xref: /openbmc/linux/scripts/kallsyms.c (revision 051d4420)
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] 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 <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 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
31 
32 #define _stringify_1(x)	#x
33 #define _stringify(x)	_stringify_1(x)
34 
35 #define KSYM_NAME_LEN		512
36 
37 /*
38  * A substantially bigger size than the current maximum.
39  *
40  * It cannot be defined as an expression because it gets stringified
41  * for the fscanf() format string. Therefore, a _Static_assert() is
42  * used instead to maintain the relationship with KSYM_NAME_LEN.
43  */
44 #define KSYM_NAME_LEN_BUFFER	2048
45 _Static_assert(
46 	KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4,
47 	"Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"
48 );
49 
50 struct sym_entry {
51 	unsigned long long addr;
52 	unsigned int len;
53 	unsigned int seq;
54 	unsigned int start_pos;
55 	unsigned int percpu_absolute;
56 	unsigned char sym[];
57 };
58 
59 struct addr_range {
60 	const char *start_sym, *end_sym;
61 	unsigned long long start, end;
62 };
63 
64 static unsigned long long _text;
65 static unsigned long long relative_base;
66 static struct addr_range text_ranges[] = {
67 	{ "_stext",     "_etext"     },
68 	{ "_sinittext", "_einittext" },
69 };
70 #define text_range_text     (&text_ranges[0])
71 #define text_range_inittext (&text_ranges[1])
72 
73 static struct addr_range percpu_range = {
74 	"__per_cpu_start", "__per_cpu_end", -1ULL, 0
75 };
76 
77 static struct sym_entry **table;
78 static unsigned int table_size, table_cnt;
79 static int all_symbols;
80 static int absolute_percpu;
81 static int base_relative;
82 static int lto_clang;
83 
84 static int token_profit[0x10000];
85 
86 /* the table that holds the result of the compression */
87 static unsigned char best_table[256][2];
88 static unsigned char best_table_len[256];
89 
90 
91 static void usage(void)
92 {
93 	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
94 			"[--base-relative] [--lto-clang] in.map > out.S\n");
95 	exit(1);
96 }
97 
98 static char *sym_name(const struct sym_entry *s)
99 {
100 	return (char *)s->sym + 1;
101 }
102 
103 static bool is_ignored_symbol(const char *name, char type)
104 {
105 	/* Symbol names that exactly match to the following are ignored.*/
106 	static const char * const ignored_symbols[] = {
107 		/*
108 		 * Symbols which vary between passes. Passes 1 and 2 must have
109 		 * identical symbol lists. The kallsyms_* symbols below are
110 		 * only added after pass 1, they would be included in pass 2
111 		 * when --all-symbols is specified so exclude them to get a
112 		 * stable symbol list.
113 		 */
114 		"kallsyms_addresses",
115 		"kallsyms_offsets",
116 		"kallsyms_relative_base",
117 		"kallsyms_num_syms",
118 		"kallsyms_names",
119 		"kallsyms_markers",
120 		"kallsyms_token_table",
121 		"kallsyms_token_index",
122 		/* Exclude linker generated symbols which vary between passes */
123 		"_SDA_BASE_",		/* ppc */
124 		"_SDA2_BASE_",		/* ppc */
125 		NULL
126 	};
127 
128 	/* Symbol names that begin with the following are ignored.*/
129 	static const char * const ignored_prefixes[] = {
130 		"__efistub_",		/* arm64 EFI stub namespace */
131 		"__kvm_nvhe_$",		/* arm64 local symbols in non-VHE KVM namespace */
132 		"__kvm_nvhe_.L",	/* arm64 local symbols in non-VHE KVM namespace */
133 		"__AArch64ADRPThunk_",	/* arm64 lld */
134 		"__ARMV5PILongThunk_",	/* arm lld */
135 		"__ARMV7PILongThunk_",
136 		"__ThumbV7PILongThunk_",
137 		"__LA25Thunk_",		/* mips lld */
138 		"__microLA25Thunk_",
139 		"__kcfi_typeid_",	/* CFI type identifiers */
140 		NULL
141 	};
142 
143 	/* Symbol names that end with the following are ignored.*/
144 	static const char * const ignored_suffixes[] = {
145 		"_from_arm",		/* arm */
146 		"_from_thumb",		/* arm */
147 		"_veneer",		/* arm */
148 		NULL
149 	};
150 
151 	/* Symbol names that contain the following are ignored.*/
