]>
git.ipfire.org Git - thirdparty/kernel/linux.git/blob - scripts/kallsyms.c
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 _stringify_1(x) #x
31 #define _stringify(x) _stringify_1(x)
33 #define KSYM_NAME_LEN 512
36 * A substantially bigger size than the current maximum.
38 * It cannot be defined as an expression because it gets stringified
39 * for the fscanf() format string. Therefore, a _Static_assert() is
40 * used instead to maintain the relationship with KSYM_NAME_LEN.
42 #define KSYM_NAME_LEN_BUFFER 2048
44 KSYM_NAME_LEN_BUFFER
== KSYM_NAME_LEN
* 4,
45 "Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"
49 unsigned long long addr
;
51 unsigned int start_pos
;
52 unsigned int percpu_absolute
;
57 const char *start_sym
, *end_sym
;
58 unsigned long long start
, end
;
61 static unsigned long long _text
;
62 static unsigned long long relative_base
;
63 static struct addr_range text_ranges
[] = {
64 { "_stext", "_etext" },
65 { "_sinittext", "_einittext" },
67 #define text_range_text (&text_ranges[0])
68 #define text_range_inittext (&text_ranges[1])
70 static struct addr_range percpu_range
= {
71 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
74 static struct sym_entry
**table
;
75 static unsigned int table_size
, table_cnt
;
76 static int all_symbols
;
77 static int absolute_percpu
;
78 static int base_relative
;
80 static int token_profit
[0x10000];
82 /* the table that holds the result of the compression */
83 static unsigned char best_table
[256][2];
84 static unsigned char best_table_len
[256];
87 static void usage(void)
89 fprintf(stderr
, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
90 "[--base-relative] < in.map > out.S\n");
94 static char *sym_name(const struct sym_entry
*s
)
96 return (char *)s
->sym
+ 1;
99 static bool is_ignored_symbol(const char *name
, char type
)
101 /* Symbol names that exactly match to the following are ignored.*/
102 static const char * const ignored_symbols
[] = {
104 * Symbols which vary between passes. Passes 1 and 2 must have
105 * identical symbol lists. The kallsyms_* symbols below are
106 * only added after pass 1, they would be included in pass 2
107 * when --all-symbols is specified so exclude them to get a
108 * stable symbol list.
110 "kallsyms_addresses",
112 "kallsyms_relative_base",
116 "kallsyms_token_table",
117 "kallsyms_token_index",
118 /* Exclude linker generated symbols which vary between passes */
119 "_SDA_BASE_", /* ppc */
120 "_SDA2_BASE_", /* ppc */
124 /* Symbol names that begin with the following are ignored.*/
125 static const char * const ignored_prefixes
[] = {
126 "$", /* local symbols for ARM, MIPS, etc. */
127 ".L", /* local labels, .LBB,.Ltmpxxx,.L__unnamed_xx,.LASANPC, etc. */
128 "__crc_", /* modversions */
129 "__efistub_", /* arm64 EFI stub namespace */
130 "__kvm_nvhe_$", /* arm64 local symbols in non-VHE KVM namespace */
131 "__kvm_nvhe_.L", /* arm64 local symbols in non-VHE KVM namespace */
132 "__AArch64ADRPThunk_", /* arm64 lld */
133 "__ARMV5PILongThunk_", /* arm lld */
134 "__ARMV7PILongThunk_",
135 "__ThumbV7PILongThunk_",
136 "__LA25Thunk_", /* mips lld */
138 "__kcfi_typeid_", /* CFI type identifiers */
142 /* Symbol names that end with the following are ignored.*/
143 static const char * const ignored_suffixes
[] = {
144 "_from_arm", /* arm */
145 "_from_thumb", /* arm */
