1 /* 2 * Today's hack: quantum tunneling in structs 3 * 4 * 'entries' and 'term' are never anywhere referenced by word in code. In fact, 5 * they serve as the hanging-off data accessed through repl.data[]. 6 */ 7 8 /* tbl has the following structure equivalent, but is C99 compliant: 9 * struct { 10 * struct type##_replace repl; 11 * struct type##_standard entries[nhooks]; 12 * struct type##_error term; 13 * } *tbl; 14 */ 15 16 #define xt_alloc_initial_table(type, typ2) ({ \ 17 unsigned int hook_mask = info->valid_hooks; \ 18 unsigned int nhooks = hweight32(hook_mask); \ 19 unsigned int bytes = 0, hooknum = 0, i = 0; \ 20 struct { \ 21 struct type##_replace repl; \ 22 struct type##_standard entries[]; \ 23 } *tbl; \ 24 struct type##_error *term; \ 25 size_t term_offset = (offsetof(typeof(*tbl), entries[nhooks]) + \ 26 __alignof__(*term) - 1) & ~(__alignof__(*term) - 1); \ 27 tbl = kzalloc(term_offset + sizeof(*term), GFP_KERNEL); \ 28 if (tbl == NULL) \ 29 return NULL; \ 30 term = (struct type##_error *)&(((char *)tbl)[term_offset]); \ 31 strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \ 32 *term = (struct type##_error)typ2##_ERROR_INIT; \ 33 tbl->repl.valid_hooks = hook_mask; \ 34 tbl->repl.num_entries = nhooks + 1; \ 35 tbl->repl.size = nhooks * sizeof(struct type##_standard) + \ 36 sizeof(struct type##_error); \ 37 for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \ 38 if (!(hook_mask & 1)) \ 39 continue; \ 40 tbl->repl.hook_entry[hooknum] = bytes; \ 41 tbl->repl.underflow[hooknum] = bytes; \ 42 tbl->entries[i++] = (struct type##_standard) \ 43 typ2##_STANDARD_INIT(NF_ACCEPT); \ 44 bytes += sizeof(struct type##_standard); \ 45 } \ 46 tbl; \ 47 }) 48