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