xref: /openbmc/linux/scripts/kallsyms.c (revision bea5b745)
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 		"kallsyms_seqs_of_names",
123 		/* Exclude linker generated symbols which vary between passes */
124 		"_SDA_BASE_",		/* ppc */
125 		"_SDA2_BASE_",		/* ppc */
126 		NULL
127 	};
128 
129 	/* Symbol names that begin with the following are ignored.*/
130 	static const char * const ignored_prefixes[] = {
131 		"__efistub_",		/* arm64 EFI stub namespace */
132 		"__kvm_nvhe_$",		/* arm64 local symbols in non-VHE KVM namespace */
133 		"__kvm_nvhe_.L",	/* arm64 local symbols in non-VHE KVM namespace */
134 		"__AArch64ADRPThunk_",	/* arm64 lld */
135 		"__ARMV5PILongThunk_",	/* arm lld */
136 		"__ARMV7PILongThunk_",
137 		"__ThumbV7PILongThunk_",
138 		"__LA25Thunk_",		/* mips lld */
139 		"__microLA25Thunk_",
140 		"__kcfi_typeid_",	/* CFI type identifiers */
141 		NULL
142 	};
143 
144 	/* Symbol names that end with the following are ignored.*/
145 	static const char * const ignored_suffixes[] = {
146 		"_from_arm",		/* arm */
147 		"_from_thumb",		/* arm */
148 		"_veneer",		/* arm */
149 		NULL
150 	};
151 
152 	/* Symbol names that contain the following are ignored.*/
153 	static const char * const ignored_matches[] = {
154 		".long_branch.",	/* ppc stub */
155 		".plt_branch.",		/* ppc stub */
156 		NULL
157 	};
158 
159 	const char * const *p;
160 
161 	for (p = ignored_symbols; *p; p++)
162 		if (!strcmp(name, *p))
163 			return true;
164 
165 	for (p = ignored_prefixes; *p; p++)
166 		if (!strncmp(name, *p, strlen(*p)))
167 			return true;
168 
169 	for (p = ignored_suffixes; *p; p++) {
170 		int l = strlen(name) - strlen(*p);
171 
172 		if (l >= 0 && !strcmp(name + l, *p))
173 			return true;
174 	}
175 
176 	for (p = ignored_matches; *p; p++) {
177 		if (strstr(name, *p))
178 			return true;
179 	}
180 
181 	if (type == 'U' || type == 'u')
182 		return true;
183 	/* exclude debugging symbols */
184 	if (type == 'N' || type == 'n')
185 		return true;
186 
187 	if (toupper(type) == 'A') {
188 		/* Keep these useful absolute symbols */
189 		if (strcmp(name, "__kernel_syscall_via_break") &&
190 		    strcmp(name, "__kernel_syscall_via_epc") &&
191 		    strcmp(name, "__kernel_sigtramp") &&
192 		    strcmp(name, "__gp"))
193 			return true;
194 	}
195 
196 	return false;
197 }
198 
199 static void check_symbol_range(const char *sym, unsigned long long addr,
200 			       struct addr_range *ranges, int entries)
201 {
202 	size_t i;
203 	struct addr_range *ar;
204 
205 	for (i = 0; i < entries; ++i) {
206 		ar = &ranges[i];
207 
208 		if (strcmp(sym, ar->start_sym) == 0) {
209 			ar->start = addr;
210 			return;
211 		} else if (strcmp(sym, ar->end_sym) == 0) {
212 			ar->end = addr;
213 			return;
214 		}
215 	}
216 }
217 
218 static struct sym_entry *read_symbol(FILE *in)
219 {
220 	char name[KSYM_NAME_LEN_BUFFER+1], type;
221 	unsigned long long addr;
222 	unsigned int len;
223 	struct sym_entry *sym;
224 	int rc;
225 
226 	rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);
227 	if (rc != 3) {
228 		if (rc != EOF && fgets(name, ARRAY_SIZE(name), in) == NULL)
229 			fprintf(stderr, "Read error or end of file.\n");
230 		return NULL;
231 	}
232 	if (strlen(name) >= KSYM_NAME_LEN) {
233 		fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
234 				"Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
235 			name, strlen(name), KSYM_NAME_LEN);
236 		return NULL;
237 	}
