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Diffstat (limited to 'scripts/kallsyms.c')
| -rw-r--r-- | scripts/kallsyms.c | 686 |
1 files changed, 686 insertions, 0 deletions
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c new file mode 100644 index 00000000000..090ffda4adb --- /dev/null +++ b/scripts/kallsyms.c @@ -0,0 +1,686 @@ +/* Generate assembler source containing symbol information + * + * Copyright 2002 by Kai Germaschewski + * + * This software may be used and distributed according to the terms + * of the GNU General Public License, incorporated herein by reference. + * + * Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S + * + * ChangeLog: + * + * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com> + * Changed the compression method from stem compression to "table lookup" + * compression + * + * Table compression uses all the unused char codes on the symbols and + * maps these to the most used substrings (tokens). For instance, it might + * map char code 0xF7 to represent "write_" and then in every symbol where + * "write_" appears it can be replaced by 0xF7, saving 5 bytes. + * The used codes themselves are also placed in the table so that the + * decompresion can work without "special cases". + * Applied to kernel symbols, this usually produces a compression ratio + * of about 50%. + * + */ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <ctype.h> + +/* maximum token length used. It doesn't pay to increase it a lot, because + * very long substrings probably don't repeat themselves too often. */ +#define MAX_TOK_SIZE 11 +#define KSYM_NAME_LEN 127 + +/* we use only a subset of the complete symbol table to gather the token count, + * to speed up compression, at the expense of a little compression ratio */ +#define WORKING_SET 1024 + +/* first find the best token only on the list of tokens that would profit more + * than GOOD_BAD_THRESHOLD. Only if this list is empty go to the "bad" list. + * Increasing this value will put less tokens on the "good" list, so the search + * is faster. However, if the good list runs out of tokens, we must painfully + * search the bad list. */ +#define GOOD_BAD_THRESHOLD 10 + +/* token hash parameters */ +#define HASH_BITS 18 +#define HASH_TABLE_SIZE (1 << HASH_BITS) +#define HASH_MASK (HASH_TABLE_SIZE - 1) +#define HASH_BASE_OFFSET 2166136261U +#define HASH_FOLD(a) ((a)&(HASH_MASK)) + +/* flags to mark symbols */ +#define SYM_FLAG_VALID 1 +#define SYM_FLAG_SAMPLED 2 + +struct sym_entry { + unsigned long long addr; + char type; + unsigned char flags; + unsigned char len; + unsigned char *sym; +}; + + +static struct sym_entry *table; +static int size, cnt; +static unsigned long long _stext, _etext, _sinittext, _einittext; +static int all_symbols = 0; + +struct token { + unsigned char data[MAX_TOK_SIZE]; + unsigned char len; + /* profit: the number of bytes that could be saved by inserting this + * token into the table */ + int profit; + struct token *next; /* next token on the hash list */ + struct token *right; /* next token on the good/bad list */ + struct token *left; /* previous token on the good/bad list */ + struct token *smaller; /* token that is less one letter than this one */ + }; + +struct token bad_head, good_head; +struct token *hash_table[HASH_TABLE_SIZE]; + +/* the table that holds the result of the compression */ +unsigned char best_table[256][MAX_TOK_SIZE+1]; +unsigned char best_table_len[256]; + + +static void +usage(void) +{ + fprintf(stderr, "Usage: kallsyms [--all-symbols] < in.map > out.S\n"); + exit(1); +} + +/* + * This ignores the intensely annoying "mapping symbols" found + * in ARM ELF files: $a, $t and $d. + */ +static inline int +is_arm_mapping_symbol(const char *str) +{ + return str[0] == '$' && strchr("atd", str[1]) + && (str[2] == '\0' || str[2] == '.'); +} + +static int +read_symbol(FILE *in, struct sym_entry *s) +{ + char str[500]; + int rc; + + rc = fscanf(in, "%llx %c %499s\n", &s->addr, &s->type, str); + if (rc != 3) { + if (rc != EOF) { + /* skip line */ + fgets(str, 500, in); + } + return -1; + } + + /* Ignore most absolute/undefined (?) symbols. */ + if (strcmp(str, "_stext") == 0) + _stext = s->addr; + else if (strcmp(str, "_etext") == 0) + _etext = s->addr; + else if (strcmp(str, "_sinittext") == 0) + _sinittext = s->addr; + else if (strcmp(str, "_einittext") == 