projects/linux·blob v4.14 · refs

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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 NULL };
225
226 static char *special_suffixes[] = {
227 "_veneer", /* arm */
228 "_from_arm", /* arm */
229 "_from_thumb", /* arm */
230 NULL };
231
232 int i;
233 char *sym_name = (char *)s->sym + 1;
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_prefixes[i]; i++) {
267 int l = strlen(special_prefixes[i]);
268
269 if (l <= strlen(sym_name) &&
270 strncmp(sym_name, special_prefixes[i], l) == 0)
271 return 0;
272 }
273
274 for (i = 0; special_suffixes[i]; i++) {
275 int l = strlen(sym_name) - strlen(special_suffixes[i]);
276
277 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0)
278 return 0;
279 }
280
281 return 1;
282}
283
284static void read_map(FILE *in)
285{
286 while (!feof(in)) {
287 if (table_cnt >= table_size) {
288 table_size += 10000;
289 table = realloc(table, sizeof(*table) * table_size);
290 if (!table) {
291 fprintf(stderr, "out of memory\n");
292 exit (1);
293 }
294 }
295 if (read_symbol(in, &table[table_cnt]) == 0) {
296 table[table_cnt].start_pos = table_cnt;
297 table_cnt++;
298 }
299 }
300}
301
302static void output_label(char *label)
303{
304 if (symbol_prefix_char)
305 printf(".globl %c%s\n", symbol_prefix_char, label);
306 else
307 printf(".globl %s\n", label);
308 printf("\tALGN\n");
309 if (symbol_prefix_char)
310 printf("%c%s:\n", symbol_prefix_char, label);
311 else
312 printf("%s:\n", label);
313}
314
315/* uncompress a compressed symbol. When this function is called, the best table
316 * might still be compressed itself, so the function needs to be recursive */
317static int expand_symbol(unsigned char *data, int len, char *result)
318{
319 int c, rlen, total=0;
320
321 while (len) {
322 c = *data;
323 /* if the table holds a single char that is the same as the one
324 * we are looking for, then end the search */
325 if (best_table[c][0]==c && best_table_len[c]==1) {
326 *result++ = c;
327 total++;
328 } else {
329 /* if not, recurse and expand */
330 rlen = expand_symbol(best_table[c], best_table_len[c], result);
331 total += rlen;
332 result += rlen;
333 }
334 data++;
335 len--;
336 }
337 *result=0;
338
339 return total;
340}
341
342static int symbol_absolute(struct sym_entry *s)
343{
344 return s->percpu_absolute;
345}
346
347static void write_src(void)
348{
349 unsigned int i, k, off;
350 unsigned int best_idx[256];
351 unsigned int *markers;
352 char buf[KSYM_NAME_LEN];
353
354 printf("#include <asm/types.h>\n");
355 printf("#if BITS_PER_LONG == 64\n");
356 printf("#define PTR .quad\n");
357 printf("#define ALGN .align 8\n");
358 printf("#else\n");
359 printf("#define PTR .long\n");
360 printf("#define ALGN .align 4\n");
361 printf("#endif\n");
362
363 printf("\t.section .rodata, \"a\"\n");
364
365 /* Provide proper symbols relocatability by their relativeness
366 * to a fixed anchor point in the runtime image, either '_text'
367 * for absolute address tables, in which case the linker will
368 * emit the final addresses at build time. Otherwise, use the
369 * offset relative to the lowest value encountered of all relative
370 * symbols, and emit non-relocatable fixed offsets that will be fixed
371 * up at runtime.
372 *
373 * The symbol names cannot be used to construct normal symbol
374 * references as the list of symbols contains symbols that are
375 * declared static and are private to their .o files. This prevents
376 * .tmp_kallsyms.o or any other object from referencing them.
