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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: kallsyms [--all-symbols] [--absolute-percpu]
9 * [--base-relative] [--lto-clang] in.map > out.S
10 *
11 * Table compression uses all the unused char codes on the symbols and
12 * maps these to the most used substrings (tokens). For instance, it might
13 * map char code 0xF7 to represent "write_" and then in every symbol where
14 * "write_" appears it can be replaced by 0xF7, saving 5 bytes.
15 * The used codes themselves are also placed in the table so that the
16 * decompresion can work without "special cases".
17 * Applied to kernel symbols, this usually produces a compression ratio
18 * of about 50%.
19 *
20 */
21
22#include <errno.h>
23#include <getopt.h>
24#include <stdbool.h>
25#include <stdio.h>
26#include <stdlib.h>
27#include <string.h>
28#include <ctype.h>
29#include <limits.h>
30
31#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
32
33#define KSYM_NAME_LEN 512
34
35struct sym_entry {
36 unsigned long long addr;
37 unsigned int len;
38 unsigned int seq;
39 unsigned int start_pos;
40 unsigned int percpu_absolute;
41 unsigned char sym[];
42};
43
44struct addr_range {
45 const char *start_sym, *end_sym;
46 unsigned long long start, end;
47};
48
49static unsigned long long _text;
50static unsigned long long relative_base;
51static struct addr_range text_ranges[] = {
52 { "_stext", "_etext" },
53 { "_sinittext", "_einittext" },
54};
55#define text_range_text (&text_ranges[0])
56#define text_range_inittext (&text_ranges[1])
57
58static struct addr_range percpu_range = {
59 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
60};
61
62static struct sym_entry **table;
63static unsigned int table_size, table_cnt;
64static int all_symbols;
65static int absolute_percpu;
66static int base_relative;
67static int lto_clang;
68
69static int token_profit[0x10000];
70
71/* the table that holds the result of the compression */
72static unsigned char best_table[256][2];
73static unsigned char best_table_len[256];
74
75
76static void usage(void)
77{
78 fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
79 "[--base-relative] [--lto-clang] in.map > out.S\n");
80 exit(1);
81}
82
83static char *sym_name(const struct sym_entry *s)
84{
85 return (char *)s->sym + 1;
86}
87
88static bool is_ignored_symbol(const char *name, char type)
89{
90 if (type == 'u' || type == 'n')
91 return true;
92
93 if (toupper(type) == 'A') {
94 /* Keep these useful absolute symbols */
95 if (strcmp(name, "__kernel_syscall_via_break") &&
96 strcmp(name, "__kernel_syscall_via_epc") &&
97 strcmp(name, "__kernel_sigtramp") &&
98 strcmp(name, "__gp"))
99 return true;
100 }
101
102 return false;
103}
104
105static void check_symbol_range(const char *sym, unsigned long long addr,
106 struct addr_range *ranges, int entries)
107{
108 size_t i;
109 struct addr_range *ar;
110
111 for (i = 0; i < entries; ++i) {
112 ar = &ranges[i];
113
114 if (strcmp(sym, ar->start_sym) == 0) {
115 ar->start = addr;
116 return;
117 } else if (strcmp(sym, ar->end_sym) == 0) {
118 ar->end = addr;
119 return;
120 }
121 }
122}
123
124static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
125{
126 char *name, type, *p;
127 unsigned long long addr;
128 size_t len;
129 ssize_t readlen;
130 struct sym_entry *sym;
131
132 errno = 0;
133 readlen = getline(buf, buf_len, in);
134 if (readlen < 0) {
135 if (errno) {
136 perror("read_symbol");
137 exit(EXIT_FAILURE);
138 }
139 return NULL;
140 }
141
142 if ((*buf)[readlen - 1] == '\n')
143 (*buf)[readlen - 1] = 0;
144
145 addr = strtoull(*buf, &p, 16);
146
147 if (*buf == p || *p++ != ' ' || !isascii((type = *p++)) || *p++ != ' ') {
148 fprintf(stderr, "line format error\n");
149 exit(EXIT_FAILURE);
150 }
151
152 name = p;
153 len = strlen(name);
154
