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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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#include <stdio.h>
28#include <stdlib.h>
29#include <string.h>
30#include <ctype.h>
31
32/* maximum token length used. It doesn't pay to increase it a lot, because
33 * very long substrings probably don't repeat themselves too often. */
34#define MAX_TOK_SIZE 11
35#define KSYM_NAME_LEN 127
36
37/* we use only a subset of the complete symbol table to gather the token count,
38 * to speed up compression, at the expense of a little compression ratio */
39#define WORKING_SET 1024
40
41/* first find the best token only on the list of tokens that would profit more
42 * than GOOD_BAD_THRESHOLD. Only if this list is empty go to the "bad" list.
43 * Increasing this value will put less tokens on the "good" list, so the search
44 * is faster. However, if the good list runs out of tokens, we must painfully
45 * search the bad list. */
46#define GOOD_BAD_THRESHOLD 10
47
48/* token hash parameters */
49#define HASH_BITS 18
50#define HASH_TABLE_SIZE (1 << HASH_BITS)
51#define HASH_MASK (HASH_TABLE_SIZE - 1)
52#define HASH_BASE_OFFSET 2166136261U
53#define HASH_FOLD(a) ((a)&(HASH_MASK))
54
55/* flags to mark symbols */
56#define SYM_FLAG_VALID 1
57#define SYM_FLAG_SAMPLED 2
58
59struct sym_entry {
60 unsigned long long addr;
61 char type;
62 unsigned char flags;
63 unsigned char len;
64 unsigned char *sym;
65};
66
67
68static struct sym_entry *table;
69static int size, cnt;
70static unsigned long long _stext, _etext, _sinittext, _einittext;
71static int all_symbols = 0;
72
73struct token {
74 unsigned char data[MAX_TOK_SIZE];
75 unsigned char len;
76 /* profit: the number of bytes that could be saved by inserting this
77 * token into the table */
78 int profit;
79 struct token *next; /* next token on the hash list */
80 struct token *right; /* next token on the good/bad list */
81 struct token *left; /* previous token on the good/bad list */
82 struct token *smaller; /* token that is less one letter than this one */
83 };
84
85struct token bad_head, good_head;
86struct token *hash_table[HASH_TABLE_SIZE];
87
88/* the table that holds the result of the compression */
89unsigned char best_table[256][MAX_TOK_SIZE+1];
90unsigned char best_table_len[256];
91
92
93static void
94usage(void)
95{
96 fprintf(stderr, "Usage: kallsyms [--all-symbols] < in.map > out.S\n");
97 exit(1);
98}
99
100/*
101 * This ignores the intensely annoying "mapping symbols" found
102 * in ARM ELF files: $a, $t and $d.
103 */
104static inline int
105is_arm_mapping_symbol(const char *str)
106{
107 return str[0] == '$' && strchr("atd", str[1])
108 && (str[2] == '\0' || str[2] == '.');
109}
110
111static int
112read_symbol(FILE *in, struct sym_entry *s)
113{
114 char str[500];
115 int rc;
116
117 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &s->type, str);
118 if (rc != 3) {
119 if (rc != EOF) {
120 /* skip line */
121 fgets(str, 500, in);
122 }
123 return -1;
124 }
125
126 /* Ignore most absolute/undefined (?) symbols. */
127 if (strcmp(str, "_stext") == 0)
128 _stext = s->addr;
129 else if (strcmp(str, "_etext") == 0)
130 _etext = s->addr;
131 else if (strcmp(str, "_sinittext") == 0)
132 _sinittext = s->addr;
133 else if (strcmp(str, "_einittext") == 0)
134 _einittext = s->addr;
135 else if (toupper(s->type) == 'A')
136 {
137 /* Keep these useful absolute symbols */
138 if (strcmp(str, "__kernel_syscall_via_break") &&
139 strcmp(str, "__kernel_syscall_via_epc") &&
140 strcmp(str, "__kernel_sigtramp") &&
141 strcmp(str, "__gp"))
142 return -1;
143
144 }
145 else if (toupper(s->type) == 'U' ||
146 is_arm_mapping_symbol(str))
147 return -1;
148
149 /* include the type field in the symbol name, so that it gets
150 * compressed together */
151 s->len = strlen(str) + 1;
152 s->sym = (char *) malloc(s->len + 1);
153 strcpy(s->sym + 1, str);
154 s->sym[0] = s->type;
155
156 return 0;
157}
158
159static int
160symbol_valid(struct sym_entry *s)
161{
162 /* Symbols which vary between passes. Passes 1 and 2 must have
163 * identical symbol lists. The kallsyms_* symbols below are only added
164 * after pass 1, they would be included in pass 2 when --all-symbols is
165 * specified so exclude them to get a stable symbol list.