377 */
378 if (!base_relative)
379 output_label("kallsyms_addresses");
380 else
381 output_label("kallsyms_offsets");
382
383 for (i = 0; i < table_cnt; i++) {
384 if (base_relative) {
385 long long offset;
386 int overflow;
387
388 if (!absolute_percpu) {
389 offset = table[i].addr - relative_base;
390 overflow = (offset < 0 || offset > UINT_MAX);
391 } else if (symbol_absolute(&table[i])) {
392 offset = table[i].addr;
393 overflow = (offset < 0 || offset > INT_MAX);
394 } else {
395 offset = relative_base - table[i].addr - 1;
396 overflow = (offset < INT_MIN || offset >= 0);
397 }
398 if (overflow) {
399 fprintf(stderr, "kallsyms failure: "
400 "%s symbol value %#llx out of range in relative mode\n",
401 symbol_absolute(&table[i]) ? "absolute" : "relative",
402 table[i].addr);
403 exit(EXIT_FAILURE);
404 }
405 printf("\t.long\t%#x\n", (int)offset);
406 } else if (!symbol_absolute(&table[i])) {
407 if (_text <= table[i].addr)
408 printf("\tPTR\t_text + %#llx\n",
409 table[i].addr - _text);
410 else
411 printf("\tPTR\t_text - %#llx\n",
412 _text - table[i].addr);
413 } else {
414 printf("\tPTR\t%#llx\n", table[i].addr);
415 }
416 }
417 printf("\n");
418
419 if (base_relative) {
420 output_label("kallsyms_relative_base");
421 printf("\tPTR\t_text - %#llx\n", _text - relative_base);
422 printf("\n");
423 }
424
425 output_label("kallsyms_num_syms");
426 printf("\tPTR\t%d\n", table_cnt);
427 printf("\n");
428
429 /* table of offset markers, that give the offset in the compressed stream
430 * every 256 symbols */
431 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
432 if (!markers) {
433 fprintf(stderr, "kallsyms failure: "
434 "unable to allocate required memory\n");
435 exit(EXIT_FAILURE);
436 }
437
438 output_label("kallsyms_names");
439 off = 0;
440 for (i = 0; i < table_cnt; i++) {
441 if ((i & 0xFF) == 0)
442 markers[i >> 8] = off;
443
444 printf("\t.byte 0x%02x", table[i].len);
445 for (k = 0; k < table[i].len; k++)
446 printf(", 0x%02x", table[i].sym[k]);
447 printf("\n");
448
449 off += table[i].len + 1;
450 }
451 printf("\n");
452
453 output_label("kallsyms_markers");
454 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
455 printf("\tPTR\t%d\n", markers[i]);
456 printf("\n");
457
458 free(markers);
459
460 output_label("kallsyms_token_table");
461 off = 0;
462 for (i = 0; i < 256; i++) {
463 best_idx[i] = off;
464 expand_symbol(best_table[i], best_table_len[i], buf);
465 printf("\t.asciz\t\"%s\"\n", buf);
466 off += strlen(buf) + 1;
467 }
468 printf("\n");
469
470 output_label("kallsyms_token_index");
471 for (i = 0; i < 256; i++)
472 printf("\t.short\t%d\n", best_idx[i]);
473 printf("\n");
474}
475
476
477/* table lookup compression functions */
478
479/* count all the possible tokens in a symbol */
480static void learn_symbol(unsigned char *symbol, int len)
481{
482 int i;
483
484 for (i = 0; i < len - 1; i++)
485 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
486}
487
488/* decrease the count for all the possible tokens in a symbol */
489static void forget_symbol(unsigned char *symbol, int len)
490{
491 int i;
492
493 for (i = 0; i < len - 1; i++)
494 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
495}
496
497/* remove all the invalid symbols from the table and do the initial token count */
498static void build_initial_tok_table(void)
499{
500 unsigned int i, pos;
501
502 pos = 0;
503 for (i = 0; i < table_cnt; i++) {
504 if ( symbol_valid(&table[i]) ) {
505 if (pos != i)
506 table[pos] = table[i];
507 learn_symbol(table[pos].sym, table[pos].len);
508 pos++;
509 }
510 }
511 table_cnt = pos;
512}
513
514static void *find_token(unsigned char *str, int len, unsigned char *token)
515{
516 int i;
517
518 for (i = 0; i < len - 1; i++) {
519 if (str[i] == token[0] && str[i+1] == token[1])
520 return &str[i];
521 }
522 return NULL;
523}
524
525/* replace a given token in all the valid symbols. Use the sampled symbols
526 * to update the counts */
527static void compress_symbols(unsigned char *str, int idx)
528{
529 unsigned int i, len, size;
530 unsigned char *p1, *p2;
531
532 for (i = 0; i < table_cnt; i++) {
533
534 len = table[i].len;
535 p1 = table[i].sym;
536
537 /* find the token on the symbol */
538 p2 = find_token(p1, len, str);
539 if (!p2) continue;
540
541 /* decrease the counts for this symbol's tokens */
542 forget_symbol(table[i].sym, len);
543
544 size = len;
545
546 do {
547 *p2 = idx;
548 p2++;
549 size -= (p2 - p1);
550 memmove(p2, p2 + 1, size);
551 p1 = p2;
552 len--;
553