155 if (len >= KSYM_NAME_LEN) {
156 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
157 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
158 name, len, KSYM_NAME_LEN);
159 return NULL;
160 }
161
162 if (strcmp(name, "_text") == 0)
163 _text = addr;
164
165 /* Ignore most absolute/undefined (?) symbols. */
166 if (is_ignored_symbol(name, type))
167 return NULL;
168
169 check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
170 check_symbol_range(name, addr, &percpu_range, 1);
171
172 /* include the type field in the symbol name, so that it gets
173 * compressed together */
174 len++;
175
176 sym = malloc(sizeof(*sym) + len + 1);
177 if (!sym) {
178 fprintf(stderr, "kallsyms failure: "
179 "unable to allocate required amount of memory\n");
180 exit(EXIT_FAILURE);
181 }
182 sym->addr = addr;
183 sym->len = len;
184 sym->sym[0] = type;
185 strcpy(sym_name(sym), name);
186 sym->percpu_absolute = 0;
187
188 return sym;
189}
190
191static int symbol_in_range(const struct sym_entry *s,
192 const struct addr_range *ranges, int entries)
193{
194 size_t i;
195 const struct addr_range *ar;
196
197 for (i = 0; i < entries; ++i) {
198 ar = &ranges[i];
199
200 if (s->addr >= ar->start && s->addr <= ar->end)
201 return 1;
202 }
203
204 return 0;
205}
206
207static int symbol_valid(const struct sym_entry *s)
208{
209 const char *name = sym_name(s);
210
211 /* if --all-symbols is not specified, then symbols outside the text
212 * and inittext sections are discarded */
213 if (!all_symbols) {
214 if (symbol_in_range(s, text_ranges,
215 ARRAY_SIZE(text_ranges)) == 0)
216 return 0;
217 /* Corner case. Discard any symbols with the same value as
218 * _etext _einittext; they can move between pass 1 and 2 when
219 * the kallsyms data are added. If these symbols move then
220 * they may get dropped in pass 2, which breaks the kallsyms
221 * rules.
222 */
223 if ((s->addr == text_range_text->end &&
224 strcmp(name, text_range_text->end_sym)) ||
225 (s->addr == text_range_inittext->end &&
226 strcmp(name, text_range_inittext->end_sym)))
227 return 0;
228 }
229
230 return 1;
231}
232
233/* remove all the invalid symbols from the table */
234static void shrink_table(void)
235{
236 unsigned int i, pos;
237
238 pos = 0;
239 for (i = 0; i < table_cnt; i++) {
240 if (symbol_valid(table[i])) {
241 if (pos != i)
242 table[pos] = table[i];
243 pos++;
244 } else {
245 free(table[i]);
246 }
247 }
248 table_cnt = pos;
249
250 /* When valid symbol is not registered, exit to error */
251 if (!table_cnt) {
252 fprintf(stderr, "No valid symbol.\n");
253 exit(1);
254 }
255}
256
257static void read_map(const char *in)
258{
259 FILE *fp;
260 struct sym_entry *sym;
261 char *buf = NULL;
262 size_t buflen = 0;
263
264 fp = fopen(in, "r");
265 if (!fp) {
266 perror(in);
267 exit(1);
268 }
269
270 while (!feof(fp)) {
271 sym = read_symbol(fp, &buf, &buflen);
272 if (!sym)
273 continue;
274
275 sym->start_pos = table_cnt;
276
277 if (table_cnt >= table_size) {
278 table_size += 10000;
279 table = realloc(table, sizeof(*table) * table_size);
280 if (!table) {
281 fprintf(stderr, "out of memory\n");
282 fclose(fp);
283 exit (1);
284 }
285 }
286
287 table[table_cnt++] = sym;
288 }
289
290 free(buf);
291 fclose(fp);
292}
293
294static void output_label(const char *label)
295{
296 printf(".globl %s\n", label);
297 printf("\tALGN\n");
298 printf("%s:\n", label);
299}
300
301/* Provide proper symbols relocatability by their '_text' relativeness. */
302static void output_address(unsigned long long addr)
303{
304 if (_text <= addr)
305 printf("\tPTR\t_text + %#llx\n", addr - _text);
306 else
307 printf("\tPTR\t_text - %#llx\n", _text - addr);
308}
309
310/* uncompress a compressed symbol. When this function is called, the best table
311 * might still be compressed itself, so the function needs to be recursive */
