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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};
52#define text_range_text (&text_ranges[0])
53#define text_range_inittext (&text_ranges[1])
54
55static struct addr_range percpu_range = {
56 "__per_cpu_start", "__per_cpu_end", -1ULL, 0
57};
58
59static struct sym_entry *table;
60static unsigned int table_size, table_cnt;
61static int all_symbols = 0;
62static int absolute_percpu = 0;
63static int base_relative = 0;
64
65static int token_profit[0x10000];
66
67/* the table that holds the result of the compression */
68static unsigned char best_table[256][2];
69static unsigned char best_table_len[256];
70
71
72static void usage(void)
73{
74 fprintf(stderr, "Usage: kallsyms [--all-symbols] "
75 "[--base-relative] < in.map > out.S\n");
76 exit(1);
77}
78
79/*
80 * This ignores the intensely annoying "mapping symbols" found
81 * in ARM ELF files: $a, $t and $d.
82 */
83static int is_arm_mapping_symbol(const char *str)
84{
85 return str[0] == '$' && strchr("axtd", str[1])
86 && (str[2] == '\0' || str[2] == '.');
87}
88
89static int check_symbol_range(const char *sym, unsigned long long addr,
90 struct addr_range *ranges, int entries)
91{
92 size_t i;
93 struct addr_range *ar;
94
95 for (i = 0; i < entries; ++i) {
96 ar = &ranges[i];
97
98 if (strcmp(sym, ar->start_sym) == 0) {
99 ar->start = addr;
100 return 0;
101 } else if (strcmp(sym, ar->end_sym) == 0) {
102 ar->end = addr;
103 return 0;
104 }
105 }
106
107 return 1;
108}
109
110static int read_symbol(FILE *in, struct sym_entry *s)
111{
112 char sym[500], stype;
113 int rc;
114
115 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, sym);
116 if (rc != 3) {
117 if (rc != EOF && fgets(sym, 500, in) == NULL)
118 fprintf(stderr, "Read error or end of file.\n");
119 return -1;
120 }
121 if (strlen(sym) >= KSYM_NAME_LEN) {
122 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
123 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
124 sym, strlen(sym), KSYM_NAME_LEN);
125 return -1;
126 }
127
128 /* Ignore most absolute/undefined (?) symbols. */
129 if (strcmp(sym, "_text") == 0)
130 _text = s->addr;
131 else if (check_symbol_range(sym, s->addr, text_ranges,
132 ARRAY_SIZE(text_ranges)) == 0)
133 /* nothing to do */;
134 else if (toupper(stype) == 'A')
135 {
136 /* Keep these useful absolute symbols */
137 if (strcmp(sym, "__kernel_syscall_via_break") &&
138 strcmp(sym, "__kernel_syscall_via_epc") &&
139 strcmp(sym, "__kernel_sigtramp") &&
140 strcmp(sym, "__gp"))
141 return -1;
142
143 }
144 else if (toupper(stype) == 'U' ||
145 is_arm_mapping_symbol(sym))
146 return -1;
147 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
148 else if (sym[0] == '$')
149 return -1;
150 /* exclude debugging symbols */
151 else if (stype == 'N' || stype == 'n')
152 return -1;
153 /* exclude s390 kasan local symbols */
154 else if (!strncmp(sym, ".LASANPC", 8))
155 return -1;
156
157 /* include the type field in the symbol name, so that it gets
158 * compressed together */
159 s->len = strlen(sym) + 1;
160 s->sym = malloc(s->len + 1);
161 if (!s->sym) {
162 fprintf(stderr, "kallsyms failure: "
163 "unable to allocate required amount of memory\n");
164 exit(EXIT_FAILURE);
165 }
166 strcpy((char *)s->sym + 1, sym);
167 s->sym[0] = stype;
168
169 s->percpu_absolute = 0;
170
171 /* Record if we've found __per_cpu_start/end. */
172 check_symbol_range(sym, s->addr, &percpu_range, 1);
173
174 return 0;
175}
176
177static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges,
178 int entries)
179{
180 size_t i;
181 struct addr_range *ar;
182
183 for (i = 0; i < entries; ++i) {
184 ar = &ranges[i];
185
186 if (s->addr >= ar->start && s->addr <= ar->end)
187 return 1;
188 }
189
190 return 0;
191}
192
193static int symbol_valid(struct sym_entry *s)
194{
195 /* Symbols which vary between passes. Passes 1 and 2 must have
196 * identical symbol lists. The kallsyms_* symbols below are only added
197 * after pass 1, they would be included in pass 2 when --all-symbols is
198 * specified so exclude them to get a stable symbol list.