238 
239 	if (strcmp(name, "_text") == 0)
240 		_text = addr;
241 
242 	/* Ignore most absolute/undefined (?) symbols. */
243 	if (is_ignored_symbol(name, type))
244 		return NULL;
245 
246 	check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
247 	check_symbol_range(name, addr, &percpu_range, 1);
248 
249 	/* include the type field in the symbol name, so that it gets
250 	 * compressed together */
251 
252 	len = strlen(name) + 1;
253 
254 	sym = malloc(sizeof(*sym) + len + 1);
255 	if (!sym) {
256 		fprintf(stderr, "kallsyms failure: "
257 			"unable to allocate required amount of memory\n");
258 		exit(EXIT_FAILURE);
259 	}
260 	sym->addr = addr;
261 	sym->len = len;
262 	sym->sym[0] = type;
263 	strcpy(sym_name(sym), name);
264 	sym->percpu_absolute = 0;
265 
266 	return sym;
267 }
268 
269 static int symbol_in_range(const struct sym_entry *s,
270 			   const struct addr_range *ranges, int entries)
271 {
272 	size_t i;
273 	const struct addr_range *ar;
274 
275 	for (i = 0; i < entries; ++i) {
276 		ar = &ranges[i];
277 
278 		if (s->addr >= ar->start && s->addr <= ar->end)
279 			return 1;
280 	}
281 
282 	return 0;
283 }
284 
285 static int symbol_valid(const struct sym_entry *s)
286 {
287 	const char *name = sym_name(s);
288 
289 	/* if --all-symbols is not specified, then symbols outside the text
290 	 * and inittext sections are discarded */
291 	if (!all_symbols) {
292 		if (symbol_in_range(s, text_ranges,
293 				    ARRAY_SIZE(text_ranges)) == 0)
294 			return 0;
295 		/* Corner case.  Discard any symbols with the same value as
296 		 * _etext _einittext; they can move between pass 1 and 2 when
297 		 * the kallsyms data are added.  If these symbols move then
298 		 * they may get dropped in pass 2, which breaks the kallsyms
299 		 * rules.
300 		 */
301 		if ((s->addr == text_range_text->end &&
302 		     strcmp(name, text_range_text->end_sym)) ||
303 		    (s->addr == text_range_inittext->end &&
304 		     strcmp(name, text_range_inittext->end_sym)))
305 			return 0;
306 	}
307 
308 	return 1;
309 }
310 
311 /* remove all the invalid symbols from the table */
312 static void shrink_table(void)
313 {
314 	unsigned int i, pos;
315 
316 	pos = 0;
317 	for (i = 0; i < table_cnt; i++) {
318 		if (symbol_valid(table[i])) {
319 			if (pos != i)
320 				table[pos] = table[i];
321 			pos++;
322 		} else {
323 			free(table[i]);
324 		}
325 	}
326 	table_cnt = pos;
327 
328 	/* When valid symbol is not registered, exit to error */
329 	if (!table_cnt) {
330 		fprintf(stderr, "No valid symbol.\n");
331 		exit(1);
332 	}
333 }
334 
335 static void read_map(const char *in)
336 {
337 	FILE *fp;
338 	struct sym_entry *sym;
339 
340 	fp = fopen(in, "r");
341 	if (!fp) {
342 		perror(in);
343 		exit(1);
344 	}
345 
346 	while (!feof(fp)) {
347 		sym = read_symbol(fp);
348 		if (!sym)
349 			continue;
350 
351 		sym->start_pos = table_cnt;
352 
353 		if (table_cnt >= table_size) {
354 			table_size += 10000;
355 			table = realloc(table, sizeof(*table) * table_size);
356 			if (!table) {
357 				fprintf(stderr, "out of memory\n");
358 				fclose(fp);
359 				exit (1);
360 			}
361 		}
362 
363 		table[table_cnt++] = sym;
364 	}
365 
366 	fclose(fp);
367 }
368 
369 static void output_label(const char *label)
370 {
371 	printf(".globl %s\n", label);
372 	printf("\tALGN\n");
373 	printf("%s:\n", label);
374 }
375 
376 /* Provide proper symbols relocatability by their '_text' relativeness. */
