Root/scripts/kallsyms.c

Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 9 years 4 months ago.
By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing
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
26#ifndef ARRAY_SIZE
27#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
28#endif
29
30#define KSYM_NAME_LEN 128
31
32struct sym_entry {
33    unsigned long long addr;
34    unsigned int len;
35    unsigned int start_pos;
36    unsigned char *sym;
37};
38
39struct text_range {
40    const char *stext, *etext;
41    unsigned long long start, end;
42};
43
44static unsigned long long _text;
45static struct text_range text_ranges[] = {
46    { "_stext", "_etext" },
47    { "_sinittext", "_einittext" },
48    { "_stext_l1", "_etext_l1" }, /* Blackfin on-chip L1 inst SRAM */
49    { "_stext_l2", "_etext_l2" }, /* Blackfin on-chip L2 SRAM */
50};
51#define text_range_text (&text_ranges[0])
52#define text_range_inittext (&text_ranges[1])
53
54static struct sym_entry *table;
55static unsigned int table_size, table_cnt;
56static int all_symbols = 0;
57static char symbol_prefix_char = '\0';
58
59int token_profit[0x10000];
60
61/* the table that holds the result of the compression */
62unsigned char best_table[256][2];
63unsigned char best_table_len[256];
64
65
66static void usage(void)
67{
68    fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
69    exit(1);
70}
71
72/*
73 * This ignores the intensely annoying "mapping symbols" found
74 * in ARM ELF files: $a, $t and $d.
75 */
76static inline int is_arm_mapping_symbol(const char *str)
77{
78    return str[0] == '$' && strchr("atd", str[1])
79           && (str[2] == '\0' || str[2] == '.');
80}
81
82static int read_symbol_tr(const char *sym, unsigned long long addr)
83{
84    size_t i;
85    struct text_range *tr;
86
87    for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
88        tr = &text_ranges[i];
89
90        if (strcmp(sym, tr->stext) == 0) {
91            tr->start = addr;
92            return 0;
93        } else if (strcmp(sym, tr->etext) == 0) {
94            tr->end = addr;
95            return 0;
96        }
97    }
98
99    return 1;
100}
101
102static int read_symbol(FILE *in, struct sym_entry *s)
103{
104    char str[500];
105    char *sym, stype;
106    int rc;
107
108    rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
109    if (rc != 3) {
110        if (rc != EOF && fgets(str, 500, in) == NULL)
111            fprintf(stderr, "Read error or end of file.\n");
112        return -1;
113    }
114
115    sym = str;
116    /* skip prefix char */
117    if (symbol_prefix_char && str[0] == symbol_prefix_char)
118        sym++;
119
120    /* Ignore most absolute/undefined (?) symbols. */
121    if (strcmp(sym, "_text") == 0)
122        _text = s->addr;
123    else if (read_symbol_tr(sym, s->addr) == 0)
124        /* nothing to do */;
125    else if (toupper(stype) == 'A')
126    {
127        /* Keep these useful absolute symbols */
128        if (strcmp(sym, "__kernel_syscall_via_break") &&
129            strcmp(sym, "__kernel_syscall_via_epc") &&
130            strcmp(sym, "__kernel_sigtramp") &&
131            strcmp(sym, "__gp"))
132            return -1;
133
134    }
135    else if (toupper(stype) == 'U' ||
136         is_arm_mapping_symbol(sym))
137        return -1;
138    /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
139    else if (str[0] == '$')
140        return -1;
141    /* exclude debugging symbols */
142    else if (stype == 'N')
143        return -1;
144
145    /* include the type field in the symbol name, so that it gets
146     * compressed together */
147    s->len = strlen(str) + 1;
148    s->sym = malloc(s->len + 1);
149    if (!s->sym) {
150        fprintf(stderr, "kallsyms failure: "
151            "unable to allocate required amount of memory\n");
152        exit(EXIT_FAILURE);
153    }
154    strcpy((char *)s->sym + 1, str);
155    s->sym[0] = stype;
156
157    return 0;
158}
159
160static int symbol_valid_tr(struct sym_entry *s)
161{
162    size_t i;
163    struct text_range *tr;
164
165    for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
166        tr = &text_ranges[i];
167
168        if (s->addr >= tr->start && s->addr <= tr->end)
169            return 1;
170    }
171
172    return 0;
173}
174
175static int symbol_valid(struct sym_entry *s)
176{
177    /* Symbols which vary between passes. Passes 1 and 2 must have
178     * identical symbol lists. The kallsyms_* symbols below are only added
179     * after pass 1, they would be included in pass 2 when --all-symbols is
180     * specified so exclude them to get a stable symbol list.
