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}