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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#include <errno.h>#include <getopt.h>#include <stdbool.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <ctype.h>#include <limits.h>
#include <xalloc.h>
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
#define KSYM_NAME_LEN 512
struct sym_entry { unsigned long long addr; unsigned int len; unsigned int seq; unsigned char sym[];};
struct addr_range { const char *start_sym, *end_sym; unsigned long long start, end;};
static unsigned long long _text;static struct addr_range text_ranges[] = { { "_stext", "_etext" }, { "_sinittext", "_einittext" },};#define text_range_text (&text_ranges[0])#define text_range_inittext (&text_ranges[1])
static struct sym_entry **table;static unsigned int table_size, table_cnt;static int all_symbols;static int pc_relative;
static int token_profit[0x10000];
/* the table that holds the result of the compression */static unsigned char best_table[256][2];static unsigned char best_table_len[256];
static void usage(void){ fprintf(stderr, "Usage: kallsyms [--all-symbols] in.map > out.S\n"); exit(1);}
static char *sym_name(const struct sym_entry *s){ return (char *)s->sym + 1;}
static bool is_ignored_symbol(const char *name, char type){ if (type == 'u' || type == 'n') return true;
if (toupper(type) == 'A') { /* Keep these useful absolute symbols */ if (strcmp(name, "__kernel_syscall_via_break") && strcmp(name, "__kernel_syscall_via_epc") && strcmp(name, "__kernel_sigtramp") && strcmp(name, "__gp")) return true; }
return false;}
static void check_symbol_range(const char *sym, unsigned long long addr, struct addr_range *ranges, int entries){ size_t i; struct addr_range *ar;
for (i = 0; i < entries; ++i) { ar = &ranges[i];
if (strcmp(sym, ar->start_sym) == 0) { ar->start = addr; return; } else if (strcmp(sym, ar->end_sym) == 0) { ar->end = addr; return; } }}
static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len){ char *name, type, *p; unsigned long long addr; size_t len; ssize_t readlen; struct sym_entry *sym;
errno = 0; readlen = getline(buf, buf_len, in); if (readlen < 0) { if (errno) { perror("read_symbol"); exit(EXIT_FAILURE); } return NULL; }
if ((*buf)[readlen - 1] == '\n') (*buf)[readlen - 1] = 0;
addr = strtoull(*buf, &p, 16);
if (*buf == p || *p++ != ' ' || !isascii((type = *p++)) || *p++ != ' ') { fprintf(stderr, "line format error\n"); exit(EXIT_FAILURE); }
name = p; len = strlen(name);
if (len >= KSYM_NAME_LEN) { fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n" "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n", name, len, KSYM_NAME_LEN); return NULL; }
if (strcmp(name, "_text") == 0) _text = addr;
/* Ignore most absolute/undefined (?) symbols. */ if (is_ignored_symbol(name, type)) return NULL;
check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
/* include the type field in the symbol name, so that it gets * compressed together */ len++;
sym = xmalloc(sizeof(*sym) + len + 1); sym->addr = addr; sym->len = len; sym->sym[0] = type; strcpy(sym_name(sym), name);
return sym;}
static int symbol_in_range(const struct sym_entry *s, const struct addr_range *ranges, int entries){ size_t i; const struct addr_range *ar;
for (i = 0; i < entries; ++i) { ar = &ranges[i];
if (s->addr >= ar->start && s->addr <= ar->end) return 1; }
return 0;}
static bool string_starts_with(const char *s, const char *prefix){ return strncmp(s, prefix, strlen(prefix)) == 0;}
static int symbol_valid(const struct sym_entry *s){ const char *name = sym_name(s);
/* if --all-symbols is not specified, then symbols outside the text * and inittext sections are discarded */ if (!all_symbols) { /* * Symbols starting with __start and __stop are used to denote * section boundaries, and should always be included: */ if (string_starts_with(name, "__start_") || string_starts_with(name, "__stop_")) return 1;
if (symbol_in_range(s, text_ranges, ARRAY_SIZE(text_ranges)) == 0) return 0; /* Corner case. Discard any symbols with the same value as * _etext _einittext; they can move between pass 1 and 2 when * the kallsyms data are added. If these symbols move then * they may get dropped in pass 2, which breaks the kallsyms * rules. */ if ((s->addr == text_range_text->end && strcmp(name, text_range_text->end_sym)) || (s->addr == text_range_inittext->end && strcmp(name, text_range_inittext->end_sym))) return 0; }
