Loading...
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 <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 unsigned long long kernel_start_addr = 0;
67static int base_relative = 0;
68
69int token_profit[0x10000];
70
71/* the table that holds the result of the compression */
72unsigned char best_table[256][2];
73unsigned char best_table_len[256];
74
75
76static void usage(void)
77{
78 fprintf(stderr, "Usage: kallsyms [--all-symbols] "
79 "[--symbol-prefix=<prefix char>] "
80 "[--page-offset=<CONFIG_PAGE_OFFSET>] "
81 "[--base-relative] < in.map > out.S\n");
82 exit(1);
83}
84
85/*
86 * This ignores the intensely annoying "mapping symbols" found
87 * in ARM ELF files: $a, $t and $d.
88 */
89static inline int is_arm_mapping_symbol(const char *str)
90{
91 return str[0] == '$' && strchr("axtd", str[1])
92 && (str[2] == '\0' || str[2] == '.');
93}
94
95static int check_symbol_range(const char *sym, unsigned long long addr,
96 struct addr_range *ranges, int entries)
97{
98 size_t i;
99 struct addr_range *ar;
100
101 for (i = 0; i < entries; ++i) {
102 ar = &ranges[i];
103
104 if (strcmp(sym, ar->start_sym) == 0) {
105 ar->start = addr;
106 return 0;
107 } else if (strcmp(sym, ar->end_sym) == 0) {
108 ar->end = addr;
109 return 0;
110 }
111 }
112
113 return 1;
114}
115
116static int read_symbol(FILE *in, struct sym_entry *s)
117{
118 char str[500];
119 char *sym, stype;
120 int rc;
121
122 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
123 if (rc != 3) {
124 if (rc != EOF && fgets(str, 500, in) == NULL)
125 fprintf(stderr, "Read error or end of file.\n");
126 return -1;
127 }
128 if (strlen(str) > KSYM_NAME_LEN) {
129 fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n"
130 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
131 str, strlen(str), KSYM_NAME_LEN);
132 return -1;
133 }
134
135 sym = str;
136 /* skip prefix char */
137 if (symbol_prefix_char && str[0] == symbol_prefix_char)
138 sym++;
139
140 /* Ignore most absolute/undefined (?) symbols. */
141 if (strcmp(sym, "_text") == 0)
142 _text = s->addr;
143 else if (check_symbol_range(sym, s->addr, text_ranges,
144 ARRAY_SIZE(text_ranges)) == 0)
145 /* nothing to do */;
146 else if (toupper(stype) == 'A')
147 {
148 /* Keep these useful absolute symbols */
149 if (strcmp(sym, "__kernel_syscall_via_break") &&
150 strcmp(sym, "__kernel_syscall_via_epc") &&
151 strcmp(sym, "__kernel_sigtramp") &&
152 strcmp(sym, "__gp"))
153 return -1;
154
155 }
156 else if (toupper(stype) == 'U' ||
157 is_arm_mapping_symbol(sym))
158 return -1;
159 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
160 else if (str[0] == '$')
161 return -1;
162 /* exclude debugging symbols */
163 else if (stype == 'N')
164 return -1;
165
166 /* include the type field in the symbol name, so that it gets
167 * compressed together */
168 s->len = strlen(str) + 1;
169 s->sym = malloc(s->len + 1);
170 if (!s->sym) {
171 fprintf(stderr, "kallsyms failure: "
172 "unable to allocate required amount of memory\n");
173 exit(EXIT_FAILURE);
174 }
175 strcpy((char *)s->sym + 1, str);
176 s->sym[0] = stype;
177
178 s->percpu_absolute = 0;
179
180 /* Record if we've found __per_cpu_start/end. */
181 check_symbol_range(sym, s->addr, &percpu_range, 1);
182
183 return 0;
184}
185
186static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges,
187 int entries)
188{
189 size_t i;
190 struct addr_range *ar;
191
192 for (i = 0; i < entries; ++i) {
193 ar = &ranges[i];
194
195 if (s->addr >= ar->start && s->addr <= ar->end)
196 return 1;
197 }
198
199 return 0;
200}
201
202static int symbol_valid(struct sym_entry *s)
203{
204 /* Symbols which vary between passes. Passes 1 and 2 must have
205 * identical symbol lists. The kallsyms_* symbols below are only added
206 * after pass 1, they would be included in pass 2 when --all-symbols is
207 * specified so exclude them to get a stable symbol list.