152 	static const char * const ignored_matches[] = {
153 		".long_branch.",	/* ppc stub */
154 		".plt_branch.",		/* ppc stub */
155 		NULL
156 	};
157 
158 	const char * const *p;
159 
160 	for (p = ignored_symbols; *p; p++)
161 		if (!strcmp(name, *p))
162 			return true;
163 
164 	for (p = ignored_prefixes; *p; p++)
165 		if (!strncmp(name, *p, strlen(*p)))
166 			return true;
167 
168 	for (p = ignored_suffixes; *p; p++) {
169 		int l = strlen(name) - strlen(*p);
170 
171 		if (l >= 0 && !strcmp(name + l, *p))
172 			return true;
173 	}
174 
175 	for (p = ignored_matches; *p; p++) {
176 		if (strstr(name, *p))
177 			return true;
178 	}
179 
180 	if (type == 'U' || type == 'u')
181 		return true;
182 	/* exclude debugging symbols */
183 	if (type == 'N' || type == 'n')
184 		return true;
185 
186 	if (toupper(type) == 'A') {
187 		/* Keep these useful absolute symbols */
188 		if (strcmp(name, "__kernel_syscall_via_break") &&
189 		    strcmp(name, "__kernel_syscall_via_epc") &&
190 		    strcmp(name, "__kernel_sigtramp") &&
191 		    strcmp(name, "__gp"))
192 			return true;
193 	}
194 
195 	return false;
196 }
197 
198 static void check_symbol_range(const char *sym, unsigned long long addr,
199 			       struct addr_range *ranges, int entries)
200 {
201 	size_t i;
202 	struct addr_range *ar;
203 
204 	for (i = 0; i < entries; ++i) {
205 		ar = &ranges[i];
206 
207 		if (strcmp(sym, ar->start_sym) == 0) {
208 			ar->start = addr;
209 			return;
210 		} else if (strcmp(sym, ar->end_sym) == 0) {
211 			ar->end = addr;
212 			return;
213 		}
214 	}
215 }
216 
217 static struct sym_entry *read_symbol(FILE *in)
218 {
219 	char name[KSYM_NAME_LEN_BUFFER+1], type;
220 	unsigned long long addr;
221 	unsigned int len;
222 	struct sym_entry *sym;
223 	int rc;
224 
225 	rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);
226 	if (rc != 3) {
227 		if (rc != EOF && fgets(name, ARRAY_SIZE(name), in) == NULL)
228 			fprintf(stderr, "Read error or end of file.\n");
229 		return NULL;
230 	}
231 	if (strlen(name) >= KSYM_NAME_LEN) {
232 		fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
233 				"Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
234 			name, strlen(name), KSYM_NAME_LEN);
235 		return NULL;
236 	}
237 
238 	if (strcmp(name, "_text") == 0)
239 		_text = addr;
240 
241 	/* Ignore most absolute/undefined (?) symbols. */
242 	if (is_ignored_symbol(name, type))
243 		return NULL;
244 
245 	check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
246 	check_symbol_range(name, addr, &percpu_range, 1);
247 
248 	/* include the type field in the symbol name, so that it gets
249 	 * compressed together */
250 
251 	len = strlen(name) + 1;
252 
253 	sym = malloc(sizeof(*sym) + len + 1);
254 	if (!sym) {
255 		fprintf(stderr, "kallsyms failure: "
256 			"unable to allocate required amount of memory\n");
257 		exit(EXIT_FAILURE);
258 	}
259 	sym->addr = addr;
260 	sym->len = len;
261 	sym->sym[0] = type;
262 	strcpy(sym_name(sym), name);
263 	sym->percpu_absolute = 0;
264 
265 	return sym;
266 }
267 
268 static int symbol_in_range(const struct sym_entry *s,
269 			   const struct addr_range *ranges, int entries)
270 {
271 	size_t i;
272 	const struct addr_range *ar;
273 
274 	for (i = 0; i < entries; ++i) {
275 		ar = &ranges[i];
276 
277 		if (s->addr >= ar->start && s->addr <= ar->end)
278 			return 1;
279 	}
280 
281 	return 0;
282 }
283 
284 static int symbol_valid(const struct sym_entry *s)
285 {
286 	const char *name = sym_name(s);
287 
288 	/* if --all-symbols is not specified, then symbols outside the text
289 	 * and inittext sections are discarded */
290 	if (!all_symbols) {
291 		if (symbol_in_range(s, text_ranges,
292 				    ARRAY_SIZE(text_ranges)) == 0)
293 			return 0;
294 		/* Corner case.  Discard any symbols with the same value as
295 		 * _etext _einittext; they can move between pass 1 and 2 when
296 		 * the kallsyms data are added.  If these symbols move then
297 		 * they may get dropped in pass 2, which breaks the kallsyms
298 		 * rules.