150 /* Symbol names that contain the following are ignored.*/
151 static const char * const ignored_matches
[] = {
152 ".long_branch.", /* ppc stub */
153 ".plt_branch.", /* ppc stub */
157 const char * const *p
;
159 for (p
= ignored_symbols
; *p
; p
++)
160 if (!strcmp(name
, *p
))
163 for (p
= ignored_prefixes
; *p
; p
++)
164 if (!strncmp(name
, *p
, strlen(*p
)))
167 for (p
= ignored_suffixes
; *p
; p
++) {
168 int l
= strlen(name
) - strlen(*p
);
170 if (l
>= 0 && !strcmp(name
+ l
, *p
))
174 for (p
= ignored_matches
; *p
; p
++) {
175 if (strstr(name
, *p
))
179 if (type
== 'U' || type
== 'u')
181 /* exclude debugging symbols */
182 if (type
== 'N' || type
== 'n')
185 if (toupper(type
) == 'A') {
186 /* Keep these useful absolute symbols */
187 if (strcmp(name
, "__kernel_syscall_via_break") &&
188 strcmp(name
, "__kernel_syscall_via_epc") &&
189 strcmp(name
, "__kernel_sigtramp") &&
190 strcmp(name
, "__gp"))
197 static void check_symbol_range(const char *sym
, unsigned long long addr
,
198 struct addr_range
*ranges
, int entries
)
201 struct addr_range
*ar
;
203 for (i
= 0; i
< entries
; ++i
) {
206 if (strcmp(sym
, ar
->start_sym
) == 0) {
209 } else if (strcmp(sym
, ar
->end_sym
) == 0) {
216 static struct sym_entry
*read_symbol(FILE *in
)
218 char name
[KSYM_NAME_LEN_BUFFER
+1], type
;
219 unsigned long long addr
;
221 struct sym_entry
*sym
;
224 rc
= fscanf(in
, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER
) "s\n", &addr
, &type
, name
);
226 if (rc
!= EOF
&& fgets(name
, ARRAY_SIZE(name
), in
) == NULL
)
227 fprintf(stderr
, "Read error or end of file.\n");
230 if (strlen(name
) >= KSYM_NAME_LEN
) {
231 fprintf(stderr
, "Symbol %s too long for kallsyms (%zu >= %d).\n"
232 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
233 name
, strlen(name
), KSYM_NAME_LEN
);
237 if (strcmp(name
, "_text") == 0)
240 /* Ignore most absolute/undefined (?) symbols. */
241 if (is_ignored_symbol(name
, type
))
244 check_symbol_range(name
, addr
, text_ranges
, ARRAY_SIZE(text_ranges
));
245 check_symbol_range(name
, addr
, &percpu_range
, 1);
247 /* include the type field in the symbol name, so that it gets
248 * compressed together */
250 len
= strlen(name
) + 1;
252 sym
= malloc(sizeof(*sym
) + len
+ 1);
254 fprintf(stderr
, "kallsyms failure: "
255 "unable to allocate required amount of memory\n");
261 strcpy(sym_name(sym
), name
);
262 sym
->percpu_absolute
= 0;
267 static int symbol_in_range(const struct sym_entry
*s
,
268 const struct addr_range
*ranges
, int entries
)
271 const struct addr_range
*ar
;
273 for (i
= 0; i
< entries
; ++i
) {
276 if (s
->addr
>= ar
->start
&& s
->addr
<= ar
->end
)
283 static int symbol_valid(const struct sym_entry
*s
)
285 const char *name
= sym_name(s
);
287 /* if --all-symbols is not specified, then symbols outside the text
288 * and inittext sections are discarded */
290 if (symbol_in_range(s
, text_ranges
,
291 ARRAY_SIZE(text_ranges
)) == 0)
293 /* Corner case. Discard any symbols with the same value as
294 * _etext _einittext; they can move between pass 1 and 2 when
295 * the kallsyms data are added. If these symbols move then
296 * they may get dropped in pass 2, which breaks the kallsyms
299 if ((s
->addr
== text_range_text
->end
&&
300 strcmp(name
, text_range_text
->end_sym
)) ||
301 (s
->addr
== text_range_inittext
->end
&&
302 strcmp(name
, text_range_inittext
->end_sym