208 */
209 static char *special_symbols[] = {
210 "kallsyms_addresses",
211 "kallsyms_offsets",
212 "kallsyms_relative_base",
213 "kallsyms_num_syms",
214 "kallsyms_names",
215 "kallsyms_markers",
216 "kallsyms_token_table",
217 "kallsyms_token_index",
218
219 /* Exclude linker generated symbols which vary between passes */
220 "_SDA_BASE_", /* ppc */
221 "_SDA2_BASE_", /* ppc */
222 NULL };
223
224 static char *special_suffixes[] = {
225 "_veneer", /* arm */
226 NULL };
227
228 int i;
229 char *sym_name = (char *)s->sym + 1;
230
231
232 if (s->addr < kernel_start_addr)
233 return 0;
234
235 /* skip prefix char */
236 if (symbol_prefix_char && *sym_name == symbol_prefix_char)
237 sym_name++;
238
239
240 /* if --all-symbols is not specified, then symbols outside the text
241 * and inittext sections are discarded */
242 if (!all_symbols) {
243 if (symbol_in_range(s, text_ranges,
244 ARRAY_SIZE(text_ranges)) == 0)
245 return 0;
246 /* Corner case. Discard any symbols with the same value as
247 * _etext _einittext; they can move between pass 1 and 2 when
248 * the kallsyms data are added. If these symbols move then
249 * they may get dropped in pass 2, which breaks the kallsyms
250 * rules.
251 */
252 if ((s->addr == text_range_text->end &&
253 strcmp(sym_name,
254 text_range_text->end_sym)) ||
255 (s->addr == text_range_inittext->end &&
256 strcmp(sym_name,
257 text_range_inittext->end_sym)))
258 return 0;
259 }
260
261 /* Exclude symbols which vary between passes. */
262 for (i = 0; special_symbols[i]; i++)
263 if (strcmp(sym_name, special_symbols[i]) == 0)
264 return 0;
265
266 for (i = 0; special_suffixes[i]; i++) {
267 int l = strlen(sym_name) - strlen(special_suffixes[i]);
268
269 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0)
270 return 0;
271 }
272
273 return 1;
274}
275
276static void read_map(FILE *in)
277{
278 while (!feof(in)) {
279 if (table_cnt >= table_size) {
280 table_size += 10000;
281 table = realloc(table, sizeof(*table) * table_size);
282 if (!table) {
283 fprintf(stderr, "out of memory\n");
284 exit (1);
285 }
286 }
287 if (read_symbol(in, &table[table_cnt]) == 0) {
288 table[table_cnt].start_pos = table_cnt;
289 table_cnt++;
290 }
291 }
292}
293
294static void output_label(char *label)
295{
296 if (symbol_prefix_char)
297 printf(".globl %c%s\n", symbol_prefix_char, label);
298 else
299 printf(".globl %s\n", label);
300 printf("\tALGN\n");
301 if (symbol_prefix_char)
302 printf("%c%s:\n", symbol_prefix_char, label);
303 else
304 printf("%s:\n", label);
305}
306
307/* uncompress a compressed symbol. When this function is called, the best table
308 * might still be compressed itself, so the function needs to be recursive */
309static int expand_symbol(unsigned char *data, int len, char *result)
310{
311 int c, rlen, total=0;
312
313 while (len) {
314 c = *data;
315 /* if the table holds a single char that is the same as the one
316 * we are looking for, then end the search */
317 if (best_table[c][0]==c && best_table_len[c]==1) {
318 *result++ = c;
319 total++;
320 } else {
321 /* if not, recurse and expand */
322 rlen = expand_symbol(best_table[c], best_table_len[c], result);
323 total += rlen;
324 result += rlen;
325 }
326 data++;
327 len--;
328 }
329 *result=0;
330
331 return total;
332}
333
334static int symbol_absolute(struct sym_entry *s)
335{
336 return s->percpu_absolute;
337}
338
339static void write_src(void)
340{
341 unsigned int i, k, off;
342 unsigned int best_idx[256];
343 unsigned int *markers;
344 char buf[KSYM_NAME_LEN];
345
346 printf("#include <asm/types.h>\n");
347 printf("#if BITS_PER_LONG == 64\n");
348 printf("#define PTR .quad\n");
349 printf("#define ALGN .align 8\n");
350 printf("#else\n");
351 printf("#define PTR .long\n");
352 printf("#define ALGN .align 4\n");
353 printf("#endif\n");
354
355 printf("\t.section .rodata, \"a\"\n");
356
357 /* Provide proper symbols relocatability by their relativeness
358 * to a fixed anchor point in the runtime image, either '_text'
359 * for absolute address tables, in which case the linker will
360 * emit the final addresses at build time. Otherwise, use the
361 * offset relative to the lowest value encountered of all relative
362 * symbols, and emit non-relocatable fixed offsets that will be fixed
363 * up at runtime.