166 */
167 static char *special_symbols[] = {
168 "kallsyms_addresses",
169 "kallsyms_num_syms",
170 "kallsyms_names",
171 "kallsyms_markers",
172 "kallsyms_token_table",
173 "kallsyms_token_index",
174
175 /* Exclude linker generated symbols which vary between passes */
176 "_SDA_BASE_", /* ppc */
177 "_SDA2_BASE_", /* ppc */
178 NULL };
179 int i;
180
181 /* if --all-symbols is not specified, then symbols outside the text
182 * and inittext sections are discarded */
183 if (!all_symbols) {
184 if ((s->addr < _stext || s->addr > _etext)
185 && (s->addr < _sinittext || s->addr > _einittext))
186 return 0;
187 /* Corner case. Discard any symbols with the same value as
188 * _etext or _einittext, they can move between pass 1 and 2
189 * when the kallsyms data is added. If these symbols move then
190 * they may get dropped in pass 2, which breaks the kallsyms
191 * rules.
192 */
193 if ((s->addr == _etext && strcmp(s->sym + 1, "_etext")) ||
194 (s->addr == _einittext && strcmp(s->sym + 1, "_einittext")))
195 return 0;
196 }
197
198 /* Exclude symbols which vary between passes. */
199 if (strstr(s->sym + 1, "_compiled."))
200 return 0;
201
202 for (i = 0; special_symbols[i]; i++)
203 if( strcmp(s->sym + 1, special_symbols[i]) == 0 )
204 return 0;
205
206 return 1;
207}
208
209static void
210read_map(FILE *in)
211{
212 while (!feof(in)) {
213 if (cnt >= size) {
214 size += 10000;
215 table = realloc(table, sizeof(*table) * size);
216 if (!table) {
217 fprintf(stderr, "out of memory\n");
218 exit (1);
219 }
220 }
221 if (read_symbol(in, &table[cnt]) == 0)
222 cnt++;
223 }
224}
225
226static void output_label(char *label)
227{
228 printf(".globl %s\n",label);
229 printf("\tALGN\n");
230 printf("%s:\n",label);
231}
232
233/* uncompress a compressed symbol. When this function is called, the best table
234 * might still be compressed itself, so the function needs to be recursive */
235static int expand_symbol(unsigned char *data, int len, char *result)
236{
237 int c, rlen, total=0;
238
239 while (len) {
240 c = *data;
241 /* if the table holds a single char that is the same as the one
242 * we are looking for, then end the search */
243 if (best_table[c][0]==c && best_table_len[c]==1) {
244 *result++ = c;
245 total++;
246 } else {
247 /* if not, recurse and expand */
248 rlen = expand_symbol(best_table[c], best_table_len[c], result);
249 total += rlen;
250 result += rlen;
251 }
252 data++;
253 len--;
254 }
255 *result=0;
256
257 return total;
258}
259
260static void
261write_src(void)
262{
263 int i, k, off, valid;
264 unsigned int best_idx[256];
265 unsigned int *markers;
266 char buf[KSYM_NAME_LEN+1];
267
268 printf("#include <asm/types.h>\n");
269 printf("#if BITS_PER_LONG == 64\n");
270 printf("#define PTR .quad\n");
271 printf("#define ALGN .align 8\n");
272 printf("#else\n");
273 printf("#define PTR .long\n");
274 printf("#define ALGN .align 4\n");
275 printf("#endif\n");
276
277 printf(".data\n");
278
279 output_label("kallsyms_addresses");
280 valid = 0;
281 for (i = 0; i < cnt; i++) {
282 if (table[i].flags & SYM_FLAG_VALID) {
283 printf("\tPTR\t%#llx\n", table[i].addr);
284 valid++;
285 }
286 }
287 printf("\n");
288
289 output_label("kallsyms_num_syms");
290 printf("\tPTR\t%d\n", valid);
291 printf("\n");
292
