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