linux/scripts/kallsyms.c

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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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#ifndef ARRAY_SIZE
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
#endif
#define KSYM_NAME_LEN 128
struct sym_entry {
unsigned long long addr;
unsigned int len;
unsigned int start_pos;
unsigned char *sym;
};
struct text_range {
const char *stext, *etext;
unsigned long long start, end;
};
static unsigned long long _text;
static struct text_range text_ranges[] = {
{ "_stext", "_etext" },
{ "_sinittext", "_einittext" },
{ "_stext_l1", "_etext_l1" }, /* Blackfin on-chip L1 inst SRAM */
{ "_stext_l2", "_etext_l2" }, /* Blackfin on-chip L2 SRAM */
};
#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 = 0;
static char symbol_prefix_char = '\0';
static unsigned long long kernel_start_addr = 0;
int token_profit[0x10000];
/* the table that holds the result of the compression */
unsigned char best_table[256][2];
unsigned char best_table_len[256];
static void usage(void)
{
fprintf(stderr, "Usage: kallsyms [--all-symbols] "
"[--symbol-prefix=<prefix char>] "
"[--page-offset=<CONFIG_PAGE_OFFSET>] "
"< 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_tr(const char *sym, unsigned long long addr)
{
size_t i;
struct text_range *tr;
for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
tr = &text_ranges[i];
if (strcmp(sym, tr->stext) == 0) {
tr->start = addr;
return 0;
} else if (strcmp(sym, tr->etext) == 0) {
tr->end = addr;
return 0;
}
}
return 1;
}
static int read_symbol(FILE *in, struct sym_entry *s)
{
char str[500];
char *sym, stype;
int rc;
rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
if (rc != 3) {
if (rc != EOF && fgets(str, 500, in) == NULL)
fprintf(stderr, "Read error or end of file.\n");
return -1;
}
if (strlen(str) > KSYM_NAME_LEN) {
fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n"
"Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
str, strlen(str), KSYM_NAME_LEN);
return -1;
}
sym = str;
/* skip prefix char */
if (symbol_prefix_char && str[0] == symbol_prefix_char)
sym++;
/* Ignore most absolute/undefined (?) symbols. */
if (strcmp(sym, "_text") == 0)
_text = s->addr;
else if (read_symbol_tr(sym, s->addr) == 0)
/* nothing to do */;
else if (toupper(stype) == 'A')
{
/* Keep these useful absolute symbols */
if (strcmp(sym, "__kernel_syscall_via_break") &&
strcmp(sym, "__kernel_syscall_via_epc") &&
strcmp(sym, "__kernel_sigtramp") &&
strcmp(sym, "__gp"))
return -1;
}
else if (toupper(stype) == 'U' ||
is_arm_mapping_symbol(sym))
return -1;
/* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
else if (str[0] == '$')
return -1;
/* exclude debugging symbols */
else if (stype == 'N')
return -1;
/* include the type field in the symbol name, so that it gets
* compressed together */
s->len = strlen(str) + 1;
s->sym = malloc(s->len + 1);
if (!s->sym) {
fprintf(stderr, "kallsyms failure: "
"unable to allocate required amount of memory\n");
exit(EXIT_FAILURE);
}
strcpy((char *)s->sym + 1, str);
s->sym[0] = stype;
return 0;
}
static int symbol_valid_tr(struct sym_entry *s)
{
size_t i;
struct text_range *tr;
for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
tr = &text_ranges[i];
if (s->addr >= tr->start && s->addr <= tr->end)
return 1;
}
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;
int offset = 1;
if (s->addr < kernel_start_addr)
return 0;
/* skip prefix char */
if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
offset++;
/* if --all-symbols is not specified, then symbols outside the text
* and inittext sections are discarded */
if (!all_symbols) {
if (symbol_valid_tr(s) == 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((char *)s->sym + offset, text_range_text->etext)) ||
(s->addr == text_range_inittext->end &&
strcmp((char *)s->sym + offset, text_range_inittext->etext)))
return 0;
}
/* Exclude symbols which vary between passes. */
if (strstr((char *)s->sym + offset, "_compiled."))