293 /* table of offset markers, that give the offset in the compressed stream
294 * every 256 symbols */
295 markers = (unsigned int *) malloc(sizeof(unsigned int)*((valid + 255) / 256));
296
297 output_label("kallsyms_names");
298 valid = 0;
299 off = 0;
300 for (i = 0; i < cnt; i++) {
301
302 if (!table[i].flags & SYM_FLAG_VALID)
303 continue;
304
305 if ((valid & 0xFF) == 0)
306 markers[valid >> 8] = off;
307
308 printf("\t.byte 0x%02x", table[i].len);
309 for (k = 0; k < table[i].len; k++)
310 printf(", 0x%02x", table[i].sym[k]);
311 printf("\n");
312
313 off += table[i].len + 1;
314 valid++;
315 }
316 printf("\n");
317
318 output_label("kallsyms_markers");
319 for (i = 0; i < ((valid + 255) >> 8); i++)
320 printf("\tPTR\t%d\n", markers[i]);
321 printf("\n");
322
323 free(markers);
324
325 output_label("kallsyms_token_table");
326 off = 0;
327 for (i = 0; i < 256; i++) {
328 best_idx[i] = off;
329 expand_symbol(best_table[i],best_table_len[i],buf);
330 printf("\t.asciz\t\"%s\"\n", buf);
331 off += strlen(buf) + 1;
332 }
333 printf("\n");
334
335 output_label("kallsyms_token_index");
336 for (i = 0; i < 256; i++)
337 printf("\t.short\t%d\n", best_idx[i]);
338 printf("\n");
339}
340
341
342/* table lookup compression functions */
343
344static inline unsigned int rehash_token(unsigned int hash, unsigned char data)
345{
346 return ((hash * 16777619) ^ data);
347}
348
349static unsigned int hash_token(unsigned char *data, int len)
350{
351 unsigned int hash=HASH_BASE_OFFSET;
352 int i;
353
354 for (i = 0; i < len; i++)
355 hash = rehash_token(hash, data[i]);
356
357 return HASH_FOLD(hash);
358}
359
360/* find a token given its data and hash value */
361static struct token *find_token_hash(unsigned char *data, int len, unsigned int hash)
362{
363 struct token *ptr;
364
365 ptr = hash_table[hash];
366
367 while (ptr) {
368 if ((ptr->len == len) && (memcmp(ptr->data, data, len) == 0))
369 return ptr;
370 ptr=ptr->next;
371 }
372
373 return NULL;
374}
375
376static inline void insert_token_in_group(struct token *head, struct token *ptr)
377{
378 ptr->right = head->right;
379 ptr->right->left = ptr;
380 head->right = ptr;
381 ptr->left = head;
382}
383
384static inline void remove_token_from_group(struct token *ptr)
385{
386 ptr->left->right = ptr->right;
387 ptr->right->left = ptr->left;
388}
389
390
391/* build the counts for all the tokens that start with "data", and have lenghts
392 * from 2 to "len" */
393static void learn_token(unsigned char *data, int len)
394{
395 struct token *ptr,*last_ptr;
396 int i, newprofit;
397 unsigned int hash = HASH_BASE_OFFSET;
398 unsigned int hashes[MAX_TOK_SIZE + 1];
399
400 if (len > MAX_TOK_SIZE)
401 len = MAX_TOK_SIZE;
402
403 /* calculate and store the hash values for all the sub-tokens */
404 hash = rehash_token(hash, data[0]);
405 for (i = 2; i <= len; i++) {
406 hash = rehash_token(hash, data[i-1]);
407 hashes[i] = HASH_FOLD(hash);
408 }
409
410 last_ptr = NULL;
411 ptr = NULL;
412
413 for (i = len; i >= 2; i--) {
414 hash = hashes[i];
415
416 if (!ptr) ptr = find_token_hash(data, i, hash);
417
418 if (!ptr) {
419 /* create a new token entry */
420 ptr = (struct token *) malloc(sizeof(*ptr));
421
422 memcpy(ptr->data, data, i);
423 ptr->len = i;
424
425 /* when we create an entry, it's profit is 0 because