return 1;}
/* remove all the invalid symbols from the table */static void shrink_table(void){ unsigned int i, pos;
pos = 0; for (i = 0; i < table_cnt; i++) { if (symbol_valid(table[i])) { if (pos != i) table[pos] = table[i]; pos++; } else { free(table[i]); } } table_cnt = pos;}
static void read_map(const char *in){ FILE *fp; struct sym_entry *sym; char *buf = NULL; size_t buflen = 0;
fp = fopen(in, "r"); if (!fp) { perror(in); exit(1); }
while (!feof(fp)) { sym = read_symbol(fp, &buf, &buflen); if (!sym) continue;
sym->seq = table_cnt;
if (table_cnt >= table_size) { table_size += 10000; table = xrealloc(table, sizeof(*table) * table_size); }
table[table_cnt++] = sym; }
free(buf); fclose(fp);}
static void output_label(const char *label){ printf(".globl %s\n", label); printf("\t.balign 4\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(const 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 int compare_names(const void *a, const void *b){ int ret; const struct sym_entry *sa = *(const struct sym_entry **)a; const struct sym_entry *sb = *(const struct sym_entry **)b;
ret = strcmp(sym_name(sa), sym_name(sb)); if (!ret) { if (sa->addr > sb->addr) return 1; else if (sa->addr < sb->addr) return -1;
/* keep old order */ return (int)(sa->seq - sb->seq); }
return ret;}
static void sort_symbols_by_name(void){ qsort(table, table_cnt, sizeof(table[0]), compare_names);}
static void write_src(void){ unsigned int i, k, off; unsigned int best_idx[256]; unsigned int *markers, markers_cnt; char buf[KSYM_NAME_LEN];
printf("\t.section .rodata, \"a\"\n");
output_label("kallsyms_num_syms"); printf("\t.long\t%u\n", table_cnt); printf("\n");
/* table of offset markers, that give the offset in the compressed stream * every 256 symbols */ markers_cnt = (table_cnt + 255) / 256; markers = xmalloc(sizeof(*markers) * markers_cnt);
output_label("kallsyms_names"); off = 0; for (i = 0; i < table_cnt; i++) { if ((i & 0xFF) == 0) markers[i >> 8] = off; table[i]->seq = i;
/* There cannot be any symbol of length zero. */ if (table[i]->len == 0) { fprintf(stderr, "kallsyms failure: " "unexpected zero symbol length\n"); exit(EXIT_FAILURE); }
/* Only lengths that fit in up-to-two-byte ULEB128 are supported. */ if (table[i]->len > 0x3FFF) { fprintf(stderr, "kallsyms failure: " "unexpected huge symbol length\n"); exit(EXIT_FAILURE); }
/* Encode length with ULEB128. */ if (table[i]->len <= 0x7F) { /* Most symbols use a single byte for the length. */ printf("\t.byte 0x%02x", table[i]->len); off += table[i]->len + 1; } else { /* "Big" symbols use two bytes. */ printf("\t.byte 0x%02x, 0x%02x", (table[i]->len & 0x7F) | 0x80, (table[i]->len >> 7) & 0x7F); off += table[i]->len + 2; } for (k = 0; k < table[i]->len; k++) printf(", 0x%02x", table[i]->sym[k]);
/* * Now that we wrote out the compressed symbol name, restore the * original name and print it in the comment. */ expand_symbol(table[i]->sym, table[i]->len, buf); strcpy((char *)table[i]->sym, buf); printf("\t/* %s */\n", table[i]->sym); } printf("\n");
output_label("kallsyms_markers"); for (i = 0; i < markers_cnt; i++) printf("\t.long\t%u\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");
output_label("kallsyms_offsets");
for (i = 0; i < table_cnt; i++) { if (pc_relative) { long long offset = table[i]->addr - _text;
if (offset < INT_MIN || offset > INT_MAX) { fprintf(stderr, "kallsyms failure: " "relative symbol value %#llx out of range\n", table[i]->addr); exit(EXIT_FAILURE); } printf("\t.long\t_text - . + (%d)\t/* %s */\n", (int)offset, table[i]->sym); } else { printf("\t.long\t%#x\t/* %s */\n", (unsigned int)table[i]->addr, table[i]->sym); } } printf("\n");
sort_symbols_by_name(); output_label("kallsyms_seqs_of_names"); for (i = 0; i < table_cnt; i++) printf("\t.byte 0x%02x, 0x%02x, 0x%02x\t/* %s */\n", (unsigned char)(table[i]->seq >> 16), (unsigned char)(table[i]->seq >> 8), (unsigned char)(table[i]->seq >> 0), table[i]->sym); printf("\n");}
/* table lookup compression functions */
/* count all the possible tokens in a symbol */static void learn_symbol(const unsigned char *symbol, int len){ int i;
for (i = 0; i < len - 1; i++) token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;}
