SkidSec WebShell

Server Address : 172.31.38.4

Web Server : Apache/2.4.58 (Ubuntu)

Uname : Linux ip-172-31-38-4 6.14.0-1017-aws #17~24.04.1-Ubuntu SMP Wed Nov 5 10:48:17 UTC 2025 x86_64

PHP Version : 7.4.33

/* 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: kallsyms [--all-symbols] [--absolute-percpu] in.map > out.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 <errno.h> #include <getopt.h> #include <stdbool.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> #include <limits.h> #include <xalloc.h> #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0])) #define KSYM_NAME_LEN 512 struct sym_entry { unsigned long long addr; unsigned int len; unsigned int seq; bool 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 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] 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) { if (type == 'u' || 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 **buf, size_t *buf_len) { char *name, type, *p; unsigned long long addr; size_t len; ssize_t readlen; struct sym_entry *sym; errno = 0; readlen = getline(buf, buf_len, in); if (readlen < 0) { if (errno) { perror("read_symbol"); exit(EXIT_FAILURE); } return NULL; } if ((*buf)[readlen - 1] == '\n') (*buf)[readlen - 1] = 0; addr = strtoull(*buf, &p, 16); if (*buf == p || *p++ != ' ' || !isascii((type = *p++)) || *p++ != ' ') { fprintf(stderr, "line format error\n"); exit(EXIT_FAILURE); } name = p; len = strlen(name); if (len >= 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, len, 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++; sym = xmalloc(sizeof(*sym) + len + 1); sym->addr = addr; sym->len = len; sym->sym[0] = type; strcpy(sym_name(sym), name); sym->percpu_absolute = false; 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 bool string_starts_with(const char *s, const char *prefix) { return strncmp(s, prefix, strlen(prefix)) == 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) { /* * Symbols starting with __start and __stop are used to denote * section boundaries, and should always be included: */ if (string_starts_with(name, "__start_") || string_starts_with(name, "__stop_")) return 1; 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; } static void read_map(const char *in) { FILE *fp; struct sym_entry *sym; char *buf = NULL; size_t buflen = 0; fp = fopen(in, "r"); if (!fp) { perror(in); exit(1); } while (!feof(fp)) { sym = read_symbol(fp, &buf, &buflen); if (!sym) continue; sym->seq = table_cnt; if (table_cnt >= table_size) { table_size += 10000; table = xrealloc(table, sizeof(*table) * table_size); } table[table_cnt++] = sym; } free(buf); fclose(fp); } static void output_label(const char *label) { printf(".globl %s\n", label); printf("\tALGN\n"); 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(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 bool symbol_absolute(const struct sym_entry *s) { return s->percpu_absolute; } static int compare_names(const void *a, const void *b) { int ret; const struct sym_entry *sa = *(const struct sym_entry **)a; const struct sym_entry *sb = *(const struct sym_entry **)b; ret = strcmp(sym_name(sa), sym_name(sb)); if (!ret) { if (sa->addr > sb->addr) return 1; else if (sa->addr < sb->addr) return -1; /* keep old order */ return (int)(sa->seq - sb->seq); } return ret; } static void sort_symbols_by_name(void) { qsort(table, table_cnt, sizeof(table[0]), compare_names); } static void write_src(void) { unsigned int i, k, off; unsigned int best_idx[256]; unsigned int *markers, markers_cnt; 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"); 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_cnt = (table_cnt + 255) / 256; markers = xmalloc(sizeof(*markers) * markers_cnt); output_label("kallsyms_names"); off = 0; for (i = 0; i < table_cnt; i++) { if ((i & 0xFF) == 0) markers[i >> 8] = off; table[i]->seq = i; /* There cannot be any symbol of length zero. */ if (table[i]->len == 0) { fprintf(stderr, "kallsyms failure: " "unexpected zero symbol length\n"); exit(EXIT_FAILURE); } /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */ if (table[i]->len > 0x3FFF) { fprintf(stderr, "kallsyms failure: " "unexpected huge symbol length\n"); exit(EXIT_FAILURE); } /* Encode length with ULEB128. */ if (table[i]->len <= 0x7F) { /* Most symbols use a single byte for the length. */ printf("\t.byte 0x%02x", table[i]->len); off += table[i]->len + 1; } else { /* "Big" symbols use two bytes. */ printf("\t.byte 0x%02x, 0x%02x", (table[i]->len & 0x7F) | 0x80, (table[i]->len >> 7) & 0x7F); off += table[i]->len + 2; } for (k = 0; k < table[i]->len; k++) printf(", 0x%02x", table[i]->sym[k]); /* * Now that we wrote out the compressed symbol name, restore the * original name and print it in the comment. */ expand_symbol(table[i]->sym, table[i]->len, buf); strcpy((char *)table[i]->sym, buf); printf("\t/* %s */\n", table[i]->sym); } printf("\n"); output_label("kallsyms_markers"); for (i = 0; i < markers_cnt; 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"); output_label("kallsyms_offsets"); for (i = 0; i < table_cnt; i++) { /* * 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; bool 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\t/* %s */\n", (int)offset, table[i]->sym); } printf("\n"); output_label("kallsyms_relative_base"); /* Provide proper symbols relocatability by their '_text' relativeness. */ if (_text <= relative_base) printf("\tPTR\t_text + %#llx\n", relative_base - _text); else printf("\tPTR\t_text - %#llx\n", _text - relative_base); printf("\n"); sort_symbols_by_name(); output_label("kallsyms_seqs_of_names"); for (i = 0; i < table_cnt; i++) printf("\t.byte 0x%02x, 0x%02x, 0x%02x\t/* %s */\n", (unsigned char)(table[i]->seq >> 16), (unsigned char)(table[i]->seq >> 8), (unsigned char)(table[i]->seq >> 0), table[i]->sym); 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_token_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_token_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->seq - sb->seq; } 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 = true; } } /* 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) { while (1) { static const struct option long_options[] = { {"all-symbols", no_argument, &all_symbols, 1}, {"absolute-percpu", no_argument, &absolute_percpu, 1}, {}, }; int c = getopt_long(argc, argv, "", long_options, NULL); if (c == -1) break; if (c != 0) usage(); } if (optind >= argc) usage(); read_map(argv[optind]); shrink_table(); if (absolute_percpu) make_percpus_absolute(); sort_symbols(); record_relative_base(); optimize_token_table(); write_src(); return 0; }