364 *
365 * The symbol names cannot be used to construct normal symbol
366 * references as the list of symbols contains symbols that are
367 * declared static and are private to their .o files. This prevents
368 * .tmp_kallsyms.o or any other object from referencing them.
369 */
370 if (!base_relative)
371 output_label("kallsyms_addresses");
372 else
373 output_label("kallsyms_offsets");
374
375 for (i = 0; i < table_cnt; i++) {
376 if (base_relative) {
377 long long offset;
378 int overflow;
379
380 if (!absolute_percpu) {
381 offset = table[i].addr - relative_base;
382 overflow = (offset < 0 || offset > UINT_MAX);
383 } else if (symbol_absolute(&table[i])) {
384 offset = table[i].addr;
385 overflow = (offset < 0 || offset > INT_MAX);
386 } else {
387 offset = relative_base - table[i].addr - 1;
388 overflow = (offset < INT_MIN || offset >= 0);
389 }
390 if (overflow) {
391 fprintf(stderr, "kallsyms failure: "
392 "%s symbol value %#llx out of range in relative mode\n",
393 symbol_absolute(&table[i]) ? "absolute" : "relative",
394 table[i].addr);
395 exit(EXIT_FAILURE);
396 }
397 printf("\t.long\t%#x\n", (int)offset);
398 } else if (!symbol_absolute(&table[i])) {
399 if (_text <= table[i].addr)
400 printf("\tPTR\t_text + %#llx\n",
401 table[i].addr - _text);
402 else
403 printf("\tPTR\t_text - %#llx\n",
404 _text - table[i].addr);
405 } else {
406 printf("\tPTR\t%#llx\n", table[i].addr);
407 }
408 }
409 printf("\n");
410
411 if (base_relative) {
412 output_label("kallsyms_relative_base");
413 printf("\tPTR\t_text - %#llx\n", _text - relative_base);
414 printf("\n");
415 }
416
417 output_label("kallsyms_num_syms");
418 printf("\tPTR\t%d\n", table_cnt);
419 printf("\n");
420
421 /* table of offset markers, that give the offset in the compressed stream
422 * every 256 symbols */
423 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
424 if (!markers) {
425 fprintf(stderr, "kallsyms failure: "
426 "unable to allocate required memory\n");
427 exit(EXIT_FAILURE);
428 }
429
430 output_label("kallsyms_names");
431 off = 0;
432 for (i = 0; i < table_cnt; i++) {
433 if ((i & 0xFF) == 0)
434 markers[i >> 8] = off;
435
436 printf("\t.byte 0x%02x", table[i].len);
437 for (k = 0; k < table[i].len; k++)
438 printf(", 0x%02x", table[i].sym[k]);
439 printf("\n");
440
441 off += table[i].len + 1;
442 }
443 printf("\n");
444
445 output_label("kallsyms_markers");
446 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
447 printf("\tPTR\t%d\n", markers[i]);
448 printf("\n");
449
450 free(markers);
451
452 output_label("kallsyms_token_table");
453 off = 0;
454 for (i = 0; i < 256; i++) {
455 best_idx[i] = off;
456 expand_symbol(best_table[i], best_table_len[i], buf);
457 printf("\t.asciz\t\"%s\"\n", buf);
458 off += strlen(buf) + 1;
459 }
460 printf("\n");
461
462 output_label("kallsyms_token_index");
463 for (i = 0; i < 256; i++)
464 printf("\t.short\t%d\n", best_idx[i]);
465 printf("\n");
466}
467
468
469/* table lookup compression functions */
470
471/* count all the possible tokens in a symbol */
472static void learn_symbol(unsigned char *symbol, int len)
473{
474 int i;
475
476 for (i = 0; i < len - 1; i++)
477 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
478}
479
480/* decrease the count for all the possible tokens in a symbol */
481static void forget_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/* remove all the invalid symbols from the table and do the initial token count */
490static void build_initial_tok_table(void)
491{
