1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Today's hack: quantum tunneling in structs 4 * 5 * 'entries' and 'term' are never anywhere referenced by word in code. In fact, 6 * they serve as the hanging-off data accessed through repl.data[]. 7 */ 8 9 /* tbl has the following structure equivalent, but is C99 compliant: 10 * struct { 11 * struct type##_replace repl; 12 * struct type##_standard entries[nhooks]; 13 * struct type##_error term; 14 * } *tbl; 15 */ 16 17 #define xt_alloc_initial_table(type, typ2) ({ \ 18 unsigned int hook_mask = info->valid_hooks; \ 19 unsigned int nhooks = hweight32(hook_mask); \ 20 unsigned int bytes = 0, hooknum = 0, i = 0; \ 21 struct { \ 22 struct type##_replace repl; \ 23 struct type##_standard entries[]; \ 24 } *tbl; \ 25 struct type##_error *term; \ 26 size_t term_offset = (offsetof(typeof(*tbl), entries[nhooks]) + \ 27 __alignof__(*term) - 1) & ~(__alignof__(*term) - 1); \ 28 tbl = kzalloc(term_offset + sizeof(*term), GFP_KERNEL); \ 29 if (tbl == NULL) \ 30 return NULL; \ 31 term = (struct type##_error *)&(((char *)tbl)[term_offset]); \ 32 strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \ 33 *term = (struct type##_error)typ2##_ERROR_INIT; \ 34 tbl->repl.valid_hooks = hook_mask; \ 35 tbl->repl.num_entries = nhooks + 1; \ 36 tbl->repl.size = nhooks * sizeof(struct type##_standard) + \ 37 sizeof(struct type##_error); \ 38 for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \ 39 if (!(hook_mask & 1)) \ 40 continue; \ 41 tbl->repl.hook_entry[hooknum] = bytes; \ 42 tbl->repl.underflow[hooknum] = bytes; \ 43 tbl->entries[i++] = (struct type##_standard) \ 44 typ2##_STANDARD_INIT(NF_ACCEPT); \ 45 bytes += sizeof(struct type##_standard); \ 46 } \ 47 tbl; \ 48 }) 49