offset, "_compiled.")) | |
187 | return 0; | |
188 | ||
189 | for (i = 0; special_symbols[i]; i++) | |
190 | if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) | |
191 | return 0; | |
192 | ||
193 | return 1; | |
194 | } | |
195 | ||
196 | static void read_map(FILE *in) | |
197 | { | |
198 | while (!feof(in)) { | |
199 | if (table_cnt >= table_size) { | |
200 | table_size += 10000; | |
201 | table = realloc(table, sizeof(*table) * table_size); | |
202 | if (!table) { | |
203 | fprintf(stderr, "out of memory\n"); | |
204 | exit (1); | |
205 | } | |
206 | } | |
207 | if (read_symbol(in, &table[table_cnt]) == 0) | |
208 | table_cnt++; | |
209 | } | |
210 | } | |
211 | ||
212 | static void output_label(char *label) | |
213 | { | |
214 | if (symbol_prefix_char) | |
215 | printf(".globl %c%s\n", symbol_prefix_char, label); | |
216 | else | |
217 | printf(".globl %s\n", label); | |
218 | printf("\tALGN\n"); | |
219 | if (symbol_prefix_char) | |
220 | printf("%c%s:\n", symbol_prefix_char, label); | |
221 | else | |
222 | printf("%s:\n", label); | |
223 | } | |
224 | ||
225 | /* uncompress a compressed symbol. When this function is called, the best table | |
226 | * might still be compressed itself, so the function needs to be recursive */ | |
227 | static int expand_symbol(unsigned char *data, int len, char *result) | |
228 | { | |
229 | int c, rlen, total=0; | |
230 | ||
231 | while (len) { | |
232 | c = *data; | |
233 | /* if the table holds a single char that is the same as the one | |
234 | * we are looking for, then end the search */ | |
235 | if (best_table[c][0]==c && best_table_len[c]==1) { | |
236 | *result++ = c; | |
237 | total++; | |
238 | } else { | |
239 | /* if not, recurse and expand */ | |
240 | rlen = expand_symbol(best_table[c], best_table_len[c], result); | |
241 | total += rlen; | |
242 | result += rlen; | |
243 | } | |
244 | data++; | |
245 | len--; | |
246 | } | |
247 | *result=0; | |
248 | ||
249 | return total; | |
250 | } | |
251 | ||
252 | static void write_src(void) | |
253 | { | |
254 | unsigned int i, k, off; | |
255 | unsigned int best_idx[256]; | |
256 | unsigned int *markers; | |
257 | char buf[KSYM_NAME_LEN+1]; | |
258 | ||
259 | printf("#include <asm/types.h>\n"); | |
260 | printf("#if BITS_PER_LONG == 64\n"); | |
261 | printf("#define PTR .quad\n"); | |
262 | printf("#define ALGN .align 8\n"); | |
263 | printf("#else\n"); | |
264 | printf("#define PTR .long\n"); | |
265 | printf("#define ALGN .align 4\n"); | |
266 | printf("#endif\n"); | |
267 | ||
268 | printf(".data\n"); | |
269 | ||
270 | /* Provide proper symbols relocatability by their '_text' | |
271 | * relativeness. The symbol names cannot be used to construct | |
272 | * normal symbol references as the list of symbols contains | |
273 | * symbols that are declared static and are private to their | |
274 | * .o files. This prevents .tmp_kallsyms.o or any other | |
275 | * object from referencing them. | |
276 | */ | |
277 | output_label("kallsyms_addresses"); | |
278 | for (i = 0; i < table_cnt; i++) { | |
279 | if (toupper(table[i].sym[0]) != 'A') { | |
280 | if (_text <= table[i].addr) | |
281 | printf("\tPTR\t_text + %#llx\n", | |
282 | table[i].addr - _text); | |
283 | else | |
284 | printf("\tPTR\t_text - %#llx\n", | |
285 | _text - table[i].addr); | |
286 | } else { | |
287 | printf("\tPTR\t%#llx\n", table[i].addr); | |
288 | } | |
289 | } | |
290 | printf("\n"); | |
291 | ||
292 | output_label("kallsyms_num_syms"); | |