426 * we also take into account the size of the token on
427 * the compressed table. We then subtract GOOD_BAD_THRESHOLD
428 * so that the test to see if this token belongs to
429 * the good or bad list, is a comparison to zero */
430 ptr->profit = -GOOD_BAD_THRESHOLD;
431
432 ptr->next = hash_table[hash];
433 hash_table[hash] = ptr;
434
435 insert_token_in_group(&bad_head, ptr);
436
437 ptr->smaller = NULL;
438 } else {
439 newprofit = ptr->profit + (ptr->len - 1);
440 /* check to see if this token needs to be moved to a
441 * different list */
442 if((ptr->profit < 0) && (newprofit >= 0)) {
443 remove_token_from_group(ptr);
444 insert_token_in_group(&good_head,ptr);
445 }
446 ptr->profit = newprofit;
447 }
448
449 if (last_ptr) last_ptr->smaller = ptr;
450 last_ptr = ptr;
451
452 ptr = ptr->smaller;
453 }
454}
455
456/* decrease the counts for all the tokens that start with "data", and have lenghts
457 * from 2 to "len". This function is much simpler than learn_token because we have
458 * more guarantees (tho tokens exist, the ->smaller pointer is set, etc.)
459 * The two separate functions exist only because of compression performance */
460static void forget_token(unsigned char *data, int len)
461{
462 struct token *ptr;
463 int i, newprofit;
464 unsigned int hash=0;
465
466 if (len > MAX_TOK_SIZE) len = MAX_TOK_SIZE;
467
468 hash = hash_token(data, len);
469 ptr = find_token_hash(data, len, hash);
470
471 for (i = len; i >= 2; i--) {
472
473 newprofit = ptr->profit - (ptr->len - 1);
474 if ((ptr->profit >= 0) && (newprofit < 0)) {
475 remove_token_from_group(ptr);
476 insert_token_in_group(&bad_head, ptr);
477 }
478 ptr->profit=newprofit;
479
480 ptr=ptr->smaller;
481 }
482}
483
484/* count all the possible tokens in a symbol */
485static void learn_symbol(unsigned char *symbol, int len)
486{
487 int i;
488
489 for (i = 0; i < len - 1; i++)
490 learn_token(symbol + i, len - i);
491}
492
493/* decrease the count for all the possible tokens in a symbol */
494static void forget_symbol(unsigned char *symbol, int len)
495{
496 int i;
497
498 for (i = 0; i < len - 1; i++)
499 forget_token(symbol + i, len - i);
500}
501
502/* set all the symbol flags and do the initial token count */
503static void build_initial_tok_table(void)
504{
505 int i, use_it, valid;
506
507 valid = 0;
508 for (i = 0; i < cnt; i++) {
509 table[i].flags = 0;
510 if ( symbol_valid(&table[i]) ) {
511 table[i].flags |= SYM_FLAG_VALID;
512 valid++;
513 }
514 }
515
516 use_it = 0;
517 for (i = 0; i < cnt; i++) {
518
519 /* subsample the available symbols. This method is almost like
520 * a Bresenham's algorithm to get uniformly distributed samples
521 * across the symbol table */
522 if (table[i].flags & SYM_FLAG_VALID) {
523
524 use_it += WORKING_SET;
525
526 if (use_it >= valid) {
527 table[i].flags |= SYM_FLAG_SAMPLED;
528 use_it -= valid;
529 }
530 }
531 if (table[i].flags & SYM_FLAG_SAMPLED)
532 learn_symbol(table[i].sym, table[i].len);
533 }
534}
535
536/* replace a given token in all the valid symbols. Use the sampled symbols
537 * to update the counts */
538static void compress_symbols(unsigned char *str, int tlen, int idx)
539{
540 int i, len, learn, size;
541 unsigned char *p;
542
543 for (i = 0; i < cnt; i++) {
544
545 if (!(table[i].flags & SYM_FLAG_VALID)) continue;
