add kallsyms.c from linux kernel

1 files changed, 534 insertions, 0 deletions

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
new file mode 100644
index 0000000000..1f11d84853
--- /dev/null
+++ b/scripts/kallsyms.c
@@ -0,0 +1,534 @@
+/* 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
+ *
+ * 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 <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#define KSYM_NAME_LEN		128
+
+
+struct sym_entry {
+	unsigned long long addr;
+	unsigned int len;
+	unsigned char *sym;
+};
+
+
+static struct sym_entry *table;
+static unsigned int table_size, table_cnt;
+static unsigned long long _text, _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
+static int all_symbols = 0;
+static char symbol_prefix_char = '\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>] < 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(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) {
+			/* skip line */
+			fgets(str, 500, in);
+		}
+		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 (strcmp(sym, "_stext") == 0)
+		_stext = s->addr;
+	else if (strcmp(sym, "_etext") == 0)
+		_etext = s->addr;
+	else if (strcmp(sym, "_sinittext") == 0)
+		_sinittext = s->addr;
+	else if (strcmp(sym, "_einittext") == 0)
+		_einittext = s->addr;
+	else if (strcmp(sym, "_sextratext") == 0)
+		_sextratext = s->addr;
+	else if (strcmp(sym, "_eextratext") == 0)
+		_eextratext = s->addr;
+	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;
+
+	/* 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(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;
+
+	/* 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 ((s->addr < _stext || s->addr > _etext)
+		    && (s->addr < _sinittext || s->addr > _einittext)
+		    && (s->addr < _sextratext || s->addr > _eextratext))
+			return 0;
+		/* Corner case.  Discard any symbols with the same value as
+		 * _etext _einittext or _eextratext; 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 == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
+		    (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
+		    (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
+			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_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_text - %#llx\n",
+					_text - 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();
+
+			/* 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();
+}
+
+
+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
+				usage();
+		}
+	} else if (argc != 1)
+		usage();
+
+	read_map(stdin);
+	optimize_token_table();
+	write_src();
+
+	return 0;
+}