1 /* Generate assembler source containing symbol information
3 * Copyright 2002 by Kai Germaschewski
5 * This software may be used and distributed according to the terms
6 * of the GNU General Public License, incorporated herein by reference.
8 * Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S
12 * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
13 * Changed the compression method from stem compression to "table lookup"
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
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
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
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
48 /* token hash parameters */
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))
55 /* flags to mark symbols */
56 #define SYM_FLAG_VALID 1
57 #define SYM_FLAG_SAMPLED 2
60 unsigned long long addr;
68 static struct sym_entry *table;
70 static unsigned long long _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
71 static int all_symbols = 0;
72 static char symbol_prefix_char = '\0';
75 unsigned char data[MAX_TOK_SIZE];
77 /* profit: the number of bytes that could be saved by inserting this
78 * token into the table */
80 struct token *next; /* next token on the hash list */
81 struct token *right; /* next token on the good/bad list */
82 struct token *left; /* previous token on the good/bad list */
83 struct token *smaller; /* token that is less one letter than this one */
86 struct token bad_head, good_head;
87 struct token *hash_table[HASH_TABLE_SIZE];
89 /* the table that holds the result of the compression */
90 unsigned char best_table[256][MAX_TOK_SIZE+1];
91 unsigned char best_table_len[256];
97 fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
102 * This ignores the intensely annoying "mapping symbols" found
103 * in ARM ELF files: $a, $t and $d.
106 is_arm_mapping_symbol(const char *str)
108 return str[0] == '$' && strchr("atd", str[1])
109 && (str[2] == '\0' || str[2] == '.');
113 read_symbol(FILE *in, struct sym_entry *s)
119 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &s->type, str);
129 /* skip prefix char */
130 if (symbol_prefix_char && str[0] == symbol_prefix_char)
133 /* Ignore most absolute/undefined (?) symbols. */
134 if (strcmp(sym, "_stext") == 0)
136 else if (strcmp(sym, "_etext") == 0)
138 else if (strcmp(sym, "_sinittext") == 0)
139 _sinittext = s->addr;
140 else if (strcmp(sym, "_einittext") == 0)
141 _einittext = s->addr;
142 else if (strcmp(sym, "_sextratext") == 0)
143 _sextratext = s->addr;
144 else if (strcmp(sym, "_eextratext") == 0)
145 _eextratext = s->addr;
146 else if (toupper(s->type) == 'A')
148 /* Keep these useful absolute symbols */
149 if (strcmp(sym, "__kernel_syscall_via_break") &&
150 strcmp(sym, "__kernel_syscall_via_epc") &&
151 strcmp(sym, "__kernel_sigtramp") &&
156 else if (toupper(s->type) == 'U' ||
157 is_arm_mapping_symbol(sym))
160 /* include the type field in the symbol name, so that it gets
161 * compressed together */
162 s->len = strlen(str) + 1;
163 s->sym = (char *) malloc(s->len + 1);
164 strcpy(s->sym + 1, str);
171 symbol_valid(struct sym_entry *s)
173 /* Symbols which vary between passes. Passes 1 and 2 must have
174 * identical symbol lists. The kallsyms_* symbols below are only added
175 * after pass 1, they would be included in pass 2 when --all-symbols is
176 * specified so exclude them to get a stable symbol list.
178 static char *special_symbols[] = {
179 "kallsyms_addresses",
183 "kallsyms_token_table",
184 "kallsyms_token_index",
186 /* Exclude linker generated symbols which vary between passes */
187 "_SDA_BASE_", /* ppc */
188 "_SDA2_BASE_", /* ppc */
193 /* skip prefix char */
194 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
197 /* if --all-symbols is not specified, then symbols outside the text
198 * and inittext sections are discarded */
200 if ((s->addr < _stext || s->addr > _etext)
201 && (s->addr < _sinittext || s->addr > _einittext)
202 && (s->addr < _sextratext || s->addr > _eextratext))
204 /* Corner case. Discard any symbols with the same value as
205 * _etext _einittext or _eextratext; they can move between pass
206 * 1 and 2 when the kallsyms data are added. If these symbols
207 * move then they may get dropped in pass 2, which breaks the
210 if ((s->addr == _etext && strcmp(s->sym + offset, "_etext")) ||
211 (s->addr == _einittext && strcmp(s->sym + offset, "_einittext")) ||
212 (s->addr == _eextratext && strcmp(s->sym + offset, "_eextratext")))
216 /* Exclude symbols which vary between passes. */
217 if (strstr(s->sym + offset, "_compiled."))