return 0;
for (i = 0; special_symbols[i]; i++)
if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
return 0;
return 1;
}
static void read_map(FILE *in)
{
while (!feof(in)) {
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);
}
}
if (read_symbol(in, &table[table_cnt]) == 0) {
table[table_cnt].start_pos = table_cnt;
table_cnt++;
}
}
}
static void output_label(char *label)
{
if (symbol_prefix_char)
printf(".globl %c%s\n", symbol_prefix_char, label);
else
printf(".globl %s\n", label);
printf("\tALGN\n");
if (symbol_prefix_char)
printf("%c%s:\n", symbol_prefix_char, label);
else
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)
{
unsigned int i, k, off;
unsigned int best_idx[256];
unsigned int *markers;
char buf[KSYM_NAME_LEN];
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("\t.section .rodata, \"a\"\n");
/* Provide proper symbols relocatability by their '_text'
* relativeness. The symbol names cannot be used to construct
* normal symbol references as the list of symbols contains
* symbols that are declared static and are private to their
* .o files. This prevents .tmp_kallsyms.o or any other
* object from referencing them.
*/
output_label("kallsyms_addresses");
for (i = 0; i < table_cnt; i++) {
if (toupper(table[i].sym[0]) != 'A') {
if (_text <= table[i].addr)
printf("\tPTR\t_text + %#llx\n",
table[i].addr - _text);
else
printf("\tPTR\t%#llx\n", table[i].addr);
} else {
printf("\tPTR\t%#llx\n", table[i].addr);
}
}
printf("\n");
output_label("kallsyms_num_syms");
printf("\tPTR\t%d\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("\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 */
/* 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++)
token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
}
/* 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++)
token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
}
/* remove all the invalid symbols from the table and do the initial token count */
static void build_initial_tok_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];
learn_symbol(table[pos].sym, table[pos].len);
pos++;
}
}
table_cnt = pos;
}
static void *find_token(unsigned char *str, int len, 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(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 breates 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;
memset(best_table, 0, sizeof(best_table));
memset(best_table_len, 0, sizeof(best_table_len));
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();
/* When valid symbol is not registered, exit to error */
if (!table_cnt) {
fprintf(stderr, "No valid symbol.\n");
exit(1);
}
optimize_result();
}
kallsyms, tracing: output more proper symbol name Impact: bugfix, output more reliable symbol lookup result Debug tools(dump_stack(), ftrace...) are like to print out symbols. But it is always print out the first aliased symbol.(Aliased symbols are symbols with the same address), and the first aliased symbol is sometime not proper. # echo function_graph > current_tracer # cat trace ...... 1) 1.923 us | select_nohz_load_balancer(); 1) + 76.692 us | } 1) | default_idle() { 1) ==========> | __irqentry_text_start() { 1) 0.000 us | native_apic_mem_write(); 1) | irq_enter() { 1) 0.000 us | idle_cpu(); 1) | tick_check_idle() { 1) 0.000 us | tick_check_oneshot_broadcast(); 1) | tick_nohz_stop_idle() { ...... It's very embarrassing, it ouputs "__irqentry_text_start()", actually, it should output "smp_apic_timer_interrupt()". (these two symbol are the same address, but "__irqentry_text_start" is deemed to the first aliased symbol by scripts/kallsyms) This patch puts symbols like "__irqentry_text_start" to the second aliased symbols. And a more proper symbol name becomes the first. Aliased symbols mostly come from linker script. The solution is guessing "is this symbol defined in linker script", the symbols defined in linker script will not become the first aliased symbol. And if symbols are found to be equal in this "linker script provided" criteria, symbols are sorted by the number of prefix underscores. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Sam Ravnborg <sam@ravnborg.org> Reviewed-by: Paulo Marques <pmarques@grupopie.com> LKML-Reference: <49BA06E2.7080807@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-13 07:10:26 +00:00
/* guess for "linker script provide" symbol */
static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
{
const char *symbol = (char *)se->sym + 1;