299 		 */
300 		if ((s->addr == text_range_text->end &&
301 		     strcmp(name, text_range_text->end_sym)) ||
302 		    (s->addr == text_range_inittext->end &&
303 		     strcmp(name, text_range_inittext->end_sym)))
304 			return 0;
305 	}
306 
307 	return 1;
308 }
309 
310 /* remove all the invalid symbols from the table */
311 static void shrink_table(void)
312 {
313 	unsigned int i, pos;
314 
315 	pos = 0;
316 	for (i = 0; i < table_cnt; i++) {
317 		if (symbol_valid(table[i])) {
318 			if (pos != i)
319 				table[pos] = table[i];
320 			pos++;
321 		} else {
322 			free(table[i]);
323 		}
324 	}
325 	table_cnt = pos;
326 
327 	/* When valid symbol is not registered, exit to error */
328 	if (!table_cnt) {
329 		fprintf(stderr, "No valid symbol.\n");
330 		exit(1);
331 	}
332 }
333 
334 static void read_map(const char *in)
335 {
336 	FILE *fp;
337 	struct sym_entry *sym;
338 
339 	fp = fopen(in, "r");
340 	if (!fp) {
341 		perror(in);
342 		exit(1);
343 	}
344 
345 	while (!feof(fp)) {
346 		sym = read_symbol(fp);
347 		if (!sym)
348 			continue;
349 
350 		sym->start_pos = table_cnt;
351 
352 		if (table_cnt >= table_size) {
353 			table_size += 10000;
354 			table = realloc(table, sizeof(*table) * table_size);
355 			if (!table) {
356 				fprintf(stderr, "out of memory\n");
357 				fclose(fp);
358 				exit (1);
359 			}
360 		}
361 
362 		table[table_cnt++] = sym;
363 	}
364 
365 	fclose(fp);
366 }
367 
368 static void output_label(const char *label)
369 {
370 	printf(".globl %s\n", label);
371 	printf("\tALGN\n");
372 	printf("%s:\n", label);
373 }
374 
375 /* Provide proper symbols relocatability by their '_text' relativeness. */
376 static void output_address(unsigned long long addr)
377 {
378 	if (_text <= addr)
379 		printf("\tPTR\t_text + %#llx\n", addr - _text);
380 	else
381 		printf("\tPTR\t_text - %#llx\n", _text - addr);
382 }
383 
384 /* uncompress a compressed symbol. When this function is called, the best table
385  * might still be compressed itself, so the function needs to be recursive */
386 static int expand_symbol(const unsigned char *data, int len, char *result)
387 {
388 	int c, rlen, total=0;
389 
390 	while (len) {
391 		c = *data;
392 		/* if the table holds a single char that is the same as the one
393 		 * we are looking for, then end the search */
394 		if (best_table[c][0]==c && best_table_len[c]==1) {
395 			*result++ = c;
396 			total++;
397 		} else {
398 			/* if not, recurse and expand */
399 			rlen = expand_symbol(best_table[c], best_table_len[c], result);
400 			total += rlen;
401 			result += rlen;
402 		}
403 		data++;
404 		len--;
405 	}
406 	*result=0;
407 
408 	return total;
409 }
410 
411 static int symbol_absolute(const struct sym_entry *s)
412 {
413 	return s->percpu_absolute;
414 }
415 
416 static char * s_name(char *buf)
417 {
418 	/* Skip the symbol type */
419 	return buf + 1;
420 }
421 
422 static void cleanup_symbol_name(char *s)
423 {
424 	char *p;
425 
426 	if (!lto_clang)
427 		return;
428 
429 	/*
430 	 * ASCII[.]   = 2e
431 	 * ASCII[0-9] = 30,39
432 	 * ASCII[A-Z] = 41,5a
433 	 * ASCII[_]   = 5f
434 	 * ASCII[a-z] = 61,7a
435 	 *
436 	 * As above, replacing '.' with '\0' does not affect the main sorting,
437 	 * but it helps us with subsorting.