220 for (i = 0; special_symbols[i]; i++)
221 if( strcmp(s->sym + offset, special_symbols[i]) == 0 )
233 table = realloc(table, sizeof(*table) * size);
235 fprintf(stderr, "out of memory\n");
239 if (read_symbol(in, &table[cnt]) == 0)
244 static void output_label(char *label)
246 if (symbol_prefix_char)
247 printf(".globl %c%s\n", symbol_prefix_char, label);
249 printf(".globl %s\n", label);
251 if (symbol_prefix_char)
252 printf("%c%s:\n", symbol_prefix_char, label);
254 printf("%s:\n", label);
257 /* uncompress a compressed symbol. When this function is called, the best table
258 * might still be compressed itself, so the function needs to be recursive */
259 static int expand_symbol(unsigned char *data, int len, char *result)
261 int c, rlen, total=0;
265 /* if the table holds a single char that is the same as the one
266 * we are looking for, then end the search */
267 if (best_table[c][0]==c && best_table_len[c]==1) {
271 /* if not, recurse and expand */
272 rlen = expand_symbol(best_table[c], best_table_len[c], result);
287 int i, k, off, valid;
288 unsigned int best_idx[256];
289 unsigned int *markers;
290 char buf[KSYM_NAME_LEN+1];
292 printf("#include <asm/types.h>\n");
293 printf("#if BITS_PER_LONG == 64\n");
294 printf("#define PTR .quad\n");
295 printf("#define ALGN .align 8\n");
297 printf("#define PTR .long\n");
298 printf("#define ALGN .align 4\n");
303 output_label("kallsyms_addresses");
305 for (i = 0; i < cnt; i++) {
306 if (table[i].flags & SYM_FLAG_VALID) {
307 printf("\tPTR\t%#llx\n", table[i].addr);
313 output_label("kallsyms_num_syms");
314 printf("\tPTR\t%d\n", valid);
317 /* table of offset markers, that give the offset in the compressed stream
318 * every 256 symbols */
319 markers = (unsigned int *) malloc(sizeof(unsigned int)*((valid + 255) / 256));
321 output_label("kallsyms_names");
324 for (i = 0; i < cnt; i++) {
326 if (!table[i].flags & SYM_FLAG_VALID)
329 if ((valid & 0xFF) == 0)
330 markers[valid >> 8] = off;
332 printf("\t.byte 0x%02x", table[i].len);
333 for (k = 0; k < table[i].len; k++)
334 printf(", 0x%02x", table[i].sym[k]);
337 off += table[i].len + 1;
342 output_label("kallsyms_markers");
343 for (i = 0; i < ((valid + 255) >> 8); i++)
344 printf("\tPTR\t%d\n", markers[i]);
349 output_label("kallsyms_token_table");
351 for (i = 0; i < 256; i++) {
353 expand_symbol(best_table[i],best_table_len[i],buf);
354 printf("\t.asciz\t\"%s\"\n", buf);
355 off += strlen(buf) + 1;
359 output_label("kallsyms_token_index");
360 for (i = 0; i < 256; i++)
361 printf("\t.short\t%d\n", best_idx[i]);
366 /* table lookup compression functions */
368 static inline unsigned int rehash_token(unsigned int hash, unsigned char data)
370 return ((hash * 16777619) ^ data);
373 static unsigned int hash_token(unsigned char *data, int len)
375 unsigned int hash=HASH_BASE_OFFSET;
378 for (i = 0; i < len; i++)
379 hash = rehash_token(hash, data[i]);
381 return HASH_FOLD(hash);
384 /* find a token given its data and hash value */
385 static struct token *find_token_hash(unsigned char *data, int len, unsigned int hash)
389 ptr = hash_table[hash];
392 if ((ptr->len == len) && (memcmp(ptr->data, data, len) == 0))
400 static inline void insert_token_in_group(struct token *head, struct token *ptr)
402 ptr->right = head->right;