492 unsigned int i, pos;
493
494 pos = 0;
495 for (i = 0; i < table_cnt; i++) {
496 if ( symbol_valid(&table[i]) ) {
497 if (pos != i)
498 table[pos] = table[i];
499 learn_symbol(table[pos].sym, table[pos].len);
500 pos++;
501 }
502 }
503 table_cnt = pos;
504}
505
506static void *find_token(unsigned char *str, int len, unsigned char *token)
507{
508 int i;
509
510 for (i = 0; i < len - 1; i++) {
511 if (str[i] == token[0] && str[i+1] == token[1])
512 return &str[i];
513 }
514 return NULL;
515}
516
517/* replace a given token in all the valid symbols. Use the sampled symbols
518 * to update the counts */
519static void compress_symbols(unsigned char *str, int idx)
520{
521 unsigned int i, len, size;
522 unsigned char *p1, *p2;
523
524 for (i = 0; i < table_cnt; i++) {
525
526 len = table[i].len;
527 p1 = table[i].sym;
528
529 /* find the token on the symbol */
530 p2 = find_token(p1, len, str);
531 if (!p2) continue;
532
533 /* decrease the counts for this symbol's tokens */
534 forget_symbol(table[i].sym, len);
535
536 size = len;
537
538 do {
539 *p2 = idx;
540 p2++;
541 size -= (p2 - p1);
542 memmove(p2, p2 + 1, size);
543 p1 = p2;
544 len--;
545
546 if (size < 2) break;
547
548 /* find the token on the symbol */
549 p2 = find_token(p1, size, str);
550
551 } while (p2);
552
553 table[i].len = len;
554
555 /* increase the counts for this symbol's new tokens */
556 learn_symbol(table[i].sym, len);
557 }
558}
559
560/* search the token with the maximum profit */
561static int find_best_token(void)
562{
563 int i, best, bestprofit;
564
565 bestprofit=-10000;
566 best = 0;
567
568 for (i = 0; i < 0x10000; i++) {
569 if (token_profit[i] > bestprofit) {
570 best = i;
571 bestprofit = token_profit[i];
572 }
573 }
574 return best;
575}
576
577/* this is the core of the algorithm: calculate the "best" table */
578static void optimize_result(void)
579{
580 int i, best;
581
582 /* using the '\0' symbol last allows compress_symbols to use standard
583 * fast string functions */
584 for (i = 255; i >= 0; i--) {
585
586 /* if this table slot is empty (it is not used by an actual
587 * original char code */
588 if (!best_table_len[i]) {
589
590 /* find the token with the breates profit value */
591 best = find_best_token();
592 if (token_profit[best] == 0)
593 break;
594
595 /* place it in the "best" table */
596 best_table_len[i] = 2;
597 best_table[i][0] = best & 0xFF;
598 best_table[i][1] = (best >> 8) & 0xFF;
599
600 /* replace this token in all the valid symbols */
601 compress_symbols(best_table[i], i);
602 }
603 }
604}
605
606/* start by placing the symbols that are actually used on the table */
607static void insert_real_symbols_in_table(void)
608{
609 unsigned int i, j, c;
610
611 memset(best_table, 0, sizeof(best_table));
612 memset(best_table_len, 0, sizeof(best_table_len));
613
614 for (i = 0; i < table_cnt; i++) {
615 for (j = 0; j < table[i].len; j++) {
616 c = table[i].sym[j];
617 best_table[c][0]=c;
618 best_table_len[c]=1;
619 }
620 }
621}
622
623static void optimize_token_table(void)
624{
625 build_initial_tok_table();
626
627 insert_real_symbols_in_table();
628
629 /* When valid symbol is not registered, exit to error */
630 if (!table_cnt) {
631 fprintf(stderr, "No valid symbol.\n");
632 exit(1);
633 }
634
635 optimize_result();
636}
637
638/* guess for "linker script provide" symbol */
639static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
640{
641 const char *symbol = (char *)se->sym + 1;
642 int len = se->len - 1;
