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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
28 #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
;
36 unsigned int percpu_absolute
;
41 const char *start_sym
, *end_sym
;
42 unsigned long long start
, end
;
45 static unsigned long long _text
;
46 static unsigned long long relative_base
;
47 static struct addr_range text_ranges
[] = {
48 { "_stext", "_etext" },
49 { "_sinittext", "_einittext" },
51 #define text_range_text (&text_ranges[0])
52 #define text_range_inittext (&text_ranges[1])
54 static struct addr_range percpu_range
= {
55 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
58 static struct sym_entry
**table
;
59 static unsigned int table_size
, table_cnt
;
60 static int all_symbols
;
61 static int absolute_percpu
;
62 static int base_relative
;
64 static int token_profit
[0x10000];
66 /* the table that holds the result of the compression */
67 static unsigned char best_table
[256][2];
68 static unsigned char best_table_len
[256];
71 static void usage(void)
73 fprintf(stderr
, "Usage: kallsyms [--all-symbols] "
74 "[--base-relative] < in.map > out.S\n");
78 static char *sym_name(const struct sym_entry
*s
)
80 return (char *)s
->sym
+ 1;
83 static bool is_ignored_symbol(const char *name
, char type
)
85 /* Symbol names that exactly match to the following are ignored.*/
86 static const char * const ignored_symbols
[] = {
88 * Symbols which vary between passes. Passes 1 and 2 must have
89 * identical symbol lists. The kallsyms_* symbols below are
90 * only added after pass 1, they would be included in pass 2
91 * when --all-symbols is specified so exclude them to get a
96 "kallsyms_relative_base",
100 "kallsyms_token_table",
101 "kallsyms_token_index",
102 /* Exclude linker generated symbols which vary between passes */
103 "_SDA_BASE_", /* ppc */
104 "_SDA2_BASE_", /* ppc */
108 /* Symbol names that begin with the following are ignored.*/
109 static const char * const ignored_prefixes
[] = {
110 "$", /* local symbols for ARM, MIPS, etc. */
111 ".LASANPC", /* s390 kasan local symbols */
112 "__crc_", /* modversions */
113 "__efistub_", /* arm64 EFI stub namespace */
114 "__kvm_nvhe_", /* arm64 non-VHE KVM namespace */
118 /* Symbol names that end with the following are ignored.*/
119 static const char * const ignored_suffixes
[] = {
120 "_from_arm", /* arm */
121 "_from_thumb", /* arm */
126 /* Symbol names that contain the following are ignored.*/
127 static const char * const ignored_matches
[] = {
128 ".long_branch.", /* ppc stub */
129 ".plt_branch.", /* ppc stub */
133 const char * const *p
;
135 for (p
= ignored_symbols
; *p
; p
++)
136 if (!strcmp(name
, *p
))
139 for (p
= ignored_prefixes
; *p
; p
++)
140 if (!strncmp(name
, *p
, strlen(*p
)))
143 for (p
= ignored_suffixes
; *p
; p
++) {
144 int l
= strlen(name
) - strlen(*p
);
146 if (l
>= 0 && !strcmp(name
+ l
, *p
))
150 for (p
= ignored_matches
; *p
; p
++) {
151 if (strstr(name
, *p
))
155 if (type
== 'U' || type
== 'u')
157 /* exclude debugging symbols */
158 if (type
== 'N' || type
== 'n')
161 if (toupper(type
) == 'A') {
162 /* Keep these useful absolute symbols */
163 if (strcmp(name
, "__kernel_syscall_via_break") &&
164 strcmp(name
, "__kernel_syscall_via_epc") &&
165 strcmp(name
, "__kernel_sigtramp") &&
166 strcmp(name
, "__gp"))
173 static void check_symbol_range(const char *sym
, unsigned long long addr
,
174 struct addr_range
*ranges
, int entries
)
177 struct addr_range
*ar
;
179 for (i
= 0; i
< entries
; ++i
) {
182 if (strcmp(sym
, ar
->start_sym
) == 0) {
185 } else if (strcmp(sym
, ar
->end_sym
) == 0) {
192 static struct sym_entry
*read_symbol(FILE *in
)
194 char name
[500], type
;
195 unsigned long long addr
;
197 struct sym_entry
*sym
;
200 rc
= fscanf(in
