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	strscpy_pad(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