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]))
29 #define KSYM_NAME_LEN 128
32 unsigned long long addr;
34 unsigned int start_pos;
36 unsigned int percpu_absolute;
40 const char *start_sym, *end_sym;
41 unsigned long long start, end;
44 static unsigned long long _text;
45 static unsigned long long relative_base;
46 static struct addr_range text_ranges[] = {
47 { "_stext", "_etext" },
48 { "_sinittext", "_einittext" },
50 #define text_range_text (&text_ranges[0])
51 #define text_range_inittext (&text_ranges[1])
53 static struct addr_range percpu_range = {
54 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
57 static struct sym_entry *table;
58 static unsigned int table_size, table_cnt;
59 static int all_symbols = 0;
60 static int absolute_percpu = 0;
61 static int base_relative = 0;
63 static int token_profit[0x10000];
65 /* the table that holds the result of the compression */
66 static unsigned char best_table[256][2];
67 static unsigned char best_table_len[256];
70 static void usage(void)
72 fprintf(stderr, "Usage: kallsyms [--all-symbols] "
73 "[--base-relative] < in.map > out.S\n");
77 static int check_symbol_range(const char *sym, unsigned long long addr,
78 struct addr_range *ranges, int entries)
81 struct addr_range *ar;
83 for (i = 0; i < entries; ++i) {
86 if (strcmp(sym, ar->start_sym) == 0) {
89 } else if (strcmp(sym, ar->end_sym) == 0) {
98 static int read_symbol(FILE *in, struct sym_entry *s)
100 char sym[500], stype;
103 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, sym);
105 if (rc != EOF && fgets(sym, 500, in) == NULL)
106 fprintf(stderr, "Read error or end of file.\n");
109 if (strlen(sym) >= KSYM_NAME_LEN) {
110 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
111 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
112 sym, strlen(sym), KSYM_NAME_LEN);
116 /* Ignore most absolute/undefined (?) symbols. */
117 if (strcmp(sym, "_text") == 0)
119 else if (check_symbol_range(sym, s->addr, text_ranges,
120 ARRAY_SIZE(text_ranges)) == 0)
122 else if (toupper(stype) == 'A')
124 /* Keep these useful absolute symbols */
125 if (strcmp(sym, "__kernel_syscall_via_break") &&
126 strcmp(sym, "__kernel_syscall_via_epc") &&
127 strcmp(sym, "__kernel_sigtramp") &&
132 else if (toupper(stype) == 'U')
135 * Ignore generated symbols such as:
136 * - mapping symbols in ARM ELF files ($a, $t, and $d)
137 * - MIPS ELF local symbols ($L123 instead of .L123)
139 else if (sym[0] == '$')
141 /* exclude debugging symbols */
142 else if (stype == 'N' || stype == 'n')
144 /* exclude s390 kasan local symbols */
145 else if (!strncmp(sym, ".LASANPC", 8))
148 /* include the type field in the symbol name, so that it gets
149 * compressed together */
150 s->len = strlen(sym) + 1;
151 s->sym = malloc(s->len + 1);
153 fprintf(stderr, "kallsyms failure: "
154 "unable to allocate required amount of memory\n");
157 strcpy((char *)s->sym + 1, sym);
160 s->percpu_absolute = 0;
162 /* Record if we've found __per_cpu_start/end. */
163 check_symbol_range(sym, s->addr, &percpu_range, 1);
168 static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges,
172 struct addr_range *ar;
174 for (i = 0; i < entries; ++i) {
177 if (s->addr >= ar->start && s->addr <= ar->end)
184 static int symbol_valid(struct sym_entry *s)
186 /* Symbols which vary between passes. Passes 1 and 2 must have
187 * identical symbol lists. The kallsyms_* symbols below are only added
188 * after pass 1, they would be included in pass 2 when --all-symbols is
189 * specified so exclude them to get a stable symbol list.
