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
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
27 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
30 #define KSYM_NAME_LEN 128
33 unsigned long long addr
;
35 unsigned int start_pos
;
40 const char *stext
, *etext
;
41 unsigned long long start
, end
;
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 */
51 #define text_range_text (&text_ranges[0])
52 #define text_range_inittext (&text_ranges[1])
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';
59 int token_profit
[0x10000];
61 /* the table that holds the result of the compression */
62 unsigned char best_table
[256][2];
63 unsigned char best_table_len
[256];
66 static void usage(void)
68 fprintf(stderr
, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
73 * This ignores the intensely annoying "mapping symbols" found
74 * in ARM ELF files: $a, $t and $d.
76 static inline int is_arm_mapping_symbol(const char *str
)
78 return str
[0] == '$' && strchr("atd", str
[1])
79 && (str
[2] == '\0' || str
[2] == '.');
82 static int read_symbol_tr(const char *sym
, unsigned long long addr
)
85 struct text_range
*tr
;
87 for (i
= 0; i
< ARRAY_SIZE(text_ranges
); ++i
) {
90 if (strcmp(sym
, tr
->stext
) == 0) {
93 } else if (strcmp(sym
, tr
->etext
) == 0) {
102 static int read_symbol(FILE *in
, struct sym_entry
*s
)
108 rc
= fscanf(in
, "%llx %c %499s\n", &s
->addr
, &stype
, str
);
110 if (rc
!= EOF
&& fgets(str
, 500, in
) == NULL
)
111 fprintf(stderr
, "Read error or end of file.\n");
116 /* skip prefix char */
117 if (symbol_prefix_char
&& str
[0] == symbol_prefix_char
)
120 /* Ignore most absolute/undefined (?) symbols. */
121 if (strcmp(sym
, "_text") == 0)
123 else if (read_symbol_tr(sym
, s
->addr
) == 0)
125 else if (toupper(stype
) == 'A')
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") &&
135 else if (toupper(stype
) == 'U' ||
136 is_arm_mapping_symbol(sym
))
138 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
139 else if (str
[0] == '$')
141 /* exclude debugging symbols */
142 else if (stype
== 'N')
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);
150 fprintf(stderr
, "kallsyms failure: "
151 "unable to allocate required amount of memory\n");
154 strcpy((char *)s
->sym
+ 1, str
);
160 static int symbol_valid_tr(struct sym_entry
*s
)
163 struct text_range
*tr
;
165 for (i
= 0; i
< ARRAY_SIZE(text_ranges
); ++i
) {
166 tr
= &text_ranges
[i
];
168 if (s
->addr
>= tr
->start
&& s
->addr
<= tr
->end
)
175 static int symbol_valid(struct sym_entry
*s
)
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.
182 static char *special_symbols
[] = {
183 "kallsyms_addresses",
187 "kallsyms_token_table",
188 "kallsyms_token_index",
190 /* Exclude linker generated symbols which vary between passes */
191 "_SDA_BASE_", /* ppc */
192 "_SDA2_BASE_", /* ppc */
197 /* skip prefix char */
198 if (symbol_prefix_char
&& *(s
->sym
+ 1) == symbol_prefix_char
)
201 /* if --all-symbols is not specified, then symbols outside the text
202 * and inittext sections are discarded */
204 if (symbol_valid_tr(s
) == 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
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
)))
219 /* Exclude symbols which vary between passes. */
220 if (strstr((char *)s
->sym
+ offset
, "_compiled."))
223 for (i
= 0; special_symbols
[i
]; i
++)
224 if( strcmp((char *)s
->sym
+ offset
, special_symbols
[i
]) == 0 )
230 static void read_map(FILE *in
)
233 if (table_cnt
>= table_size
) {
235 table
= realloc(table
, sizeof(*table
) * table_size
);
237 fprintf(stderr
, "out of memory\n");
241 if (read_symbol(in
, &table
[table_cnt
]) == 0) {
242 table
[table_cnt
].start_pos
= table_cnt
;
248 static void output_label(char *label
)
250 if (symbol_prefix_char
)
251 printf(".globl %c%s\n", symbol_prefix_char
, label
);
253 printf(".globl %s\n", label
);
255 if (symbol_prefix_char
)
256 printf("%c%s:\n", symbol_prefix_char
, label
);
258 printf("%s:\n", label
);
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 */
263 static int expand_symbol(unsigned char *data
, int len
, char *result
)
265 int c
, rlen
, total
=0;
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) {
275 /* if not, recurse and expand */
276 rlen
= expand_symbol(best_table
[c
], best_table_len
[c
], result
);
288 static void write_src(void)
290 unsigned int i
, k
, off
;
291 unsigned int best_idx
[256];
292 unsigned int *markers
;
293 char buf
[KSYM_NAME_LEN
];
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");
300 printf("#define PTR .long\n");
301 printf("#define ALGN .align 4\n");
304 printf("\t.section .rodata, \"a\"\n");
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.
