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1/* Generate assembler source containing symbol information
2 *
3 * Copyright 2002 by Kai Germaschewski
4 *
5 * This software may be used and distributed according to the terms
6 * of the GNU General Public License, incorporated herein by reference.
7 *
8 * Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S
9 *
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
17 * of about 50%.
18 *
19 */
20
21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
24#include <ctype.h>
25#include <limits.h>
26
27#ifndef ARRAY_SIZE
28#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
29#endif
30
31#define KSYM_NAME_LEN 128
32
33struct sym_entry {
34 unsigned long long addr;
35 unsigned int len;
36 unsigned int start_pos;
37 unsigned char *sym;
38 unsigned int percpu_absolute;
39};
40
41struct addr_range {
42 const char *start_sym, *end_sym;
43 unsigned long long start, end;
44};
45
46static unsigned long long _text;
47static unsigned long long relative_base;
48static struct addr_range text_ranges[] = {
49 { "_stext", "_etext" },
50 { "_sinittext", "_einittext" },
51 { "_stext_l1", "_etext_l1" }, /* Blackfin on-chip L1 inst SRAM */
52 { "_stext_l2", "_etext_l2" }, /* Blackfin on-chip L2 SRAM */
53};
54#define text_range_text (&text_ranges[0])
55#define text_range_inittext (&text_ranges[1])
56
57static struct addr_range percpu_range = {
58 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
59};
60
61static struct sym_entry *table;
62static unsigned int table_size, table_cnt;
63static int all_symbols = 0;
64static int absolute_percpu = 0;
65static char symbol_prefix_char = '\0';
66static int base_relative = 0;
67
68int token_profit[0x10000];
69
70/* the table that holds the result of the compression */
71unsigned char best_table[256][2];
72unsigned char best_table_len[256];
73
74
75static void usage(void)
76{
77 fprintf(stderr, "Usage: kallsyms [--all-symbols] "
78 "[--symbol-prefix=<prefix char>] "
79 "[--base-relative] < in.map > out.S\n");
80 exit(1);
81}
82
83/*
84 * This ignores the intensely annoying "mapping symbols" found
85 * in ARM ELF files: $a, $t and $d.
86 */
87static inline int is_arm_mapping_symbol(const char *str)
88{
89 return str[0] == '$' && strchr("axtd", str[1])
90 && (str[2] == '\0' || str[2] == '.');
91}
92
93static int check_symbol_range(const char *sym, unsigned long long addr,
94 struct addr_range *ranges, int entries)
95{
96 size_t i;
97 struct addr_range *ar;
98
99 for (i = 0; i < entries; ++i) {
100 ar = &ranges[i];
101
102 if (strcmp(sym, ar->start_sym) == 0) {
103 ar->start = addr;
104 return 0;
105 } else if (strcmp(sym, ar->end_sym) == 0) {
106 ar->end = addr;
107 return 0;
108 }
109 }
110
111 return 1;
112}
113
114static int read_symbol(FILE *in, struct sym_entry *s)
115{
116 char str[500];
117 char *sym, stype;
118 int rc;
119
120 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
121 if (rc != 3) {
122 if (rc != EOF && fgets(str, 500, in) == NULL)
123 fprintf(stderr, "Read error or end of file.\n");
124 return -1;
125 }
126 if (strlen(str) > KSYM_NAME_LEN) {
127 fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n"
128 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
129 str, strlen(str), KSYM_NAME_LEN);
130 return -1;
131 }
132
133 sym = str;
134 /* skip prefix char */
135 if (symbol_prefix_char && str[0] == symbol_prefix_char)
136 sym++;
137
138 /* Ignore most absolute/undefined (?) symbols. */
139 if (strcmp(sym, "_text") == 0)
140 _text = s->addr;
141 else if (check_symbol_range(sym, s->addr, text_ranges,
142 ARRAY_SIZE(text_ranges)) == 0)
143 /* nothing to do */;
144 else if (toupper(stype) == 'A')
145 {
146 /* Keep these useful absolute symbols */
147 if (strcmp(sym, "__kernel_syscall_via_break") &&
148 strcmp(sym, "__kernel_syscall_via_epc") &&
149 strcmp(sym, "__kernel_sigtramp") &&
150 strcmp(sym, "__gp"))
151 return -1;
152
153 }
154 else if (toupper(stype) == 'U' ||
155 is_arm_mapping_symbol(sym))
156 return -1;
157 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
158 else if (str[0] == '$')
159 return -1;
160 /* exclude debugging symbols */
161 else if (stype == 'N' || stype == 'n')
162 return -1;
163
164 /* include the type field in the symbol name, so that it gets
165 * compressed together */
166 s->len = strlen(str) + 1;
167 s->sym = malloc(s->len + 1);
168 if (!s->sym) {
169 fprintf(stderr, "kallsyms failure: "
170 "unable to allocate required amount of memory\n");
171 exit(EXIT_FAILURE);
172 }
173 strcpy((char *)s->sym + 1, str);
174 s->sym[0] = stype;
175
176 s->percpu_absolute = 0;
177
178 /* Record if we've found __per_cpu_start/end. */
179 check_symbol_range(sym, s->addr, &percpu_range, 1);
180
181 return 0;
182}
183
184static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges,
185 int entries)
186{
187 size_t i;
188 struct addr_range *ar;
189
190 for (i = 0; i < entries; ++i) {
191 ar = &ranges[i];
192
193 if (s->addr >= ar->start && s->addr <= ar->end)
194 return 1;
195 }
196
197 return 0;
198}
199
200static int symbol_valid(struct sym_entry *s)
201{
202 /* Symbols which vary between passes. Passes 1 and 2 must have
203 * identical symbol lists. The kallsyms_* symbols below are only added
204 * after pass 1, they would be included in pass 2 when --all-symbols is
205 * specified so exclude them to get a stable symbol list.
