| #include <stdlib.h> |
| #include <fcntl.h> |
| #include <string.h> |
| #include <sys/stat.h> |
| #include <sys/mman.h> |
| |
| #include "symbol_table.h" |
| #include "utility.h" |
| |
| #include <linux/elf.h> |
| |
| // Compare func for qsort |
| static int qcompar(const void *a, const void *b) |
| { |
| return ((struct symbol*)a)->addr - ((struct symbol*)b)->addr; |
| } |
| |
| // Compare func for bsearch |
| static int bcompar(const void *addr, const void *element) |
| { |
| struct symbol *symbol = (struct symbol*)element; |
| |
| if((unsigned int)addr < symbol->addr) { |
| return -1; |
| } |
| |
| if((unsigned int)addr - symbol->addr >= symbol->size) { |
| return 1; |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * Create a symbol table from a given file |
| * |
| * Parameters: |
| * filename - Filename to process |
| * |
| * Returns: |
| * A newly-allocated SymbolTable structure, or NULL if error. |
| * Free symbol table with symbol_table_free() |
| */ |
| struct symbol_table *symbol_table_create(const char *filename) |
| { |
| struct symbol_table *table = NULL; |
| |
| // Open the file, and map it into memory |
| struct stat sb; |
| int length; |
| char *base; |
| |
| XLOG("Creating symbol table for %s\n", filename); |
| int fd = open(filename, O_RDONLY); |
| |
| if(fd < 0) { |
| goto out; |
| } |
| |
| fstat(fd, &sb); |
| length = sb.st_size; |
| |
| base = mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd, 0); |
| |
| if(!base) { |
| goto out_close; |
| } |
| |
| // Parse the file header |
| Elf32_Ehdr *hdr = (Elf32_Ehdr*)base; |
| Elf32_Shdr *shdr = (Elf32_Shdr*)(base + hdr->e_shoff); |
| |
| // Search for the dynamic symbols section |
| int sym_idx = -1; |
| int dynsym_idx = -1; |
| int i; |
| |
| for(i = 0; i < hdr->e_shnum; i++) { |
| if(shdr[i].sh_type == SHT_SYMTAB ) { |
| sym_idx = i; |
| } |
| if(shdr[i].sh_type == SHT_DYNSYM ) { |
| dynsym_idx = i; |
| } |
| } |
| if ((dynsym_idx == -1) || (sym_idx == -1)) { |
| goto out_unmap; |
| } |
| |
| table = malloc(sizeof(struct symbol_table)); |
| if(!table) { |
| goto out_unmap; |
| } |
| table->name = strdup(filename); |
| table->num_symbols = 0; |
| |
| Elf32_Sym *dynsyms = (Elf32_Sym*)(base + shdr[dynsym_idx].sh_offset); |
| Elf32_Sym *syms = (Elf32_Sym*)(base + shdr[sym_idx].sh_offset); |
| |
| int dynnumsyms = shdr[dynsym_idx].sh_size / shdr[dynsym_idx].sh_entsize; |
| int numsyms = shdr[sym_idx].sh_size / shdr[sym_idx].sh_entsize; |
| |
| int dynstr_idx = shdr[dynsym_idx].sh_link; |
| int str_idx = shdr[sym_idx].sh_link; |
| |
| char *dynstr = base + shdr[dynstr_idx].sh_offset; |
| char *str = base + shdr[str_idx].sh_offset; |
| |
| int symbol_count = 0; |
| int dynsymbol_count = 0; |
| |
| if (dynsym_idx != -1) { |
| // Iterate through the dynamic symbol table, and count how many symbols |
| // are actually defined |
| for(i = 0; i < dynnumsyms; i++) { |
| if(dynsyms[i].st_shndx != SHN_UNDEF) { |
| dynsymbol_count++; |
| } |
| } |
| XLOG("Dynamic Symbol count: %d\n", dynsymbol_count); |
| } |
| |
| if (sym_idx != -1) { |
| // Iterate through the symbol table, and count how many symbols |
| // are actually defined |
| for(i = 0; i < numsyms; i++) { |
| if((syms[i].st_shndx != SHN_UNDEF) && |
| (strlen(str+syms[i].st_name)) && |
| (syms[i].st_value != 0) && (syms[i].st_size != 0)) { |
| symbol_count++; |
| } |
| } |
| XLOG("Symbol count: %d\n", symbol_count); |
| } |
| |
| // Now, create an entry in our symbol table structure for each symbol... |
| table->num_symbols += symbol_count + dynsymbol_count;; |
| table->symbols = malloc(table->num_symbols * sizeof(struct symbol)); |
| if(!table->symbols) { |
| free(table); |
| table = NULL; |
| goto out_unmap; |
| } |
| |
| |
| int j = 0; |
| if (dynsym_idx != -1) { |
| // ...and populate them |
| for(i = 0; i < dynnumsyms; i++) { |
| if(dynsyms[i].st_shndx != SHN_UNDEF) { |
| table->symbols[j].name = strdup(dynstr + dynsyms[i].st_name); |
| table->symbols[j].addr = dynsyms[i].st_value; |
| table->symbols[j].size = dynsyms[i].st_size; |
| XLOG("name: %s, addr: %x, size: %x\n", |
| table->symbols[j].name, table->symbols[j].addr, table->symbols[j].size); |
| j++; |
| } |
| } |
| } |
| |
| if (sym_idx != -1) { |
| // ...and populate them |
| for(i = 0; i < numsyms; i++) { |
| if((syms[i].st_shndx != SHN_UNDEF) && |
| (strlen(str+syms[i].st_name)) && |
| (syms[i].st_value != 0) && (syms[i].st_size != 0)) { |
| table->symbols[j].name = strdup(str + syms[i].st_name); |
| table->symbols[j].addr = syms[i].st_value; |
| table->symbols[j].size = syms[i].st_size; |
| XLOG("name: %s, addr: %x, size: %x\n", |
| table->symbols[j].name, table->symbols[j].addr, table->symbols[j].size); |
| j++; |
| } |
| } |
| } |
| |
| // Sort the symbol table entries, so they can be bsearched later |
| qsort(table->symbols, table->num_symbols, sizeof(struct symbol), qcompar); |
| |
| out_unmap: |
| munmap(base, length); |
| |
| out_close: |
| close(fd); |
| |
| out: |
| return table; |
| } |
| |
| /* |
| * Free a symbol table |
| * |
| * Parameters: |
| * table - Table to free |
| */ |
| void symbol_table_free(struct symbol_table *table) |
| { |
| int i; |
| |
| if(!table) { |
| return; |
| } |
| |
| for(i=0; i<table->num_symbols; i++) { |
| free(table->symbols[i].name); |
| } |
| |
| free(table->symbols); |
| free(table); |
| } |
| |
| /* |
| * Search for an address in the symbol table |
| * |
| * Parameters: |
| * table - Table to search in |
| * addr - Address to search for. |
| * |
| * Returns: |
| * A pointer to the Symbol structure corresponding to the |
| * symbol which contains this address, or NULL if no symbol |
| * contains it. |
| */ |
| const struct symbol *symbol_table_lookup(struct symbol_table *table, unsigned int addr) |
| { |
| if(!table) { |
| return NULL; |
| } |
| |
| return bsearch((void*)addr, table->symbols, table->num_symbols, sizeof(struct symbol), bcompar); |
| } |