546
547 len = table[i].len;
548 learn = 0;
549 p = table[i].sym;
550
551 do {
552 /* find the token on the symbol */
553 p = (unsigned char *) strstr((char *) p, (char *) str);
554 if (!p) break;
555
556 if (!learn) {
557 /* if this symbol was used to count, decrease it */
558 if (table[i].flags & SYM_FLAG_SAMPLED)
559 forget_symbol(table[i].sym, len);
560 learn = 1;
561 }
562
563 *p = idx;
564 size = (len - (p - table[i].sym)) - tlen + 1;
565 memmove(p + 1, p + tlen, size);
566 p++;
567 len -= tlen - 1;
568
569 } while (size >= tlen);
570
571 if(learn) {
572 table[i].len = len;
573 /* if this symbol was used to count, learn it again */
574 if(table[i].flags & SYM_FLAG_SAMPLED)
575 learn_symbol(table[i].sym, len);
576 }
577 }
578}
579
580/* search the token with the maximum profit */
581static struct token *find_best_token(void)
582{
583 struct token *ptr,*best,*head;
584 int bestprofit;
585
586 bestprofit=-10000;
587
588 /* failsafe: if the "good" list is empty search from the "bad" list */
589 if(good_head.right == &good_head) head = &bad_head;
590 else head = &good_head;
591
592 ptr = head->right;
593 best = NULL;
594 while (ptr != head) {
595 if (ptr->profit > bestprofit) {
596 bestprofit = ptr->profit;
597 best = ptr;
598 }
599 ptr = ptr->right;
600 }
601
602 return best;
603}
604
605/* this is the core of the algorithm: calculate the "best" table */
606static void optimize_result(void)
607{
608 struct token *best;
609 int i;
610
611 /* using the '\0' symbol last allows compress_symbols to use standard
612 * fast string functions */
613 for (i = 255; i >= 0; i--) {
614
615 /* if this table slot is empty (it is not used by an actual
616 * original char code */
617 if (!best_table_len[i]) {
618
619 /* find the token with the breates profit value */
620 best = find_best_token();
621
622 /* place it in the "best" table */
623 best_table_len[i] = best->len;
624 memcpy(best_table[i], best->data, best_table_len[i]);
625 /* zero terminate the token so that we can use strstr
626 in compress_symbols */
627 best_table[i][best_table_len[i]]='\0';
628
629 /* replace this token in all the valid symbols */
630 compress_symbols(best_table[i], best_table_len[i], i);
631 }
632 }
633}
634
635/* start by placing the symbols that are actually used on the table */
636static void insert_real_symbols_in_table(void)
637{
638 int i, j, c;
639
640 memset(best_table, 0, sizeof(best_table));
641 memset(best_table_len, 0, sizeof(best_table_len));
642
643 for (i = 0; i < cnt; i++) {
644 if (table[i].flags & SYM_FLAG_VALID) {
645 for (j = 0; j < table[i].len; j++) {
646 c = table[i].sym[j];
647 best_table[c][0]=c;
648 best_table_len[c]=1;
649 }
650 }
651 }
652}
653
654static void optimize_token_table(void)
655{
656 memset(hash_table, 0, sizeof(hash_table));
657
658 good_head.left = &good_head;
659 good_head.right = &good_head;
660
661 bad_head.left = &bad_head;
662 bad_head.right = &bad_head;
663
664 build_initial_tok_table();
665
666 insert_real_symbols_in_table();
667
668 optimize_result();
669}
670
671
672int
673main(int argc, char **argv)
674{
675 if (argc == 2 && strcmp(argv[1], "--all-symbols") == 0)
676 all_symbols = 1;
677 else if (argc != 1)
678 usage();
679
680 read_map(stdin);
681 optimize_token_table();
682 write_src();
683
684 return 0;
685}
686