191 static char *special_symbols[] = {
192 "kallsyms_addresses",
194 "kallsyms_relative_base",
198 "kallsyms_token_table",
199 "kallsyms_token_index",
201 /* Exclude linker generated symbols which vary between passes */
202 "_SDA_BASE_", /* ppc */
203 "_SDA2_BASE_", /* ppc */
206 static char *special_prefixes[] = {
207 "__crc_", /* modversions */
208 "__efistub_", /* arm64 EFI stub namespace */
211 static char *special_suffixes[] = {
213 "_from_arm", /* arm */
214 "_from_thumb", /* arm */
218 char *sym_name = (char *)s->sym + 1;
220 /* if --all-symbols is not specified, then symbols outside the text
221 * and inittext sections are discarded */
223 if (symbol_in_range(s, text_ranges,
224 ARRAY_SIZE(text_ranges)) == 0)
226 /* Corner case. Discard any symbols with the same value as
227 * _etext _einittext; they can move between pass 1 and 2 when
228 * the kallsyms data are added. If these symbols move then
229 * they may get dropped in pass 2, which breaks the kallsyms
232 if ((s->addr == text_range_text->end &&
234 text_range_text->end_sym)) ||
235 (s->addr == text_range_inittext->end &&
237 text_range_inittext->end_sym)))
241 /* Exclude symbols which vary between passes. */
242 for (i = 0; special_symbols[i]; i++)
243 if (strcmp(sym_name, special_symbols[i]) == 0)
246 for (i = 0; special_prefixes[i]; i++) {
247 int l = strlen(special_prefixes[i]);
249 if (strncmp(sym_name, special_prefixes[i], l) == 0)
253 for (i = 0; special_suffixes[i]; i++) {
254 int l = strlen(sym_name) - strlen(special_suffixes[i]);
256 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0)
263 /* remove all the invalid symbols from the table */
264 static void shrink_table(void)
269 for (i = 0; i < table_cnt; i++) {
270 if (symbol_valid(&table[i])) {
272 table[pos] = table[i];
280 /* When valid symbol is not registered, exit to error */
282 fprintf(stderr, "No valid symbol.\n");
287 static void read_map(FILE *in)
290 if (table_cnt >= table_size) {
292 table = realloc(table, sizeof(*table) * table_size);
294 fprintf(stderr, "out of memory\n");
298 if (read_symbol(in, &table[table_cnt]) == 0) {
299 table[table_cnt].start_pos = table_cnt;
305 static void output_label(char *label)
307 printf(".globl %s\n", label);
309 printf("%s:\n", label);
312 /* uncompress a compressed symbol. When this function is called, the best table
313 * might still be compressed itself, so the function needs to be recursive */
314 static int expand_symbol(unsigned char *data, int len, char *result)
316 int c, rlen, total=0;
320 /* if the table holds a single char that is the same as the one
321 * we are looking for, then end the search */
322 if (best_table[c][0]==c && best_table_len[c]==1) {
326 /* if not, recurse and expand */
327 rlen = expand_symbol(best_table[c], best_table_len[c], result);
339 static int symbol_absolute(struct sym_entry *s)
341 return s->percpu_absolute;
344 static void write_src(void)
346 unsigned int i, k, off;
347 unsigned int best_idx[256];
348 unsigned int *markers;
349 char buf[KSYM_NAME_LEN];
351 printf("#include <asm/bitsperlong.h>\n");
352 printf("#if BITS_PER_LONG == 64\n");
353 printf("#define PTR .quad\n");
354 printf("#define ALGN .balign 8\n");
356 printf("#define PTR .long\n");
357 printf("#define ALGN .balign 4\n");
360 printf("\t.section .rodata, \"a\"\n");
362 /* Provide proper symbols relocatability by their relativeness
363 * to a fixed anchor point in the runtime image, either '_text'
364 * for absolute address tables, in which case the linker will
365 * emit the final addresses at build time. Otherwise, use the
366 * offset relative to the lowest value encountered of all relative
367 * symbols, and emit non-relocatable fixed offsets that will be fixed
370 * The symbol names cannot be used to construct normal symbol
371 * references as the list of symbols contains symbols that are
372 * declared static and are private to their .o files. This prevents
373 * .tmp_kallsyms.o or any other object from referencing them.
