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/* 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
*
* 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 <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
#define KSYM_NAME_LEN 128
struct sym_entry {
unsigned long long addr;
unsigned int len;
unsigned int start_pos;
unsigned int percpu_absolute;
unsigned char sym[];
};
struct addr_range {
const char *start_sym, *end_sym;
unsigned long long start, end;
};
static unsigned long long _text;
static unsigned long long relative_base;
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 addr_range percpu_range = {
"__per_cpu_start", "__per_cpu_end", -1ULL, 0
};
static struct sym_entry **table;
static unsigned int table_size, table_cnt;
static int all_symbols;
static int absolute_percpu;
static int base_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] "
"[--base-relative] < 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)
{
/* Symbol names that exactly match to the following are ignored.*/
static const char * const ignored_symbols[] = {
/*
* 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.
*/
"kallsyms_addresses",
"kallsyms_offsets",
"kallsyms_relative_base",
"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
};
/* Symbol names that begin with the following are ignored.*/
static const char * const ignored_prefixes[] = {
"$", /* local symbols for ARM, MIPS, etc. */
".LASANPC", /* s390 kasan local symbols */
"__crc_", /* modversions */
"__efistub_", /* arm64 EFI stub namespace */
"__kvm_nvhe_", /* arm64 non-VHE KVM namespace */
"__AArch64ADRPThunk_", /* arm64 lld */
"__ARMV5PILongThunk_", /* arm lld */
"__ARMV7PILongThunk_",
"__ThumbV7PILongThunk_",
"__LA25Thunk_", /* mips lld */
"__microLA25Thunk_",
NULL
};
/* Symbol names that end with the following are ignored.*/
static const char * const ignored_suffixes[] = {
"_from_arm", /* arm */
"_from_thumb", /* arm */
"_veneer", /* arm */
NULL
};
/* Symbol names that contain the following are ignored.*/
static const char * const ignored_matches[] = {
".long_branch.", /* ppc stub */
".plt_branch.", /* ppc stub */
NULL
};
const char * const *p;
for (p = ignored_symbols; *p; p++)
if (!strcmp(name, *p))
return true;
for (p = ignored_prefixes; *p; p++)
if (!strncmp(name, *p, strlen(*p)))
return true;
for (p = ignored_suffixes; *p; p++) {
int l = strlen(name) - strlen(*p);
if (l >= 0 && !strcmp(name + l, *p))
return true;
}
for (p = ignored_matches; *p; p++) {
if (strstr(name, *p))
return true;
}
if (type == 'U' || type == 'u')
return true;
/* exclude debugging symbols */
if (type == 'N' || 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 name[500], type;
unsigned long long addr;
unsigned int len;
struct sym_entry *sym;
int rc;
rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
if (rc != 3) {
if (rc != EOF && fgets(name, 500, in) == NULL)
fprintf(stderr, "Read error or end of file.\n");
return NULL;
}
if (strlen(name) >= 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, strlen(name), 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));
check_symbol_range(name, addr, &percpu_range, 1);
/* include the type field in the symbol name, so that it gets
* compressed together */
len = strlen(name) + 1;
sym = malloc(sizeof(*sym) + len + 1);
if (!sym) {
fprintf(stderr, "kallsyms failure: "
"unable to allocate required amount of memory\n");
exit(EXIT_FAILURE);
}
sym->addr = addr;
sym->len = len;
sym->sym[0] = type;
strcpy(sym_name(sym), name);
sym->percpu_absolute = 0;
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 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) {
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;
/* When valid symbol is not registered, exit to error */
if (!table_cnt) {
fprintf(stderr, "No valid symbol.\n");
exit(1);
}
}
static void read_map(FILE *in)
{
struct sym_entry *sym;
while (!feof(in)) {
sym = read_symbol(in);
if (!sym)
continue;
sym->start_pos = table_cnt;
if (table_cnt >= table_size) {
table_size += 10000;
table = realloc(table, sizeof(*table) * table_size);
if (!table) {
fprintf(stderr, "out of memory\n");
exit (1);
}
}
table[table_cnt++] = sym;
}
}
static void output_label(const char *label)
{
printf(".globl %s\n", label);
printf("\tALGN\n");
printf("%s:\n", label);
}
/* Provide proper symbols relocatability by their '_text' relativeness. */
static void output_address(unsigned long long addr)
{
if (_text <= addr)
printf("\tPTR\t_text + %#llx\n", addr - _text);
else
printf("\tPTR\t_text - %#llx\n", _text - addr);
}
/* 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 symbol_absolute(const struct sym_entry *s)
{
return s->percpu_absolute;
}
static void write_src(void)
{
unsigned int i, k, off;
unsigned int best_idx[256];
unsigned int *markers;
char buf[KSYM_NAME_LEN];
printf("#include <asm/bitsperlong.h>\n");
printf("#if BITS_PER_LONG == 64\n");
printf("#define PTR .quad\n");
printf("#define ALGN .balign 8\n");
printf("#else\n");
printf("#define PTR .long\n");
printf("#define ALGN .balign 4\n");
printf("#endif\n");
printf("\t.section .rodata, \"a\"\n");
if (!base_relative)
output_label("kallsyms_addresses");
else
output_label("kallsyms_offsets");
for (i = 0; i < table_cnt; i++) {
if (base_relative) {
/*
* Use the offset relative to the lowest value
* encountered of all relative symbols, and emit
* non-relocatable fixed offsets that will be fixed
* up at runtime.
