static void perform_rebinding_with_section()

in fishhook.c [114:165]

• 36 lines of code
• 13 McCabe index (conditional complexity)

static void perform_rebinding_with_section(struct rebindings_entry *rebindings,
                                           section_t *section,
                                           intptr_t slide,
                                           nlist_t *symtab,
                                           char *strtab,
                                           uint32_t *indirect_symtab) {
  uint32_t *indirect_symbol_indices = indirect_symtab + section->reserved1;
  void **indirect_symbol_bindings = (void **)((uintptr_t)slide + section->addr);

  for (uint i = 0; i < section->size / sizeof(void *); i++) {
    uint32_t symtab_index = indirect_symbol_indices[i];
    if (symtab_index == INDIRECT_SYMBOL_ABS || symtab_index == INDIRECT_SYMBOL_LOCAL ||
        symtab_index == (INDIRECT_SYMBOL_LOCAL   | INDIRECT_SYMBOL_ABS)) {
      continue;
    }
    uint32_t strtab_offset = symtab[symtab_index].n_un.n_strx;
    char *symbol_name = strtab + strtab_offset;
    bool symbol_name_longer_than_1 = symbol_name[0] && symbol_name[1];
    struct rebindings_entry *cur = rebindings;
    while (cur) {
      for (uint j = 0; j < cur->rebindings_nel; j++) {
        if (symbol_name_longer_than_1 && strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) {
          kern_return_t err;

          if (cur->rebindings[j].replaced != NULL && indirect_symbol_bindings[i] != cur->rebindings[j].replacement)
            *(cur->rebindings[j].replaced) = indirect_symbol_bindings[i];

          /**
           * 1. Moved the vm protection modifying codes to here to reduce the
           *    changing scope.
           * 2. Adding VM_PROT_WRITE mode unconditionally because vm_region
           *    API on some iOS/Mac reports mismatch vm protection attributes.
           * -- Lianfu Hao Jun 16th, 2021
           **/
          err = vm_protect (mach_task_self (), (uintptr_t)indirect_symbol_bindings, section->size, 0, VM_PROT_READ | VM_PROT_WRITE | VM_PROT_COPY);
          if (err == KERN_SUCCESS) {
            /**
             * Once we failed to change the vm protection, we
             * MUST NOT continue the following write actions!
             * iOS 15 has corrected the const segments prot.
             * -- Lionfore Hao Jun 11th, 2021
             **/
            indirect_symbol_bindings[i] = cur->rebindings[j].replacement;
          }
          goto symbol_loop;
        }
      }
      cur = cur->next;
    }
  symbol_loop:;
  }
}