377 static void output_address(unsigned long long addr)
378 {
379 	if (_text <= addr)
380 		printf("\tPTR\t_text + %#llx\n", addr - _text);
381 	else
382 		printf("\tPTR\t_text - %#llx\n", _text - addr);
383 }
384 
385 /* uncompress a compressed symbol. When this function is called, the best table
386  * might still be compressed itself, so the function needs to be recursive */
387 static int expand_symbol(const unsigned char *data, int len, char *result)
388 {
389 	int c, rlen, total=0;
390 
391 	while (len) {
392 		c = *data;
393 		/* if the table holds a single char that is the same as the one
394 		 * we are looking for, then end the search */
395 		if (best_table[c][0]==c && best_table_len[c]==1) {
396 			*result++ = c;
397 			total++;
398 		} else {
399 			/* if not, recurse and expand */
400 			rlen = expand_symbol(best_table[c], best_table_len[c], result);
401 			total += rlen;
402 			result += rlen;
403 		}
404 		data++;
405 		len--;
406 	}
407 	*result=0;
408 
409 	return total;
410 }
411 
412 static int symbol_absolute(const struct sym_entry *s)
413 {
414 	return s->percpu_absolute;
415 }
416 
417 static char * s_name(char *buf)
418 {
419 	/* Skip the symbol type */
420 	return buf + 1;
421 }
422 
423 static void cleanup_symbol_name(char *s)
424 {
425 	char *p;
426 
427 	if (!lto_clang)
428 		return;
429 
430 	/*
431 	 * ASCII[.]   = 2e
432 	 * ASCII[0-9] = 30,39
433 	 * ASCII[A-Z] = 41,5a
434 	 * ASCII[_]   = 5f
435 	 * ASCII[a-z] = 61,7a
436 	 *
437 	 * As above, replacing '.' with '\0' does not affect the main sorting,
438 	 * but it helps us with subsorting.
439 	 */
440 	p = strchr(s, '.');
441 	if (p)
442 		*p = '\0';
443 }
444 
445 static int compare_names(const void *a, const void *b)
446 {
447 	int ret;
448 	char sa_namebuf[KSYM_NAME_LEN];
449 	char sb_namebuf[KSYM_NAME_LEN];
450 	const struct sym_entry *sa = *(const struct sym_entry **)a;
451 	const struct sym_entry *sb = *(const struct sym_entry **)b;
452 
453 	expand_symbol(sa->sym, sa->len, sa_namebuf);
454 	expand_symbol(sb->sym, sb->len, sb_namebuf);
455 	cleanup_symbol_name(s_name(sa_namebuf));
456 	cleanup_symbol_name(s_name(sb_namebuf));
457 	ret = strcmp(s_name(sa_namebuf), s_name(sb_namebuf));
458 	if (!ret) {
459 		if (sa->addr > sb->addr)
460 			return 1;
461 		else if (sa->addr < sb->addr)
462 			return -1;
463 
464 		/* keep old order */
465 		return (int)(sa->seq - sb->seq);
466 	}
467 
468 	return ret;
469 }
470 
471 static void sort_symbols_by_name(void)
472 {
473 	qsort(table, table_cnt, sizeof(table[0]), compare_names);
474 }
475 
476 static void write_src(void)
477 {
478 	unsigned int i, k, off;
479 	unsigned int best_idx[256];
480 	unsigned int *markers;
481 	char buf[KSYM_NAME_LEN];
482 
483 	printf("#include <asm/bitsperlong.h>\n");
484 	printf("#if BITS_PER_LONG == 64\n");
485 	printf("#define PTR .quad\n");
486 	printf("#define ALGN .balign 8\n");
487 	printf("#else\n");
488 	printf("#define PTR .long\n");
489 	printf("#define ALGN .balign 4\n");
490 	printf("#endif\n");
491 
492 	printf("\t.section .rodata, \"a\"\n");
493 
494 	if (!base_relative)
495 		output_label("kallsyms_addresses");
496 	else
497 		output_label("kallsyms_offsets");
498 
499 	for (i = 0; i < table_cnt; i++) {
500 		if (base_relative) {
501 			/*
502 			 * Use the offset relative to the lowest value
503 			 * encountered of all relative symbols, and emit
504 			 * non-relocatable fixed offsets that will be fixed
505 			 * up at runtime.