181     */
182    static char *special_symbols[] = {
183        "kallsyms_addresses",
184        "kallsyms_num_syms",
185        "kallsyms_names",
186        "kallsyms_markers",
187        "kallsyms_token_table",
188        "kallsyms_token_index",
189
190    /* Exclude linker generated symbols which vary between passes */
191        "_SDA_BASE_", /* ppc */
192        "_SDA2_BASE_", /* ppc */
193        NULL };
194    int i;
195    int offset = 1;
196
197    /* skip prefix char */
198    if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
199        offset++;
200
201    /* if --all-symbols is not specified, then symbols outside the text
202     * and inittext sections are discarded */
203    if (!all_symbols) {
204        if (symbol_valid_tr(s) == 0)
205            return 0;
206        /* Corner case. Discard any symbols with the same value as
207         * _etext _einittext; they can move between pass 1 and 2 when
208         * the kallsyms data are added. If these symbols move then
209         * they may get dropped in pass 2, which breaks the kallsyms
210         * rules.
211         */
212        if ((s->addr == text_range_text->end &&
213                strcmp((char *)s->sym + offset, text_range_text->etext)) ||
214            (s->addr == text_range_inittext->end &&
215                strcmp((char *)s->sym + offset, text_range_inittext->etext)))
216            return 0;
217    }
218
219    /* Exclude symbols which vary between passes. */
220    if (strstr((char *)s->sym + offset, "_compiled."))
221        return 0;
222
223    for (i = 0; special_symbols[i]; i++)
224        if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
225            return 0;
226
227    return 1;
228}
229
230static void read_map(FILE *in)
231{
232    while (!feof(in)) {
233        if (table_cnt >= table_size) {
234            table_size += 10000;
235            table = realloc(table, sizeof(*table) * table_size);
236            if (!table) {
237                fprintf(stderr, "out of memory\n");
238                exit (1);
239            }
240        }
241        if (read_symbol(in, &table[table_cnt]) == 0) {
242            table[table_cnt].start_pos = table_cnt;
243            table_cnt++;
244        }
245    }
246}
247
248static void output_label(char *label)
249{
250    if (symbol_prefix_char)
251        printf(".globl %c%s\n", symbol_prefix_char, label);
252    else
253        printf(".globl %s\n", label);
254    printf("\tALGN\n");
255    if (symbol_prefix_char)
256        printf("%c%s:\n", symbol_prefix_char, label);
257    else
258        printf("%s:\n", label);
259}
260
261/* uncompress a compressed symbol. When this function is called, the best table
262 * might still be compressed itself, so the function needs to be recursive */
263static int expand_symbol(unsigned char *data, int len, char *result)
264{
265    int c, rlen, total=0;
266
267    while (len) {
268        c = *data;
269        /* if the table holds a single char that is the same as the one
270         * we are looking for, then end the search */
271        if (best_table[c][0]==c && best_table_len[c]==1) {
272            *result++ = c;
273            total++;
274        } else {
275            /* if not, recurse and expand */
276            rlen = expand_symbol(best_table[c], best_table_len[c], result);
277            total += rlen;
278            result += rlen;
279        }
280        data++;
281        len--;
282    }
283    *result=0;
284
285    return total;
286}
287
288static void write_src(void)
289{
290    unsigned int i, k, off;
291    unsigned int best_idx[256];
292    unsigned int *markers;
293    char buf[KSYM_NAME_LEN];
294
295    printf("#include <asm/types.h>\n");
296    printf("#if BITS_PER_LONG == 64\n");
297    printf("#define PTR .quad\n");
298    printf("#define ALGN .align 8\n");
299    printf("#else\n");
300    printf("#define PTR .long\n");
301    printf("#define ALGN .align 4\n");
302    printf("#endif\n");
303
304    printf("\t.section .rodata, \"a\"\n");
305
306    /* Provide proper symbols relocatability by their '_text'
307     * relativeness. The symbol names cannot be used to construct
308     * normal symbol references as the list of symbols contains
309     * symbols that are declared static and are private to their
310     * .o files. This prevents .tmp_kallsyms.o or any other
311     * object from referencing them.