438 	 */
439 	p = strchr(s, '.');
440 	if (p)
441 		*p = '\0';
442 }
443 
444 static int compare_names(const void *a, const void *b)
445 {
446 	int ret;
447 	char sa_namebuf[KSYM_NAME_LEN];
448 	char sb_namebuf[KSYM_NAME_LEN];
449 	const struct sym_entry *sa = *(const struct sym_entry **)a;
450 	const struct sym_entry *sb = *(const struct sym_entry **)b;
451 
452 	expand_symbol(sa->sym, sa->len, sa_namebuf);
453 	expand_symbol(sb->sym, sb->len, sb_namebuf);
454 	cleanup_symbol_name(s_name(sa_namebuf));
455 	cleanup_symbol_name(s_name(sb_namebuf));
456 	ret = strcmp(s_name(sa_namebuf), s_name(sb_namebuf));
457 	if (!ret) {
458 		if (sa->addr > sb->addr)
459 			return 1;
460 		else if (sa->addr < sb->addr)
461 			return -1;
462 
463 		/* keep old order */
464 		return (int)(sa->seq - sb->seq);
465 	}
466 
467 	return ret;
468 }
469 
470 static void sort_symbols_by_name(void)
471 {
472 	qsort(table, table_cnt, sizeof(table[0]), compare_names);
473 }
474 
475 static void write_src(void)
476 {
477 	unsigned int i, k, off;
478 	unsigned int best_idx[256];
479 	unsigned int *markers;
480 	char buf[KSYM_NAME_LEN];
481 
482 	printf("#include <asm/bitsperlong.h>\n");
483 	printf("#if BITS_PER_LONG == 64\n");
484 	printf("#define PTR .quad\n");
485 	printf("#define ALGN .balign 8\n");
486 	printf("#else\n");
487 	printf("#define PTR .long\n");
488 	printf("#define ALGN .balign 4\n");
489 	printf("#endif\n");
490 
491 	printf("\t.section .rodata, \"a\"\n");
492 
493 	if (!base_relative)
494 		output_label("kallsyms_addresses");
495 	else
496 		output_label("kallsyms_offsets");
497 
498 	for (i = 0; i < table_cnt; i++) {
499 		if (base_relative) {
500 			/*
501 			 * Use the offset relative to the lowest value
502 			 * encountered of all relative symbols, and emit
503 			 * non-relocatable fixed offsets that will be fixed
504 			 * up at runtime.