0) + _einittext = s->addr; + else if (toupper(s->type) == 'A') + { + /* Keep these useful absolute symbols */ + if (strcmp(str, "__kernel_syscall_via_break") && + strcmp(str, "__kernel_syscall_via_epc") && + strcmp(str, "__kernel_sigtramp") && + strcmp(str, "__gp")) + return -1; + + } + else if (toupper(s->type) == 'U' || + is_arm_mapping_symbol(str)) + return -1; + + /* include the type field in the symbol name, so that it gets + * compressed together */ + s->len = strlen(str) + 1; + s->sym = (char *) malloc(s->len + 1); + strcpy(s->sym + 1, str); + s->sym[0] = s->type; + + return 0; +} + +static int +symbol_valid(struct sym_entry *s) +{ + /* Symbols which vary between passes. Passes 1 and 2 must have + * identical symbol lists. The kallsyms_* symbols below are only added + * after pass 1, they would be included in pass 2 when --all-symbols is + * specified so exclude them to get a stable symbol list. + */ + static char *special_symbols[] = { + "kallsyms_addresses", + "kallsyms_num_syms", + "kallsyms_names", + "kallsyms_markers", + "kallsyms_token_table", + "kallsyms_token_index", + + /* Exclude linker generated symbols which vary between passes */ + "_SDA_BASE_", /* ppc */ + "_SDA2_BASE_", /* ppc */ + NULL }; + int i; + + /* if --all-symbols is not specified, then symbols outside the text + * and inittext sections are discarded */ + if (!all_symbols) { + if ((s->addr < _stext || s->addr > _etext) + && (s->addr < _sinittext || s->addr > _einittext)) + return 0; + /* Corner case. Discard any symbols with the same value as + * _etext or _einittext, they can move between pass 1 and 2 + * when the kallsyms data is added. If these symbols move then + * they may get dropped in pass 2, which breaks the kallsyms + * rules. + */ + if ((s->addr == _etext && strcmp(s->sym + 1, "_etext")) || + (s->addr == _einittext && strcmp(s->sym + 1, "_einittext"))) + return 0; + } + + /* Exclude symbols which vary between passes. */ + if (strstr(s->sym + 1, "_compiled.")) + return 0; + + for (i = 0; special_symbols[i]; i++) + if( strcmp(s->sym + 1, special_symbols[i]) == 0 ) + return 0; + + return 1; +} + +static void +read_map(FILE *in) +{ + while (!feof(in)) { + if (cnt >= size) { + size += 10000; + table = realloc(table, sizeof(*table) * size); + if (!table) { + fprintf(stderr, "out of memory\n"); + exit (1); + } + } + if (read_symbol(in, &table[cnt]) == 0) + cnt++; + } +} + +static void output_label(char *label) +{ + printf(".globl %s\n",label); + printf("\tALGN\n"); + printf("%s:\n",label); +} + +/* uncompress a compressed symbol. When this function is called, the best table + * might still be compressed itself, so the function needs to be recursive */ +static int expand_symbol(unsigned char *data, int len, char *result) +{ + int c, rlen, total=0; + + while (len) { + c = *data; + /* if the table holds a single char that is the same as the one + * we are looking for, then end the search */ + if (best_table[c][0]==c && best_table_len[c]==1) { + *result++ = c; + total++; + } else { + /* if not, recurse and expand */ + rlen = expand_symbol(best_table[c], best_table_len[c], result); + total += rlen; + result += rlen; + } + data++; + len--; + } + *result=0; + + return total; +} + +static void +write_src(void) +{ + int i, k, off, valid; + unsigned int best_idx[256]; + unsigned int *markers; + char buf[KSYM_NAME_LEN+1]; + + printf("#include <asm/types.h>\n"); + printf("#if BITS_PER_LONG == 64\n"); + printf("#define PTR .quad\n"); + printf("#define ALGN .align 8\n"); + printf("#else\n"); + printf("#define PTR .long\n"); + printf("#define ALGN .align 4\n"); + printf("#endif\n"); + + printf(".data\n"); + + output_label("kallsyms_addresses"); + valid = 0; + for (i = 0; i < cnt; i++) { + if (table[i].flags & SYM_FLAG_VALID) { + printf("\tPTR\t%#llx\n", table[i].addr); + valid++; + } + } + printf("\n"); + + output_label("kallsyms_num_syms"); + printf("\tPTR\t%d\n", valid); + printf("\n"); + + /* table of offset markers, that give the offset in the compressed stream + * every 256 symbols */ + markers = (unsigned int *) malloc(sizeof(unsigned int)*((valid + 255) / 256)); + + output_label("kallsyms_names"); + valid = 0; + off = 0; + for (i = 0; i < cnt; i++) { + + if (!table[i].flags & SYM_FLAG_VALID) + continue; + + if ((valid & 0xFF) == 0) + markers[valid >> 8] = off; + + printf("\t.byte 