312static int expand_symbol(const unsigned char *data, int len, char *result)
313{
314 int c, rlen, total=0;
315
316 while (len) {
317 c = *data;
318 /* if the table holds a single char that is the same as the one
319 * we are looking for, then end the search */
320 if (best_table[c][0]==c && best_table_len[c]==1) {
321 *result++ = c;
322 total++;
323 } else {
324 /* if not, recurse and expand */
325 rlen = expand_symbol(best_table[c], best_table_len[c], result);
326 total += rlen;
327 result += rlen;
328 }
329 data++;
330 len--;
331 }
332 *result=0;
333
334 return total;
335}
336
337static int symbol_absolute(const struct sym_entry *s)
338{
339 return s->percpu_absolute;
340}
341
342static void cleanup_symbol_name(char *s)
343{
344 char *p;
345
346 /*
347 * ASCII[.] = 2e
348 * ASCII[0-9] = 30,39
349 * ASCII[A-Z] = 41,5a
350 * ASCII[_] = 5f
351 * ASCII[a-z] = 61,7a
352 *
353 * As above, replacing the first '.' in ".llvm." with '\0' does not
354 * affect the main sorting, but it helps us with subsorting.
355 */
356 p = strstr(s, ".llvm.");
357 if (p)
358 *p = '\0';
359}
360
361static int compare_names(const void *a, const void *b)
362{
363 int ret;
364 const struct sym_entry *sa = *(const struct sym_entry **)a;
365 const struct sym_entry *sb = *(const struct sym_entry **)b;
366
367 ret = strcmp(sym_name(sa), sym_name(sb));
368 if (!ret) {
369 if (sa->addr > sb->addr)
370 return 1;
371 else if (sa->addr < sb->addr)
372 return -1;
373
374 /* keep old order */
375 return (int)(sa->seq - sb->seq);
376 }
377
378 return ret;
379}
380
381static void sort_symbols_by_name(void)
382{
383 qsort(table, table_cnt, sizeof(table[0]), compare_names);
384}
385
386static void write_src(void)
387{
388 unsigned int i, k, off;
389 unsigned int best_idx[256];
390 unsigned int *markers;
391 char buf[KSYM_NAME_LEN];
392
393 printf("#include <asm/bitsperlong.h>\n");
394 printf("#if BITS_PER_LONG == 64\n");
395 printf("#define PTR .quad\n");
396 printf("#define ALGN .balign 8\n");
397 printf("#else\n");
398 printf("#define PTR .long\n");
399 printf("#define ALGN .balign 4\n");
400 printf("#endif\n");
401
402 printf("\t.section .rodata, \"a\"\n");
403
404 output_label("kallsyms_num_syms");
405 printf("\t.long\t%u\n", table_cnt);
406 printf("\n");
407
408 /* table of offset markers, that give the offset in the compressed stream
409 * every 256 symbols */
410 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
411 if (!markers) {
412 fprintf(stderr, "kallsyms failure: "
413 "unable to allocate required memory\n");
414 exit(EXIT_FAILURE);
415 }
416
417 output_label("kallsyms_names");
418 off = 0;
419 for (i = 0; i < table_cnt; i++) {
420 if ((i & 0xFF) == 0)
421 markers[i >> 8] = off;
422 table[i]->seq = i;
423
424 /* There cannot be any symbol of length zero. */
425 if (table[i]->len == 0) {
426 fprintf(stderr, "kallsyms failure: "
427 "unexpected zero symbol length\n");
428 exit(EXIT_FAILURE);
429 }
430
431 /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
432 if (table[i]->len > 0x3FFF) {
433 fprintf(stderr, "kallsyms failure: "
434 "unexpected huge symbol length\n");
435 exit(EXIT_FAILURE);
436 }
437
438 /* Encode length with ULEB128. */
439 if (table[i]->len <= 0x7F) {
440 /* Most symbols use a single byte for the length. */
441 printf("\t.byte 0x%02x", table[i]->len);
442 off += table[i]->len + 1;
443 } else {
444 /* "Big" symbols use two bytes. */
445 printf("\t.byte 0x%02x, 0x%02x",
446 (table[i]->len & 0x7F) | 0x80,
447 (table[i]->len >> 7) & 0x7F);
448 off += table[i]->len + 2;
449 }
450 for (k = 0; k < table[i]->len; k++)
451 printf(", 0x%02x", table[i]->sym[k]);
452 printf("\n");
453 }
454 printf("\n");
455
456 /*
457 * Now that we wrote out the compressed symbol names, restore the
458 * original names, which are needed in some of the later steps.
