* 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 <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;
- char *sym;
+ unsigned char flags;
+ unsigned char len;
+ unsigned char *sym;
};
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)
{
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)
{
_sinittext = s->addr;
else if (strcmp(str, "_einittext") == 0)
_einittext = s->addr;
- else if (toupper(s->type) == 'A' || toupper(s->type) == 'U')
+ 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;
- s->sym = strdup(str);
+ /* 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. 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.
- */
- if (strstr(s->sym, "_compiled.") ||
- strcmp(s->sym, "kallsyms_addresses") == 0 ||
- strcmp(s->sym, "kallsyms_num_syms") == 0 ||
- strcmp(s->sym, "kallsyms_names") == 0)
+ /* Exclude symbols which vary between passes. */
+ if (strstr(s->sym + 1, "_compiled."))
return 0;
- /* Exclude linker generated symbols which vary between passes */
- if (strcmp(s->sym, "_SDA_BASE_") == 0 || /* ppc */
- strcmp(s->sym, "_SDA2_BASE_") == 0) /* ppc */
- return 0;
+ for (i = 0; special_symbols[i]; i++)
+ if( strcmp(s->sym + 1, special_symbols[i]) == 0 )
+ return 0;
return 1;
}
}
}
+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, valid = 0;
- char *prev;
+ 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(".data\n");
- printf(".globl kallsyms_addresses\n");
- printf("\tALGN\n");
- printf("kallsyms_addresses:\n");
+ output_label("kallsyms_addresses");
+ valid = 0;
for (i = 0; i < cnt; i++) {
- if (!symbol_valid(&table[i]))
- continue;
-
- printf("\tPTR\t%#llx\n", table[i].addr);
- valid++;
+ if (table[i].flags & SYM_FLAG_VALID) {
+ printf("\tPTR\t%#llx\n", table[i].addr);
+ valid++;
+ }
}
printf("\n");
- printf(".globl kallsyms_num_syms\n");
- printf("\tALGN\n");
- printf("kallsyms_num_syms:\n");
+ output_label("kallsyms_num_syms");
printf("\tPTR\t%d\n", valid);
printf("\n");
- printf(".globl kallsyms_names\n");
- printf("\tALGN\n");
- printf("kallsyms_names:\n");
- prev = "";
+ /* 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++) {
- int k;
- if (!symbol_valid(&table[i]))
+ if (!table[i].flags & SYM_FLAG_VALID)
continue;
- for (k = 0; table[i].sym[k] && table[i].sym[k] == prev[k]; ++k)
- ;
+ 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);
- printf("\t.byte 0x%02x\n\t.asciz\t\"%s\"\n", k, table[i].sym + k);
- prev = table[i].sym;
+ 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)
{
usage();
read_map(stdin);
+ optimize_token_table();
write_src();
return 0;
git://git.onelab.eu / linux-2.6.git / blobdiff