0x%02x", table[i].len); + for (k = 0; k < table[i].len; k++) + printf(", 0x%02x", table[i].sym[k]); + printf("\n"); + + off += table[i].len + 1; + valid++; + } + printf("\n"); + + output_label("kallsyms_markers"); + for (i = 0; i < ((valid + 255) >> 8); i++) + printf("\tPTR\t%d\n", markers[i]); + printf("\n"); + + free(markers); + + output_label("kallsyms_token_table"); + off = 0; + for (i = 0; i < 256; i++) { + best_idx[i] = off; + expand_symbol(best_table[i],best_table_len[i],buf); + printf("\t.asciz\t\"%s\"\n", buf); + off += strlen(buf) + 1; + } + printf("\n"); + + output_label("kallsyms_token_index"); + for (i = 0; i < 256; i++) + printf("\t.short\t%d\n", best_idx[i]); + printf("\n"); +} + + +/* table lookup compression functions */ + +static inline unsigned int rehash_token(unsigned int hash, unsigned char data) +{ + return ((hash * 16777619) ^ data); +} + +static unsigned int hash_token(unsigned char *data, int len) +{ + unsigned int hash=HASH_BASE_OFFSET; + int i; + + for (i = 0; i < len; i++) + hash = rehash_token(hash, data[i]); + + return HASH_FOLD(hash); +} + +/* find a token given its data and hash value */ +static struct token *find_token_hash(unsigned char *data, int len, unsigned int hash) +{ + struct token *ptr; + + ptr = hash_table[hash]; + + while (ptr) { + if ((ptr->len == len) && (memcmp(ptr->data, data, len) == 0)) + return ptr; + ptr=ptr->next; + } + + return NULL; +} + +static inline void insert_token_in_group(struct token *head, struct token *ptr) +{ + ptr->right = head->right; + ptr->right->left = ptr; + head->right = ptr; + ptr->left = head; +} + +static inline void remove_token_from_group(struct token *ptr) +{ + ptr->left->right = ptr->right; + ptr->right->left = ptr->left; +} + + +/* build the counts for all the tokens that start with "data", and have lenghts + * from 2 to "len" */ +static void learn_token(unsigned char *data, int len) +{ + struct token *ptr,*last_ptr; + int i, newprofit; + unsigned int hash = HASH_BASE_OFFSET; + unsigned int hashes[MAX_TOK_SIZE + 1]; + + if (len > MAX_TOK_SIZE) + len = MAX_TOK_SIZE; + + /* calculate and store the hash values for all the sub-tokens */ + hash = rehash_token(hash, data[0]); + for (i = 2; i <= len; i++) { + hash = rehash_token(hash, data[i-1]); + hashes[i] = HASH_FOLD(hash); + } + + last_ptr = NULL; + ptr = NULL; + + for (i = len; i >= 2; i--) { + hash = hashes[i]; + + if (!ptr) ptr = find_token_hash(data, i, hash); + + if (!ptr) { + /* create a new token entry */ + ptr = (struct token *) malloc(sizeof(*ptr)); + + memcpy(ptr->data, data, i); + ptr->len = i; + + /* when we create an entry, it's profit is 0 because + * we also take into account the size of the token on + * the compressed table. We then subtract GOOD_BAD_THRESHOLD + * so that the test to see if this token belongs to + * the good or bad list, is a comparison to zero */ + ptr->profit = -GOOD_BAD_THRESHOLD; + + ptr->next = hash_table[hash]; + hash_table[hash] = ptr; + + insert_token_in_group(&bad_head, ptr); + + ptr->smaller = NULL; + } else { + newprofit = ptr->profit + (ptr->len - 1); + /* check to see if this token needs to be moved to a + * different list */ + if((ptr->profit < 0) && (newprofit >= 0)) { + remove_token_from_group(ptr); + insert_token_in_group(&good_head,ptr); + } + ptr->profit = newprofit; + } + + if (last_ptr) last_ptr->smaller = ptr; + last_ptr = ptr; + + ptr = ptr->smaller; + } +} + +/* decrease the counts for all the tokens that start with "data", and have lenghts + * from 2 to "len". This function is much simpler than learn_token because we have + * more guarantees (tho tokens exist, the ->smaller pointer is set, etc.) + * The two separate functions exist only because of compression performance */ +static void forget_token(unsigned char *data, int len) +{ + struct token *ptr; + int i, newprofit; + unsigned int hash=0; + + if (len > MAX_TOK_SIZE) len = MAX_TOK_SIZE; + + hash = hash_token(data, len); + ptr = find_token_hash(data, len, hash); + + for (i = len; i >= 2; i--) { + + newprofit = ptr->profit - (ptr->len - 1); + if ((ptr->profit >= 0) && (newprofit < 0)) { + remove_token_from_group(ptr); + insert_token_in_group(&bad_head, ptr); + } + ptr->profit=newprofit; + + ptr=ptr->smaller; + } +} + +/* count all the possible tokens in a symbol */ +static void learn_symbol(unsigned char *symbol, int len) +{ + int i; + + for (i = 0; i < len - 1; i++) + learn_token(symbol + i, len - i); +} + +/* decrease the count for all the possible tokens in a symbol */ +static void forget_symbol(unsigned char *symbol, int len) +{ + int i; + + for (i = 0; i < len - 1; i++) + forget_token(symbol + i, len - i); +} + +/* set all the symbol flags and do the initial token count */ +static void build_initial_tok_table(void) +{ + int i, use_it, valid; + + valid = 0; + for (i = 0; i < cnt; i++) { + table[i].flags = 0; + if ( symbol_valid(&table[i]) ) { + table[i].flags |= SYM_FLAG_VALID; + valid++; + } + } + + use_it = 0; + for (i = 0; i < cnt; i++) { + + /* subsample the available symbols. This method is almost like + * a Bresenham's algorithm to get uniformly distributed samples + * across the symbol table */ + if (table[i].flags & SYM_FLAG_VALID) { + + use_it += WORKING_SET; + + if (use_it >= valid) { + table[i].flags |= SYM_FLAG_SAMPLED; + use_it -= valid; + } + } + if (table[i].flags & SYM_FLAG_SAMPLED) + learn_symbol(table[i].sym, table[i].len); + } +} + +/* replace a given token in all the valid symbols. Use the sampled symbols + * to update the counts */ +static void compress_symbols(unsigned char *str, int tlen, int idx) +{ + int i, len, learn, size; + unsigned char *p; + + for (i = 0; i < cnt; i++) { + + if (!(table[i].flags & SYM_FLAG_VALID)) continue; + + len = table[i].len; + learn = 0; + p = table[i].sym; + + do { + /* find the token on the symbol */ + p = (unsigned char *) strstr((char *) p, (char *) str); + if (!p) break; + + if (!learn) { + /* if this symbol was used to count, decrease it */ + if (table[i].flags & SYM_FLAG_SAMPLED) + forget_symbol(table[i].sym, len); + learn = 1; + } + + *p = idx; + size = (len - (p - table[i].sym)) - tlen + 1; + memmove(p + 1, p + tlen, size); + p++; + len -= tlen - 1; + + } while (size >= tlen); + + if(learn) { + table[i].len = len; + /* if this symbol was used to count, learn it again */ + if(table[i].flags & SYM_FLAG_SAMPLED) + learn_symbol(table[i].sym, len); + } + } +} + +/* search the token with the maximum profit */ +static struct token *find_best_token(void) +{ + struct token *ptr,*best,*head; + int bestprofit; + + bestprofit=-10000; + + /* failsafe: if the "good" list is empty search from the "bad" list */ + if(good_head.right == &good_head) head = &bad_head; + else head = &good_head; + + ptr = head->right; + best = NULL; + while (ptr != head) { + if (ptr->profit > bestprofit) { + bestprofit = ptr->profit; + best = ptr; + } + ptr = ptr->right; + } + + return best; +} + +/* this is the core of the algorithm: calculate the "best" table */ +static void optimize_result(void) +{ + struct token *best; + int i; + + /* using the '\0' symbol last allows compress_symbols to use standard + * fast string functions */ + for (i = 255; i >= 0; i--) { + + /* if this table slot is empty (it is not used by an actual + * original char code */ + if (!best_table_len[i]) { + + /* find the token with the breates profit value */ + best = find_best_token(); + + /* place it in the "best" table */ + best_table_len[i] = best->len; + memcpy(best_table[i], best->data, best_table_len[i]); + /* zero terminate the token so that we can use strstr + in compress_symbols */ + best_table[i][best_table_len[i]]='\0'; + + /* replace this token in all the valid symbols */ + compress_symbols(best_table[i], best_table_len[i], i); + } + } +} + +/* start by placing the symbols that are actually used on the table */ +static void insert_real_symbols_in_table(void) +{ + int i, j, c; + + memset(best_table, 0, sizeof(best_table)); + memset(best_table_len, 0, sizeof(best_table_len)); + + for (i = 0; i < cnt; i++) { + if (table[i].flags & SYM_FLAG_VALID) { + for (j = 0; j < table[i].len; j++) { + c = table[i].sym[j]; + best_table[c][0]=c; + best_table_len[c]=1; + } + } + } +} + +static void optimize_token_table(void) +{ + memset(hash_table, 0, sizeof(hash_table)); + + good_head.left = &good_head; + good_head.right = &good_head; + + bad_head.left = &bad_head; + bad_head.right = &bad_head; + + build_initial_tok_table(); + + insert_real_symbols_in_table(); + + optimize_result(); +} + + +int +main(int argc, char **argv) +{ + if (argc == 2 && strcmp(argv[1], "--all-symbols") == 0) + all_symbols = 1; + else if (argc != 1) + usage(); + + read_map(stdin); + optimize_token_table(); + write_src(); + + return 0; +} + |