)))
309 /* remove all the invalid symbols from the table */
310 static void shrink_table(void)
315 for (i
= 0; i
< table_cnt
; i
++) {
316 if (symbol_valid(table
[i
])) {
318 table
[pos
] = table
[i
];
326 /* When valid symbol is not registered, exit to error */
328 fprintf(stderr
, "No valid symbol.\n");
333 static void read_map(FILE *in
)
335 struct sym_entry
*sym
;
338 sym
= read_symbol(in
);
342 sym
->start_pos
= table_cnt
;
344 if (table_cnt
>= table_size
) {
346 table
= realloc(table
, sizeof(*table
) * table_size
);
348 fprintf(stderr
, "out of memory\n");
353 table
[table_cnt
++] = sym
;
357 static void output_label(const char *label
)
359 printf(".globl %s\n", label
);
361 printf("%s:\n", label
);
364 /* Provide proper symbols relocatability by their '_text' relativeness. */
365 static void output_address(unsigned long long addr
)
368 printf("\tPTR\t_text + %#llx\n", addr
- _text
);
370 printf("\tPTR\t_text - %#llx\n", _text
- addr
);
373 /* uncompress a compressed symbol. When this function is called, the best table
374 * might still be compressed itself, so the function needs to be recursive */
375 static int expand_symbol(const unsigned char *data
, int len
, char *result
)
377 int c
, rlen
, total
=0;
381 /* if the table holds a single char that is the same as the one
382 * we are looking for, then end the search */
383 if (best_table
[c
][0]==c
&& best_table_len
[c
]==1) {
387 /* if not, recurse and expand */
388 rlen
= expand_symbol(best_table
[c
], best_table_len
[c
], result
);
400 static int symbol_absolute(const struct sym_entry
*s
)
402 return s
->percpu_absolute
;
405 static void write_src(void)
407 unsigned int i
, k
, off
;
408 unsigned int best_idx
[256];
409 unsigned int *markers
;
410 char buf
[KSYM_NAME_LEN
];
412 printf("#include <asm/bitsperlong.h>\n");
413 printf("#if BITS_PER_LONG == 64\n");
414 printf("#define PTR .quad\n");
415 printf("#define ALGN .balign 8\n");
417 printf("#define PTR .long\n");
418 printf("#define ALGN .balign 4\n");
421 printf("\t.section .rodata, \"a\"\n");
424 output_label("kallsyms_addresses");
426 output_label("kallsyms_offsets");
428 for (i
= 0; i
< table_cnt
; i
++) {
431 * Use the offset relative to the lowest value
432 * encountered of all relative symbols, and emit
433 * non-relocatable fixed offsets that will be fixed
440 if (!absolute_percpu
) {
441 offset
= table
[i
]->addr
- relative_base
;
442 overflow
= (offset
< 0 || offset
> UINT_MAX
);
443 } else if (symbol_absolute(table
[i
])) {
444 offset
= table
[i
]->addr
;
445 overflow
= (offset
< 0 || offset
> INT_MAX
);
447 offset
= relative_base
- table
[i
]->addr
- 1;
448 overflow
= (offset
< INT_MIN
|| offset
>= 0);
451 fprintf(stderr
, "kallsyms failure: "
452 "%s symbol value %#llx out of range in relative mode\n",
453 symbol_absolute(table
[i
]) ? "absolute" : "relative",
457 printf("\t.long\t%#x\n", (int)offset
);
458 } else if (!symbol_absolute(table
[i
])) {
459 output_address(table
[i
]->addr
);
461 printf("\tPTR\t%#llx\n", table
[i
]->addr
);
467 output_label("kallsyms_relative_base");
468 output_address(relative_base
);
472 output_label("kallsyms_num_syms");
473 printf("\t.long\t%u\n", table_cnt
);
476 /* table of offset markers, that give the offset in the compressed stream
477 * every 256 symbols */
478 markers
= malloc(sizeof(unsigned int) * ((table_cnt
+ 255) / 256));
480 fprintf(stderr
