/* 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 <stdbool.h>

  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <ctype.h>

  #include <limits.h>

  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))

  #define KSYM_NAME_LEN		128

  struct sym_entry {
  	unsigned long long addr;

  	unsigned int len;

  	unsigned int start_pos;

  	unsigned int percpu_absolute;

  	unsigned char sym[];

  };

  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;
  static int absolute_percpu;
  static int base_relative;

  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);
  }

  static char *sym_name(const struct sym_entry *s)
  {
  	return (char *)s->sym + 1;
  }

  static bool is_ignored_symbol(const char *name, char type)
  {

  	/* Symbol names that exactly match to the following are ignored.*/

  	static const char * const ignored_symbols[] = {
  		/*
  		 * 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.
  		 */
  		"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
  	};

  	/* Symbol names that begin with the following are ignored.*/

  	static const char * const ignored_prefixes[] = {

  		"$",			/* local symbols for ARM, MIPS, etc. */
  		".LASANPC",		/* s390 kasan local symbols */

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

  		"__kvm_nvhe_",		/* arm64 non-VHE KVM namespace */

  		NULL
  	};

  	/* Symbol names that end with the following are ignored.*/

  	static const char * const ignored_suffixes[] = {
  		"_from_arm",		/* arm */
  		"_from_thumb",		/* arm */
  		"_veneer",		/* arm */
  		NULL
  	};

  	/* Symbol names that contain the following are ignored.*/
  	static const char * const ignored_matches[] = {
  		".long_branch.",	/* ppc stub */
  		".plt_branch.",		/* ppc stub */
  		NULL
  	};

  	const char * const *p;

  	for (p = ignored_symbols; *p; p++)
  		if (!strcmp(name, *p))
  			return true;
  
  	for (p = ignored_prefixes; *p; p++)
  		if (!strncmp(name, *p, strlen(*p)))
  			return true;
  
  	for (p = ignored_suffixes; *p; p++) {
  		int l = strlen(name) - strlen(*p);
  
  		if (l >= 0 && !strcmp(name + l, *p))
  			return true;
  	}

  	for (p = ignored_matches; *p; p++) {
  		if (strstr(name, *p))
  			return true;
  	}

  	if (type == 'U' || type == 'u')
  		return true;
  	/* exclude debugging symbols */
  	if (type == 'N' || type == 'n')
  		return true;
  
  	if (toupper(type) == 'A') {
  		/* Keep these useful absolute symbols */
  		if (strcmp(name, "__kernel_syscall_via_break") &&
  		    strcmp(name, "__kernel_syscall_via_epc") &&
  		    strcmp(name, "__kernel_sigtramp") &&
  		    strcmp(name, "__gp"))
  			return true;
  	}

  	return false;
  }

  static void 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;

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

  			return;

  		}
  	}

  }

  static struct sym_entry *read_symbol(FILE *in)

  {

  	char name[500], type;

  	unsigned long long addr;
  	unsigned int len;
  	struct sym_entry *sym;

  	int rc;

  	rc = fscanf(in, "%llx %c %499s
  ", &addr, &type, name);

  	if (rc != 3) {

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

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

  		return NULL;

  	}

  	if (strlen(name) >= KSYM_NAME_LEN) {

  		fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).
  "

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

  			name, strlen(name), KSYM_NAME_LEN);

  		return NULL;

  	}

  	if (strcmp(name, "_text") == 0)

  		_text = addr;

  	/* Ignore most absolute/undefined (?) symbols. */
  	if (is_ignored_symbol(name, type))
  		return NULL;

  	check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
  	check_symbol_range(name, addr, &percpu_range, 1);

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

  
  	len = strlen(name) + 1;

  	sym = malloc(sizeof(*sym) + len + 1);

  	if (!sym) {

  		fprintf(stderr, "kallsyms failure: "
  			"unable to allocate required amount of memory
  ");
  		exit(EXIT_FAILURE);
  	}

  	sym->addr = addr;
  	sym->len = len;
  	sym->sym[0] = type;

  	strcpy(sym_name(sym), name);

  	sym->percpu_absolute = 0;

  	return sym;

  }

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

  {
  	size_t i;

  	const 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(const struct sym_entry *s)

  {

  	const char *name = sym_name(s);

  	/* 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(name, text_range_text->end_sym)) ||

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

  		     strcmp(name, text_range_inittext->end_sym)))

  			return 0;
  	}

  	return 1;
  }

  /* remove all the invalid symbols from the table */
  static void shrink_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];
  			pos++;
  		} else {

  			free(table[i]);

  		}
  	}
  	table_cnt = pos;
  
  	/* When valid symbol is not registered, exit to error */
  	if (!table_cnt) {
  		fprintf(stderr, "No valid symbol.
  ");
  		exit(1);
  	}
  }

  static void read_map(FILE *in)

  {

  	struct sym_entry *sym;

  	while (!feof(in)) {

  		sym = read_symbol(in);
  		if (!sym)
  			continue;
  
  		sym->start_pos = table_cnt;

  		if (table_cnt >= table_size) {
  			table_size += 10000;
  			table = realloc(table, sizeof(*table) * table_size);

  			if (!table) {
  				fprintf(stderr, "out of memory
  ");
  				exit (1);
  			}
  		}

  
  		table[table_cnt++] = sym;

  	}
  }

  static void output_label(const char *label)

  {

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

  	printf("\tALGN
  ");

  	printf("%s:
  ", label);

  }

  /* Provide proper symbols relocatability by their '_text' relativeness. */
  static void output_address(unsigned long long addr)
  {
  	if (_text <= addr)
  		printf("\tPTR\t_text + %#llx
  ", addr - _text);
  	else
  		printf("\tPTR\t_text - %#llx
  ", _text - addr);
  }

  /* 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(const 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(const 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\"
  ");

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

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

  		if (base_relative) {

  			/*
  			 * 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.
  			 */

  			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])) {
  			output_address(table[i]->addr);

  		} else {

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

  		}

  	}
  	printf("
  ");

  	if (base_relative) {
  		output_label("kallsyms_relative_base");

  		output_address(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(const 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(const unsigned char *symbol, int len)

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

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

  }

  /* do the initial token count */

  static void build_initial_tok_table(void)
  {

  	unsigned int i;

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

  		learn_symbol(table[i]->sym, table[i]->len);

  }

  static unsigned char *find_token(unsigned char *str, int len,

  				 const 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(const 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();
  
  	optimize_result();
  }

  /* guess for "linker script provide" symbol */
  static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
  {

  	const char *symbol = sym_name(se);

  	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 compare_symbols(const void *a, const void *b)
  {

  	const struct sym_entry *sa = *(const struct sym_entry **)a;
  	const struct sym_entry *sb = *(const struct sym_entry **)b;

  	int wa, wb;

  	/* 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 = strspn(sym_name(sa), "_");
  	wb = strspn(sym_name(sb), "_");

  	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(table[0]), 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;

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

  		if (!symbol_absolute(table[i])) {

  			/*
  			 * The table is sorted by address.
  			 * Take the first non-absolute symbol value.
  			 */

  			relative_base = table[i]->addr;

  			return;
  		}

  }

  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);

  	shrink_table();

  	if (absolute_percpu)
  		make_percpus_absolute();

  	sort_symbols();

  	if (base_relative)
  		record_relative_base();

  	optimize_token_table();

  	write_src();
  
  	return 0;
  }