293 | printf("\tPTR\t%d\n", table_cnt); | |
294 | printf("\n"); | |
295 | ||
296 | /* table of offset markers, that give the offset in the compressed stream | |
297 | * every 256 symbols */ | |
298 | markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); | |
299 | if (!markers) { | |
300 | fprintf(stderr, "kallsyms failure: " | |
301 | "unable to allocate required memory\n"); | |
302 | exit(EXIT_FAILURE); | |
303 | } | |
304 | ||
305 | output_label("kallsyms_names"); | |
306 | off = 0; | |
307 | for (i = 0; i < table_cnt; i++) { | |
308 | if ((i & 0xFF) == 0) | |
309 | markers[i >> 8] = off; | |
310 | ||
311 | printf("\t.byte 0x%02x", table[i].len); | |
312 | for (k = 0; k < table[i].len; k++) | |
313 | printf(", 0x%02x", table[i].sym[k]); | |
314 | printf("\n"); | |
315 | ||
316 | off += table[i].len + 1; | |
317 | } | |
318 | printf("\n"); | |
319 | ||
320 | output_label("kallsyms_markers"); | |
321 | for (i = 0; i < ((table_cnt + 255) >> 8); i++) | |
322 | printf("\tPTR\t%d\n", markers[i]); | |
323 | printf("\n"); | |
324 | ||
325 | free(markers); | |
326 | ||
327 | output_label("kallsyms_token_table"); | |
328 | off = 0; | |
329 | for (i = 0; i < 256; i++) { | |
330 | best_idx[i] = off; | |
331 | expand_symbol(best_table[i], best_table_len[i], buf); | |
332 | printf("\t.asciz\t\"%s\"\n", buf); | |
333 | off += strlen(buf) + 1; | |
334 | } | |
335 | printf("\n"); | |
336 | ||
337 | output_label("kallsyms_token_index"); | |
338 | for (i = 0; i < 256; i++) | |
339 | printf("\t.short\t%d\n", best_idx[i]); | |
340 | printf("\n"); | |
341 | } | |
342 | ||
343 | ||
344 | /* table lookup compression functions */ | |
345 | ||
346 | /* count all the possible tokens in a symbol */ | |
347 | static void learn_symbol(unsigned char *symbol, int len) | |
348 | { | |
349 | int i; | |
350 | ||
351 | for (i = 0; i < len - 1; i++) | |
352 | token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; | |
353 | } | |
354 | ||
355 | /* decrease the count for all the possible tokens in a symbol */ | |
356 | static void forget_symbol(unsigned char *symbol, int len) | |
357 | { | |
358 | int i; | |
359 | ||
360 | for (i = 0; i < len - 1; i++) | |
361 | token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; | |
362 | } | |
363 | ||
364 | /* remove all the invalid symbols from the table and do the initial token count */ | |
365 | static void build_initial_tok_table(void) | |
366 | { | |
367 | unsigned int i, pos; | |
368 | ||
369 | pos = 0; | |
370 | for (i = 0; i < table_cnt; i++) { | |
371 | if ( symbol_valid(&table[i]) ) { | |
372 | if (pos != i) | |
373 | table[pos] = table[i]; | |
374 | learn_symbol(table[pos].sym, table[pos].len); | |
375 | pos++; | |
376 | } | |
377 | } | |
378 | table_cnt = pos; | |
379 | } | |
380 | ||
381 | /* replace a given token in all the valid symbols. Use the sampled symbols | |
382 | * to update the counts */ | |
383 | static void compress_symbols(unsigned char *str, int idx) | |
384 | { | |
385 | unsigned int i, len, size; | |
386 | unsigned char *p1, *p2; | |
387 | ||
388 | for (i = 0; i < table_cnt; i++) { | |
389 | ||
390 | len = table[i].len; | |
391 | p1 = table[i].sym; | |
392 | ||
393 | /* find the token on the symbol */ | |
394 | p2 = memmem(p1, len, str, 2); | |
395 | if (!p2) continue; | |
396 | ||
397 | /* decrease the counts for this symbol's tokens */ | |
398 | forget_symbol(table[i].sym, len); | |
399 | ||
400 | size = len; | |
401 | ||
402 | do { | |