506 			 */
507 
508 			long long offset;
509 			int overflow;
510 
511 			if (!absolute_percpu) {
512 				offset = table[i]->addr - relative_base;
513 				overflow = (offset < 0 || offset > UINT_MAX);
514 			} else if (symbol_absolute(table[i])) {
515 				offset = table[i]->addr;
516 				overflow = (offset < 0 || offset > INT_MAX);
517 			} else {
518 				offset = relative_base - table[i]->addr - 1;
519 				overflow = (offset < INT_MIN || offset >= 0);
520 			}
521 			if (overflow) {
522 				fprintf(stderr, "kallsyms failure: "
523 					"%s symbol value %#llx out of range in relative mode\n",
524 					symbol_absolute(table[i]) ? "absolute" : "relative",
525 					table[i]->addr);
526 				exit(EXIT_FAILURE);
527 			}
528 			expand_symbol(table[i]->sym, table[i]->len, buf);
529 			printf("\t.long\t%#x	/* %s */\n", (int)offset, buf);
530 		} else if (!symbol_absolute(table[i])) {
531 			output_address(table[i]->addr);
532 		} else {
533 			printf("\tPTR\t%#llx\n", table[i]->addr);
534 		}
535 	}
536 	printf("\n");
537 
538 	if (base_relative) {
539 		output_label("kallsyms_relative_base");
540 		output_address(relative_base);
541 		printf("\n");
542 	}
543 
544 	output_label("kallsyms_num_syms");
545 	printf("\t.long\t%u\n", table_cnt);
546 	printf("\n");
547 
548 	/* table of offset markers, that give the offset in the compressed stream
549 	 * every 256 symbols */
550 	markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
551 	if (!markers) {
552 		fprintf(stderr, "kallsyms failure: "
553 			"unable to allocate required memory\n");
554 		exit(EXIT_FAILURE);
555 	}
556 
557 	output_label("kallsyms_names");
558 	off = 0;
559 	for (i = 0; i < table_cnt; i++) {
560 		if ((i & 0xFF) == 0)
561 			markers[i >> 8] = off;
562 		table[i]->seq = i;
563 
564 		/* There cannot be any symbol of length zero. */
565 		if (table[i]->len == 0) {
566 			fprintf(stderr, "kallsyms failure: "
567 				"unexpected zero symbol length\n");
568 			exit(EXIT_FAILURE);
569 		}
570 
571 		/* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
572 		if (table[i]->len > 0x3FFF) {
573 			fprintf(stderr, "kallsyms failure: "
574 				"unexpected huge symbol length\n");
575 			exit(EXIT_FAILURE);
576 		}
577 
578 		/* Encode length with ULEB128. */
579 		if (table[i]->len <= 0x7F) {
580 			/* Most symbols use a single byte for the length. */
581 			printf("\t.byte 0x%02x", table[i]->len);
582 			off += table[i]->len + 1;
583 		} else {
584 			/* "Big" symbols use two bytes. */
585 			printf("\t.byte 0x%02x, 0x%02x",
586 				(table[i]->len & 0x7F) | 0x80,
587 				(table[i]->len >> 7) & 0x7F);
588 			off += table[i]->len + 2;
589 		}
590 		for (k = 0; k < table[i]->len; k++)
591 			printf(", 0x%02x", table[i]->sym[k]);
592 		printf("\n");
593 	}
594 	printf("\n");
595 
596 	output_label("kallsyms_markers");
597 	for (i = 0; i < ((table_cnt + 255) >> 8); i++)
598 		printf("\t.long\t%u\n", markers[i]);
599 	printf("\n");
600 
601 	free(markers);
602 
603 	sort_symbols_by_name();
604 	output_label("kallsyms_seqs_of_names");
605 	for (i = 0; i < table_cnt; i++)
606 		printf("\t.byte 0x%02x, 0x%02x, 0x%02x\n",
607 			(unsigned char)(table[i]->seq >> 16),
608 			(unsigned char)(table[i]->seq >> 8),
609 			(unsigned char)(table[i]->seq >> 0));
610 	printf("\n");
611 
612 	output_label("kallsyms_token_table");
613 	off = 0;
614 	for (i = 0; i < 256; i++) {
615 		best_idx[i] = off;
616 		expand_symbol(best_table[i], best_table_len[i], buf);
617 		printf("\t.asciz\t\"%s\"\n", buf);
618 		off += strlen(buf) + 1;
619 	}
620 	printf("\n");
621 
622 	output_label("kallsyms_token_index");
623 	for (i = 0; i < 256; i++)
624 		printf("\t.short\t%d\n", best_idx[i]);
625 	printf("\n");