, "%llx %c %499s\n", &addr
, &type
, name
);
202 if (rc
!= EOF
&& fgets(name
, 500, in
) == NULL
)
203 fprintf(stderr
, "Read error or end of file.\n");
206 if (strlen(name
) >= KSYM_NAME_LEN
) {
207 fprintf(stderr
, "Symbol %s too long for kallsyms (%zu >= %d).\n"
208 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
209 name
, strlen(name
), KSYM_NAME_LEN
);
213 if (strcmp(name
, "_text") == 0)
216 /* Ignore most absolute/undefined (?) symbols. */
217 if (is_ignored_symbol(name
, type
))
220 check_symbol_range(name
, addr
, text_ranges
, ARRAY_SIZE(text_ranges
));
221 check_symbol_range(name
, addr
, &percpu_range
, 1);
223 /* include the type field in the symbol name, so that it gets
224 * compressed together */
226 len
= strlen(name
) + 1;
228 sym
= malloc(sizeof(*sym
) + len
+ 1);
230 fprintf(stderr
, "kallsyms failure: "
231 "unable to allocate required amount of memory\n");
237 strcpy(sym_name(sym
), name
);
238 sym
->percpu_absolute
= 0;
243 static int symbol_in_range(const struct sym_entry
*s
,
244 const struct addr_range
*ranges
, int entries
)
247 const struct addr_range
*ar
;
249 for (i
= 0; i
< entries
; ++i
) {
252 if (s
->addr
>= ar
->start
&& s
->addr
<= ar
->end
)
259 static int symbol_valid(const struct sym_entry
*s
)
261 const char *name
= sym_name(s
);
263 /* if --all-symbols is not specified, then symbols outside the text
264 * and inittext sections are discarded */
266 if (symbol_in_range(s
, text_ranges
,
267 ARRAY_SIZE(text_ranges
)) == 0)
269 /* Corner case. Discard any symbols with the same value as
270 * _etext _einittext; they can move between pass 1 and 2 when
271 * the kallsyms data are added. If these symbols move then
272 * they may get dropped in pass 2, which breaks the kallsyms
275 if ((s
->addr
== text_range_text
->end
&&
276 strcmp(name
, text_range_text
->end_sym
)) ||
277 (s
->addr
== text_range_inittext
->end
&&
278 strcmp(name
, text_range_inittext
->end_sym
)))
285 /* remove all the invalid symbols from the table */
286 static void shrink_table(void)
291 for (i
= 0; i
< table_cnt
; i
++) {
292 if (symbol_valid(table
[i
])) {
294 table
[pos
] = table
[i
];
302 /* When valid symbol is not registered, exit to error */
304 fprintf(stderr
, "No valid symbol.\n");
309 static void read_map(FILE *in
)
311 struct sym_entry
*sym
;
314 sym
= read_symbol(in
);
318 sym
->start_pos
= table_cnt
;
320 if (table_cnt
>= table_size
) {
322 table
= realloc(table
, sizeof(*table
) * table_size
);
324 fprintf(stderr
, "out of memory\n");
329 table
[table_cnt
++] = sym
;
333 static void output_label(const char *label
)
335 printf(".globl %s\n", label
);
337 printf("%s:\n", label
);
340 /* Provide proper symbols relocatability by their '_text' relativeness. */
341 static void output_address(unsigned long long addr
)
344 printf("\tPTR\t_text + %#llx\n", addr
- _text
);
346 printf("\tPTR\t_text - %#llx\n", _text
- addr
);
349 /* uncompress a compressed symbol. When this function is called, the best table
350 * might still be compressed itself, so the function needs to be recursive */
351 static int expand_symbol(const unsigned char *data
, int len
, char *result
)
353 int c
, rlen
, total
=0;
357 /* if the table holds a single char that is the same as the one
358 * we are looking for, then end the search */
359 if (best_table
[c
][0]==c
&& best_table_len
[c
]==1) {
363 /* if not, recurse and expand */
364 rlen
= expand_symbol(best_table
[c
], best_table_len
[c
], result
);
376 static int symbol_absolute(const struct sym_entry
*s
)
378 return s
->percpu_absolute
;
381 static void write_src(void)
383 unsigned int i
, k
, off
;
384 unsigned int best_idx
[256];
385 unsigned int *markers
;
386 char buf
[KSYM_NAME_LEN
];
388 printf("#include <asm/bitsperlong.h>\n");
389 printf("#if BITS_PER_LONG == 64\n");