459 */
460 for (i = 0; i < table_cnt; i++) {
461 expand_symbol(table[i]->sym, table[i]->len, buf);
462 strcpy((char *)table[i]->sym, buf);
463 }
464
465 output_label("kallsyms_markers");
466 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
467 printf("\t.long\t%u\n", markers[i]);
468 printf("\n");
469
470 free(markers);
471
472 output_label("kallsyms_token_table");
473 off = 0;
474 for (i = 0; i < 256; i++) {
475 best_idx[i] = off;
476 expand_symbol(best_table[i], best_table_len[i], buf);
477 printf("\t.asciz\t\"%s\"\n", buf);
478 off += strlen(buf) + 1;
479 }
480 printf("\n");
481
482 output_label("kallsyms_token_index");
483 for (i = 0; i < 256; i++)
484 printf("\t.short\t%d\n", best_idx[i]);
485 printf("\n");
486
487 if (!base_relative)
488 output_label("kallsyms_addresses");
489 else
490 output_label("kallsyms_offsets");
491
492 for (i = 0; i < table_cnt; i++) {
493 if (base_relative) {
494 /*
495 * Use the offset relative to the lowest value
496 * encountered of all relative symbols, and emit
497 * non-relocatable fixed offsets that will be fixed
498 * up at runtime.
499 */
500
501 long long offset;
502 int overflow;
503
504 if (!absolute_percpu) {
505 offset = table[i]->addr - relative_base;
506 overflow = (offset < 0 || offset > UINT_MAX);
507 } else if (symbol_absolute(table[i])) {
508 offset = table[i]->addr;
509 overflow = (offset < 0 || offset > INT_MAX);
510 } else {
511 offset = relative_base - table[i]->addr - 1;
512 overflow = (offset < INT_MIN || offset >= 0);
513 }
514 if (overflow) {
515 fprintf(stderr, "kallsyms failure: "
516 "%s symbol value %#llx out of range in relative mode\n",
517 symbol_absolute(table[i]) ? "absolute" : "relative",
518 table[i]->addr);
519 exit(EXIT_FAILURE);
520 }
521 printf("\t.long\t%#x /* %s */\n", (int)offset, table[i]->sym);
522 } else if (!symbol_absolute(table[i])) {
523 output_address(table[i]->addr);
524 } else {
525 printf("\tPTR\t%#llx\n", table[i]->addr);
526 }
527 }
528 printf("\n");
529
530 if (base_relative) {
531 output_label("kallsyms_relative_base");
532 output_address(relative_base);
533 printf("\n");
534 }
535
536 if (lto_clang)
537 for (i = 0; i < table_cnt; i++)
538 cleanup_symbol_name((char *)table[i]->sym);
539
540 sort_symbols_by_name();
541 output_label("kallsyms_seqs_of_names");
542 for (i = 0; i < table_cnt; i++)
543 printf("\t.byte 0x%02x, 0x%02x, 0x%02x\n",
544 (unsigned char)(table[i]->seq >> 16),
545 (unsigned char)(table[i]->seq >> 8),
546 (unsigned char)(table[i]->seq >> 0));
547 printf("\n");
548}
549
550
551/* table lookup compression functions */
552
553/* count all the possible tokens in a symbol */
554static void learn_symbol(const unsigned char *symbol, int len)
555{
556 int i;
557
558 for (i = 0; i < len - 1; i++)
559 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
560}
561
562/* decrease the count for all the possible tokens in a symbol */
563static void forget_symbol(const unsigned char *symbol, int len)
564{
565 int i;
566
567 for (i = 0; i < len - 1; i++)
568 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
569}
570
571/* do the initial token count */
572static void build_initial_token_table(void)
573{
