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