206 */
207 static char *special_symbols[] = {
208 "kallsyms_addresses",
209 "kallsyms_offsets",
210 "kallsyms_relative_base",
211 "kallsyms_num_syms",
212 "kallsyms_names",
213 "kallsyms_markers",
214 "kallsyms_token_table",
215 "kallsyms_token_index",
216
217 /* Exclude linker generated symbols which vary between passes */
218 "_SDA_BASE_", /* ppc */
219 "_SDA2_BASE_", /* ppc */
220 NULL };
221
222 static char *special_prefixes[] = {
223 "__crc_", /* modversions */
224 "__efistub_", /* arm64 EFI stub namespace */
225 NULL };
226
227 static char *special_suffixes[] = {
228 "_veneer", /* arm */
229 "_from_arm", /* arm */
230 "_from_thumb", /* arm */
231 NULL };
232
233 int i;
234 char *sym_name = (char *)s->sym + 1;
235
236 /* skip prefix char */
237 if (symbol_prefix_char && *sym_name == symbol_prefix_char)
238 sym_name++;
239
240
241 /* if --all-symbols is not specified, then symbols outside the text
242 * and inittext sections are discarded */
243 if (!all_symbols) {
244 if (symbol_in_range(s, text_ranges,
245 ARRAY_SIZE(text_ranges)) == 0)
246 return 0;
247 /* Corner case. Discard any symbols with the same value as
248 * _etext _einittext; they can move between pass 1 and 2 when
249 * the kallsyms data are added. If these symbols move then
250 * they may get dropped in pass 2, which breaks the kallsyms
251 * rules.
252 */
253 if ((s->addr == text_range_text->end &&
254 strcmp(sym_name,
255 text_range_text->end_sym)) ||
256 (s->addr == text_range_inittext->end &&
257 strcmp(sym_name,
258 text_range_inittext->end_sym)))
259 return 0;
260 }
261
262 /* Exclude symbols which vary between passes. */
263 for (i = 0; special_symbols[i]; i++)
264 if (strcmp(sym_name, special_symbols[i]) == 0)
265 return 0;
266
267 for (i = 0; special_prefixes[i]; i++) {
268 int l = strlen(special_prefixes[i]);
269
270 if (l <= strlen(sym_name) &&
271 strncmp(sym_name, special_prefixes[i], l) == 0)
272 return 0;
273 }
274
275 for (i = 0; special_suffixes[i]; i++) {
276 int l = strlen(sym_name) - strlen(special_suffixes[i]);
277
278 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0)
279 return 0;
280 }
281
282 return 1;
283}
284
285static void read_map(FILE *in)
286{
287 while (!feof(in)) {
288 if (table_cnt >= table_size) {
289 table_size += 10000;
290 table = realloc(table, sizeof(*table) * table_size);
291 if (!table) {
292 fprintf(stderr, "out of memory\n");
293 exit (1);
294 }
295 }
296 if (read_symbol(in, &table[table_cnt]) == 0) {
297 table[table_cnt].start_pos = table_cnt;
298 table_cnt++;
299 }
300 }
301}
302
303static void output_label(char *label)
304{
305 if (symbol_prefix_char)
306 printf(".globl %c%s\n", symbol_prefix_char, label);
307 else
308 printf(".globl %s\n", label);
309 printf("\tALGN\n");
310 if (symbol_prefix_char)
311 printf("%c%s:\n", symbol_prefix_char, label);
312 else
313 printf("%s:\n", label);
314}
315
316/* uncompress a compressed symbol. When this function is called, the best table
317 * might still be compressed itself, so the function needs to be recursive */
318static int expand_symbol(unsigned char *data, int len, char *result)
319{
320 int c, rlen, total=0;
321
322 while (len) {
323 c = *data;
324 /* if the table holds a single char that is the same as the one
325 * we are looking for, then end the search */
326 if (best_table[c][0]==c && best_table_len[c]==1) {
327 *result++ = c;
328 total++;
329 } else {
330 /* if not, recurse and expand */
331 rlen = expand_symbol(best_table[c], best_table_len[c], result);
332 total += rlen;
333 result += rlen;
334 }
335 data++;
336 len--;
337 }
338 *result=0;
339
340 return total;
341}
342
343static int symbol_absolute(struct sym_entry *s)
344{
345 return s->percpu_absolute;
346}
347
348static void write_src(void)
349{
350 unsigned int i, k, off;
351 unsigned int best_idx[256];
352 unsigned int *markers;
353 char buf[KSYM_NAME_LEN];
354
355 printf("#include <asm/types.h>\n");
356 printf("#if BITS_PER_LONG == 64\n");
357 printf("#define PTR .quad\n");
358 printf("#define ALGN .align 8\n");
359 printf("#else\n");
360 printf("#define PTR .long\n");
361 printf("#define ALGN .align 4\n");
362 printf("#endif\n");
363
364 printf("\t.section .rodata, \"a\"\n");
365
366 /* Provide proper symbols relocatability by their relativeness
367 * to a fixed anchor point in the runtime image, either '_text'
368 * for absolute address tables, in which case the linker will
369 * emit the final addresses at build time. Otherwise, use the
370 * offset relative to the lowest value encountered of all relative
371 * symbols, and emit non-relocatable fixed offsets that will be fixed
372 * up at runtime.