626 }
627 
628 
629 /* table lookup compression functions */
630 
631 /* count all the possible tokens in a symbol */
632 static void learn_symbol(const unsigned char *symbol, int len)
633 {
634 	int i;
635 
636 	for (i = 0; i < len - 1; i++)
637 		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
638 }
639 
640 /* decrease the count for all the possible tokens in a symbol */
641 static void forget_symbol(const unsigned char *symbol, int len)
642 {
643 	int i;
644 
645 	for (i = 0; i < len - 1; i++)
646 		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
647 }
648 
649 /* do the initial token count */
650 static void build_initial_token_table(void)
651 {
652 	unsigned int i;
653 
654 	for (i = 0; i < table_cnt; i++)
655 		learn_symbol(table[i]->sym, table[i]->len);
656 }
657 
658 static unsigned char *find_token(unsigned char *str, int len,
659 				 const unsigned char *token)
660 {
661 	int i;
662 
663 	for (i = 0; i < len - 1; i++) {
664 		if (str[i] == token[0] && str[i+1] == token[1])
665 			return &str[i];
666 	}
667 	return NULL;
668 }
669 
670 /* replace a given token in all the valid symbols. Use the sampled symbols
671  * to update the counts */
672 static void compress_symbols(const unsigned char *str, int idx)
673 {
674 	unsigned int i, len, size;
675 	unsigned char *p1, *p2;
676 
677 	for (i = 0; i < table_cnt; i++) {
678 
679 		len = table[i]->len;
680 		p1 = table[i]->sym;
681 
682 		/* find the token on the symbol */
683 		p2 = find_token(p1, len, str);
684 		if (!p2) continue;
685 
686 		/* decrease the counts for this symbol's tokens */
687 		forget_symbol(table[i]->sym, len);
688 
689 		size = len;
690 
691 		do {
692 			*p2 = idx;
693 			p2++;
694 			size -= (p2 - p1);
695 			memmove(p2, p2 + 1, size);
696 			p1 = p2;
697 			len--;
698 
699 			if (size < 2) break;
700 
701 			/* find the token on the symbol */
702 			p2 = find_token(p1, size, str);
703 
704 		} while (p2);
705 
706 		table[i]->len = len;
707 
708 		/* increase the counts for this symbol's new tokens */
709 		learn_symbol(table[i]->sym, len);
710 	}
711 }
712 
713 /* search the token with the maximum profit */
714 static int find_best_token(void)
715 {
716 	int i, best, bestprofit;
717 
718 	bestprofit=-10000;
719 	best = 0;
720 
721 	for (i = 0; i < 0x10000; i++) {
722 		if (token_profit[i] > bestprofit) {
723 			best = i;
724 			bestprofit = token_profit[i];
725 		}
726 	}
727 	return best;
728 }
729 
730 /* this is the core of the algorithm: calculate the "best" table */
731 static void optimize_result(void)
732 {
733 	int i, best;
734 
735 	/* using the '\0' symbol last allows compress_symbols to use standard
736 	 * fast string functions */
737 	for (i = 255; i >= 0; i--) {
738 
739 		/* if this table slot is empty (it is not used by an actual
740 		 * original char code */
741 		if (!best_table_len[i]) {
742 
743 			/* find the token with the best profit value */
744 			best = find_best_token();
745 			if (token_profit[best] == 0)
746 				break;
747 
748 			/* place it in the "best" table */
749 			best_table_len[i] = 2;
750 			best_table[i][0] = best & 0xFF;
751 			best_table[i][1] = (best >> 8) & 0xFF;
752 
753 			/* replace this token in all the valid symbols */
754 			compress_symbols(best_table[i], i);
755 		}
756 	}
757 }
758 
759 /* start by placing the symbols that are actually used on the table */
760 static void insert_real_symbols_in_table(void)
761 {
762 	unsigned int i, j, c;
763 
764 	for (i = 0; i < table_cnt; i++) {
765 		for (j = 0; j < table[i]->len; j++) {
766 			c = table[i]->sym[j];
767 			best_table[c][0]=c;
768 			best_table_len[c]=1;
769 		}
770 	}
771 }
772 
773 static void optimize_token_table(void)