, "kallsyms failure: "
481 "unable to allocate required memory\n");
485 output_label("kallsyms_names");
487 for (i
= 0; i
< table_cnt
; i
++) {
489 markers
[i
>> 8] = off
;
491 /* There cannot be any symbol of length zero. */
492 if (table
[i
]->len
== 0) {
493 fprintf(stderr
, "kallsyms failure: "
494 "unexpected zero symbol length\n");
498 /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
499 if (table
[i
]->len
> 0x3FFF) {
500 fprintf(stderr
, "kallsyms failure: "
501 "unexpected huge symbol length\n");
505 /* Encode length with ULEB128. */
506 if (table
[i
]->len
<= 0x7F) {
507 /* Most symbols use a single byte for the length. */
508 printf("\t.byte 0x%02x", table
[i
]->len
);
509 off
+= table
[i
]->len
+ 1;
511 /* "Big" symbols use two bytes. */
512 printf("\t.byte 0x%02x, 0x%02x",
513 (table
[i
]->len
& 0x7F) | 0x80,
514 (table
[i
]->len
>> 7) & 0x7F);
515 off
+= table
[i
]->len
+ 2;
517 for (k
= 0; k
< table
[i
]->len
; k
++)
518 printf(", 0x%02x", table
[i
]->sym
[k
]);
523 output_label("kallsyms_markers");
524 for (i
= 0; i
< ((table_cnt
+ 255) >> 8); i
++)
525 printf("\t.long\t%u\n", markers
[i
]);
530 output_label("kallsyms_token_table");
532 for (i
= 0; i
< 256; i
++) {
534 expand_symbol(best_table
[i
], best_table_len
[i
], buf
);
535 printf("\t.asciz\t\"%s\"\n", buf
);
536 off
+= strlen(buf
) + 1;
540 output_label("kallsyms_token_index");
541 for (i
= 0; i
< 256; i
++)
542 printf("\t.short\t%d\n", best_idx
[i
]);
547 /* table lookup compression functions */
549 /* count all the possible tokens in a symbol */
550 static void learn_symbol(const unsigned char *symbol
, int len
)
554 for (i
= 0; i
< len
- 1; i
++)
555 token_profit
[ symbol
[i
] + (symbol
[i
+ 1] << 8) ]++;
558 /* decrease the count for all the possible tokens in a symbol */
559 static void forget_symbol(const unsigned char *symbol
, int len
)
563 for (i
= 0; i
< len
- 1; i
++)
564 token_profit
[ symbol
[i
] + (symbol
[i
+ 1] << 8) ]--;
567 /* do the initial token count */
568 static void build_initial_tok_table(void)
572 for (i
= 0; i
< table_cnt
; i
++)
573 learn_symbol(table
[i
]->sym
, table
[i
]->len
);
576 static unsigned char *find_token(unsigned char *str
, int len
,
577 const unsigned char *token
)
581 for (i
= 0; i
< len
- 1; i
++) {
582 if (str
[i
] == token
[0] && str
[i
+1] == token
[1])
588 /* replace a given token in all the valid symbols. Use the sampled symbols
589 * to update the counts */
590 static void compress_symbols(const unsigned char *str
, int idx
)
592 unsigned int i
, len
, size
;
593 unsigned char *p1
, *p2
;
595 for (i
= 0; i
< table_cnt
; i
++) {
600 /* find the token on the symbol */
601 p2
= find_token(p1
, len
, str
);
604 /* decrease the counts for this symbol's tokens */
605 forget_symbol(table
[i
]->sym
, len
);
613 memmove(p2
, p2
+ 1, size
);
619 /* find the token on the symbol */
620 p2
= find_token(p1
, size
, str
);
626 /* increase the counts for this symbol's new tokens */
627 learn_symbol(table
[i
]->sym
, len
);
631 /* search the token with the maximum profit */
632 static int find_best_token(void)
634 int i
, best
, bestprofit
;
639 for (i
= 0; i
< 0x10000; i
++) {
640 if (token_profit
[i
] > bestprofit
) {
642 bestprofit
= token_profit
[i
];
648 /* this is the core of the algorithm: calculate the "best" table */
649 static void optimize_result(void)