373 *
374 * The symbol names cannot be used to construct normal symbol
375 * references as the list of symbols contains symbols that are
376 * declared static and are private to their .o files. This prevents
377 * .tmp_kallsyms.o or any other object from referencing them.
378 */
379 if (!base_relative)
380 output_label("kallsyms_addresses");
381 else
382 output_label("kallsyms_offsets");
383
384 for (i = 0; i < table_cnt; i++) {
385 if (base_relative) {
386 long long offset;
387 int overflow;
388
389 if (!absolute_percpu) {
390 offset = table[i].addr - relative_base;
391 overflow = (offset < 0 || offset > UINT_MAX);
392 } else if (symbol_absolute(&table[i])) {
393 offset = table[i].addr;
394 overflow = (offset < 0 || offset > INT_MAX);
395 } else {
396 offset = relative_base - table[i].addr - 1;
397 overflow = (offset < INT_MIN || offset >= 0);
398 }
399 if (overflow) {
400 fprintf(stderr, "kallsyms failure: "
401 "%s symbol value %#llx out of range in relative mode\n",
402 symbol_absolute(&table[i]) ? "absolute" : "relative",
403 table[i].addr);
404 exit(EXIT_FAILURE);
405 }
406 printf("\t.long\t%#x\n", (int)offset);
407 } else if (!symbol_absolute(&table[i])) {
408 if (_text <= table[i].addr)
409 printf("\tPTR\t_text + %#llx\n",
410 table[i].addr - _text);
411 else
412 printf("\tPTR\t_text - %#llx\n",
413 _text - table[i].addr);
414 } else {
415 printf("\tPTR\t%#llx\n", table[i].addr);
416 }
417 }
418 printf("\n");
419
420 if (base_relative) {
421 output_label("kallsyms_relative_base");
422 printf("\tPTR\t_text - %#llx\n", _text - relative_base);
423 printf("\n");
424 }
425
426 output_label("kallsyms_num_syms");
427 printf("\tPTR\t%d\n", table_cnt);
428 printf("\n");
429
430 /* table of offset markers, that give the offset in the compressed stream
431 * every 256 symbols */
432 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
433 if (!markers) {
434 fprintf(stderr, "kallsyms failure: "
435 "unable to allocate required memory\n");
436 exit(EXIT_FAILURE);
437 }
438
439 output_label("kallsyms_names");
440 off = 0;
441 for (i = 0; i < table_cnt; i++) {
442 if ((i & 0xFF) == 0)
443 markers[i >> 8] = off;
444
445 printf("\t.byte 0x%02x", table[i].len);
446 for (k = 0; k < table[i].len; k++)
447 printf(", 0x%02x", table[i].sym[k]);
448 printf("\n");
449
450 off += table[i].len + 1;
451 }
452 printf("\n");
453
454 output_label("kallsyms_markers");
455 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
456 printf("\tPTR\t%d\n", markers[i]);
457 printf("\n");
458
459 free(markers);
460
461 output_label("kallsyms_token_table");
462 off = 0;
463 for (i = 0; i < 256; i++) {
464 best_idx[i] = off;
465 expand_symbol(best_table[i], best_table_len[i], buf);
466 printf("\t.asciz\t\"%s\"\n", buf);
467 off += strlen(buf) + 1;
468 }
469 printf("\n");
470
471 output_label("kallsyms_token_index");
472 for (i = 0; i < 256; i++)
473 printf("\t.short\t%d\n", best_idx[i]);
474 printf("\n");
475}
476
477
478/* table lookup compression functions */
479
480/* count all the possible tokens in a symbol */
481static void learn_symbol(unsigned char *symbol, int len)
482{
483 int i;
484
485 for (i = 0; i < len - 1; i++)
486 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
487}
488
489/* decrease the count for all the possible tokens in a symbol */
490static void forget_symbol(unsigned char *symbol, int len)
491{
492 int i;
493
494 for (i = 0; i < len - 1; i++)
495 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
496}
497
498/* remove all the invalid symbols from the table and do the initial token count */
499static void build_initial_tok_table(void)
500{
501 unsigned int i, pos;
502
503 pos = 0;
504 for (i = 0; i < table_cnt; i++) {
505 if ( symbol_valid(&table[i]) ) {
506 if (pos != i)
507 table[pos] = table[i];
508 learn_symbol(table[pos].sym, table[pos].len);
509 pos++;
510 }
511 }
512 table_cnt = pos;
513}
514
515static void *find_token(unsigned char *str, int len, unsigned char *token)
516{
517 int i;
518
519 for (i = 0; i < len - 1; i++) {
520 if (str[i] == token[0] && str[i+1] == token[1])
521 return &str[i];
522 }
523 return NULL;
524}
525
526/* replace a given token in all the valid symbols. Use the sampled symbols
527 * to update the counts */
528static void compress_symbols(unsigned char *str, int idx)
529{
530 unsigned int i, len, size;
531 unsigned char *p1, *p2;
532
533 for (i = 0; i < table_cnt; i++) {
534
535 len = table[i].len;
536 p1 = table[i].sym;
537
538 /* find the token on the symbol */
539 p2 = find_token(p1, len, str);
540 if (!p2) continue;
541
542 /* decrease the counts for this symbol's tokens */
543 forget_symbol(table[i].sym, len);