199 */
200 static char *special_symbols[] = {
201 "kallsyms_addresses",
202 "kallsyms_offsets",
203 "kallsyms_relative_base",
204 "kallsyms_num_syms",
205 "kallsyms_names",
206 "kallsyms_markers",
207 "kallsyms_token_table",
208 "kallsyms_token_index",
209
210 /* Exclude linker generated symbols which vary between passes */
211 "_SDA_BASE_", /* ppc */
212 "_SDA2_BASE_", /* ppc */
213 NULL };
214
215 static char *special_prefixes[] = {
216 "__crc_", /* modversions */
217 "__efistub_", /* arm64 EFI stub namespace */
218 NULL };
219
220 static char *special_suffixes[] = {
221 "_veneer", /* arm */
222 "_from_arm", /* arm */
223 "_from_thumb", /* arm */
224 NULL };
225
226 int i;
227 char *sym_name = (char *)s->sym + 1;
228
229 /* if --all-symbols is not specified, then symbols outside the text
230 * and inittext sections are discarded */
231 if (!all_symbols) {
232 if (symbol_in_range(s, text_ranges,
233 ARRAY_SIZE(text_ranges)) == 0)
234 return 0;
235 /* Corner case. Discard any symbols with the same value as
236 * _etext _einittext; they can move between pass 1 and 2 when
237 * the kallsyms data are added. If these symbols move then
238 * they may get dropped in pass 2, which breaks the kallsyms
239 * rules.
240 */
241 if ((s->addr == text_range_text->end &&
242 strcmp(sym_name,
243 text_range_text->end_sym)) ||
244 (s->addr == text_range_inittext->end &&
245 strcmp(sym_name,
246 text_range_inittext->end_sym)))
247 return 0;
248 }
249
250 /* Exclude symbols which vary between passes. */
251 for (i = 0; special_symbols[i]; i++)
252 if (strcmp(sym_name, special_symbols[i]) == 0)
253 return 0;
254
255 for (i = 0; special_prefixes[i]; i++) {
256 int l = strlen(special_prefixes[i]);
257
258 if (l <= strlen(sym_name) &&
259 strncmp(sym_name, special_prefixes[i], l) == 0)
260 return 0;
261 }
262
263 for (i = 0; special_suffixes[i]; i++) {
264 int l = strlen(sym_name) - strlen(special_suffixes[i]);
265
266 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0)
267 return 0;
268 }
269
270 return 1;
271}
272
273static void read_map(FILE *in)
274{
275 while (!feof(in)) {
276 if (table_cnt >= table_size) {
277 table_size += 10000;
278 table = realloc(table, sizeof(*table) * table_size);
279 if (!table) {
280 fprintf(stderr, "out of memory\n");
281 exit (1);
282 }
283 }
284 if (read_symbol(in, &table[table_cnt]) == 0) {
285 table[table_cnt].start_pos = table_cnt;
286 table_cnt++;
287 }
288 }
289}
290
291static void output_label(char *label)
292{
293 printf(".globl %s\n", label);
294 printf("\tALGN\n");
295 printf("%s:\n", label);
296}
297
298/* uncompress a compressed symbol. When this function is called, the best table
299 * might still be compressed itself, so the function needs to be recursive */
300static int expand_symbol(unsigned char *data, int len, char *result)
301{
302 int c, rlen, total=0;
303
304 while (len) {
305 c = *data;
306 /* if the table holds a single char that is the same as the one
307 * we are looking for, then end the search */
308 if (best_table[c][0]==c && best_table_len[c]==1) {
309 *result++ = c;
310 total++;
311 } else {
312 /* if not, recurse and expand */
313 rlen = expand_symbol(best_table[c], best_table_len[c], result);
314 total += rlen;
315 result += rlen;
316 }
317 data++;
318 len--;
319 }
320 *result=0;
321
322 return total;
323}
324
325static int symbol_absolute(struct sym_entry *s)
326{
327 return s->percpu_absolute;
328}
329
330static void write_src(void)
331{
332 unsigned int i, k, off;
333 unsigned int best_idx[256];
334 unsigned int *markers;
335 char buf[KSYM_NAME_LEN];
336
337 printf("#include <asm/bitsperlong.h>\n");
338 printf("#if BITS_PER_LONG == 64\n");
339 printf("#define PTR .quad\n");
340 printf("#define ALGN .balign 8\n");
341 printf("#else\n");
342 printf("#define PTR .long\n");
343 printf("#define ALGN .balign 4\n");
344 printf("#endif\n");
345
346 printf("\t.section .rodata, \"a\"\n");
347
348 /* Provide proper symbols relocatability by their relativeness
349 * to a fixed anchor point in the runtime image, either '_text'
350 * for absolute address tables, in which case the linker will
351 * emit the final addresses at build time. Otherwise, use the
352 * offset relative to the lowest value encountered of all relative
353 * symbols, and emit non-relocatable fixed offsets that will be fixed
354 * up at runtime.