*/
long long offset;
int overflow;
if (!absolute_percpu) {
offset = table[i]->addr - relative_base;
overflow = (offset < 0 || offset > UINT_MAX);
} else if (symbol_absolute(table[i])) {
offset = table[i]->addr;
overflow = (offset < 0 || offset > INT_MAX);
} else {
offset = relative_base - table[i]->addr - 1;
overflow = (offset < INT_MIN || offset >= 0);
}
if (overflow) {
fprintf(stderr, "kallsyms failure: "
"%s symbol value %#llx out of range in relative mode\n",
symbol_absolute(table[i]) ? "absolute" : "relative",
table[i]->addr);
exit(EXIT_FAILURE);
}
printf("\t.long\t%#x\n", (int)offset);
} else if (!symbol_absolute(table[i])) {
output_address(table[i]->addr);
} else {
printf("\tPTR\t%#llx\n", table[i]->addr);
}
}
printf("\n");
if (base_relative) {
output_label("kallsyms_relative_base");
output_address(relative_base);
printf("\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 = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
if (!markers) {
fprintf(stderr, "kallsyms failure: "
"unable to allocate required memory\n");
exit(EXIT_FAILURE);
}
output_label("kallsyms_names");
off = 0;
for (i = 0; i < table_cnt; i++) {
if ((i & 0xFF) == 0)
markers[i >> 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;
}
printf("\n");
output_label("kallsyms_markers");
for (i = 0; i < ((table_cnt + 255) >> 8); 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");
}
/* 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_tok_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_tok_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->start_pos - sb->start_pos;
}
static void sort_symbols(void)
{
qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
}
static void make_percpus_absolute(void)
{
unsigned int i;
for (i = 0; i < table_cnt; i++)
if (symbol_in_range(table[i], &percpu_range, 1)) {
/*
* Keep the 'A' override for percpu symbols to
* ensure consistent behavior compared to older
* versions of this tool.
*/
table[i]->sym[0] = 'A';
table[i]->percpu_absolute = 1;
}
}
/* find the minimum non-absolute symbol address */
static void record_relative_base(void)
{
unsigned int i;
for (i = 0; i < table_cnt; i++)
if (!symbol_absolute(table[i])) {
/*
* The table is sorted by address.
* Take the first non-absolute symbol value.
*/
relative_base = table[i]->addr;
return;
}
}
int main(int argc, char **argv)
{
if (argc >= 2) {
int i;
for (i = 1; i < argc; i++) {
if(strcmp(argv[i], "--all-symbols") == 0)
all_symbols = 1;
else if (strcmp(argv[i], "--absolute-percpu") == 0)
absolute_percpu = 1;
else if (strcmp(argv[i], "--base-relative") == 0)
base_relative = 1;
else
usage();
}
} else if (argc != 1)
usage();
read_map(stdin);
shrink_table();
if (absolute_percpu)
make_percpus_absolute();
sort_symbols();
if (base_relative)
record_relative_base();
optimize_token_table();
write_src();
return 0;
}
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