505 			 */
506 
507 			long long offset;
508 			int overflow;
509 
510 			if (!absolute_percpu) {
511 				offset = table[i]->addr - relative_base;
512 				overflow = (offset < 0 || offset > UINT_MAX);
513 			} else if (symbol_absolute(table[i])) {
514 				offset = table[i]->addr;
515 				overflow = (offset < 0 || offset > INT_MAX);
516 			} else {
517 				offset = relative_base - table[i]->addr - 1;
518 				overflow = (offset < INT_MIN || offset >= 0);
519 			}
520 			if (overflow) {
521 				fprintf(stderr, "kallsyms failure: "
522 					"%s symbol value %#llx out of range in relative mode\n",
523 					symbol_absolute(table[i]) ? "absolute" : "relative",
524 					table[i]->addr);
525 				exit(EXIT_FAILURE);
526 			}
527 			printf("\t.long\t%#x\n", (int)offset);
528 		} else if (!symbol_absolute(table[i])) {
529 			output_address(table[i]->addr);
530 		} else {
531 			printf("\tPTR\t%#llx\n", table[i]->addr);
532 		}
533 	}
534 	printf("\n");
535 
536 	if (base_relative) {
537 		output_label("kallsyms_relative_base");
538 		output_address(relative_base);
539 		printf("\n");
540 	}
541 
542 	output_label("kallsyms_num_syms");
543 	printf("\t.long\t%u\n", table_cnt);
544 	printf("\n");
545 
546 	/* table of offset markers, that give the offset in the compressed stream
547 	 * every 256 symbols */
548 	markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
549 	if (!markers) {
550 		fprintf(stderr, "kallsyms failure: "
551 			"unable to allocate required memory\n");
552 		exit(EXIT_FAILURE);
553 	}
554 
555 	output_label("kallsyms_names");
556 	off = 0;
557 	for (i = 0; i < table_cnt; i++) {
558 		if ((i & 0xFF) == 0)
559 			markers[i >> 8] = off;
560 		table[i]->seq = i;
561 
562 		/* There cannot be any symbol of length zero. */
563 		if (table[i]->len == 0) {
564 			fprintf(stderr, "kallsyms failure: "
565 				"unexpected zero symbol length\n");
566 			exit(EXIT_FAILURE);
567 		}
568 
569 		/* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
570 		if (table[i]->len > 0x3FFF) {
571 			fprintf(stderr, "kallsyms failure: "
572 				"unexpected huge symbol length\n");
573 			exit(EXIT_FAILURE);
574 		}
575 
576 		/* Encode length with ULEB128. */
577 		if (table[i]->len <= 0x7F) {
578 			/* Most symbols use a single byte for the length. */
579 			printf("\t.byte 0x%02x", table[i]->len);
580 			off += table[i]->len + 1;
581 		} else {
582 			/* "Big" symbols use two bytes. */
583 			printf("\t.byte 0x%02x, 0x%02x",
584 				(table[i]->len & 0x7F) | 0x80,
585 				(table[i]->len >> 7) & 0x7F);
586 			off += table[i]->len + 2;
587 		}
588 		for (k = 0; k < table[i]->len; k++)
589 			printf(", 0x%02x", table[i]->sym[k]);
590 		printf("\n");
591 	}
592 	printf("\n");
593 
594 	output_label("kallsyms_markers");
595 	for (i = 0; i < ((table_cnt + 255) >> 8); i++)
596 		printf("\t.long\t%u\n", markers[i]);
597 	printf("\n");
598 
599 	free(markers);
600 
601 	sort_symbols_by_name();
602 	output_label("kallsyms_seqs_of_names");
603 	for (i = 0; i < table_cnt; i++)
604 		printf("\t.byte 0x%02x, 0x%02x, 0x%02x\n",
605 			(unsigned char)(table[i]->seq >> 16),
606 			(unsigned char)(table[i]->seq >> 8),
607 			(unsigned char)(table[i]->seq >> 0));
608 	printf("\n");
609 
610 	output_label("kallsyms_token_table");
611 	off = 0;
612 	for (i = 0; i < 256; i++) {
613 		best_idx[i] = off;
614 		expand_symbol(best_table[i], best_table_len[i], buf);
615 		printf("\t.asciz\t\"%s\"\n", buf);
616 		off += strlen(buf) + 1;
617 	}
618 	printf("\n");
619 
620 	output_label("kallsyms_token_index");
621 	for (i = 0; i < 256; i++)
622 		printf("\t.short\t%d\n", best_idx[i]);
623 	printf("\n");
624 }
625 
626 
627 /* table lookup compression functions */