355 *
356 * The symbol names cannot be used to construct normal symbol
357 * references as the list of symbols contains symbols that are
358 * declared static and are private to their .o files. This prevents
359 * .tmp_kallsyms.o or any other object from referencing them.
360 */
361 if (!base_relative)
362 output_label("kallsyms_addresses");
363 else
364 output_label("kallsyms_offsets");
365
366 for (i = 0; i < table_cnt; i++) {
367 if (base_relative) {
368 long long offset;
369 int overflow;
370
371 if (!absolute_percpu) {
372 offset = table[i].addr - relative_base;
373 overflow = (offset < 0 || offset > UINT_MAX);
374 } else if (symbol_absolute(&table[i])) {
375 offset = table[i].addr;
376 overflow = (offset < 0 || offset > INT_MAX);
377 } else {
378 offset = relative_base - table[i].addr - 1;
379 overflow = (offset < INT_MIN || offset >= 0);
380 }
381 if (overflow) {
382 fprintf(stderr, "kallsyms failure: "
383 "%s symbol value %#llx out of range in relative mode\n",
384 symbol_absolute(&table[i]) ? "absolute" : "relative",
385 table[i].addr);
386 exit(EXIT_FAILURE);
387 }
388 printf("\t.long\t%#x\n", (int)offset);
389 } else if (!symbol_absolute(&table[i])) {
390 if (_text <= table[i].addr)
391 printf("\tPTR\t_text + %#llx\n",
392 table[i].addr - _text);
393 else
394 printf("\tPTR\t_text - %#llx\n",
395 _text - table[i].addr);
396 } else {
397 printf("\tPTR\t%#llx\n", table[i].addr);
398 }
399 }
400 printf("\n");
401
402 if (base_relative) {
403 output_label("kallsyms_relative_base");
404 printf("\tPTR\t_text - %#llx\n", _text - relative_base);
405 printf("\n");
406 }
407
408 output_label("kallsyms_num_syms");
409 printf("\t.long\t%u\n", table_cnt);
410 printf("\n");
411
412 /* table of offset markers, that give the offset in the compressed stream
413 * every 256 symbols */
414 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
415 if (!markers) {
416 fprintf(stderr, "kallsyms failure: "
417 "unable to allocate required memory\n");
418 exit(EXIT_FAILURE);
419 }
420
421 output_label("kallsyms_names");
422 off = 0;
423 for (i = 0; i < table_cnt; i++) {
424 if ((i & 0xFF) == 0)
425 markers[i >> 8] = off;
426
427 printf("\t.byte 0x%02x", table[i].len);
428 for (k = 0; k < table[i].len; k++)
429 printf(", 0x%02x", table[i].sym[k]);
430 printf("\n");
431
432 off += table[i].len + 1;
433 }
434 printf("\n");
435
436 output_label("kallsyms_markers");
437 for (i = 0; i < ((table_cnt + 255) >> 8); i++)
438 printf("\t.long\t%u\n", markers[i]);
439 printf("\n");
440
441 free(markers);
442
443 output_label("kallsyms_token_table");
444 off = 0;
445 for (i = 0; i < 256; i++) {
446 best_idx[i] = off;
447 expand_symbol(best_table[i], best_table_len[i], buf);
448 printf("\t.asciz\t\"%s\"\n", buf);
449 off += strlen(buf) + 1;
450 }
451 printf("\n");
452
453 output_label("kallsyms_token_index");
454 for (i = 0; i < 256; i++)
455 printf("\t.short\t%d\n", best_idx[i]);
456 printf("\n");
457}
458
459
460/* table lookup compression functions */
461
462/* count all the possible tokens in a symbol */
463static void learn_symbol(unsigned char *symbol, int len)
464{
465 int i;
466
467 for (i = 0; i < len - 1; i++)
468 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
469}
470
471/* decrease the count for all the possible tokens in a symbol */
472static void forget_symbol(unsigned char *symbol, int len)
473{
474 int i;
475