403 | *p2 = idx; | |
404 | p2++; | |
405 | size -= (p2 - p1); | |
406 | memmove(p2, p2 + 1, size); | |
407 | p1 = p2; | |
408 | len--; | |
409 | ||
410 | if (size < 2) break; | |
411 | ||
412 | /* find the token on the symbol */ | |
413 | p2 = memmem(p1, size, str, 2); | |
414 | ||
415 | } while (p2); | |
416 | ||
417 | table[i].len = len; | |
418 | ||
419 | /* increase the counts for this symbol's new tokens */ | |
420 | learn_symbol(table[i].sym, len); | |
421 | } | |
422 | } | |
423 | ||
424 | /* search the token with the maximum profit */ | |
425 | static int find_best_token(void) | |
426 | { | |
427 | int i, best, bestprofit; | |
428 | ||
429 | bestprofit=-10000; | |
430 | best = 0; | |
431 | ||
432 | for (i = 0; i < 0x10000; i++) { | |
433 | if (token_profit[i] > bestprofit) { | |
434 | best = i; | |
435 | bestprofit = token_profit[i]; | |
436 | } | |
437 | } | |
438 | return best; | |
439 | } | |
440 | ||
441 | /* this is the core of the algorithm: calculate the "best" table */ | |
442 | static void optimize_result(void) | |
443 | { | |
444 | int i, best; | |
445 | ||
446 | /* using the '\0' symbol last allows compress_symbols to use standard | |
447 | * fast string functions */ | |
448 | for (i = 255; i >= 0; i--) { | |
449 | ||
450 | /* if this table slot is empty (it is not used by an actual | |
451 | * original char code */ | |
452 | if (!best_table_len[i]) { | |
453 | ||
454 | /* find the token with the breates profit value */ | |
455 | best = find_best_token(); | |
456 | ||
457 | /* place it in the "best" table */ | |
458 | best_table_len[i] = 2; | |
459 | best_table[i][0] = best & 0xFF; | |
460 | best_table[i][1] = (best >> 8) & 0xFF; | |
461 | ||
462 | /* replace this token in all the valid symbols */ | |
463 | compress_symbols(best_table[i], i); | |
464 | } | |
465 | } | |
466 | } | |
467 | ||
468 | /* start by placing the symbols that are actually used on the table */ | |
469 | static void insert_real_symbols_in_table(void) | |
470 | { | |
471 | unsigned int i, j, c; | |
472 | ||
473 | memset(best_table, 0, sizeof(best_table)); | |
474 | memset(best_table_len, 0, sizeof(best_table_len)); | |
475 | ||
476 | for (i = 0; i < table_cnt; i++) { | |
477 | for (j = 0; j < table[i].len; j++) { | |
478 | c = table[i].sym[j]; | |
479 | best_table[c][0]=c; | |
480 | best_table_len[c]=1; | |
481 | } | |
482 | } | |
483 | } | |
484 | ||
485 | static void optimize_token_table(void) | |
486 | { | |
487 | build_initial_tok_table(); | |
488 | ||
489 | insert_real_symbols_in_table(); | |
490 | ||
491 | /* When valid symbol is not registered, exit to error */ | |
492 | if (!table_cnt) { | |
493 | fprintf(stderr, "No valid symbol.\n"); | |
494 | exit(1); | |
495 | } | |
496 | ||
497 | optimize_result(); | |
498 | } | |
499 | ||
500 | ||
501 | int main(int argc, char **argv) | |
502 | { | |
503 | if (argc >= 2) { | |
504 | int i; | |
505 | for (i = 1; i < argc; i++) { | |
506 | if(strcmp(argv[i], "--all-symbols") == 0) | |
507 | all_symbols = 1; | |
508 | else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { | |
509 | char *p = &argv[i][16]; | |
510 | /* skip quote */ | |
511 | if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) | |
512 | p++; | |
513 | symbol_prefix_char = *p; | |
514 | } else | |
515 | usage(); | |
516 | } | |
517 | } else if (argc != 1) | |
518 | usage(); | |
519 | ||
520 | read_map(stdin); | |
521 | optimize_token_table(); | |
522 | write_src(); | |
523 | ||
524 | return 0; | |
525 | } |