403 ptr->right->left = ptr;
408 static inline void remove_token_from_group(struct token *ptr)
410 ptr->left->right = ptr->right;
411 ptr->right->left = ptr->left;
415 /* build the counts for all the tokens that start with "data", and have lenghts
417 static void learn_token(unsigned char *data, int len)
419 struct token *ptr,*last_ptr;
421 unsigned int hash = HASH_BASE_OFFSET;
422 unsigned int hashes[MAX_TOK_SIZE + 1];
424 if (len > MAX_TOK_SIZE)
427 /* calculate and store the hash values for all the sub-tokens */
428 hash = rehash_token(hash, data[0]);
429 for (i = 2; i <= len; i++) {
430 hash = rehash_token(hash, data[i-1]);
431 hashes[i] = HASH_FOLD(hash);
437 for (i = len; i >= 2; i--) {
440 if (!ptr) ptr = find_token_hash(data, i, hash);
443 /* create a new token entry */
444 ptr = (struct token *) malloc(sizeof(*ptr));
446 memcpy(ptr->data, data, i);
449 /* when we create an entry, it's profit is 0 because
450 * we also take into account the size of the token on
451 * the compressed table. We then subtract GOOD_BAD_THRESHOLD
452 * so that the test to see if this token belongs to
453 * the good or bad list, is a comparison to zero */
454 ptr->profit = -GOOD_BAD_THRESHOLD;
456 ptr->next = hash_table[hash];
457 hash_table[hash] = ptr;
459 insert_token_in_group(&bad_head, ptr);
463 newprofit = ptr->profit + (ptr->len - 1);
464 /* check to see if this token needs to be moved to a
466 if((ptr->profit < 0) && (newprofit >= 0)) {
467 remove_token_from_group(ptr);
468 insert_token_in_group(&good_head,ptr);
470 ptr->profit = newprofit;
473 if (last_ptr) last_ptr->smaller = ptr;
480 /* decrease the counts for all the tokens that start with "data", and have lenghts
481 * from 2 to "len". This function is much simpler than learn_token because we have
482 * more guarantees (tho tokens exist, the ->smaller pointer is set, etc.)
483 * The two separate functions exist only because of compression performance */
484 static void forget_token(unsigned char *data, int len)
490 if (len > MAX_TOK_SIZE) len = MAX_TOK_SIZE;
492 hash = hash_token(data, len);
493 ptr = find_token_hash(data, len, hash);
495 for (i = len; i >= 2; i--) {
497 newprofit = ptr->profit - (ptr->len - 1);
498 if ((ptr->profit >= 0) && (newprofit < 0)) {
499 remove_token_from_group(ptr);
500 insert_token_in_group(&bad_head, ptr);
502 ptr->profit=newprofit;
508 /* count all the possible tokens in a symbol */
509 static void learn_symbol(unsigned char *symbol, int len)
513 for (i = 0; i < len - 1; i++)
514 learn_token(symbol + i, len - i);
517 /* decrease the count for all the possible tokens in a symbol */
518 static void forget_symbol(unsigned char *symbol, int len)
522 for (i = 0; i < len - 1; i++)
523 forget_token(symbol + i, len - i);
526 /* set all the symbol flags and do the initial token count */
527 static void build_initial_tok_table(void)
529 int i, use_it, valid;
532 for (i = 0; i < cnt; i++) {
534 if ( symbol_valid(&table[i]) ) {
535 table[i].flags |= SYM_FLAG_VALID;
541 for (i = 0; i < cnt; i++) {
543 /* subsample the available symbols. This method is almost like
544 * a Bresenham's algorithm to get uniformly distributed samples
545 * across the symbol table */
546 if (table[i].flags & SYM_FLAG_VALID) {
548 use_it += WORKING_SET;
550 if (use_it >= valid) {