476 for (i = 0; i < len - 1; i++)
477 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
478}
479
480/* remove all the invalid symbols from the table and do the initial token count */
481static void build_initial_tok_table(void)
482{
483 unsigned int i, pos;
484
485 pos = 0;
486 for (i = 0; i < table_cnt; i++) {
487 if ( symbol_valid(&table[i]) ) {
488 if (pos != i)
489 table[pos] = table[i];
490 learn_symbol(table[pos].sym, table[pos].len);
491 pos++;
492 }
493 }
494 table_cnt = pos;
495}
496
497static void *find_token(unsigned char *str, int len, unsigned char *token)
498{
499 int i;
500
501 for (i = 0; i < len - 1; i++) {
502 if (str[i] == token[0] && str[i+1] == token[1])
503 return &str[i];
504 }
505 return NULL;
506}
507
508/* replace a given token in all the valid symbols. Use the sampled symbols
509 * to update the counts */
510static void compress_symbols(unsigned char *str, int idx)
511{
512 unsigned int i, len, size;
513 unsigned char *p1, *p2;
514
515 for (i = 0; i < table_cnt; i++) {
516
517 len = table[i].len;
518 p1 = table[i].sym;
519
520 /* find the token on the symbol */
521 p2 = find_token(p1, len, str);
522 if (!p2) continue;
523
524 /* decrease the counts for this symbol's tokens */
525 forget_symbol(table[i].sym, len);
526
527 size = len;
528
529 do {
530 *p2 = idx;
531 p2++;
532 size -= (p2 - p1);
533 memmove(p2, p2 + 1, size);
534 p1 = p2;
535 len--;
536
537 if (size < 2) break;
538
539 /* find the token on the symbol */
540 p2 = find_token(p1, size, str);
541
542 } while (p2);
543
544 table[i].len = len;
545
546 /* increase the counts for this symbol's new tokens */
547 learn_symbol(table[i].sym, len);
548 }
549}
550
551/* search the token with the maximum profit */
552static int find_best_token(void)
553{
554 int i, best, bestprofit;
555
556 bestprofit=-10000;
557 best = 0;
558
559 for (i = 0; i < 0x10000; i++) {
560 if (token_profit[i] > bestprofit) {
561 best = i;
562 bestprofit = token_profit[i];
563 }
564 }
565 return best;
566}
567
568/* this is the core of the algorithm: calculate the "best" table */
569static void optimize_result(void)
570{
571 int i, best;
572
573 /* using the '\0' symbol last allows compress_symbols to use standard
574 * fast string functions */
575 for (i = 255; i >= 0; i--) {
576
577 /* if this table slot is empty (it is not used by an actual
578 * original char code */
579 if (!best_table_len[i]) {
580
581 /* find the token with the best profit value */
582 best = find_best_token();
583 if (token_profit[best] == 0)
584 break;
585
586 /* place it in the "best" table */
587 best_table_len[i] = 2;
588 best_table[i][0] = best & 0xFF;
589 best_table[i][1] = (best >> 8) & 0xFF;
590
591 /* replace this token in all the valid symbols */
592 compress_symbols(best_table[i], i);
593 }
594 }
595}
596
597/* start by placing the symbols that are actually used on the table */
598static void insert_real_symbols_in_table(void)
599{
600 unsigned int i, j, c;
601
602 for (i = 0; i < table_cnt; i++) {
603 for (j = 0; j < table[i].len; j++) {
604 c = table[i].sym[j];
605 best_table[c][0]=c;
606 best_table_len[c]=1;
607 }
608 }
609}
610
611static void optimize_token_table(void)
612{
613 build_initial_tok_table();
614
615 insert_real_symbols_in_table();
616
617 /* When valid symbol is not registered, exit to error */
618 if (!table_cnt) {
619 fprintf(stderr, "No valid symbol.\n");
620 exit(1);
