508 lines
12 KiB
C
508 lines
12 KiB
C
/* Generate assembler source containing symbol information
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*
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* Copyright 2002 by Kai Germaschewski
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*
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* This software may be used and distributed according to the terms
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* of the GNU General Public License, incorporated herein by reference.
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*
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* Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S
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*
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* ChangeLog:
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*
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* (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
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* Changed the compression method from stem compression to "table lookup"
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* compression
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*
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* Table compression uses all the unused char codes on the symbols and
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* maps these to the most used substrings (tokens). For instance, it might
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* map char code 0xF7 to represent "write_" and then in every symbol where
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* "write_" appears it can be replaced by 0xF7, saving 5 bytes.
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* The used codes themselves are also placed in the table so that the
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* decompresion can work without "special cases".
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* Applied to kernel symbols, this usually produces a compression ratio
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* of about 50%.
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*
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#define KSYM_NAME_LEN 127
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struct sym_entry {
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unsigned long long addr;
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unsigned int len;
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unsigned char *sym;
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};
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static struct sym_entry *table;
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static unsigned int table_size, table_cnt;
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static unsigned long long _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
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static int all_symbols = 0;
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static char symbol_prefix_char = '\0';
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int token_profit[0x10000];
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/* the table that holds the result of the compression */
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unsigned char best_table[256][2];
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unsigned char best_table_len[256];
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static void usage(void)
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{
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fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
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exit(1);
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}
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/*
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* This ignores the intensely annoying "mapping symbols" found
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* in ARM ELF files: $a, $t and $d.
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*/
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static inline int is_arm_mapping_symbol(const char *str)
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{
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return str[0] == '$' && strchr("atd", str[1])
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&& (str[2] == '\0' || str[2] == '.');
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}
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static int read_symbol(FILE *in, struct sym_entry *s)
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{
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char str[500];
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char *sym, stype;
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int rc;
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rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
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if (rc != 3) {
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if (rc != EOF) {
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/* skip line */
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fgets(str, 500, in);
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}
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return -1;
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}
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sym = str;
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/* skip prefix char */
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if (symbol_prefix_char && str[0] == symbol_prefix_char)
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sym++;
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/* Ignore most absolute/undefined (?) symbols. */
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if (strcmp(sym, "_stext") == 0)
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_stext = s->addr;
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else if (strcmp(sym, "_etext") == 0)
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_etext = s->addr;
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else if (strcmp(sym, "_sinittext") == 0)
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_sinittext = s->addr;
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else if (strcmp(sym, "_einittext") == 0)
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_einittext = s->addr;
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else if (strcmp(sym, "_sextratext") == 0)
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_sextratext = s->addr;
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else if (strcmp(sym, "_eextratext") == 0)
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_eextratext = s->addr;
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else if (toupper(stype) == 'A')
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{
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/* Keep these useful absolute symbols */
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if (strcmp(sym, "__kernel_syscall_via_break") &&
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strcmp(sym, "__kernel_syscall_via_epc") &&
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strcmp(sym, "__kernel_sigtramp") &&
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strcmp(sym, "__gp"))
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return -1;
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}
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else if (toupper(stype) == 'U' ||
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is_arm_mapping_symbol(sym))
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return -1;
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/* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
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else if (str[0] == '$')
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return -1;
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/* include the type field in the symbol name, so that it gets
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* compressed together */
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s->len = strlen(str) + 1;
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s->sym = malloc(s->len + 1);
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if (!s->sym) {
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fprintf(stderr, "kallsyms failure: "
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"unable to allocate required amount of memory\n");
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exit(EXIT_FAILURE);
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}
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strcpy((char *)s->sym + 1, str);
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s->sym[0] = stype;
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return 0;
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}
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static int symbol_valid(struct sym_entry *s)
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{
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/* Symbols which vary between passes. Passes 1 and 2 must have
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* identical symbol lists. The kallsyms_* symbols below are only added
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* after pass 1, they would be included in pass 2 when --all-symbols is
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* specified so exclude them to get a stable symbol list.