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 prefix_underscores_count(const char *str)
{
const char *tail = str;
while (*tail == '_')
kallsyms, tracing: output more proper symbol name Impact: bugfix, output more reliable symbol lookup result Debug tools(dump_stack(), ftrace...) are like to print out symbols. But it is always print out the first aliased symbol.(Aliased symbols are symbols with the same address), and the first aliased symbol is sometime not proper. # echo function_graph > current_tracer # cat trace ...... 1) 1.923 us | select_nohz_load_balancer(); 1) + 76.692 us | } 1) | default_idle() { 1) ==========> | __irqentry_text_start() { 1) 0.000 us | native_apic_mem_write(); 1) | irq_enter() { 1) 0.000 us | idle_cpu(); 1) | tick_check_idle() { 1) 0.000 us | tick_check_oneshot_broadcast(); 1) | tick_nohz_stop_idle() { ...... It's very embarrassing, it ouputs "__irqentry_text_start()", actually, it should output "smp_apic_timer_interrupt()". (these two symbol are the same address, but "__irqentry_text_start" is deemed to the first aliased symbol by scripts/kallsyms) This patch puts symbols like "__irqentry_text_start" to the second aliased symbols. And a more proper symbol name becomes the first. Aliased symbols mostly come from linker script. The solution is guessing "is this symbol defined in linker script", the symbols defined in linker script will not become the first aliased symbol. And if symbols are found to be equal in this "linker script provided" criteria, symbols are sorted by the number of prefix underscores. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Sam Ravnborg <sam@ravnborg.org> Reviewed-by: Paulo Marques <pmarques@grupopie.com> LKML-Reference: <49BA06E2.7080807@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-13 07:10:26 +00:00
tail++;
return tail - str;
}
static int compare_symbols(const void *a, const void *b)
{
const struct sym_entry *sa;
const struct sym_entry *sb;
int wa, wb;
sa = a;
sb = b;
/* 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;
kallsyms, tracing: output more proper symbol name Impact: bugfix, output more reliable symbol lookup result Debug tools(dump_stack(), ftrace...) are like to print out symbols. But it is always print out the first aliased symbol.(Aliased symbols are symbols with the same address), and the first aliased symbol is sometime not proper. # echo function_graph > current_tracer # cat trace ...... 1) 1.923 us | select_nohz_load_balancer(); 1) + 76.692 us | } 1) | default_idle() { 1) ==========> | __irqentry_text_start() { 1) 0.000 us | native_apic_mem_write(); 1) | irq_enter() { 1) 0.000 us | idle_cpu(); 1) | tick_check_idle() { 1) 0.000 us | tick_check_oneshot_broadcast(); 1) | tick_nohz_stop_idle() { ...... It's very embarrassing, it ouputs "__irqentry_text_start()", actually, it should output "smp_apic_timer_interrupt()". (these two symbol are the same address, but "__irqentry_text_start" is deemed to the first aliased symbol by scripts/kallsyms) This patch puts symbols like "__irqentry_text_start" to the second aliased symbols. And a more proper symbol name becomes the first. Aliased symbols mostly come from linker script. The solution is guessing "is this symbol defined in linker script", the symbols defined in linker script will not become the first aliased symbol. And if symbols are found to be equal in this "linker script provided" criteria, symbols are sorted by the number of prefix underscores. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Sam Ravnborg <sam@ravnborg.org> Reviewed-by: Paulo Marques <pmarques@grupopie.com> LKML-Reference: <49BA06E2.7080807@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-13 07:10:26 +00:00
/* 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 = prefix_underscores_count((const char *)sa->sym + 1);
wb = prefix_underscores_count((const char *)sb->sym + 1);
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(struct sym_entry), compare_symbols);
}
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 (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
char *p = &argv[i][16];
/* skip quote */
if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
p++;
symbol_prefix_char = *p;
} else if (strncmp(argv[i], "--page-offset=", 14) == 0) {
const char *p = &argv[i][14];
kernel_start_addr = strtoull(p, NULL, 16);
} else
usage();
}
} else if (argc != 1)
usage();
read_map(stdin);
sort_symbols();
optimize_token_table();
write_src();
return 0;
}