621 }
622
623 optimize_result();
624}
625
626/* guess for "linker script provide" symbol */
627static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
628{
629 const char *symbol = (char *)se->sym + 1;
630 int len = se->len - 1;
631
632 if (len < 8)
633 return 0;
634
635 if (symbol[0] != '_' || symbol[1] != '_')
636 return 0;
637
638 /* __start_XXXXX */
639 if (!memcmp(symbol + 2, "start_", 6))
640 return 1;
641
642 /* __stop_XXXXX */
643 if (!memcmp(symbol + 2, "stop_", 5))
644 return 1;
645
646 /* __end_XXXXX */
647 if (!memcmp(symbol + 2, "end_", 4))
648 return 1;
649
650 /* __XXXXX_start */
651 if (!memcmp(symbol + len - 6, "_start", 6))
652 return 1;
653
654 /* __XXXXX_end */
655 if (!memcmp(symbol + len - 4, "_end", 4))
656 return 1;
657
658 return 0;
659}
660
661static int prefix_underscores_count(const char *str)
662{
663 const char *tail = str;
664
665 while (*tail == '_')
666 tail++;
667
668 return tail - str;
669}
670
671static int compare_symbols(const void *a, const void *b)
672{
673 const struct sym_entry *sa;
674 const struct sym_entry *sb;
675 int wa, wb;
676
677 sa = a;
678 sb = b;
679
680 /* sort by address first */
681 if (sa->addr > sb->addr)
682 return 1;
683 if (sa->addr < sb->addr)
684 return -1;
685
686 /* sort by "weakness" type */
687 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
688 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
689 if (wa != wb)
690 return wa - wb;
691
692 /* sort by "linker script provide" type */
693 wa = may_be_linker_script_provide_symbol(sa);
694 wb = may_be_linker_script_provide_symbol(sb);
695 if (wa != wb)
696 return wa - wb;
697
698 /* sort by the number of prefix underscores */
699 wa = prefix_underscores_count((const char *)sa->sym + 1);
700 wb = prefix_underscores_count((const char *)sb->sym + 1);
701 if (wa != wb)
702 return wa - wb;
703
704 /* sort by initial order, so that other symbols are left undisturbed */
705 return sa->start_pos - sb->start_pos;
706}
707
708static void sort_symbols(void)
709{
710 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
711}
712
713static void make_percpus_absolute(void)
714{
715 unsigned int i;
716
717 for (i = 0; i < table_cnt; i++)
718 if (symbol_in_range(&table[i], &percpu_range, 1)) {
719 /*
720 * Keep the 'A' override for percpu symbols to
721 * ensure consistent behavior compared to older
722 * versions of this tool.
723 */
724 table[i].sym[0] = 'A';
725 table[i].percpu_absolute = 1;
726 }
727}
728
729/* find the minimum non-absolute symbol address */
730static void record_relative_base(void)
731{
732 unsigned int i;
733
734 relative_base = -1ULL;
735 for (i = 0; i < table_cnt; i++)
736 if (!symbol_absolute(&table[i]) &&
737 table[i].addr < relative_base)
738 relative_base = table[i].addr;
739}
740
741int main(int argc, char **argv)
742{
743 if (argc >= 2) {
744 int i;
745 for (i = 1; i < argc; i++) {
746 if(strcmp(argv[i], "--all-symbols") == 0)
747 all_symbols = 1;
748 else if (strcmp(argv[i], "--absolute-percpu") == 0)
749 absolute_percpu = 1;
750 else if (strcmp(argv[i], "--base-relative") == 0)
751 base_relative = 1;
752 else
753 usage();
754 }
755 } else if (argc != 1)
756 usage();
757
758 read_map(stdin);
759 if (absolute_percpu)
760 make_percpus_absolute();
761 if (base_relative)
762 record_relative_base();
763 sort_symbols();
764 optimize_token_table();
765 write_src();
766
767 return 0;
768}