390 printf("#define PTR .quad\n");
391 printf("#define ALGN .balign 8\n");
393 printf("#define PTR .long\n");
394 printf("#define ALGN .balign 4\n");
397 printf("\t.section .rodata, \"a\"\n");
400 output_label("kallsyms_addresses");
402 output_label("kallsyms_offsets");
404 for (i
= 0; i
< table_cnt
; i
++) {
407 * Use the offset relative to the lowest value
408 * encountered of all relative symbols, and emit
409 * non-relocatable fixed offsets that will be fixed
416 if (!absolute_percpu
) {
417 offset
= table
[i
]->addr
- relative_base
;
418 overflow
= (offset
< 0 || offset
> UINT_MAX
);
419 } else if (symbol_absolute(table
[i
])) {
420 offset
= table
[i
]->addr
;
421 overflow
= (offset
< 0 || offset
> INT_MAX
);
423 offset
= relative_base
- table
[i
]->addr
- 1;
424 overflow
= (offset
< INT_MIN
|| offset
>= 0);
427 fprintf(stderr
, "kallsyms failure: "
428 "%s symbol value %#llx out of range in relative mode\n",
429 symbol_absolute(table
[i
]) ? "absolute" : "relative",
433 printf("\t.long\t%#x\n", (int)offset
);
434 } else if (!symbol_absolute(table
[i
])) {
435 output_address(table
[i
]->addr
);
437 printf("\tPTR\t%#llx\n", table
[i
]->addr
);
443 output_label("kallsyms_relative_base");
444 output_address(relative_base
);
448 output_label("kallsyms_num_syms");
449 printf("\t.long\t%u\n", table_cnt
);
452 /* table of offset markers, that give the offset in the compressed stream
453 * every 256 symbols */
454 markers
= malloc(sizeof(unsigned int) * ((table_cnt
+ 255) / 256));
456 fprintf(stderr
, "kallsyms failure: "
457 "unable to allocate required memory\n");
461 output_label("kallsyms_names");
463 for (i
= 0; i
< table_cnt
; i
++) {
465 markers
[i
>> 8] = off
;
467 printf("\t.byte 0x%02x", table
[i
]->len
);
468 for (k
= 0; k
< table
[i
]->len
; k
++)
469 printf(", 0x%02x", table
[i
]->sym
[k
]);
472 off
+= table
[i
]->len
+ 1;
476 output_label("kallsyms_markers");
477 for (i
= 0; i
< ((table_cnt
+ 255) >> 8); i
++)
478 printf("\t.long\t%u\n", markers
[i
]);
483 output_label("kallsyms_token_table");
485 for (i
= 0; i
< 256; i
++) {
487 expand_symbol(best_table
[i
], best_table_len
[i
], buf
);
488 printf("\t.asciz\t\"%s\"\n", buf
);
489 off
+= strlen(buf
) + 1;
493 output_label("kallsyms_token_index");
494 for (i
= 0; i
< 256; i
++)
495 printf("\t.short\t%d\n", best_idx
[i
]);
500 /* table lookup compression functions */
502 /* count all the possible tokens in a symbol */
503 static void learn_symbol(const unsigned char *symbol
, int len
)
507 for (i
= 0; i
< len
- 1; i
++)
508 token_profit
[ symbol
[i
] + (symbol
[i
+ 1] << 8) ]++;
511 /* decrease the count for all the possible tokens in a symbol */
512 static void forget_symbol(const unsigned char *symbol
, int len
)
516 for (i
= 0; i
< len
- 1; i
++)
517 token_profit
[ symbol
[i
] + (symbol
[i
+ 1] << 8) ]--;
520 /* do the initial token count */
521 static void build_initial_tok_table(void)
525 for (i
= 0; i
< table_cnt
; i
++)
526 learn_symbol(table
[i
]->sym
, table
[i
]->len
);
529 static unsigned char *find_token(unsigned char *str
, int len
,
530 const unsigned char *token
)
534 for (i
= 0; i
< len
- 1; i
++) {
535 if (str
[i
] == token
[0] && str
[i
+1] == token
[1])
541 /* replace a given token in all the valid symbols. Use the sampled symbols
542 * to update the counts */
543 static void compress_symbols(const unsigned char *str
, int idx
)
545 unsigned int i
, len
, size
;
546 unsigned char *p1
, *p2
;
548 for (i
= 0; i
< table_cnt
; i
++) {
553 /* find the token on the symbol */
554 p2
= find_token(p1
, len
, str
);
557 /* decrease the counts for this symbol's tokens */
558 forget_symbol(table
[i
]->sym
, len
);
566 memmove(p2
, p2
+ 1, size
);
572 /* find the token on the symbol */
573 p2
= find_token(p1
, size
, str
);
579 /* increase the counts for this symbol's new tokens */