628 
629 /* count all the possible tokens in a symbol */
630 static void learn_symbol(const unsigned char *symbol, int len)
631 {
632 	int i;
633 
634 	for (i = 0; i < len - 1; i++)
635 		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
636 }
637 
638 /* decrease the count for all the possible tokens in a symbol */
639 static void forget_symbol(const unsigned char *symbol, int len)
640 {
641 	int i;
642 
643 	for (i = 0; i < len - 1; i++)
644 		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
645 }
646 
647 /* do the initial token count */
648 static void build_initial_token_table(void)
649 {
650 	unsigned int i;
651 
652 	for (i = 0; i < table_cnt; i++)
653 		learn_symbol(table[i]->sym, table[i]->len);
654 }
655 
656 static unsigned char *find_token(unsigned char *str, int len,
657 				 const unsigned char *token)
658 {
659 	int i;
660 
661 	for (i = 0; i < len - 1; i++) {
662 		if (str[i] == token[0] && str[i+1] == token[1])
663 			return &str[i];
664 	}
665 	return NULL;
666 }
667 
668 /* replace a given token in all the valid symbols. Use the sampled symbols
669  * to update the counts */
670 static void compress_symbols(const unsigned char *str, int idx)
671 {
672 	unsigned int i, len, size;
673 	unsigned char *p1, *p2;
674 
675 	for (i = 0; i < table_cnt; i++) {
676 
677 		len = table[i]->len;
678 		p1 = table[i]->sym;
679 
680 		/* find the token on the symbol */
681 		p2 = find_token(p1, len, str);
682 		if (!p2) continue;
683 
684 		/* decrease the counts for this symbol's tokens */
685 		forget_symbol(table[i]->sym, len);
686 
687 		size = len;
688 
689 		do {
690 			*p2 = idx;
691 			p2++;
692 			size -= (p2 - p1);
693 			memmove(p2, p2 + 1, size);
694 			p1 = p2;
695 			len--;
696 
697 			if (size < 2) break;
698 
699 			/* find the token on the symbol */
700 			p2 = find_token(p1, size, str);
701 
702 		} while (p2);
703 
704 		table[i]->len = len;
705 
706 		/* increase the counts for this symbol's new tokens */
707 		learn_symbol(table[i]->sym, len);
708 	}
709 }
710 
711 /* search the token with the maximum profit */
712 static int find_best_token(void)
713 {
714 	int i, best, bestprofit;
715 
716 	bestprofit=-10000;
717 	best = 0;
718 
719 	for (i = 0; i < 0x10000; i++) {
720 		if (token_profit[i] > bestprofit) {
721 			best = i;
722 			bestprofit = token_profit[i];
723 		}
724 	}
725 	return best;
726 }
727 
728 /* this is the core of the algorithm: calculate the "best" table */
729 static void optimize_result(void)
730 {
731 	int i, best;
732 
733 	/* using the '\0' symbol last allows compress_symbols to use standard
734 	 * fast string functions */
735 	for (i = 255; i >= 0; i--) {
736 
737 		/* if this table slot is empty (it is not used by an actual
738 		 * original char code */
739 		if (!best_table_len[i]) {
740 
741 			/* find the token with the best profit value */
742 			best = find_best_token();
743 			if (token_profit[best] == 0)
744 				break;
745 
746 			/* place it in the "best" table */
747 			best_table_len[i] = 2;
748 			best_table[i][0] = best & 0xFF;
749 			best_table[i][1] = (best >> 8) & 0xFF;
750 
751 			/* replace this token in all the valid symbols */
752 			compress_symbols(best_table[i], i);
753 		}
754 	}
755 }
756 
757 /* start by placing the symbols that are actually used on the table */
758 static void insert_real_symbols_in_table(void)
759 {
760 	unsigned int i, j, c;
761 
762 	for (i = 0; i < table_cnt; i++) {
763 		for (j = 0; j < table[i]->len; j++) {
764 			c = table[i]->sym[j];
765 			best_table[c][0]=c;
766 			best_table_len[c]=1;
767 		}
768 	}
769 }
770 
771 static void optimize_token_table(void)
772 {
773 	build_initial_token_table();
