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
;
71 static int all_symbols
= 0;
74 unsigned char data
[MAX_TOK_SIZE
];
76 /* profit: the number of bytes that could be saved by inserting this
77 * token into the table */
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 */
85 struct token bad_head
, good_head
;
86 struct token
*hash_table
[HASH_TABLE_SIZE
];
88 /* the table that holds the result of the compression */
89 unsigned char best_table
[256][MAX_TOK_SIZE
+1];
90 unsigned char best_table_len
[256];
96 fprintf(stderr
, "Usage: kallsyms [--all-symbols] < in.map > out.S\n");
101 * This ignores the intensely annoying "mapping symbols" found
102 * in ARM ELF files: $a, $t and $d.
105 is_arm_mapping_symbol(const char *str
)
107 return str
[0] == '$' && strchr("atd", str
[1])
108 && (str
[2] == '\0' || str
[2] == '.');
112 read_symbol(FILE *in
, struct sym_entry
*s
)
117 rc
= fscanf(in
, "%llx %c %499s\n", &s
->addr
, &s
->type
, str
);
126 /* Ignore most absolute/undefined (?) symbols. */
127 if (strcmp(str
, "_stext") == 0)
129 else if (strcmp(str
, "_etext") == 0)
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')
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") &&
145 else if (toupper(s
->type
) == 'U' ||
146 is_arm_mapping_symbol(str
))
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
);
160 symbol_valid(struct sym_entry
*s
)
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.
167 static char *special_symbols
[] = {
168 "kallsyms_addresses",
172 "kallsyms_token_table",
173 "kallsyms_token_index",
175 /* Exclude linker generated symbols which vary between passes */
176 "_SDA_BASE_", /* ppc */
177 "_SDA2_BASE_", /* ppc */
181 /* if --all-symbols is not specified, then symbols outside the text
182 * and inittext sections are discarded */
184 if ((s
->addr
< _stext
|| s
->addr
> _etext
)
185 && (s
->addr
< _sinittext
|| s
->addr
> _einittext
))
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
193 if ((s
->addr
== _etext
&& strcmp(s
->sym
+ 1, "_etext")) ||
194 (s
->addr
== _einittext
&& strcmp(s
->sym
+ 1, "_einittext")))
198 /* Exclude symbols which vary between passes. */
199 if (strstr(s
->sym
+ 1, "_compiled."))
202 for (i
= 0; special_symbols
[i
]; i
++)
203 if( strcmp(s
->sym
+ 1, special_symbols
[i
]) == 0 )
215 table
= realloc(table
, sizeof(*table
) * size
);
217 fprintf(stderr
, "out of memory\n");
221 if (read_symbol(in
, &table
[cnt
]) == 0)
226 static void output_label(char *label
)
228 printf(".globl %s\n",label
);
230 printf("%s:\n",label
);
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 */
235 static int expand_symbol(unsigned char *data
, int len
, char *result
)
237 int c
, rlen
, total
=0;
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) {
247 /* if not, recurse and expand */
248 rlen
= expand_symbol(best_table
[c
], best_table_len
[c
], result
);
263 int i
, k
, off
, valid
;
264 unsigned int best_idx
[256];
265 unsigned int *markers
;
266 char buf
[KSYM_NAME_LEN
+1];
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");
273 printf("#define PTR .long\n");
274 printf("#define ALGN .align 4\n");
279 output_label("kallsyms_addresses");
281 for (i
= 0; i
< cnt
; i
++) {
282 if (table
[i
].flags
& SYM_FLAG_VALID
) {
283 printf("\tPTR\t%#llx\n", table
[i
].addr
);
289 output_label("kallsyms_num_syms");
290 printf("\tPTR\t%d\n", valid
);
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));
297 output_label("kallsyms_names");
300 for (i
= 0; i
< cnt
; i
++) {
302 if (!table
[i
].flags
& SYM_FLAG_VALID
)
305 if ((valid
& 0xFF) == 0)
306 markers
[valid
>> 8] = off
;
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
]);
313 off
+= table
[i
].len
+ 1;
318 output_label("kallsyms_markers");
319 for (i
= 0; i
< ((valid
+ 255) >> 8); i
++)
320 printf("\tPTR\t%d\n", markers
[i
]);
325 output_label("kallsyms_token_table");
327 for (i
= 0; i
< 256; i
++) {
329 expand_symbol(best_table
[i
],best_table_len
[i
],buf
);
330 printf("\t.asciz\t\"%s\"\n", buf
);
331 off
+= strlen(buf
) + 1;
335 output_label("kallsyms_token_index");
336 for (i
= 0; i
< 256; i
++)
337 printf("\t.short\t%d\n", best_idx
[i
]);
342 /* table lookup compression functions */
344 static inline unsigned int rehash_token(unsigned int hash
, unsigned char data
)
346 return ((hash
* 16777619) ^ data
);
349 static unsigned int hash_token(unsigned char *data
, int len
)
351 unsigned int hash
=HASH_BASE_OFFSET
;
354 for (i
= 0; i
< len
; i
++)
355 hash
= rehash_token(hash
, data
[i
]);
357 return HASH_FOLD(hash
);
360 /* find a token given its data and hash value */
361 static struct token
*find_token_hash(unsigned char *data
, int len
, unsigned int hash
)
365 ptr
= hash_table
[hash
];
368 if ((ptr
->len
== len
) && (memcmp(ptr
->data
, data
, len
) == 0))
376 static inline void insert_token_in_group(struct token
*head
, struct token
*ptr
)
378 ptr
->right
= head