574 unsigned int i;
575
576 for (i = 0; i < table_cnt; i++)
577 learn_symbol(table[i]->sym, table[i]->len);
578}
579
580static unsigned char *find_token(unsigned char *str, int len,
581 const unsigned char *token)
582{
583 int i;
584
585 for (i = 0; i < len - 1; i++) {
586 if (str[i] == token[0] && str[i+1] == token[1])
587 return &str[i];
588 }
589 return NULL;
590}
591
592/* replace a given token in all the valid symbols. Use the sampled symbols
593 * to update the counts */
594static void compress_symbols(const unsigned char *str, int idx)
595{
596 unsigned int i, len, size;
597 unsigned char *p1, *p2;
598
599 for (i = 0; i < table_cnt; i++) {
600
601 len = table[i]->len;
602 p1 = table[i]->sym;
603
604 /* find the token on the symbol */
605 p2 = find_token(p1, len, str);
606 if (!p2) continue;
607
608 /* decrease the counts for this symbol's tokens */
609 forget_symbol(table[i]->sym, len);
610
611 size = len;
612
613 do {
614 *p2 = idx;
615 p2++;
616 size -= (p2 - p1);
617 memmove(p2, p2 + 1, size);
618 p1 = p2;
619 len--;
620
621 if (size < 2) break;
622
623 /* find the token on the symbol */
624 p2 = find_token(p1, size, str);
625
626 } while (p2);
627
628 table[i]->len = len;
629
630 /* increase the counts for this symbol's new tokens */
631 learn_symbol(table[i]->sym, len);
632 }
633}
634
635/* search the token with the maximum profit */
636static int find_best_token(void)
637{
638 int i, best, bestprofit;
639
640 bestprofit=-10000;
641 best = 0;
642
643 for (i = 0; i < 0x10000; i++) {
644 if (token_profit[i] > bestprofit) {
645 best = i;
646 bestprofit = token_profit[i];
647 }
648 }
649 return best;
650}
651
652/* this is the core of the algorithm: calculate the "best" table */
653static void optimize_result(void)
654{
655 int i, best;
656
657 /* using the '\0' symbol last allows compress_symbols to use standard
658 * fast string functions */
659 for (i = 255; i >= 0; i--) {
660
661 /* if this table slot is empty (it is not used by an actual
662 * original char code */
663 if (!best_table_len[i]) {
664
665 /* find the token with the best profit value */
666 best = find_best_token();
667 if (token_profit[best] == 0)
668 break;
669
670 /* place it in the "best" table */
671 best_table_len[i] = 2;
672 best_table[i][0] = best & 0xFF;
673 best_table[i][1] = (best >> 8) & 0xFF;
674
675 /* replace this token in all the valid symbols */
676 compress_symbols(best_table[i], i);
677 }
678 }
679}
680
681/* start by placing the symbols that are actually used on the table */
682static void insert_real_symbols_in_table(void)
683{
684 unsigned int i, j, c;
685
686 for (i = 0; i < table_cnt; i++) {
687 for (j = 0; j < table[i]->len; j++) {
688 c = table[i]->sym[j];
689 best_table[c][0]=c;
690 best_table_len[c]=1;
691 }
692 }
693}
694
695static void optimize_token_table(void)
696{
697 build_initial_token_table();
698
699 insert_real_symbols_in_table();
700
701 optimize_result();
702}
703
704/* guess for "linker script provide" symbol */
705static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
706{
707 const char *symbol = sym_name(se);
708 int len = se->len - 1;
709
710 if (len < 8)
711 return 0;
712