554 if (size < 2) break;
555
556 /* find the token on the symbol */
557 p2 = find_token(p1, size, str);
558
559 } while (p2);
560
561 table[i].len = len;
562
563 /* increase the counts for this symbol's new tokens */
564 learn_symbol(table[i].sym, len);
565 }
566}
567
568/* search the token with the maximum profit */
569static int find_best_token(void)
570{
571 int i, best, bestprofit;
572
573 bestprofit=-10000;
574 best = 0;
575
576 for (i = 0; i < 0x10000; i++) {
577 if (token_profit[i] > bestprofit) {
578 best = i;
579 bestprofit = token_profit[i];
580 }
581 }
582 return best;
583}
584
585/* this is the core of the algorithm: calculate the "best" table */
586static void optimize_result(void)
587{
588 int i, best;
589
590 /* using the '\0' symbol last allows compress_symbols to use standard
591 * fast string functions */
592 for (i = 255; i >= 0; i--) {
593
594 /* if this table slot is empty (it is not used by an actual
595 * original char code */
596 if (!best_table_len[i]) {
597
598 /* find the token with the breates profit value */
599 best = find_best_token();
600 if (token_profit[best] == 0)
601 break;
602
603 /* place it in the "best" table */
604 best_table_len[i] = 2;
605 best_table[i][0] = best & 0xFF;
606 best_table[i][1] = (best >> 8) & 0xFF;
607
608 /* replace this token in all the valid symbols */
609 compress_symbols(best_table[i], i);
610 }
611 }
612}
613
614/* start by placing the symbols that are actually used on the table */
615static void insert_real_symbols_in_table(void)
616{
617 unsigned int i, j, c;
618
619 memset(best_table, 0, sizeof(best_table));
620 memset(best_table_len, 0, sizeof(best_table_len));
621
622 for (i = 0; i < table_cnt; i++) {
623 for (j = 0; j < table[i].len; j++) {
624 c = table[i].sym[j];
625 best_table[c][0]=c;
626 best_table_len[c]=1;
627 }
628 }
629}
630
631static void optimize_token_table(void)
632{
633 build_initial_tok_table();
634
635 insert_real_symbols_in_table();
636
637 /* When valid symbol is not registered, exit to error */
638 if (!table_cnt) {
639 fprintf(stderr, "No valid symbol.\n");
640 exit(1);
641 }
642
643 optimize_result();
644}
645
646/* guess for "linker script provide" symbol */
647static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
648{
649 const char *symbol = (char *)se->sym + 1;
650 int len = se->len - 1;
651
652 if (len < 8)
653 return 0;
654
655 if (symbol[0] != '_' || symbol[1] != '_')
656 return 0;
657
658 /* __start_XXXXX */
659 if (!memcmp(symbol + 2, "start_", 6))
660 return 1;
661
662 /* __stop_XXXXX */
663 if (!memcmp(symbol + 2, "stop_", 5))
664 return 1;
665
666 /* __end_XXXXX */
667 if (!memcmp(symbol + 2, "end_", 4))
668 return 1;
669
670 /* __XXXXX_start */
671 if (!memcmp(symbol + len - 6, "_start", 6))
672 return 1;
673
674 /* __XXXXX_end */
675 if (!memcmp(symbol + len - 4, "_end", 4))
676 return 1;
677
678 return 0;
679}
680
681static int prefix_underscores_count(const char *str)
682{
683 const char *tail = str;
684
685 while (*tail == '_')
686 tail++;
687
688 return tail - str;
689}
690
691static int compare_symbols(const void *a, const void *b)
692{
693 const struct sym_entry *sa;
694 const struct sym_entry *sb;
695 int wa, wb;
696
697 sa = a;
698 sb = b;
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 = prefix_underscores_count((const char *)sa->sym + 1);
720 wb = prefix_underscores_count((const char *)sb->sym + 1);
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(struct sym_entry), 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 relative_base = -1ULL;
755 for (i = 0; i < table_cnt; i++)
756 if (!symbol_absolute(&table[i]) &&
757 table[i].addr < relative_base)
758 relative_base = table[i].addr;
759}
760
761int main(int argc, char **argv)
762{
763 if (argc >= 2) {
764 int i;
765 for (i = 1; i < argc; i++) {
766 if(strcmp(argv[i], "--all-symbols") == 0)
767 all_symbols = 1;
768 else if (strcmp(argv[i], "--absolute-percpu") == 0)
769 absolute_percpu = 1;
770 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
771 char *p = &argv[i][16];
772 /* skip quote */
773 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
774 p++;
775 symbol_prefix_char = *p;
776 } else if (strcmp(argv[i], "--base-relative") == 0)
777 base_relative = 1;
778 else
779 usage();
780 }
781 } else if (argc != 1)
782 usage();
783
784 read_map(stdin);
785 if (absolute_percpu)
786 make_percpus_absolute();
787 if (base_relative)
788 record_relative_base();
789 sort_symbols();
790 optimize_token_table();
791 write_src();
792
793 return 0;
794}