/* 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>

  #include <limits.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;

  	unsigned int percpu_absolute;

  };

  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 = 0;

  static int absolute_percpu = 0;

  static int base_relative = 0;

  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
  ");

  	exit(1);
  }
  
  /*
   * This ignores the intensely annoying "mapping symbols" found
   * in ARM ELF files: $a, $t and $d.
   */

  static int is_arm_mapping_symbol(const char *str)

  {

  	return str[0] == '$' && strchr("axtd", str[1])

  	       && (str[2] == '\0' || str[2] == '.');
  }

  static int 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 0;

  		} else if (strcmp(sym, ar->end_sym) == 0) {
  			ar->end = addr;

  			return 0;
  		}
  	}
  
  	return 1;
  }

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

  {

  	char sym[500], stype;

  	int rc;

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

  	if (rc != 3) {

  		if (rc != EOF && fgets(sym, 500, in) == NULL)

  			fprintf(stderr, "Read error or end of file.
  ");

  		return -1;
  	}

  	if (strlen(sym) >= KSYM_NAME_LEN) {
  		fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).
  "

  				"Please increase KSYM_NAME_LEN both in kernel and kallsyms.c
  ",

  			sym, strlen(sym), KSYM_NAME_LEN);

  		return -1;
  	}

  
  	/* Ignore most absolute/undefined (?) symbols. */

  	if (strcmp(sym, "_text") == 0)
  		_text = s->addr;

  	else if (check_symbol_range(sym, s->addr, text_ranges,
  				    ARRAY_SIZE(text_ranges)) == 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 (sym[0] == '$')

  		return -1;

  	/* exclude debugging symbols */

  	else if (stype == 'N' || stype == 'n')

  		return -1;

  	/* exclude s390 kasan local symbols */
  	else if (!strncmp(sym, ".LASANPC", 8))
  		return -1;

  
  	/* include the type field in the symbol name, so that it gets
  	 * compressed together */

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

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

  	if (!s->sym) {
  		fprintf(stderr, "kallsyms failure: "
  			"unable to allocate required amount of memory
  ");
  		exit(EXIT_FAILURE);
  	}

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

  	s->sym[0] = stype;

  	s->percpu_absolute = 0;

  	/* Record if we've found __per_cpu_start/end. */
  	check_symbol_range(sym, s->addr, &percpu_range, 1);

  	return 0;
  }

  static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges,
  			   int entries)

  {
  	size_t i;

  	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(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_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 };

  	static char *special_prefixes[] = {
  		"__crc_",		/* modversions */

  		"__efistub_",		/* arm64 EFI stub namespace */

  		NULL };

  	static char *special_suffixes[] = {

  		"_veneer",		/* arm */

  		"_from_arm",		/* arm */
  		"_from_thumb",		/* arm */

  		NULL };

  	int i;

  	char *sym_name = (char *)s->sym + 1;

  	/* 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(sym_name,

  				       text_range_text->end_sym)) ||

  		    (s->addr == text_range_inittext->end &&

  				strcmp(sym_name,

  				       text_range_inittext->end_sym)))

  			return 0;
  	}
  
  	/* Exclude symbols which vary between passes. */

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

  		if (strcmp(sym_name, special_symbols[i]) == 0)

  			return 0;

  	for (i = 0; special_prefixes[i]; i++) {
  		int l = strlen(special_prefixes[i]);
  
  		if (l <= strlen(sym_name) &&
  		    strncmp(sym_name, special_prefixes[i], l) == 0)
  			return 0;
  	}

  	for (i = 0; special_suffixes[i]; i++) {
  		int l = strlen(sym_name) - strlen(special_suffixes[i]);
  
  		if (l >= 0 && strcmp(sym_name + l, special_suffixes[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
  ");
  				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)
  {

  	printf(".globl %s
  ", label);

  	printf("\tALGN
  ");

  	printf("%s:
  ", 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 int symbol_absolute(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>
  ");

  	printf("#if BITS_PER_LONG == 64
  ");
  	printf("#define PTR .quad
  ");

  	printf("#define ALGN .balign 8
  ");

  	printf("#else
  ");
  	printf("#define PTR .long
  ");

  	printf("#define ALGN .balign 4
  ");

  	printf("#endif
  ");

  	printf("\t.section .rodata, \"a\"
  ");

  	/* Provide proper symbols relocatability by their relativeness
  	 * to a fixed anchor point in the runtime image, either '_text'
  	 * for absolute address tables, in which case the linker will
  	 * emit the final addresses at build time. Otherwise, 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.
  	 *
  	 * 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.

  	 */

  	if (!base_relative)
  		output_label("kallsyms_addresses");
  	else
  		output_label("kallsyms_offsets");

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

  		if (base_relative) {
  			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
  ",
  					symbol_absolute(&table[i]) ? "absolute" : "relative",
  					table[i].addr);
  				exit(EXIT_FAILURE);
  			}
  			printf("\t.long\t%#x
  ", (int)offset);
  		} else if (!symbol_absolute(&table[i])) {

  			if (_text <= table[i].addr)
  				printf("\tPTR\t_text + %#llx
  ",
  					table[i].addr - _text);
  			else

  				printf("\tPTR\t_text - %#llx
  ",
  					_text - table[i].addr);

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

  	}
  	printf("
  ");

  	if (base_relative) {
  		output_label("kallsyms_relative_base");
  		printf("\tPTR\t_text - %#llx
  ", _text - relative_base);
  		printf("
  ");
  	}

  	output_label("kallsyms_num_syms");

  	printf("\t.long\t%u
  ", table_cnt);

  	printf("
  ");
  
  	/* 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
  ");
  		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("
  ");
  
  		off += table[i].len + 1;

  	}
  	printf("
  ");
  
  	output_label("kallsyms_markers");

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

  		printf("\t.long\t%u
  ", markers[i]);

  	printf("
  ");
  
  	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\"
  ", buf);
  		off += strlen(buf) + 1;
  	}
  	printf("
  ");
  
  	output_label("kallsyms_token_index");
  	for (i = 0; i < 256; i++)
  		printf("\t.short\t%d
  ", best_idx[i]);
  	printf("
  ");
  }
  
  
  /* 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++;

  		} else {
  			free(table[i].sym);

  		}

  	}

  	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 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();

  	/* When valid symbol is not registered, exit to error */

  	if (!table_cnt) {

  		fprintf(stderr, "No valid symbol.
  ");
  		exit(1);
  	}

  	optimize_result();
  }

  /* 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 == '_')

  		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;

  	/* 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);
  }

  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;
  
  	relative_base = -1ULL;
  	for (i = 0; i < table_cnt; i++)
  		if (!symbol_absolute(&table[i]) &&
  		    table[i].addr < relative_base)
  			relative_base = table[i].addr;
  }

  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);

  	if (absolute_percpu)
  		make_percpus_absolute();

  	if (base_relative)
  		record_relative_base();

  	sort_symbols();
  	optimize_token_table();

  	write_src();
  
  	return 0;
  }