580 learn_symbol(table
[i
]->sym
, len
);
584 /* search the token with the maximum profit */
585 static int find_best_token(void)
587 int i
, best
, bestprofit
;
592 for (i
= 0; i
< 0x10000; i
++) {
593 if (token_profit
[i
] > bestprofit
) {
595 bestprofit
= token_profit
[i
];
601 /* this is the core of the algorithm: calculate the "best" table */
602 static void optimize_result(void)
606 /* using the '\0' symbol last allows compress_symbols to use standard
607 * fast string functions */
608 for (i
= 255; i
>= 0; i
--) {
610 /* if this table slot is empty (it is not used by an actual
611 * original char code */
612 if (!best_table_len
[i
]) {
614 /* find the token with the best profit value */
615 best
= find_best_token();
616 if (token_profit
[best
] == 0)
619 /* place it in the "best" table */
620 best_table_len
[i
] = 2;
621 best_table
[i
][0] = best
& 0xFF;
622 best_table
[i
][1] = (best
>> 8) & 0xFF;
624 /* replace this token in all the valid symbols */
625 compress_symbols(best_table
[i
], i
);
630 /* start by placing the symbols that are actually used on the table */
631 static void insert_real_symbols_in_table(void)
633 unsigned int i
, j
, c
;
635 for (i
= 0; i
< table_cnt
; i
++) {
636 for (j
= 0; j
< table
[i
]->len
; j
++) {
637 c
= table
[i
]->sym
[j
];
644 static void optimize_token_table(void)
646 build_initial_tok_table();
648 insert_real_symbols_in_table();
653 /* guess for "linker script provide" symbol */
654 static int may_be_linker_script_provide_symbol(const struct sym_entry
*se
)
656 const char *symbol
= sym_name(se
);
657 int len
= se
->len
- 1;
662 if (symbol
[0] != '_' || symbol
[1] != '_')
666 if (!memcmp(symbol
+ 2, "start_", 6))
670 if (!memcmp(symbol
+ 2, "stop_", 5))
674 if (!memcmp(symbol
+ 2, "end_", 4))
678 if (!memcmp(symbol
+ len
- 6, "_start", 6))
682 if (!memcmp(symbol
+ len
- 4, "_end", 4))
688 static int compare_symbols(const void *a
, const void *b
)
690 const struct sym_entry
*sa
= *(const struct sym_entry
**)a
;
691 const struct sym_entry
*sb
= *(const struct sym_entry
**)b
;
694 /* sort by address first */
695 if (sa
->addr
> sb
->addr
)
697 if (sa
->addr
< sb
->addr
)
700 /* sort by "weakness" type */
701 wa
= (sa
->sym
[0] == 'w') || (sa
->sym
[0] == 'W');
702 wb
= (sb
->sym
[0] == 'w') || (sb
->sym
[0] == 'W');
706 /* sort by "linker script provide" type */
707 wa
= may_be_linker_script_provide_symbol(sa
);
708 wb
= may_be_linker_script_provide_symbol(sb
);
712 /* sort by the number of prefix underscores */
713 wa
= strspn(sym_name(sa
), "_");
714 wb
= strspn(sym_name(sb
), "_");
718 /* sort by initial order, so that other symbols are left undisturbed */
719 return sa
->start_pos
- sb
->start_pos
;
722 static void sort_symbols(void)
724 qsort(table
, table_cnt
, sizeof(table
[0]), compare_symbols
);
727 static void make_percpus_absolute(void)
731 for (i
= 0; i
< table_cnt
; i
++)
732 if (symbol_in_range(table
[i
], &percpu_range
, 1)) {
734 * Keep the 'A' override for percpu symbols to
735 * ensure consistent behavior compared to older
736 * versions of this tool.
738 table
[i
]->sym
[0] = 'A';
739 table
[i
]->percpu_absolute
= 1;
743 /* find the minimum non-absolute symbol address */
744 static void record_relative_base(void)
748 for (i
= 0; i
< table_cnt
; i
++)
749 if (!symbol_absolute(table
[i
])) {
751 * The table is sorted by address.
752 * Take the first non-absolute symbol value.
754 relative_base
= table
[i
]->addr
;
759 int main(int argc
, char **argv
)
763 for (i
= 1; i
< argc
; i
++) {
764 if(strcmp(argv
[i
], "--all-symbols") == 0)
766 else if (strcmp(argv
[i
], "--absolute-percpu") == 0)
768 else if (strcmp(argv
[i
], "--base-relative") == 0)
773 } else if (argc
!= 1)
779 make_percpus_absolute();
782 record_relative_base();
783 optimize_token_table();