376 output_label("kallsyms_addresses");
378 output_label("kallsyms_offsets");
380 for (i = 0; i < table_cnt; i++) {
385 if (!absolute_percpu) {
386 offset = table[i].addr - relative_base;
387 overflow = (offset < 0 || offset > UINT_MAX);
388 } else if (symbol_absolute(&table[i])) {
389 offset = table[i].addr;
390 overflow = (offset < 0 || offset > INT_MAX);
392 offset = relative_base - table[i].addr - 1;
393 overflow = (offset < INT_MIN || offset >= 0);
396 fprintf(stderr, "kallsyms failure: "
397 "%s symbol value %#llx out of range in relative mode\n",
398 symbol_absolute(&table[i]) ? "absolute" : "relative",
402 printf("\t.long\t%#x\n", (int)offset);
403 } else if (!symbol_absolute(&table[i])) {
404 if (_text <= table[i].addr)
405 printf("\tPTR\t_text + %#llx\n",
406 table[i].addr - _text);
408 printf("\tPTR\t_text - %#llx\n",
409 _text - table[i].addr);
411 printf("\tPTR\t%#llx\n", table[i].addr);
417 output_label("kallsyms_relative_base");
418 printf("\tPTR\t_text - %#llx\n", _text - relative_base);
422 output_label("kallsyms_num_syms");
423 printf("\t.long\t%u\n", table_cnt);
426 /* table of offset markers, that give the offset in the compressed stream
427 * every 256 symbols */
428 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
430 fprintf(stderr, "kallsyms failure: "
431 "unable to allocate required memory\n");
435 output_label("kallsyms_names");
437 for (i = 0; i < table_cnt; i++) {
439 markers[i >> 8] = off;
441 printf("\t.byte 0x%02x", table[i].len);
442 for (k = 0; k < table[i].len; k++)
443 printf(", 0x%02x", table[i].sym[k]);
446 off += table[i].len + 1;
450 output_label("kallsyms_markers");
451 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
452 printf("\t.long\t%u\n", markers[i]);
457 output_label("kallsyms_token_table");
459 for (i = 0; i < 256; i++) {
461 expand_symbol(best_table[i], best_table_len[i], buf);
462 printf("\t.asciz\t\"%s\"\n", buf);
463 off += strlen(buf) + 1;
467 output_label("kallsyms_token_index");
468 for (i = 0; i < 256; i++)
469 printf("\t.short\t%d\n", best_idx[i]);
474 /* table lookup compression functions */
476 /* count all the possible tokens in a symbol */
477 static void learn_symbol(unsigned char *symbol, int len)
481 for (i = 0; i < len - 1; i++)
482 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
485 /* decrease the count for all the possible tokens in a symbol */
486 static void forget_symbol(unsigned char *symbol, int len)
490 for (i = 0; i < len - 1; i++)
491 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
494 /* do the initial token count */
495 static void build_initial_tok_table(void)
499 for (i = 0; i < table_cnt; i++)
500 learn_symbol(table[i].sym, table[i].len);
503 static void *find_token(unsigned char *str, int len, unsigned char *token)
507 for (i = 0; i < len - 1; i++) {
508 if (str[i] == token[0] && str[i+1] == token[1])
514 /* replace a given token in all the valid symbols. Use the sampled symbols
515 * to update the counts */
516 static void compress_symbols(unsigned char *str, int idx)
518 unsigned int i, len, size;
519 unsigned char *p1, *p2;
521 for (i = 0; i < table_cnt; i++) {
526 /* find the token on the symbol */
527 p2 = find_token(p1, len, str);
530 /* decrease the counts for this symbol's tokens */
531 forget_symbol(table[i].sym, len);
539 memmove(p2, p2 + 1, size);
545 /* find the token on the symbol */
546 p2 = find_token(p1, size, str);
552 /* increase the counts for this symbol's new tokens */
553 learn_symbol(table[i].sym, len);
557 /* search the token with the maximum profit */
558 static int find_best_token(void)