643
644 if (len < 8)
645 return 0;
646
647 if (symbol[0] != '_' || symbol[1] != '_')
648 return 0;
649
650 /* __start_XXXXX */
651 if (!memcmp(symbol + 2, "start_", 6))
652 return 1;
653
654 /* __stop_XXXXX */
655 if (!memcmp(symbol + 2, "stop_", 5))
656 return 1;
657
658 /* __end_XXXXX */
659 if (!memcmp(symbol + 2, "end_", 4))
660 return 1;
661
662 /* __XXXXX_start */
663 if (!memcmp(symbol + len - 6, "_start", 6))
664 return 1;
665
666 /* __XXXXX_end */
667 if (!memcmp(symbol + len - 4, "_end", 4))
668 return 1;
669
670 return 0;
671}
672
673static int prefix_underscores_count(const char *str)
674{
675 const char *tail = str;
676
677 while (*tail == '_')
678 tail++;
679
680 return tail - str;
681}
682
683static int compare_symbols(const void *a, const void *b)
684{
685 const struct sym_entry *sa;
686 const struct sym_entry *sb;
687 int wa, wb;
688
689 sa = a;
690 sb = b;
691
692 /* sort by address first */
693 if (sa->addr > sb->addr)
694 return 1;
695 if (sa->addr < sb->addr)
696 return -1;
697
698 /* sort by "weakness" type */
699 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
700 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
701 if (wa != wb)
702 return wa - wb;
703
704 /* sort by "linker script provide" type */
705 wa = may_be_linker_script_provide_symbol(sa);
706 wb = may_be_linker_script_provide_symbol(sb);
707 if (wa != wb)
708 return wa - wb;
709
710 /* sort by the number of prefix underscores */
711 wa = prefix_underscores_count((const char *)sa->sym + 1);
712 wb = prefix_underscores_count((const char *)sb->sym + 1);
713 if (wa != wb)
714 return wa - wb;
715
716 /* sort by initial order, so that other symbols are left undisturbed */
717 return sa->start_pos - sb->start_pos;
718}
719
720static void sort_symbols(void)
721{
722 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
723}
724
725static void make_percpus_absolute(void)
726{
727 unsigned int i;
728
729 for (i = 0; i < table_cnt; i++)
730 if (symbol_in_range(&table[i], &percpu_range, 1)) {
731 /*
732 * Keep the 'A' override for percpu symbols to
733 * ensure consistent behavior compared to older
734 * versions of this tool.
735 */
736 table[i].sym[0] = 'A';
737 table[i].percpu_absolute = 1;
738 }
739}
740
741/* find the minimum non-absolute symbol address */
742static void record_relative_base(void)
743{
744 unsigned int i;
745
746 relative_base = -1ULL;
747 for (i = 0; i < table_cnt; i++)
748 if (!symbol_absolute(&table[i]) &&
749 table[i].addr < relative_base)
750 relative_base = table[i].addr;
751}
752
753int main(int argc, char **argv)
754{
755 if (argc >= 2) {
756 int i;
757 for (i = 1; i < argc; i++) {
758 if(strcmp(argv[i], "--all-symbols") == 0)
759 all_symbols = 1;
760 else if (strcmp(argv[i], "--absolute-percpu") == 0)
761 absolute_percpu = 1;
762 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
763 char *p = &argv[i][16];
764 /* skip quote */
765 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
766 p++;
767 symbol_prefix_char = *p;
768 } else if (strncmp(argv[i], "--page-offset=", 14) == 0) {
769 const char *p = &argv[i][14];
770 kernel_start_addr = strtoull(p, NULL, 16);
771 } else if (strcmp(argv[i], "--base-relative") == 0)
772 base_relative = 1;
773 else
774 usage();
775 }
776 } else if (argc != 1)
777 usage();
778
779 read_map(stdin);
780 if (absolute_percpu)
781 make_percpus_absolute();
782 if (base_relative)
783 record_relative_base();
784 sort_symbols();
785 optimize_token_table();
786 write_src();
787
788 return 0;
789}