/* decrease the count for all the possible tokens in a symbol */static void forget_symbol(const unsigned char *symbol, int len){ int i;
for (i = 0; i < len - 1; i++) token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;}
/* do the initial token count */static void build_initial_token_table(void){ unsigned int i;
for (i = 0; i < table_cnt; i++) learn_symbol(table[i]->sym, table[i]->len);}
static unsigned char *find_token(unsigned char *str, int len, const unsigned char *token){ int i;
for (i = 0; i < len - 1; i++) { if (str[i] == token[0] && str[i+1] == token[1]) return &str[i]; } return NULL;}
/* replace a given token in all the valid symbols. Use the sampled symbols * to update the counts */static void compress_symbols(const unsigned char *str, int idx){ unsigned int i, len, size; unsigned char *p1, *p2;
for (i = 0; i < table_cnt; i++) {
len = table[i]->len; p1 = table[i]->sym;
/* find the token on the symbol */ p2 = find_token(p1, len, str); if (!p2) continue;
/* decrease the counts for this symbol's tokens */ forget_symbol(table[i]->sym, len);
size = len;
do { *p2 = idx; p2++; size -= (p2 - p1); memmove(p2, p2 + 1, size); p1 = p2; len--;
if (size < 2) break;
/* find the token on the symbol */ p2 = find_token(p1, size, str);
} while (p2);
table[i]->len = len;
/* increase the counts for this symbol's new tokens */ learn_symbol(table[i]->sym, len); }}
/* search the token with the maximum profit */static int find_best_token(void){ int i, best, bestprofit;
bestprofit=-10000; best = 0;
for (i = 0; i < 0x10000; i++) { if (token_profit[i] > bestprofit) { best = i; bestprofit = token_profit[i]; } } return best;}
/* this is the core of the algorithm: calculate the "best" table */static void optimize_result(void){ int i, best;
/* 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 best profit value */ best = find_best_token(); if (token_profit[best] == 0) break;
/* place it in the "best" table */ best_table_len[i] = 2; best_table[i][0] = best & 0xFF; best_table[i][1] = (best >> 8) & 0xFF;
/* replace this token in all the valid symbols */ compress_symbols(best_table[i], i); } }}
/* start by placing the symbols that are actually used on the table */static void insert_real_symbols_in_table(void){ unsigned int i, j, c;
for (i = 0; i < table_cnt; i++) { 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){ build_initial_token_table();
insert_real_symbols_in_table();
optimize_result();}
/* guess for "linker script provide" symbol */static int may_be_linker_script_provide_symbol(const struct sym_entry *se){ const char *symbol = sym_name(se); int len = se->len - 1;
if (len < 8) return 0;
if (symbol[0] != '_' || symbol[1] != '_') return 0;
/* __start_XXXXX */ if (!memcmp(symbol + 2, "start_", 6)) return 1;
/* __stop_XXXXX */ if (!memcmp(symbol + 2, "stop_", 5)) return 1;
/* __end_XXXXX */ if (!memcmp(symbol + 2, "end_", 4)) return 1;
/* __XXXXX_start */ if (!memcmp(symbol + len - 6, "_start", 6)) return 1;
/* __XXXXX_end */ if (!memcmp(symbol + len - 4, "_end", 4)) return 1;
return 0;}
static int compare_symbols(const void *a, const void *b){ const struct sym_entry *sa = *(const struct sym_entry **)a; const struct sym_entry *sb = *(const struct sym_entry **)b; int wa, wb;
/* sort by address first */ if (sa->addr > sb->addr) return 1; if (sa->addr < sb->addr) return -1;
/* sort by "weakness" type */ wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); if (wa != wb) return wa - wb;
/* sort by "linker script provide" type */ wa = may_be_linker_script_provide_symbol(sa); wb = may_be_linker_script_provide_symbol(sb); if (wa != wb) return wa - wb;
/* sort by the number of prefix underscores */ wa = strspn(sym_name(sa), "_"); wb = strspn(sym_name(sb), "_"); if (wa != wb) return wa - wb;
/* sort by initial order, so that other symbols are left undisturbed */ return sa->seq - sb->seq;}
static void sort_symbols(void){ qsort(table, table_cnt, sizeof(table[0]), compare_symbols);}
int main(int argc, char **argv){ while (1) { static const struct option long_options[] = { {"all-symbols", no_argument, &all_symbols, 1}, {"pc-relative", no_argument, &pc_relative, 1}, {}, };
int c = getopt_long(argc, argv, "", long_options, NULL);
if (c == -1) break; if (c != 0) usage(); }
if (optind >= argc) usage();
read_map(argv[optind]); shrink_table(); sort_symbols(); optimize_token_table(); write_src();
return 0;}