560 int i, best, bestprofit;
565 for (i = 0; i < 0x10000; i++) {
566 if (token_profit[i] > bestprofit) {
568 bestprofit = token_profit[i];
574 /* this is the core of the algorithm: calculate the "best" table */
575 static void optimize_result(void)
579 /* using the '\0' symbol last allows compress_symbols to use standard
580 * fast string functions */
581 for (i = 255; i >= 0; i--) {
583 /* if this table slot is empty (it is not used by an actual
584 * original char code */
585 if (!best_table_len[i]) {
587 /* find the token with the best profit value */
588 best = find_best_token();
589 if (token_profit[best] == 0)
592 /* place it in the "best" table */
593 best_table_len[i] = 2;
594 best_table[i][0] = best & 0xFF;
595 best_table[i][1] = (best >> 8) & 0xFF;
597 /* replace this token in all the valid symbols */
598 compress_symbols(best_table[i], i);
603 /* start by placing the symbols that are actually used on the table */
604 static void insert_real_symbols_in_table(void)
606 unsigned int i, j, c;
608 for (i = 0; i < table_cnt; i++) {
609 for (j = 0; j < table[i].len; j++) {
617 static void optimize_token_table(void)
619 build_initial_tok_table();
621 insert_real_symbols_in_table();
626 /* guess for "linker script provide" symbol */
627 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
629 const char *symbol = (char *)se->sym + 1;
630 int len = se->len - 1;
635 if (symbol[0] != '_' || symbol[1] != '_')
639 if (!memcmp(symbol + 2, "start_", 6))
643 if (!memcmp(symbol + 2, "stop_", 5))
647 if (!memcmp(symbol + 2, "end_", 4))
651 if (!memcmp(symbol + len - 6, "_start", 6))
655 if (!memcmp(symbol + len - 4, "_end", 4))
661 static int prefix_underscores_count(const char *str)
663 const char *tail = str;
671 static int compare_symbols(const void *a, const void *b)
673 const struct sym_entry *sa;
674 const struct sym_entry *sb;
680 /* sort by address first */
681 if (sa->addr > sb->addr)
683 if (sa->addr < sb->addr)
686 /* sort by "weakness" type */
687 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
688 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
692 /* sort by "linker script provide" type */
693 wa = may_be_linker_script_provide_symbol(sa);
694 wb = may_be_linker_script_provide_symbol(sb);
698 /* sort by the number of prefix underscores */
699 wa = prefix_underscores_count((const char *)sa->sym + 1);
700 wb = prefix_underscores_count((const char *)sb->sym + 1);
704 /* sort by initial order, so that other symbols are left undisturbed */
705 return sa->start_pos - sb->start_pos;
708 static void sort_symbols(void)
710 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
713 static void make_percpus_absolute(void)
717 for (i = 0; i < table_cnt; i++)
718 if (symbol_in_range(&table[i], &percpu_range, 1)) {
720 * Keep the 'A' override for percpu symbols to
721 * ensure consistent behavior compared to older
722 * versions of this tool.
724 table[i].sym[0] = 'A';
725 table[i].percpu_absolute = 1;
729 /* find the minimum non-absolute symbol address */
730 static void record_relative_base(void)
734 for (i = 0; i < table_cnt; i++)
735 if (!symbol_absolute(&table[i])) {
737 * The table is sorted by address.
738 * Take the first non-absolute symbol value.
740 relative_base = table[i].addr;
745 int main(int argc, char **argv)
749 for (i = 1; i < argc; i++) {
750 if(strcmp(argv[i], "--all-symbols") == 0)
752 else if (strcmp(argv[i], "--absolute-percpu") == 0)
754 else if (strcmp(argv[i], "--base-relative") == 0)
759 } else if (argc != 1)
765 make_percpus_absolute();
768 record_relative_base();
769 optimize_token_table();