774 {
775 	build_initial_token_table();
776 
777 	insert_real_symbols_in_table();
778 
779 	optimize_result();
780 }
781 
782 /* guess for "linker script provide" symbol */
783 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
784 {
785 	const char *symbol = sym_name(se);
786 	int len = se->len - 1;
787 
788 	if (len < 8)
789 		return 0;
790 
791 	if (symbol[0] != '_' || symbol[1] != '_')
792 		return 0;
793 
794 	/* __start_XXXXX */
795 	if (!memcmp(symbol + 2, "start_", 6))
796 		return 1;
797 
798 	/* __stop_XXXXX */
799 	if (!memcmp(symbol + 2, "stop_", 5))
800 		return 1;
801 
802 	/* __end_XXXXX */
803 	if (!memcmp(symbol + 2, "end_", 4))
804 		return 1;
805 
806 	/* __XXXXX_start */
807 	if (!memcmp(symbol + len - 6, "_start", 6))
808 		return 1;
809 
810 	/* __XXXXX_end */
811 	if (!memcmp(symbol + len - 4, "_end", 4))
812 		return 1;
813 
814 	return 0;
815 }
816 
817 static int compare_symbols(const void *a, const void *b)
818 {
819 	const struct sym_entry *sa = *(const struct sym_entry **)a;
820 	const struct sym_entry *sb = *(const struct sym_entry **)b;
821 	int wa, wb;
822 
823 	/* sort by address first */
824 	if (sa->addr > sb->addr)
825 		return 1;
826 	if (sa->addr < sb->addr)
827 		return -1;
828 
829 	/* sort by "weakness" type */
830 	wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
831 	wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
832 	if (wa != wb)
833 		return wa - wb;
834 
835 	/* sort by "linker script provide" type */
836 	wa = may_be_linker_script_provide_symbol(sa);
837 	wb = may_be_linker_script_provide_symbol(sb);
838 	if (wa != wb)
839 		return wa - wb;
840 
841 	/* sort by the number of prefix underscores */
842 	wa = strspn(sym_name(sa), "_");
843 	wb = strspn(sym_name(sb), "_");
844 	if (wa != wb)
845 		return wa - wb;
846 
847 	/* sort by initial order, so that other symbols are left undisturbed */
848 	return sa->start_pos - sb->start_pos;
849 }
850 
851 static void sort_symbols(void)
852 {
853 	qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
854 }
855 
856 static void make_percpus_absolute(void)
857 {
858 	unsigned int i;
859 
860 	for (i = 0; i < table_cnt; i++)
861 		if (symbol_in_range(table[i], &percpu_range, 1)) {
862 			/*
863 			 * Keep the 'A' override for percpu symbols to
864 			 * ensure consistent behavior compared to older
865 			 * versions of this tool.
866 			 */
867 			table[i]->sym[0] = 'A';
868 			table[i]->percpu_absolute = 1;
869 		}
870 }
871 
872 /* find the minimum non-absolute symbol address */
873 static void record_relative_base(void)
874 {
875 	unsigned int i;
876 
877 	for (i = 0; i < table_cnt; i++)
878 		if (!symbol_absolute(table[i])) {
879 			/*
880 			 * The table is sorted by address.
881 			 * Take the first non-absolute symbol value.
882 			 */
883 			relative_base = table[i]->addr;
884 			return;
885 		}
886 }
887 
888 int main(int argc, char **argv)
889 {
890 	while (1) {
891 		static struct option long_options[] = {
892 			{"all-symbols",     no_argument, &all_symbols,     1},
893 			{"absolute-percpu", no_argument, &absolute_percpu, 1},
894 			{"base-relative",   no_argument, &base_relative,   1},
895 			{"lto-clang",       no_argument, &lto_clang,       1},
896 			{},
897 		};
898 
899 		int c = getopt_long(argc, argv, "", long_options, NULL);
900 
901 		if (c == -1)
902 			break;
903 		if (c != 0)
904 			usage();
905 	}
906 
907 	if (optind >= argc)
908 		usage();
909 
910 	read_map(argv[optind]);
911 	shrink_table();
912 	if (absolute_percpu)
913 		make_percpus_absolute();
914 	sort_symbols();
915 	if (base_relative)
916 		record_relative_base();
917 	optimize_token_table();
918 	write_src();
919 
920 	return 0;
921 }
922