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