312     */
313    output_label("kallsyms_addresses");
314    for (i = 0; i < table_cnt; i++) {
315        if (toupper(table[i].sym[0]) != 'A') {
316            if (_text <= table[i].addr)
317                printf("\tPTR\t_text + %#llx\n",
318                    table[i].addr - _text);
319            else
320                printf("\tPTR\t_text - %#llx\n",
321                    _text - table[i].addr);
322        } else {
323            printf("\tPTR\t%#llx\n", table[i].addr);
324        }
325    }
326    printf("\n");
327
328    output_label("kallsyms_num_syms");
329    printf("\tPTR\t%d\n", table_cnt);
330    printf("\n");
331
332    /* table of offset markers, that give the offset in the compressed stream
333     * every 256 symbols */
334    markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
335    if (!markers) {
336        fprintf(stderr, "kallsyms failure: "
337            "unable to allocate required memory\n");
338        exit(EXIT_FAILURE);
339    }
340
341    output_label("kallsyms_names");
342    off = 0;
343    for (i = 0; i < table_cnt; i++) {
344        if ((i & 0xFF) == 0)
345            markers[i >> 8] = off;
346
347        printf("\t.byte 0x%02x", table[i].len);
348        for (k = 0; k < table[i].len; k++)
349            printf(", 0x%02x", table[i].sym[k]);
350        printf("\n");
351
352        off += table[i].len + 1;
353    }
354    printf("\n");
355
356    output_label("kallsyms_markers");
357    for (i = 0; i < ((table_cnt + 255) >> 8); i++)
358        printf("\tPTR\t%d\n", markers[i]);
359    printf("\n");
360
361    free(markers);
362
363    output_label("kallsyms_token_table");
364    off = 0;
365    for (i = 0; i < 256; i++) {
366        best_idx[i] = off;
367        expand_symbol(best_table[i], best_table_len[i], buf);
368        printf("\t.asciz\t\"%s\"\n", buf);
369        off += strlen(buf) + 1;
370    }
371    printf("\n");
372
373    output_label("kallsyms_token_index");
374    for (i = 0; i < 256; i++)
375        printf("\t.short\t%d\n", best_idx[i]);
376    printf("\n");
377}
378
379
380/* table lookup compression functions */
381
382/* count all the possible tokens in a symbol */
383static void learn_symbol(unsigned char *symbol, int len)
384{
385    int i;
386
387    for (i = 0; i < len - 1; i++)
388        token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
389}
390
391/* decrease the count for all the possible tokens in a symbol */
392static void forget_symbol(unsigned char *symbol, int len)
393{
394    int i;
395
396    for (i = 0; i < len - 1; i++)
397        token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
398}
399
400/* remove all the invalid symbols from the table and do the initial token count */
401static void build_initial_tok_table(void)
402{
403    unsigned int i, pos;
404
405    pos = 0;
406    for (i = 0; i < table_cnt; i++) {
407        if ( symbol_valid(&table[i]) ) {
408            if (pos != i)
409                table[pos] = table[i];
410            learn_symbol(table[pos].sym, table[pos].len);
411            pos++;
412        }
413    }
414    table_cnt = pos;
415}
416
417static void *find_token(unsigned char *str, int len, unsigned char *token)
418{
419    int i;
420
421    for (i = 0; i < len - 1; i++) {
422        if (str[i] == token[0] && str[i+1] == token[1])
423            return &str[i];
424    }
425    return NULL;
426}
427
428/* replace a given token in all the valid symbols. Use the sampled symbols
429 * to update the counts */
430static void compress_symbols(unsigned char *str, int idx)
431{
432    unsigned int i, len, size;
433    unsigned char *p1, *p2;
434
435    for (i = 0; i < table_cnt; i++) {
436
437        len = table[i].len;
438        p1 = table[i].sym;
439
440        /* find the token on the symbol */
441        p2 = find_token(p1, len, str);
442        if (!p2) continue;
443
444        /* decrease the counts for this symbol's tokens */
445        forget_symbol(table[i].sym, len);
446
447        size = len;
448
449        do {
450            *p2 = idx;
451            p2++;
452            size -= (p2 - p1);
453            memmove(p2, p2 + 1, size);
454            p1 = p2;
455            len--;
456
457            if (size < 2) break;
458
459            /* find the token on the symbol */
460            p2 = find_token(p1, size, str);
461
462        } while (p2);
463
464        table[i].len = len;
465
466        /* increase the counts for this symbol's new tokens */
467        learn_symbol(table[i].sym, len);
468    }
469}
470
471/* search the token with the maximum profit */
472static int find_best_token(void)
473{
474    int i, best, bestprofit;
475
476    bestprofit=-10000;
477    best = 0;
478
479    for (i = 0; i < 0x10000; i++) {
480        if (token_profit[i] > bestprofit) {
481            best = i;
482            bestprofit = token_profit[i];
483        }
484    }
485    return best;