544
545 size = len;
546
547 do {
548 *p2 = idx;
549 p2++;
550 size -= (p2 - p1);
551 memmove(p2, p2 + 1, size);
552 p1 = p2;
553 len--;
554
555 if (size < 2) break;
556
557 /* find the token on the symbol */
558 p2 = find_token(p1, size, str);
559
560 } while (p2);
561
562 table[i].len = len;
563
564 /* increase the counts for this symbol's new tokens */
565 learn_symbol(table[i].sym, len);
566 }
567}
568
569/* search the token with the maximum profit */
570static int find_best_token(void)
571{
572 int i, best, bestprofit;
573
574 bestprofit=-10000;
575 best = 0;
576
577 for (i = 0; i < 0x10000; i++) {
578 if (token_profit[i] > bestprofit) {
579 best = i;
580 bestprofit = token_profit[i];
581 }
582 }
583 return best;
584}
585
586/* this is the core of the algorithm: calculate the "best" table */
587static void optimize_result(void)
588{
589 int i, best;
590
591 /* using the '\0' symbol last allows compress_symbols to use standard
592 * fast string functions */
593 for (i = 255; i >= 0; i--) {
594
595 /* if this table slot is empty (it is not used by an actual
596 * original char code */
597 if (!best_table_len[i]) {
598
599 /* find the token with the best profit value */
600 best = find_best_token();
601 if (token_profit[best] == 0)
602 break;
603
604 /* place it in the "best" table */
605 best_table_len[i] = 2;
606 best_table[i][0] = best & 0xFF;
607 best_table[i][1] = (best >> 8) & 0xFF;
608
609 /* replace this token in all the valid symbols */
610 compress_symbols(best_table[i], i);
611 }
612 }
613}
614
615/* start by placing the symbols that are actually used on the table */
616static void insert_real_symbols_in_table(void)
617{
618 unsigned int i, j, c;
619
620 memset(best_table, 0, sizeof(best_table));
621 memset(best_table_len, 0, sizeof(best_table_len));
622
623 for (i = 0; i < table_cnt; i++) {
624 for (j = 0; j < table[i].len; j++) {
625 c = table[i].sym[j];
626 best_table[c][0]=c;
627 best_table_len[c]=1;
628 }
629 }
630}
631
632static void optimize_token_table(void)
633{
634 build_initial_tok_table();
635
636 insert_real_symbols_in_table();
637
638 /* When valid symbol is not registered, exit to error */
639 if (!table_cnt) {
640 fprintf(stderr, "No valid symbol.\n");
641 exit(1);
642 }
643
644 optimize_result();
645}
646
647/* guess for "linker script provide" symbol */
648static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
649{
650 const char *symbol = (char *)se->sym + 1;
651 int len = se->len - 1;
652
653 if (len < 8)
654 return 0;
655
656 if (symbol[0] != '_' || symbol[1] != '_')
657 return 0;
658
659 /* __start_XXXXX */
660 if (!memcmp(symbol + 2, "start_", 6))
661 return 1;
662
663 /* __stop_XXXXX */
664 if (!memcmp(symbol + 2, "stop_", 5))
665 return 1;
666
667 /* __end_XXXXX */
668 if (!memcmp(symbol + 2, "end_", 4))
669 return 1;
670
671 /* __XXXXX_start */
672 if (!memcmp(symbol + len - 6, "_start", 6))
673 return 1;
674
675 /* __XXXXX_end */
676 if (!memcmp(symbol + len - 4, "_end", 4))
677 return 1;
678
679 return 0;
680}
681
682static int prefix_underscores_count(const char *str)
683{
684 const char *tail = str;
685
686 while (*tail == '_')
687 tail++;
688
689 return tail - str;
690}
691
692static int compare_symbols(const void *a, const void *b)
693{
694 const struct sym_entry *sa;
695 const struct sym_entry *sb;
696 int wa, wb;
697
698 sa = a;
699 sb = b;
700
701 /* sort by address first */
702 if (sa->addr > sb->addr)
703 return 1;
704 if (sa->addr < sb->addr)
705 return -1;
706
707 /* sort by "weakness" type */
708 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
709 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
710 if (wa != wb)
711 return wa - wb;
712
713 /* sort by "linker script provide" type */
714 wa = may_be_linker_script_provide_symbol(sa);
715 wb = may_be_linker_script_provide_symbol(sb);
716 if (wa != wb)
717 return wa - wb;
718
719 /* sort by the number of prefix underscores */
720 wa = prefix_underscores_count((const char *)sa->sym + 1);
721 wb = prefix_underscores_count((const char *)sb->sym + 1);
722 if (wa != wb)
723 return wa - wb;
724
725 /* sort by initial order, so that other symbols are left undisturbed */
726 return sa->start_pos - sb->start_pos;
727}
728
729static void sort_symbols(void)
730{
731 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
732}
733
734static void make_percpus_absolute(void)
735{
736 unsigned int i;
737
738 for (i = 0; i < table_cnt; i++)
739 if (symbol_in_range(&table[i], &percpu_range, 1)) {
740 /*
741 * Keep the 'A' override for percpu symbols to
742 * ensure consistent behavior compared to older
743 * versions of this tool.