->right
;
379 ptr
->right
->left
= ptr
;
384 static inline void remove_token_from_group(struct token
*ptr
)
386 ptr
->left
->right
= ptr
->right
;
387 ptr
->right
->left
= ptr
->left
;
391 /* build the counts for all the tokens that start with "data", and have lenghts
393 static void learn_token(unsigned char *data
, int len
)
395 struct token
*ptr
,*last_ptr
;
397 unsigned int hash
= HASH_BASE_OFFSET
;
398 unsigned int hashes
[MAX_TOK_SIZE
+ 1];
400 if (len
> MAX_TOK_SIZE
)
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
);
413 for (i
= len
; i
>= 2; i
--) {
416 if (!ptr
) ptr
= find_token_hash(data
, i
, hash
);
419 /* create a new token entry */
420 ptr
= (struct token
*) malloc(sizeof(*ptr
));
422 memcpy(ptr
->data
, data
, i
);
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
;
432 ptr
->next
= hash_table
[hash
];
433 hash_table
[hash
] = ptr
;
435 insert_token_in_group(&bad_head
, ptr
);
439 newprofit
= ptr
->profit
+ (ptr
->len
- 1);
440 /* check to see if this token needs to be moved to a
442 if((ptr
->profit
< 0) && (newprofit
>= 0)) {
443 remove_token_from_group(ptr
);
444 insert_token_in_group(&good_head
,ptr
);
446 ptr
->profit
= newprofit
;
449 if (last_ptr
) last_ptr
->smaller
= ptr
;
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 */
460 static void forget_token(unsigned char *data
, int len
)
466 if (len
> MAX_TOK_SIZE
) len
= MAX_TOK_SIZE
;
468 hash
= hash_token(data
, len
);
469 ptr
= find_token_hash(data
, len
, hash
);
471 for (i
= len
; i
>= 2; i
--) {
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
);
478 ptr
->profit
=newprofit
;
484 /* count all the possible tokens in a symbol */
485 static void learn_symbol(unsigned char *symbol
, int len
)
489 for (i
= 0; i
< len
- 1; i
++)
490 learn_token(symbol
+ i
, len
- i
);
493 /* decrease the count for all the possible tokens in a symbol */
494 static void forget_symbol(unsigned char *symbol
, int len
)
498 for (i
= 0; i
< len
- 1; i
++)
499 forget_token(symbol
+ i
, len
- i
);
502 /* set all the symbol flags and do the initial token count */
503 static void build_initial_tok_table(void)
505 int i
, use_it
, valid
;
508 for (i
= 0; i
< cnt
; i
++) {
510 if ( symbol_valid(&table
[i
]) ) {
511 table
[i
].flags
|= SYM_FLAG_VALID
;
517 for (i
= 0; i
< cnt
; i
++) {
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
) {
524 use_it
+= WORKING_SET
;
526 if (use_it
>= valid
) {
527 table
[i
].flags
|= SYM_FLAG_SAMPLED
;
531 if (table
[i
].flags
& SYM_FLAG_SAMPLED
)
532 learn_symbol(table
[i
].sym
, table
[i
].len
);
536 /* replace a given token in all the valid symbols. Use the sampled symbols
537 * to update the counts */
538 static void compress_symbols(unsigned char *str
, int tlen
, int idx
)
540 int i
, len
, learn
, size
;
543 for (i
= 0; i
< cnt
; i
++) {
545 if (!(table
[i
].flags
& SYM_FLAG_VALID
)) continue;
552 /* find the token on the symbol */
553 p
= (unsigned char *) strstr((char *) p
, (char *) str
);
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
);
564 size
= (len
- (p
- table
[i
].sym
)) - tlen
+ 1;
565 memmove(p
+ 1, p
+ tlen
, size
);
569 } while (size
>= tlen
);
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
);
580 /* search the token with the maximum profit */
581 static struct token
*find_best_token(void)
583 struct token
*ptr
,*best
,*head
;
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
;
594 while (ptr
!= head
) {
595 if (ptr
->profit
> bestprofit
) {
596 bestprofit
= ptr
->profit
;
605 /* this is the core of the algorithm: calculate the "best" table */
606 static void optimize_result(void)
611 /* using the '\0' symbol last allows compress_symbols to use standard
612 * fast string functions */
613 for (i
= 255; i
>= 0; i
--) {
615 /* if this table slot is empty (it is not used by an actual
616 * original char code */
617 if (!best_table_len
[i
]) {
619 /* find the token with the breates profit value */
620 best
= find_best_token();
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';
629 /* replace this token in all the valid symbols */
630 compress_symbols(best_table
[i
], best_table_len
[i
], i
);
635 /* start by placing the symbols that are actually used on the table */
636 static void insert_real_symbols_in_table(void)
640 memset(best_table
, 0, sizeof(best_table
));
641 memset(best_table_len
, 0, sizeof(best_table_len
));
643 for (i
= 0; i
< cnt
; i
++) {
644 if (table
[i
].flags
& SYM_FLAG_VALID
) {
645 for (j
= 0; j
< table
[i
].len
; j
++) {
654 static void optimize_token_table(void)
656 memset(hash_table
, 0, sizeof(hash_table
));
658 good_head
.left
= &good_head
;
659 good_head
.right
= &good_head
;
661 bad_head
.left
= &bad_head
;
662 bad_head
.right
= &bad_head
;
664 build_initial_tok_table();
666 insert_real_symbols_in_table();
673 main(int argc
, char **argv
)
675 if (argc
== 2 && strcmp(argv
[1], "--all-symbols") == 0)
681 optimize_token_table();