713 if (symbol[0] != '_' || symbol[1] != '_')
714 return 0;
715
716 /* __start_XXXXX */
717 if (!memcmp(symbol + 2, "start_", 6))
718 return 1;
719
720 /* __stop_XXXXX */
721 if (!memcmp(symbol + 2, "stop_", 5))
722 return 1;
723
724 /* __end_XXXXX */
725 if (!memcmp(symbol + 2, "end_", 4))
726 return 1;
727
728 /* __XXXXX_start */
729 if (!memcmp(symbol + len - 6, "_start", 6))
730 return 1;
731
732 /* __XXXXX_end */
733 if (!memcmp(symbol + len - 4, "_end", 4))
734 return 1;
735
736 return 0;
737}
738
739static int compare_symbols(const void *a, const void *b)
740{
741 const struct sym_entry *sa = *(const struct sym_entry **)a;
742 const struct sym_entry *sb = *(const struct sym_entry **)b;
743 int wa, wb;
744
745 /* sort by address first */
746 if (sa->addr > sb->addr)
747 return 1;
748 if (sa->addr < sb->addr)
749 return -1;
750
751 /* sort by "weakness" type */
752 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
753 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
754 if (wa != wb)
755 return wa - wb;
756
757 /* sort by "linker script provide" type */
758 wa = may_be_linker_script_provide_symbol(sa);
759 wb = may_be_linker_script_provide_symbol(sb);
760 if (wa != wb)
761 return wa - wb;
762
763 /* sort by the number of prefix underscores */
764 wa = strspn(sym_name(sa), "_");
765 wb = strspn(sym_name(sb), "_");
766 if (wa != wb)
767 return wa - wb;
768
769 /* sort by initial order, so that other symbols are left undisturbed */
770 return sa->start_pos - sb->start_pos;
771}
772
773static void sort_symbols(void)
774{
775 qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
776}
777
778static void make_percpus_absolute(void)
779{
780 unsigned int i;
781
782 for (i = 0; i < table_cnt; i++)
783 if (symbol_in_range(table[i], &percpu_range, 1)) {
784 /*
785 * Keep the 'A' override for percpu symbols to
786 * ensure consistent behavior compared to older
787 * versions of this tool.
788 */
789 table[i]->sym[0] = 'A';
790 table[i]->percpu_absolute = 1;
791 }
792}
793
794/* find the minimum non-absolute symbol address */
795static void record_relative_base(void)
796{
797 unsigned int i;
798
799 for (i = 0; i < table_cnt; i++)
800 if (!symbol_absolute(table[i])) {
801 /*
802 * The table is sorted by address.
803 * Take the first non-absolute symbol value.
804 */
805 relative_base = table[i]->addr;
806 return;
807 }
808}
809
810int main(int argc, char **argv)
811{
812 while (1) {
813 static const struct option long_options[] = {
814 {"all-symbols", no_argument, &all_symbols, 1},
815 {"absolute-percpu", no_argument, &absolute_percpu, 1},
816 {"base-relative", no_argument, &base_relative, 1},
817 {"lto-clang", no_argument, <o_clang, 1},
818 {},
819 };
820
821 int c = getopt_long(argc, argv, "", long_options, NULL);
822
823 if (c == -1)
824 break;
825 if (c != 0)
826 usage();
827 }
828
829 if (optind >= argc)
830 usage();
831
832 read_map(argv[optind]);
833 shrink_table();
834 if (absolute_percpu)
835 make_percpus_absolute();
836 sort_symbols();
837 if (base_relative)
838 record_relative_base();
839 optimize_token_table();
840 write_src();
841
842 return 0;
843}
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}