744 */
745 table[i].sym[0] = 'A';
746 table[i].percpu_absolute = 1;
747 }
748}
749
750/* find the minimum non-absolute symbol address */
751static void record_relative_base(void)
752{
753 unsigned int i;
754
755 relative_base = -1ULL;
756 for (i = 0; i < table_cnt; i++)
757 if (!symbol_absolute(&table[i]) &&
758 table[i].addr < relative_base)
759 relative_base = table[i].addr;
760}
761
762int main(int argc, char **argv)
763{
764 if (argc >= 2) {
765 int i;
766 for (i = 1; i < argc; i++) {
767 if(strcmp(argv[i], "--all-symbols") == 0)
768 all_symbols = 1;
769 else if (strcmp(argv[i], "--absolute-percpu") == 0)
770 absolute_percpu = 1;
771 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
772 char *p = &argv[i][16];
773 /* skip quote */
774 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
775 p++;
776 symbol_prefix_char = *p;
777 } else if (strcmp(argv[i], "--base-relative") == 0)
778 base_relative = 1;
779 else
780 usage();
781 }
782 } else if (argc != 1)
783 usage();
784
785 read_map(stdin);
786 if (absolute_percpu)
787 make_percpus_absolute();
788 if (base_relative)
789 record_relative_base();
790 sort_symbols();
791 optimize_token_table();
792 write_src();
793
794 return 0;
795}
1/* Generate assembler source containing symbol information
2 *
3 * Copyright 2002 by Kai Germaschewski
4 *
5 * This software may be used and distributed according to the terms
6 * of the GNU General Public License, incorporated herein by reference.
7 *
8 * Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S
9 *
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
17 * of about 50%.
18 *
19 */
20
21#include <stdbool.h>
22#include <stdio.h>
23#include <stdlib.h>
24#include <string.h>
25#include <ctype.h>
26#include <limits.h>
27
28#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
29
30#define KSYM_NAME_LEN 128
31
32struct sym_entry {
33 unsigned long long addr;
34 unsigned int len;
35 unsigned int start_pos;
36 unsigned int percpu_absolute;
37 unsigned char sym[];
38};
39
40struct addr_range {
41 const char *start_sym, *end_sym;
42 unsigned long long start, end;
43};
44
45static unsigned long long _text;
46static unsigned long long relative_base;
47static struct addr_range text_ranges[] = {
48 { "_stext", "_etext" },
49 { "_sinittext", "_einittext" },
50};
51#define text_range_text (&text_ranges[0])
52#define text_range_inittext (&text_ranges[1])
53
54static struct addr_range percpu_range = {
55 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
56};
57
58static struct sym_entry **table;
59static unsigned int table_size, table_cnt;
60static int all_symbols;
61static int absolute_percpu;
62static int base_relative;
63
64static int token_profit[0x10000];
65
66/* the table that holds the result of the compression */
67static unsigned char best_table[256][2];
68static unsigned char best_table_len[256];
69
70
71static void usage(void)
72{
73 fprintf(stderr, "Usage: kallsyms [--all-symbols] "
74 "[--base-relative] < in.map > out.S\n");
75 exit(1);
76}
77
78static char *sym_name(const struct sym_entry *s)
79{
80 return (char *)s->sym + 1;
81}
82
83static bool is_ignored_symbol(const char *name, char type)
84{
85 /* Symbol names that exactly match to the following are ignored.*/
86 static const char * const ignored_symbols[] = {
87 /*
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
92 * stable symbol list.
93 */
94 "kallsyms_addresses",
95 "kallsyms_offsets",
96 "kallsyms_relative_base",
97 "kallsyms_num_syms",
98 "kallsyms_names",
99 "kallsyms_markers",
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 */
105 NULL
106 };
107
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 */
115 "__AArch64ADRPThunk_", /* arm64 lld */
116 "__ARMV5PILongThunk_", /* arm lld */
117 "__ARMV7PILongThunk_",
118 "__ThumbV7PILongThunk_",
119 "__LA25Thunk_", /* mips lld */
120 "__microLA25Thunk_",
121 NULL
122 };
123
124 /* Symbol names that end with the following are ignored.*/
125 static const char * const ignored_suffixes[] = {
126 "_from_arm", /* arm */
127 "_from_thumb", /* arm */
128 "_veneer", /* arm */
129 NULL
130 };
131
132 /* Symbol names that contain the following are ignored.*/
133 static const char * const ignored_matches[] = {
134 ".long_branch.", /* ppc stub */
135 ".plt_branch.", /* ppc stub */
136 NULL
137 };
138
139 const char * const *p;
140
141 for (p = ignored_symbols; *p; p++)
142 if (!strcmp(name, *p))
143 return true;
144
145 for (p = ignored_prefixes; *p; p++)
146 if (!strncmp(name, *p, strlen(*p)))
147 return true;
148
149 for (p = ignored_suffixes; *p; p++) {
150 int l = strlen(name) - strlen(*p);
151
152 if (l >= 0 && !strcmp(name + l, *p))
153 return true;
154 }
155
156 for (p = ignored_matches; *p; p++) {
157 if (strstr(name, *p))
158 return true;
159 }
160
161 if (type == 'U' || type == 'u')
162 return true;
163 /* exclude debugging symbols */
164 if (type == 'N' || type == 'n')
165 return true;
166
167 if (toupper(type) == 'A') {
168 /* Keep these useful absolute symbols */
169 if (strcmp(name, "__kernel_syscall_via_break") &&
170 strcmp(name, "__kernel_syscall_via_epc") &&
171 strcmp(name, "__kernel_sigtramp") &&
172 strcmp(name, "__gp"))
173 return true;
174 }
175
176 return false;
177}
178
179static void check_symbol_range(const char *sym, unsigned long long addr,
180 struct addr_range *ranges, int entries)
181{
182 size_t i;
183 struct addr_range *ar;
184
185 for (i = 0; i < entries; ++i) {
186 ar = &ranges[i];
187
188 if (strcmp(sym, ar->start_sym) == 0) {
189 ar->start = addr;
190 return;
191 } else if (strcmp(sym, ar->end_sym) == 0) {
192 ar->end = addr;
193 return;
194 }
195 }
