[PATCH] kallsyms: change compression algorithm

 *

 */

#define _GNU_SOURCE

#include <stdio.h>

#include <stdlib.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;

	unsigned char flags;

	unsigned char len;

	unsigned int len;

	unsigned char *sym;

};

static struct sym_entry *table;

static int size, cnt;

static unsigned int table_size, table_cnt;

static unsigned long long _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;

static int all_symbols = 0;

static char symbol_prefix_char = '\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];

int token_profit[0x10000];

/* the table that holds the result of the compression */

unsigned char best_table[256][MAX_TOK_SIZE+1];

unsigned char best_table[256][2];

unsigned char best_table_len[256];

static void

usage(void)

static void usage(void)

{

	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < 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)

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)

static int read_symbol(FILE *in, struct sym_entry *s)

{

	char str[500];

	char *sym;

	char *sym, stype;

	int rc;

	rc = fscanf(in, "%llx %c %499s\n", &s->addr, &s->type, str);

	rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);

	if (rc != 3) {

		if (rc != EOF) {

			/* skip line */

		_sextratext = s->addr;

	else if (strcmp(sym, "_eextratext") == 0)

		_eextratext = s->addr;

	else if (toupper(s->type) == 'A')

	else if (toupper(stype) == 'A')

	{

		/* Keep these useful absolute symbols */

		if (strcmp(sym, "__kernel_syscall_via_break") &&

			return -1;

	}

	else if (toupper(s->type) == 'U' ||

	else if (toupper(stype) == 'U' ||

		 is_arm_mapping_symbol(sym))

		return -1;

	/* 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;

	s->sym = malloc(s->len + 1);

	strcpy((char *)s->sym + 1, str);

	s->sym[0] = stype;

	return 0;

}

static int

symbol_valid(struct sym_entry *s)

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

	}

	/* Exclude symbols which vary between passes. */

	if (strstr(s->sym + offset, "_compiled."))

	if (strstr((char *)s->sym + offset, "_compiled."))

		return 0;

	for (i = 0; special_symbols[i]; i++)

		if( strcmp(s->sym + offset, special_symbols[i]) == 0 )

		if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )

			return 0;

	return 1;

}

static void

read_map(FILE *in)

static void read_map(FILE *in)

{

	while (!feof(in)) {

		if (cnt >= size) {

			size += 10000;

			table = realloc(table, sizeof(*table) * size);

		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[cnt]) == 0)

			cnt++;

		if (read_symbol(in, &table[table_cnt]) == 0)

			table_cnt++;

	}

}

	return total;

}

static void

write_src(void)

static void write_src(void)

{

	int i, k, off, valid;

	unsigned int i, k, off;

	unsigned int best_idx[256];

	unsigned int *markers;

	char buf[KSYM_NAME_LEN+1];

	printf(".data\n");

	output_label("kallsyms_addresses");

	valid = 0;

	for (i = 0; i < cnt; i++) {

		if (table[i].flags & SYM_FLAG_VALID) {

	for (i = 0; i < table_cnt; i++) {

		printf("\tPTR\t%#llx\n", table[i].addr);

			valid++;

		}

	}

	printf("\n");

	output_label("kallsyms_num_syms");

	printf("\tPTR\t%d\n", valid);

	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 = (unsigned int *) malloc(sizeof(unsigned int)*((valid + 255) / 256));

	markers = (unsigned int *) malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));

	output_label("kallsyms_names");

	valid = 0;

	off = 0;

	for (i = 0; i < cnt; i++) {

		if (!table[i].flags & SYM_FLAG_VALID)

			continue;

		if ((valid & 0xFF) == 0)

			markers[valid >> 8] = off;

	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("\n");

		off += table[i].len + 1;

		valid++;

	}

	printf("\n");

	output_label("kallsyms_markers");

	for (i = 0; i < ((valid + 255) >> 8); i++)

	for (i = 0; i < ((table_cnt + 255) >> 8); i++)

		printf("\tPTR\t%d\n", markers[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);

		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;

}

/* decrease the count for all the possible tokens in a symbol */

	int i;

	for (i = 0; i < len - 1; i++)

		forget_token(symbol + i, len - i);

		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;

}

/* set all the symbol flags and do the initial token count */

/* remove all the invalid symbols from the table and do the initial token count */

static void build_initial_tok_table(void)

{

	int i, use_it, valid;

	unsigned int i, pos;

	valid = 0;

	for (i = 0; i < cnt; i++) {

		table[i].flags = 0;

	pos = 0;

	for (i = 0; i < table_cnt; i++) {

		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 (pos != i)

				table[pos] = table[i];

			learn_symbol(table[pos].sym, table[pos].len);

			pos++;

		}

		if (table[i].flags & SYM_FLAG_SAMPLED)

			learn_symbol(table[i].sym, table[i].len);

	}

	table_cnt = pos;

}

/* 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)

static void compress_symbols(unsigned char *str, int idx)

{

	int i, len, learn, size;

	unsigned char *p;

	unsigned int i, len, size;

	unsigned char *p1, *p2;

	for (i = 0; i < cnt; i++) {

		if (!(table[i].flags & SYM_FLAG_VALID)) continue;

	for (i = 0; i < table_cnt; i++) {

		len = table[i].len;

		learn = 0;

		p = table[i].sym;

		p1 = table[i].sym;

		do {

		/* find the token on the symbol */

			p = (unsigned char *) strstr((char *) p, (char *) str);

			if (!p) break;

		p2 = memmem(p1, len, str, 2);

		if (!p2) continue;

			if (!learn) {

				/* if this symbol was used to count, decrease it */

				if (table[i].flags & SYM_FLAG_SAMPLED)

		/* decrease the counts for this symbol's tokens */

		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;

		size = len;

		do {

			*p2 = idx;

			p2++;

			size -= (p2 - p1);

			memmove(p2, p2 + 1, size);

			p1 = p2;

			len--;

			if (size < 2) break;

		} while (size >= tlen);

			/* find the token on the symbol */

			p2 = memmem(p1, size, str, 2);

		} while (p2);

		if(learn) {

		table[i].len = len;

			/* if this symbol was used to count, learn it again */

			if(table[i].flags & SYM_FLAG_SAMPLED)

		/* increase the counts for this symbol's new tokens */

		learn_symbol(table[i].sym, len);

	}

}

}

/* search the token with the maximum profit */

static struct token *find_best_token(void)

static int find_best_token(void)

{

	struct token *ptr,*best,*head;

	int bestprofit;

	int i, best, bestprofit;

	bestprofit=-10000;

	best = 0;

	/* 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;

	for (i = 0; i < 0x10000; i++) {

		if (token_profit[i] > bestprofit) {

			best = i;

			bestprofit = token_profit[i];

		}

		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;

	int i, best;

	/* using the '\0' symbol last allows compress_symbols to use standard

	 * fast string functions */

			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';

			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], best_table_len[i], i);

			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)

{

	int i, j, c;

	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 < cnt; i++) {

		if (table[i].flags & SYM_FLAG_VALID) {

	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;

		}

	}

}

}

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;