653 /* using the '\0' symbol last allows compress_symbols to use standard
654 * fast string functions */
655 for (i
= 255; i
>= 0; i
--) {
657 /* if this table slot is empty (it is not used by an actual
658 * original char code */
659 if (!best_table_len
[i
]) {
661 /* find the token with the best profit value */
662 best
= find_best_token();
663 if (token_profit
[best
] == 0)
666 /* place it in the "best" table */
667 best_table_len
[i
] = 2;
668 best_table
[i
][0] = best
& 0xFF;
669 best_table
[i
][1] = (best
>> 8) & 0xFF;
671 /* replace this token in all the valid symbols */
672 compress_symbols(best_table
[i
], i
);
677 /* start by placing the symbols that are actually used on the table */
678 static void insert_real_symbols_in_table(void)
680 unsigned int i
, j
, c
;
682 for (i
= 0; i
< table_cnt
; i
++) {
683 for (j
= 0; j
< table
[i
]->len
; j
++) {
684 c
= table
[i
]->sym
[j
];
691 static void optimize_token_table(void)
693 build_initial_tok_table();
695 insert_real_symbols_in_table();
700 /* guess for "linker script provide" symbol */
701 static int may_be_linker_script_provide_symbol(const struct sym_entry
*se
)
703 const char *symbol
= sym_name(se
);
704 int len
= se
->len
- 1;
709 if (symbol
[0] != '_' || symbol
[1] != '_')
713 if (!memcmp(symbol
+ 2, "start_", 6))
717 if (!memcmp(symbol
+ 2, "stop_", 5))
721 if (!memcmp(symbol
+ 2, "end_", 4))
725 if (!memcmp(symbol
+ len
- 6, "_start", 6))
729 if (!memcmp(symbol
+ len
- 4, "_end", 4))
735 static int compare_symbols(const void *a
, const void *b
)
737 const struct sym_entry
*sa
= *(const struct sym_entry
**)a
;
738 const struct sym_entry
*sb
= *(const struct sym_entry
**)b
;
741 /* sort by address first */
742 if (sa
->addr
> sb
->addr
)
744 if (sa
->addr
< sb
->addr
)
747 /* sort by "weakness" type */
748 wa
= (sa
->sym
[0] == 'w') || (sa
->sym
[0] == 'W');
749 wb
= (sb
->sym
[0] == 'w') || (sb
->sym
[0] == 'W');
753 /* sort by "linker script provide" type */
754 wa
= may_be_linker_script_provide_symbol(sa
);
755 wb
= may_be_linker_script_provide_symbol(sb
);
759 /* sort by the number of prefix underscores */
760 wa
= strspn(sym_name(sa
), "_");
761 wb
= strspn(sym_name(sb
), "_");
765 /* sort by initial order, so that other symbols are left undisturbed */
766 return sa
->start_pos
- sb
->start_pos
;
769 static void sort_symbols(void)
771 qsort(table
, table_cnt
, sizeof(table
[0]), compare_symbols
);
774 static void make_percpus_absolute(void)
778 for (i
= 0; i
< table_cnt
; i
++)
779 if (symbol_in_range(table
[i
], &percpu_range
, 1)) {
781 * Keep the 'A' override for percpu symbols to
782 * ensure consistent behavior compared to older
783 * versions of this tool.
785 table
[i
]->sym
[0] = 'A';
786 table
[i
]->percpu_absolute
= 1;
790 /* find the minimum non-absolute symbol address */
791 static void record_relative_base(void)
795 for (i
= 0; i
< table_cnt
; i
++)
796 if (!symbol_absolute(table
[i
])) {
798 * The table is sorted by address.
799 * Take the first non-absolute symbol value.
801 relative_base
= table
[i
]->addr
;
806 int main(int argc
, char **argv
)
810 for (i
= 1; i
< argc
; i
++) {
811 if(strcmp(argv
[i
], "--all-symbols") == 0)
813 else if (strcmp(argv
[i
], "--absolute-percpu") == 0)
815 else if (strcmp(argv
[i
], "--base-relative") == 0)
820 } else if (argc
!= 1)
826 make_percpus_absolute();
829 record_relative_base();
830 optimize_token_table();