196}
197
198static struct sym_entry *read_symbol(FILE *in)
199{
200 char name[500], type;
201 unsigned long long addr;
202 unsigned int len;
203 struct sym_entry *sym;
204 int rc;
205
206 rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
207 if (rc != 3) {
208 if (rc != EOF && fgets(name, 500, in) == NULL)
209 fprintf(stderr, "Read error or end of file.\n");
210 return NULL;
211 }
212 if (strlen(name) >= KSYM_NAME_LEN) {
213 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
214 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
215 name, strlen(name), KSYM_NAME_LEN);
216 return NULL;
217 }
218
219 if (strcmp(name, "_text") == 0)
220 _text = addr;
221
222 /* Ignore most absolute/undefined (?) symbols. */
223 if (is_ignored_symbol(name, type))
224 return NULL;
225
226 check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
227 check_symbol_range(name, addr, &percpu_range, 1);
228
229 /* include the type field in the symbol name, so that it gets
230 * compressed together */
231
232 len = strlen(name) + 1;
233
234 sym = malloc(sizeof(*sym) + len + 1);
235 if (!sym) {
236 fprintf(stderr, "kallsyms failure: "
237 "unable to allocate required amount of memory\n");
238 exit(EXIT_FAILURE);
239 }
240 sym->addr = addr;
241 sym->len = len;
242 sym->sym[0] = type;
243 strcpy(sym_name(sym), name);
244 sym->percpu_absolute = 0;
245
246 return sym;
247}
248
249static int symbol_in_range(const struct sym_entry *s,
250 const struct addr_range *ranges, int entries)
251{
252 size_t i;
253 const struct addr_range *ar;
254
255 for (i = 0; i < entries; ++i) {
256 ar = &ranges[i];
257
258 if (s->addr >= ar->start && s->addr <= ar->end)
259 return 1;
260 }
261
262 return 0;
263}
264
265static int symbol_valid(const struct sym_entry *s)
266{
267 const char *name = sym_name(s);
268
269 /* if --all-symbols is not specified, then symbols outside the text
270 * and inittext sections are discarded */
271 if (!all_symbols) {
272 if (symbol_in_range(s, text_ranges,
273 ARRAY_SIZE(text_ranges)) == 0)
274 return 0;
275 /* Corner case. Discard any symbols with the same value as
276 * _etext _einittext; they can move between pass 1 and 2 when
277 * the kallsyms data are added. If these symbols move then
278 * they may get dropped in pass 2, which breaks the kallsyms
279 * rules.
280 */
281 if ((s->addr == text_range_text->end &&
282 strcmp(name, text_range_text->end_sym)) ||
283 (s->addr == text_range_inittext->end &&
284 strcmp(name, text_range_inittext->end_sym)))
285 return 0;
286 }
287
288 return 1;
289}
290
291/* remove all the invalid symbols from the table */
292static void shrink_table(void)
293{
294 unsigned int i, pos;
295
296 pos = 0;
297 for (i = 0; i < table_cnt; i++) {
298 if (symbol_valid(table[i])) {
299 if (pos != i)
300 table[pos] = table[i];
301 pos++;
302 } else {
303 free(table[i]);
304 }
305 }
306 table_cnt = pos;
307
308 /* When valid symbol is not registered, exit to error */
309 if (!table_cnt) {
310 fprintf(stderr, "No valid symbol.\n");
311 exit(1);
312 }
313}
314
315static void read_map(FILE *in)
316{
317 struct sym_entry *sym;
318
319 while (!feof(in)) {
320 sym = read_symbol(in);
321 if (!sym)
322 continue;
323
324 sym->start_pos = table_cnt;
325
326 if (table_cnt >= table_size) {
327 table_size += 10000;
328 table = realloc(table, sizeof(*table) * table_size);
329 if (!table) {
330 fprintf(stderr, "out of memory\n");
331 exit (1);
332 }
333 }
334
335 table[table_cnt++] = sym;
336 }
337}
338
339static void output_label(const char *label)
340{
341 printf(".globl %s\n", label);
342 printf("\tALGN\n");
343 printf("%s:\n", label);
344}
345
346/* Provide proper symbols relocatability by their '_text' relativeness. */
347static void output_address(unsigned long long addr)
348{
349 if (_text <= addr)
350 printf("\tPTR\t_text + %#llx\n", addr - _text);
351 else
352 printf("\tPTR\t_text - %#llx\n", _text - addr);
353}
354
355/* uncompress a compressed symbol. When this function is called, the best table
356 * might still be compressed itself, so the function needs to be recursive */
357static int expand_symbol(const unsigned char *data, int len, char *result)
358{
359 int c, rlen, total=0;
360
361 while (len) {
362 c = *data;
363 /* if the table holds a single char that is the same as the one
364 * we are looking for, then end the search */
365 if (best_table[c][0]==c && best_table_len[c]==1) {
366 *result++ = c;
367 total++;
368 } else {
369 /* if not, recurse and expand */
370 rlen = expand_symbol(best_table[c], best_table_len[c], result);
371 total += rlen;
372 result += rlen;
373 }
374 data++;
375 len--;
376 }
377 *result=0;
378
379 return total;
380}
381
382static int symbol_absolute(const struct sym_entry *s)
383{
384 return s->percpu_absolute;
385}
386
387static void write_src(void)
388{
389 unsigned int i, k, off;
390 unsigned int best_idx[256];
391 unsigned int *markers;
392 char buf[KSYM_NAME_LEN];
393
394 printf("#include <asm/bitsperlong.h>\n");
395 printf("#if BITS_PER_LONG == 64\n");
396 printf("#define PTR .quad\n");
397 printf("#define ALGN .balign 8\n");
398 printf("#else\n");
399 printf("#define PTR .long\n");
400 printf("#define ALGN .balign 4\n");
401 printf("#endif\n");
402
403 printf("\t.section .rodata, \"a\"\n");
404
405 if (!base_relative)
406 output_label("kallsyms_addresses");
407 else
408 output_label("kallsyms_offsets");
409
410 for (i = 0; i < table_cnt; i++) {
411 if (base_relative) {
412 /*
413 * Use the offset relative to the lowest value
414 * encountered of all relative symbols, and emit
415 * non-relocatable fixed offsets that will be fixed
416 * up at runtime.