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
);
320 printf("\tPTR\t_text - %#llx\n",
321 _text
- table
[i
].addr
);
323 printf("\tPTR\t%#llx\n", table
[i
].addr
);
328 output_label("kallsyms_num_syms");
329 printf("\tPTR\t%d\n", table_cnt
);
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));
336 fprintf(stderr
, "kallsyms failure: "
337 "unable to allocate required memory\n");
341 output_label("kallsyms_names");
343 for (i
= 0; i
< table_cnt
; i
++) {
345 markers
[i
>> 8] = off
;
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
]);
352 off
+= table
[i
].len
+ 1;
356 output_label("kallsyms_markers");
357 for (i
= 0; i
< ((table_cnt
+ 255) >> 8); i
++)
358 printf("\tPTR\t%d\n", markers
[i
]);
363 output_label("kallsyms_token_table");
365 for (i
= 0; i
< 256; i
++) {
367 expand_symbol(best_table
[i
], best_table_len
[i
], buf
);
368 printf("\t.asciz\t\"%s\"\n", buf
);
369 off
+= strlen(buf
) + 1;
373 output_label("kallsyms_token_index");
374 for (i
= 0; i
< 256; i
++)
375 printf("\t.short\t%d\n", best_idx
[i
]);
380 /* table lookup compression functions */
382 /* count all the possible tokens in a symbol */
383 static void learn_symbol(unsigned char *symbol
, int len
)
387 for (i
= 0; i
< len
- 1; i
++)
388 token_profit
[ symbol
[i
] + (symbol
[i
+ 1] << 8) ]++;
391 /* decrease the count for all the possible tokens in a symbol */
392 static void forget_symbol(unsigned char *symbol
, int len
)
396 for (i
= 0; i
< len
- 1; i
++)
397 token_profit
[ symbol
[i
] + (symbol
[i
+ 1] << 8) ]--;
400 /* remove all the invalid symbols from the table and do the initial token count */
401 static void build_initial_tok_table(void)
406 for (i
= 0; i
< table_cnt
; i
++) {
407 if ( symbol_valid(&table
[i
]) ) {
409 table
[pos
] = table
[i
];
410 learn_symbol(table
[pos
].sym
, table
[pos
].len
);
417 static void *find_token(unsigned char *str
, int len
, unsigned char *token
)
421 for (i
= 0; i
< len
- 1; i
++) {
422 if (str
[i
] == token
[0] && str
[i
+1] == token
[1])
428 /* replace a given token in all the valid symbols. Use the sampled symbols
429 * to update the counts */
430 static void compress_symbols(unsigned char *str
, int idx
)
432 unsigned int i
, len
, size
;
433 unsigned char *p1
, *p2
;
435 for (i
= 0; i
< table_cnt
; i
++) {
440 /* find the token on the symbol */
441 p2
= find_token(p1
, len
, str
);
444 /* decrease the counts for this symbol's tokens */
445 forget_symbol(table
[i
].sym
, len
);
453 memmove(p2
, p2
+ 1, size
);
459 /* find the token on the symbol */
460 p2
= find_token(p1
, size
, str
);
466 /* increase the counts for this symbol's new tokens */
467 learn_symbol(table
[i
].sym
, len
);
471 /* search the token with the maximum profit */
472 static int find_best_token(void)
474 int i
, best
, bestprofit
;
479 for (i
= 0; i
< 0x10000; i
++) {
480 if (token_profit
[i
] > bestprofit
) {
482 bestprofit
= token_profit
[i
];
488 /* this is the core of the algorithm: calculate the "best" table */
489 static void optimize_result(void)
493 /* using the '\0' symbol last allows compress_symbols to use standard
494 * fast string functions */
495 for (i
= 255; i
>= 0; i
--) {
497 /* if this table slot is empty (it is not used by an actual
498 * original char code */
499 if (!best_table_len
[i
]) {
501 /* find the token with the breates profit value */
502 best
= find_best_token();
503 if (token_profit
[best
] == 0)
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;
511 /* replace this token in all the valid symbols */
512 compress_symbols(best_table
[i
], i
);
517 /* start by placing the symbols that are actually used on the table */
518 static void insert_real_symbols_in_table(void)
520 unsigned int i
, j
, c
;
522 memset(best_table
, 0, sizeof(best_table
));
523 memset(best_table_len
, 0, sizeof(best_table_len
));
525 for (i
= 0; i
< table_cnt
; i
++) {
526 for (j
= 0; j
< table
[i
].len
; j
++) {
534 static void optimize_token_table(void)
536 build_initial_tok_table();
538 insert_real_symbols_in_table();
540 /* When valid symbol is not registered, exit to error */
542 fprintf(stderr
, "No valid symbol.\n");
549 /* guess for "linker script provide" symbol */
550 static int may_be_linker_script_provide_symbol(const struct sym_entry
*se
)
552 const char *symbol
= (char *)se
->sym
+ 1;
553 int len
= se
->len
- 1;
558 if (symbol
[0] != '_' || symbol
[1] != '_')
562 if (!memcmp(symbol
+ 2, "start_", 6))
566 if (!memcmp(symbol
+ 2, "stop_", 5))
570 if (!memcmp(symbol
+ 2, "end_", 4))
574 if (!memcmp(symbol
+ len
- 6, "_start", 6))
578 if (!memcmp(symbol
+ len
- 4, "_end", 4))
584 static int prefix_underscores_count(const char *str
)
586 const char *tail
= str
;
594 static int compare_symbols(const void *a
, const void *b
)
596 const struct sym_entry
*sa
;
597 const struct sym_entry
*sb
;
603 /* sort by address first */
604 if (sa
->addr
> sb
->addr
)
606 if (sa
->addr
< sb
->addr
)
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');
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
);
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);
627 /* sort by initial order, so that other symbols are left undisturbed */
628 return sa
->start_pos
- sb
->start_pos
;
631 static void sort_symbols(void)
633 qsort(table
, table_cnt
, sizeof(struct sym_entry
), compare_symbols
);
636 int main(int argc
, char **argv
)
640 for (i
= 1; i
< argc
; i
++) {
641 if(strcmp(argv
[i
], "--all-symbols") == 0)
643 else if (strncmp(argv
[i
], "--symbol-prefix=", 16) == 0) {
644 char *p
= &argv
[i
][16];
646 if ((*p
== '"' && *(p
+2) == '"') || (*p
== '\'' && *(p
+2) == '\''))
648 symbol_prefix_char
= *p
;
652 } else if (argc
!= 1)
657 optimize_token_table();
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