774 
775 	insert_real_symbols_in_table();
776 
777 	optimize_result();
778 }
779 
780 /* guess for "linker script provide" symbol */
781 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
782 {
783 	const char *symbol = sym_name(se);
784 	int len = se->len - 1;
785 
786 	if (len < 8)
787 		return 0;
788 
789 	if (symbol[0] != '_' || symbol[1] != '_')
790 		return 0;
791 
792 	/* __start_XXXXX */
793 	if (!memcmp(symbol + 2, "start_", 6))
794 		return 1;
795 
796 	/* __stop_XXXXX */
797 	if (!memcmp(symbol + 2, "stop_", 5))
798 		return 1;
799 
800 	/* __end_XXXXX */
801 	if (!memcmp(symbol + 2, "end_", 4))
802 		return 1;
803 
804 	/* __XXXXX_start */
805 	if (!memcmp(symbol + len - 6, "_start", 6))
806 		return 1;
807 
808 	/* __XXXXX_end */
809 	if (!memcmp(symbol + len - 4, "_end", 4))
810 		return 1;
811 
812 	return 0;
813 }
814 
815 static int compare_symbols(const void *a, const void *b)
816 {
817 	const struct sym_entry *sa = *(const struct sym_entry **)a;
818 	const struct sym_entry *sb = *(const struct sym_entry **)b;
819 	int wa, wb;
820 
821 	/* sort by address first */
822 	if (sa->addr > sb->addr)
823 		return 1;
824 	if (sa->addr < sb->addr)
825 		return -1;
826 
827 	/* sort by "weakness" type */
828 	wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
829 	wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
830 	if (wa != wb)
831 		return wa - wb;
832 
833 	/* sort by "linker script provide" type */
834 	wa = may_be_linker_script_provide_symbol(sa);
835 	wb = may_be_linker_script_provide_symbol(sb);
836 	if (wa != wb)
837 		return wa - wb;
838 
839 	/* sort by the number of prefix underscores */
840 	wa = strspn(sym_name(sa), "_");
841 	wb = strspn(sym_name(sb), "_");
842 	if (wa != wb)
843 		return wa - wb;
844 
845 	/* sort by initial order, so that other symbols are left undisturbed */
846 	return sa->start_pos - sb->start_pos;
847 }
848 
849 static void sort_symbols(void)
850 {
851 	qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
852 }
853 
854 static void make_percpus_absolute(void)
855 {
856 	unsigned int i;
857 
858 	for (i = 0; i < table_cnt; i++)
859 		if (symbol_in_range(table[i], &percpu_range, 1)) {
860 			/*
861 			 * Keep the 'A' override for percpu symbols to
862 			 * ensure consistent behavior compared to older
863 			 * versions of this tool.
864 			 */
865 			table[i]->sym[0] = 'A';
866 			table[i]->percpu_absolute = 1;
867 		}
868 }
869 
870 /* find the minimum non-absolute symbol address */
871 static void record_relative_base(void)
872 {
873 	unsigned int i;
874 
875 	for (i = 0; i < table_cnt; i++)
876 		if (!symbol_absolute(table[i])) {
877 			/*
878 			 * The table is sorted by address.
879 			 * Take the first non-absolute symbol value.
880 			 */
881 			relative_base = table[i]->addr;
882 			return;
883 		}
884 }
885 
886 int main(int argc, char **argv)
887 {
888 	while (1) {
889 		static struct option long_options[] = {
890 			{"all-symbols",     no_argument, &all_symbols,     1},
891 			{"absolute-percpu", no_argument, &absolute_percpu, 1},
892 			{"base-relative",   no_argument, &base_relative,   1},
893 			{"lto-clang",       no_argument, &lto_clang,       1},
894 			{},
895 		};
896 
897 		int c = getopt_long(argc, argv, "", long_options, NULL);
898 
899 		if (c == -1)
900 			break;
901 		if (c != 0)
902 			usage();
903 	}
904 
905 	if (optind >= argc)
906 		usage();
907 
908 	read_map(argv[optind]);
909 	shrink_table();
910 	if (absolute_percpu)
911 		make_percpus_absolute();
912 	sort_symbols();
913 	if (base_relative)
914 		record_relative_base();
915 	optimize_token_table();
916 	write_src();
917 
918 	return 0;
919 }
920