417 */
418
419 long long offset;
420 int overflow;
421
422 if (!absolute_percpu) {
423 offset = table[i]->addr - relative_base;
424 overflow = (offset < 0 || offset > UINT_MAX);
425 } else if (symbol_absolute(table[i])) {
426 offset = table[i]->addr;
427 overflow = (offset < 0 || offset > INT_MAX);
428 } else {
429 offset = relative_base - table[i]->addr - 1;
430 overflow = (offset < INT_MIN || offset >= 0);
431 }
432 if (overflow) {
433 fprintf(stderr, "kallsyms failure: "
434 "%s symbol value %#llx out of range in relative mode\n",
435 symbol_absolute(table[i]) ? "absolute" : "relative",
436 table[i]->addr);
437 exit(EXIT_FAILURE);
438 }
439 printf("\t.long\t%#x\n", (int)offset);
440 } else if (!symbol_absolute(table[i])) {
441 output_address(table[i]->addr);
442 } else {
443 printf("\tPTR\t%#llx\n", table[i]->addr);
444 }
445 }
446 printf("\n");
447
448 if (base_relative) {
449 output_label("kallsyms_relative_base");
450 output_address(relative_base);
451 printf("\n");
452 }
453
454 output_label("kallsyms_num_syms");
455 printf("\t.long\t%u\n", table_cnt);
456 printf("\n");
457
458 /* table of offset markers, that give the offset in the compressed stream
459 * every 256 symbols */
460 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
461 if (!markers) {
462 fprintf(stderr, "kallsyms failure: "
463 "unable to allocate required memory\n");
464 exit(EXIT_FAILURE);
465 }
466
467 output_label("kallsyms_names");
468 off = 0;
469 for (i = 0; i < table_cnt; i++) {
470 if ((i & 0xFF) == 0)
471 markers[i >> 8] = off;
472
473 printf("\t.byte 0x%02x", table[i]->len);
474 for (k = 0; k < table[i]->len; k++)
475 printf(", 0x%02x", table[i]->sym[k]);
476 printf("\n");
477
478 off += table[i]->len + 1;
479 }
480 printf("\n");
481
482 output_label("kallsyms_markers");
483 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
484 printf("\t.long\t%u\n", markers[i]);
485 printf("\n");
486
487 free(markers);
488
489 output_label("kallsyms_token_table");
490 off = 0;
491 for (i = 0; i < 256; i++) {
492 best_idx[i] = off;
493 expand_symbol(best_table[i], best_table_len[i], buf);
494 printf("\t.asciz\t\"%s\"\n", buf);
495 off += strlen(buf) + 1;
496 }
497 printf("\n");
498
499 output_label("kallsyms_token_index");
500 for (i = 0; i < 256; i++)
501 printf("\t.short\t%d\n", best_idx[i]);
502 printf("\n");
503}
504
505
506/* table lookup compression functions */
507
508/* count all the possible tokens in a symbol */
509static void learn_symbol(const unsigned char *symbol, int len)
510{
511 int i;
512
513 for (i = 0; i < len - 1; i++)
514 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
515}
516
517/* decrease the count for all the possible tokens in a symbol */
518static void forget_symbol(const unsigned char *symbol, int len)
519{
520 int i;
521
522 for (i = 0; i < len - 1; i++)
523 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
524}
525
526/* do the initial token count */
527static void build_initial_tok_table(void)
528{
529 unsigned int i;
530
531 for (i = 0; i < table_cnt; i++)
532 learn_symbol(table[i]->sym, table[i]->len);
533}
534
535static unsigned char *find_token(unsigned char *str, int len,
536 const unsigned char *token)
537{
538 int i;
539
540 for (i = 0; i < len - 1; i++) {
541 if (str[i] == token[0] && str[i+1] == token[1])
542 return &str[i];
543 }
544 return NULL;
545}
546
547/* replace a given token in all the valid symbols. Use the sampled symbols
548 * to update the counts */
549static void compress_symbols(const unsigned char *str, int idx)
550{
551 unsigned int i, len, size;
552 unsigned char *p1, *p2;
553
554 for (i = 0; i < table_cnt; i++) {
555
556 len = table[i]->len;
557 p1 = table[i]->sym;
558
559 /* find the token on the symbol */
560 p2 = find_token(p1, len, str);
561 if (!p2) continue;
562
563 /* decrease the counts for this symbol's tokens */
564 forget_symbol(table[i]->sym, len);
565
566 size = len;
567
568 do {
569 *p2 = idx;
570 p2++;
571 size -= (p2 - p1);
572 memmove(p2, p2 + 1, size);
573 p1 = p2;
574 len--;
575
576 if (size < 2) break;
577
578 /* find the token on the symbol */
579 p2 = find_token(p1, size, str);
580
581 } while (p2);
582
583 table[i]->len = len;
584
585 /* increase the counts for this symbol's new tokens */
586 learn_symbol(table[i]->sym, len);
587 }
588}
589
590/* search the token with the maximum profit */
591static int find_best_token(void)
592{
593 int i, best, bestprofit;
594
595 bestprofit=-10000;
596 best = 0;
597
598 for (i = 0; i < 0x10000; i++) {
599 if (token_profit[i] > bestprofit) {
600 best = i;
601 bestprofit = token_profit[i];