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*/
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static char *special_symbols[] = {
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"kallsyms_addresses",
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"kallsyms_num_syms",
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"kallsyms_names",
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"kallsyms_markers",
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"kallsyms_token_table",
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"kallsyms_token_index",
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/* Exclude linker generated symbols which vary between passes */
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"_SDA_BASE_", /* ppc */
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"_SDA2_BASE_", /* ppc */
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NULL };
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int i;
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int offset = 1;
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/* skip prefix char */
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if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
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offset++;
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/* if --all-symbols is not specified, then symbols outside the text
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* and inittext sections are discarded */
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if (!all_symbols) {
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if ((s->addr < _stext || s->addr > _etext)
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&& (s->addr < _sinittext || s->addr > _einittext)
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&& (s->addr < _sextratext || s->addr > _eextratext))
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return 0;
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/* Corner case. Discard any symbols with the same value as
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* _etext _einittext or _eextratext; they can move between pass
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* 1 and 2 when the kallsyms data are added. If these symbols
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* move then they may get dropped in pass 2, which breaks the
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* kallsyms rules.
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*/
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if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
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(s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
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(s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
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return 0;
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}
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/* Exclude symbols which vary between passes. */
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if (strstr((char *)s->sym + offset, "_compiled."))
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return 0;
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for (i = 0; special_symbols[i]; i++)
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if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
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return 0;
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return 1;
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}
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static void read_map(FILE *in)
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{
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while (!feof(in)) {
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if (table_cnt >= table_size) {
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table_size += 10000;
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table = realloc(table, sizeof(*table) * table_size);
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if (!table) {
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fprintf(stderr, "out of memory\n");
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exit (1);
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}
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}
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if (read_symbol(in, &table[table_cnt]) == 0)
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table_cnt++;
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}
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}
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static void output_label(char *label)
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{
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if (symbol_prefix_char)
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printf(".globl %c%s\n", symbol_prefix_char, label);
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else
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printf(".globl %s\n", label);
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printf("\tALGN\n");
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if (symbol_prefix_char)
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printf("%c%s:\n", symbol_prefix_char, label);
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else
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printf("%s:\n", label);
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}
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/* uncompress a compressed symbol. When this function is called, the best table
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* might still be compressed itself, so the function needs to be recursive */
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static int expand_symbol(unsigned char *data, int len, char *result)
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{
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int c, rlen, total=0;
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while (len) {
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c = *data;
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/* if the table holds a single char that is the same as the one
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* we are looking for, then end the search */
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if (best_table[c][0]==c && best_table_len[c]==1) {
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*result++ = c;
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total++;
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} else {
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/* if not, recurse and expand */
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rlen = expand_symbol(best_table[c], best_table_len[c], result);
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total += rlen;
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result += rlen;
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}
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data++;
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len--;
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}
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*result=0;
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return total;
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}
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static void write_src(void)
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{
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unsigned int i, k, off;
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unsigned int best_idx[256];
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unsigned int *markers;
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char buf[KSYM_NAME_LEN+1];
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printf("#include <asm/types.h>\n");
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printf("#if BITS_PER_LONG == 64\n");
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printf("#define PTR .quad\n");
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printf("#define ALGN .align 8\n");
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printf("#else\n");
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printf("#define PTR .long\n");
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printf("#define ALGN .align 4\n");
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printf("#endif\n");
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printf(".data\n");
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output_label("kallsyms_addresses");
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for (i = 0; i < table_cnt; i++) {
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printf("\tPTR\t%#llx\n", table[i].addr);
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}
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printf("\n");
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output_label("kallsyms_num_syms");
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printf("\tPTR\t%d\n", table_cnt);
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printf("\n");
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/* table of offset markers, that give the offset in the compressed stream
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* every 256 symbols */
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markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
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if (!markers) {
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fprintf(stderr, "kallsyms failure: "
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"unable to allocate required memory\n");
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exit(EXIT_FAILURE);
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}
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output_label("kallsyms_names");
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off = 0;
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for (i = 0; i < table_cnt; i++) {
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if ((i & 0xFF) == 0)
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markers[i >> 8] = off;
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printf("\t.byte 0x%02x", table[i].len);
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for (k = 0; k < table[i].len; k++)
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printf(", 0x%02x", table[i].sym[k]);
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printf("\n");
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off += table[i].len + 1;
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}
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printf("\n");
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output_label("kallsyms_markers");
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for (i = 0; i < ((table_cnt + 255) >> 8); i++)
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printf("\tPTR\t%d\n", markers[i]);
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printf("\n");
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free(markers);
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output_label("kallsyms_token_table");
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off = 0;
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for (i = 0; i < 256; i++) {
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best_idx[i] = off;
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expand_symbol(best_table[i], best_table_len[i], buf);
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printf("\t.asciz\t\"%s\"\n", buf);