486}
487
488/* this is the core of the algorithm: calculate the "best" table */
489static void optimize_result(void)
490{
491    int i, best;
492
493    /* using the '\0' symbol last allows compress_symbols to use standard
494     * fast string functions */
495    for (i = 255; i >= 0; i--) {
496
497        /* if this table slot is empty (it is not used by an actual
498         * original char code */
499        if (!best_table_len[i]) {
500
501            /* find the token with the breates profit value */
502            best = find_best_token();
503            if (token_profit[best] == 0)
504                break;
505
506            /* place it in the "best" table */
507            best_table_len[i] = 2;
508            best_table[i][0] = best & 0xFF;
509            best_table[i][1] = (best >> 8) & 0xFF;
510
511            /* replace this token in all the valid symbols */
512            compress_symbols(best_table[i], i);
513        }
514    }
515}
516
517/* start by placing the symbols that are actually used on the table */
518static void insert_real_symbols_in_table(void)
519{
520    unsigned int i, j, c;
521
522    memset(best_table, 0, sizeof(best_table));
523    memset(best_table_len, 0, sizeof(best_table_len));
524
525    for (i = 0; i < table_cnt; i++) {
526        for (j = 0; j < table[i].len; j++) {
527            c = table[i].sym[j];
528            best_table[c][0]=c;
529            best_table_len[c]=1;
530        }
531    }
532}
533
534static void optimize_token_table(void)
535{
536    build_initial_tok_table();
537
538    insert_real_symbols_in_table();
539
540    /* When valid symbol is not registered, exit to error */
541    if (!table_cnt) {
542        fprintf(stderr, "No valid symbol.\n");
543        exit(1);
544    }
545
546    optimize_result();
547}
548
549/* guess for "linker script provide" symbol */
550static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
551{
552    const char *symbol = (char *)se->sym + 1;
553    int len = se->len - 1;
554
555    if (len < 8)
556        return 0;
557
558    if (symbol[0] != '_' || symbol[1] != '_')
559        return 0;
560
561    /* __start_XXXXX */
562    if (!memcmp(symbol + 2, "start_", 6))
563        return 1;
564
565    /* __stop_XXXXX */
566    if (!memcmp(symbol + 2, "stop_", 5))
567        return 1;
568
569    /* __end_XXXXX */
570    if (!memcmp(symbol + 2, "end_", 4))
571        return 1;
572
573    /* __XXXXX_start */
574    if (!memcmp(symbol + len - 6, "_start", 6))
575        return 1;
576
577    /* __XXXXX_end */
578    if (!memcmp(symbol + len - 4, "_end", 4))
579        return 1;
580
581    return 0;
582}
583
584static int prefix_underscores_count(const char *str)
585{
586    const char *tail = str;
587
588    while (*tail == '_')
589        tail++;
590
591    return tail - str;
592}
593
594static int compare_symbols(const void *a, const void *b)
595{
596    const struct sym_entry *sa;
597    const struct sym_entry *sb;
598    int wa, wb;
599
600    sa = a;
601    sb = b;
602
603    /* sort by address first */
604    if (sa->addr > sb->addr)
605        return 1;
606    if (sa->addr < sb->addr)
607        return -1;
608
609    /* sort by "weakness" type */
610    wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
611    wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
612    if (wa != wb)
613        return wa - wb;
614
615    /* sort by "linker script provide" type */
616    wa = may_be_linker_script_provide_symbol(sa);
617    wb = may_be_linker_script_provide_symbol(sb);
618    if (wa != wb)
619        return wa - wb;
620
621    /* sort by the number of prefix underscores */
622    wa = prefix_underscores_count((const char *)sa->sym + 1);
623    wb = prefix_underscores_count((const char *)sb->sym + 1);
624    if (wa != wb)
625        return wa - wb;
626
627    /* sort by initial order, so that other symbols are left undisturbed */
628    return sa->start_pos - sb->start_pos;
629}
630
631static void sort_symbols(void)
632{
633    qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
634}
635
636int main(int argc, char **argv)
637{
638    if (argc >= 2) {
639        int i;
640        for (i = 1; i < argc; i++) {
641            if(strcmp(argv[i], "--all-symbols") == 0)
642                all_symbols = 1;
643            else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
644                char *p = &argv[i][16];
645                /* skip quote */
646                if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
647                    p++;
648                symbol_prefix_char = *p;
649            } else
650                usage();
651        }
652    } else if (argc != 1)
653        usage();
654
655    read_map(stdin);
656    sort_symbols();
657    optimize_token_table();
658    write_src();
659
660    return 0;
661}
662

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