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 /* 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] [--absolute-percpu] "
             "[--base-relative] < in.map > out.S\n");
     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[] = {
         "$",            /* local symbols for ARM, MIPS, etc. */
         ".L",           /* local labels, .LBB,.Ltmpxxx,.L__unnamed_xx,.LASANPC, etc. */
         "__crc_",       /* modversions */
         "__efistub_",       /* arm64 EFI stub namespace */
         "__kvm_nvhe_$",     /* arm64 local symbols in non-VHE KVM namespace */
         "__kvm_nvhe_.L",    /* arm64 local symbols in non-VHE KVM namespace */
         "__AArch64ADRPThunk_",  /* arm64 lld */
         "__ARMV5PILongThunk_",  /* arm lld */
         "__ARMV7PILongThunk_",
         "__ThumbV7PILongThunk_",
         "__LA25Thunk_",     /* mips lld */
         "__microLA25Thunk_",
         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\n", &addr, &type, name);
     if (rc != 3) {
         if (rc != EOF && fgets(name, 500, in) == NULL)
             fprintf(stderr, "Read error or end of file.\n");
         return NULL;
     }
     if (strlen(name) >= KSYM_NAME_LEN) {
         fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
                 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
             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\n");
         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.\n");
         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\n");
                 exit (1);
             }
         }
 
         table[table_cnt++] = sym;
     }
 }
 
 static void output_label(const char *label)
 {
     printf(".globl %s\n", label);
     printf("\tALGN\n");
     printf("%s:\n", 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\n", addr - _text);
     else
         printf("\tPTR\t_text - %#llx\n", _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>\n");
     printf("#if BITS_PER_LONG == 64\n");
     printf("#define PTR .quad\n");
     printf("#define ALGN .balign 8\n");
     printf("#else\n");
     printf("#define PTR .long\n");
     printf("#define ALGN .balign 4\n");
     printf("#endif\n");
 
     printf("\t.section .rodata, \"a\"\n");
 
     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\n",
                     symbol_absolute(table[i]) ? "absolute" : "relative",
                     table[i]->addr);
                 exit(EXIT_FAILURE);
             }
             printf("\t.long\t%#x\n", (int)offset);
         } else if (!symbol_absolute(table[i])) {
             output_address(table[i]->addr);
         } else {
             printf("\tPTR\t%#llx\n", table[i]->addr);
         }
     }
     printf("\n");
 
     if (base_relative) {
         output_label("kallsyms_relative_base");
         output_address(relative_base);
         printf("\n");
     }
 
     output_label("kallsyms_num_syms");
     printf("\t.long\t%u\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("\t.long\t%u\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(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;
 }

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