551 table[i].flags |= SYM_FLAG_SAMPLED;
555 if (table[i].flags & SYM_FLAG_SAMPLED)
556 learn_symbol(table[i].sym, table[i].len);
560 /* replace a given token in all the valid symbols. Use the sampled symbols
561 * to update the counts */
562 static void compress_symbols(unsigned char *str, int tlen, int idx)
564 int i, len, learn, size;
567 for (i = 0; i < cnt; i++) {
569 if (!(table[i].flags & SYM_FLAG_VALID)) continue;
576 /* find the token on the symbol */
577 p = (unsigned char *) strstr((char *) p, (char *) str);
581 /* if this symbol was used to count, decrease it */
582 if (table[i].flags & SYM_FLAG_SAMPLED)
583 forget_symbol(table[i].sym, len);
588 size = (len - (p - table[i].sym)) - tlen + 1;
589 memmove(p + 1, p + tlen, size);
593 } while (size >= tlen);
597 /* if this symbol was used to count, learn it again */
598 if(table[i].flags & SYM_FLAG_SAMPLED)
599 learn_symbol(table[i].sym, len);
604 /* search the token with the maximum profit */
605 static struct token *find_best_token(void)
607 struct token *ptr,*best,*head;
612 /* failsafe: if the "good" list is empty search from the "bad" list */
613 if(good_head.right == &good_head) head = &bad_head;
614 else head = &good_head;
618 while (ptr != head) {
619 if (ptr->profit > bestprofit) {
620 bestprofit = ptr->profit;
629 /* this is the core of the algorithm: calculate the "best" table */
630 static void optimize_result(void)
635 /* using the '\0' symbol last allows compress_symbols to use standard
636 * fast string functions */
637 for (i = 255; i >= 0; i--) {
639 /* if this table slot is empty (it is not used by an actual
640 * original char code */
641 if (!best_table_len[i]) {
643 /* find the token with the breates profit value */
644 best = find_best_token();
646 /* place it in the "best" table */
647 best_table_len[i] = best->len;
648 memcpy(best_table[i], best->data, best_table_len[i]);
649 /* zero terminate the token so that we can use strstr
650 in compress_symbols */
651 best_table[i][best_table_len[i]]='\0';
653 /* replace this token in all the valid symbols */
654 compress_symbols(best_table[i], best_table_len[i], i);
659 /* start by placing the symbols that are actually used on the table */
660 static void insert_real_symbols_in_table(void)
664 memset(best_table, 0, sizeof(best_table));
665 memset(best_table_len, 0, sizeof(best_table_len));
667 for (i = 0; i < cnt; i++) {
668 if (table[i].flags & SYM_FLAG_VALID) {
669 for (j = 0; j < table[i].len; j++) {
678 static void optimize_token_table(void)
680 memset(hash_table, 0, sizeof(hash_table));
682 good_head.left = &good_head;
683 good_head.right = &good_head;
685 bad_head.left = &bad_head;
686 bad_head.right = &bad_head;
688 build_initial_tok_table();
690 insert_real_symbols_in_table();
692 /* When valid symbol is not registered, exit to error */
693 if (good_head.left == good_head.right &&
694 bad_head.left == bad_head.right) {
695 fprintf(stderr, "No valid symbol.\n");
704 main(int argc, char **argv)
708 for (i = 1; i < argc; i++) {
709 if(strcmp(argv[i], "--all-symbols") == 0)
711 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
712 char *p = &argv[i][16];
714 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
716 symbol_prefix_char = *p;
720 } else if (argc != 1)
724 optimize_token_table();