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off += strlen(buf) + 1;
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}
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printf("\n");
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output_label("kallsyms_token_index");
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for (i = 0; i < 256; i++)
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printf("\t.short\t%d\n", best_idx[i]);
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printf("\n");
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}
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/* table lookup compression functions */
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/* count all the possible tokens in a symbol */
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static void learn_symbol(unsigned char *symbol, int len)
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{
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int i;
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for (i = 0; i < len - 1; i++)
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token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
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}
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/* decrease the count for all the possible tokens in a symbol */
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static void forget_symbol(unsigned char *symbol, int len)
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{
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int i;
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for (i = 0; i < len - 1; i++)
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token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
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}
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/* remove all the invalid symbols from the table and do the initial token count */
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static void build_initial_tok_table(void)
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{
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unsigned int i, pos;
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pos = 0;
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for (i = 0; i < table_cnt; i++) {
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if ( symbol_valid(&table[i]) ) {
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if (pos != i)
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table[pos] = table[i];
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learn_symbol(table[pos].sym, table[pos].len);
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pos++;
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}
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}
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table_cnt = pos;
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}
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/* replace a given token in all the valid symbols. Use the sampled symbols
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* to update the counts */
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static void compress_symbols(unsigned char *str, int idx)
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{
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unsigned int i, len, size;
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unsigned char *p1, *p2;
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for (i = 0; i < table_cnt; i++) {
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len = table[i].len;
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p1 = table[i].sym;
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/* find the token on the symbol */
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p2 = memmem(p1, len, str, 2);
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if (!p2) continue;
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/* decrease the counts for this symbol's tokens */
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forget_symbol(table[i].sym, len);
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size = len;
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do {
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*p2 = idx;
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p2++;
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size -= (p2 - p1);
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memmove(p2, p2 + 1, size);
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p1 = p2;
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len--;
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if (size < 2) break;
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/* find the token on the symbol */
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p2 = memmem(p1, size, str, 2);
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} while (p2);
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table[i].len = len;
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/* increase the counts for this symbol's new tokens */
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learn_symbol(table[i].sym, len);
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}
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}
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/* search the token with the maximum profit */
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static int find_best_token(void)
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{
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int i, best, bestprofit;
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bestprofit=-10000;
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best = 0;
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for (i = 0; i < 0x10000; i++) {
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if (token_profit[i] > bestprofit) {
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best = i;
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bestprofit = token_profit[i];
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}
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}
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return best;
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}
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/* this is the core of the algorithm: calculate the "best" table */
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static void optimize_result(void)
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{
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int i, best;
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/* using the '\0' symbol last allows compress_symbols to use standard
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* fast string functions */
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for (i = 255; i >= 0; i--) {
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/* if this table slot is empty (it is not used by an actual
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* original char code */
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if (!best_table_len[i]) {
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/* find the token with the breates profit value */
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best = find_best_token();
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/* place it in the "best" table */
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best_table_len[i] = 2;
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best_table[i][0] = best & 0xFF;
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best_table[i][1] = (best >> 8) & 0xFF;
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/* replace this token in all the valid symbols */
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compress_symbols(best_table[i], i);
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}
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}
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}
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/* start by placing the symbols that are actually used on the table */
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static void insert_real_symbols_in_table(void)
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{
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unsigned int i, j, c;
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memset(best_table, 0, sizeof(best_table));
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memset(best_table_len, 0, sizeof(best_table_len));
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for (i = 0; i < table_cnt; i++) {
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for (j = 0; j < table[i].len; j++) {
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c = table[i].sym[j];
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best_table[c][0]=c;
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best_table_len[c]=1;
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}
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}
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}
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static void optimize_token_table(void)
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{
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build_initial_tok_table();
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insert_real_symbols_in_table();
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/* When valid symbol is not registered, exit to error */
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if (!table_cnt) {
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fprintf(stderr, "No valid symbol.\n");
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exit(1);
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}
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optimize_result();
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}
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int main(int argc, char **argv)
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{
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if (argc >= 2) {
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int i;
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for (i = 1; i < argc; i++) {
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if(strcmp(argv[i], "--all-symbols") == 0)
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all_symbols = 1;
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else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
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char *p = &argv[i][16];
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/* skip quote */
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if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
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p++;
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symbol_prefix_char = *p;
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} else
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usage();
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}
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} else if (argc != 1)
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usage();
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read_map(stdin);
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optimize_token_table();
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write_src();
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return 0;
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}
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