602 }
603 }
604 return best;
605}
606
607/* this is the core of the algorithm: calculate the "best" table */
608static void optimize_result(void)
609{
610 int i, best;
611
612 /* using the '\0' symbol last allows compress_symbols to use standard
613 * fast string functions */
614 for (i = 255; i >= 0; i--) {
615
616 /* if this table slot is empty (it is not used by an actual
617 * original char code */
618 if (!best_table_len[i]) {
619
620 /* find the token with the best profit value */
621 best = find_best_token();
622 if (token_profit[best] == 0)
623 break;
624
625 /* place it in the "best" table */
626 best_table_len[i] = 2;
627 best_table[i][0] = best & 0xFF;
628 best_table[i][1] = (best >> 8) & 0xFF;
629
630 /* replace this token in all the valid symbols */
631 compress_symbols(best_table[i], i);
632 }
633 }
634}
635
636/* start by placing the symbols that are actually used on the table */
637static void insert_real_symbols_in_table(void)
638{
639 unsigned int i, j, c;
640
641 for (i = 0; i < table_cnt; i++) {
642 for (j = 0; j < table[i]->len; j++) {
643 c = table[i]->sym[j];
644 best_table[c][0]=c;
645 best_table_len[c]=1;
646 }
647 }
648}
649
650static void optimize_token_table(void)
651{
652 build_initial_tok_table();
653
654 insert_real_symbols_in_table();
655
656 optimize_result();
657}
658
659/* guess for "linker script provide" symbol */
660static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
661{
662 const char *symbol = sym_name(se);
663 int len = se->len - 1;
664
665 if (len < 8)
666 return 0;
667
668 if (symbol[0] != '_' || symbol[1] != '_')
669 return 0;
670
671 /* __start_XXXXX */
672 if (!memcmp(symbol + 2, "start_", 6))
673 return 1;
674
675 /* __stop_XXXXX */
676 if (!memcmp(symbol + 2, "stop_", 5))
677 return 1;
678
679 /* __end_XXXXX */
680 if (!memcmp(symbol + 2, "end_", 4))
681 return 1;
682
683 /* __XXXXX_start */
684 if (!memcmp(symbol + len - 6, "_start", 6))
685 return 1;
686
687 /* __XXXXX_end */
688 if (!memcmp(symbol + len - 4, "_end", 4))
689 return 1;
690
691 return 0;
692}
693
694static int compare_symbols(const void *a, const void *b)
695{
696 const struct sym_entry *sa = *(const struct sym_entry **)a;
697 const struct sym_entry *sb = *(const struct sym_entry **)b;
698 int wa, wb;
699
700 /* sort by address first */
701 if (sa->addr > sb->addr)
702 return 1;
703 if (sa->addr < sb->addr)
704 return -1;
705
706 /* sort by "weakness" type */
707 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
708 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
709 if (wa != wb)
710 return wa - wb;
711
712 /* sort by "linker script provide" type */
713 wa = may_be_linker_script_provide_symbol(sa);
714 wb = may_be_linker_script_provide_symbol(sb);
715 if (wa != wb)
716 return wa - wb;
717
718 /* sort by the number of prefix underscores */
719 wa = strspn(sym_name(sa), "_");
720 wb = strspn(sym_name(sb), "_");
721 if (wa != wb)
722 return wa - wb;
723
724 /* sort by initial order, so that other symbols are left undisturbed */
725 return sa->start_pos - sb->start_pos;
726}
727
728static void sort_symbols(void)
729{
730 qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
731}
732
733static void make_percpus_absolute(void)
734{
735 unsigned int i;
736
737 for (i = 0; i < table_cnt; i++)
738 if (symbol_in_range(table[i], &percpu_range, 1)) {
739 /*
740 * Keep the 'A' override for percpu symbols to
741 * ensure consistent behavior compared to older
742 * versions of this tool.
743 */
744 table[i]->sym[0] = 'A';
745 table[i]->percpu_absolute = 1;
746 }
747}
748
749/* find the minimum non-absolute symbol address */
750static void record_relative_base(void)
751{
752 unsigned int i;
753
754 for (i = 0; i < table_cnt; i++)
755 if (!symbol_absolute(table[i])) {
756 /*
757 * The table is sorted by address.
758 * Take the first non-absolute symbol value.
759 */
760 relative_base = table[i]->addr;
761 return;
762 }
763}
764
765int main(int argc, char **argv)
766{
767 if (argc >= 2) {
768 int i;
769 for (i = 1; i < argc; i++) {
770 if(strcmp(argv[i], "--all-symbols") == 0)
771 all_symbols = 1;
772 else if (strcmp(argv[i], "--absolute-percpu") == 0)
773 absolute_percpu = 1;
774 else if (strcmp(argv[i], "--base-relative") == 0)
775 base_relative = 1;
776 else
777 usage();
778 }
779 } else if (argc != 1)
780 usage();
781
782 read_map(stdin);
783 shrink_table();
784 if (absolute_percpu)
785 make_percpus_absolute();
786 sort_symbols();
787 if (base_relative)
788 record_relative_base();
789 optimize_token_table();
790 write_src();
791
792 return 0;
793}