1#ifndef _M68K_SHM_H
2#define _M68K_SHM_H
3
4
5/* format of page table entries that correspond to shared memory pages
6   currently out in swap space (see also mm/swap.c):
7   bits 0-1 (PAGE_PRESENT) is  = 0
8   bits 8..2 (SWP_TYPE) are = SHM_SWP_TYPE
9   bits 31..9 are used like this:
10   bits 15..9 (SHM_ID) the id of the shared memory segment
11   bits 30..16 (SHM_IDX) the index of the page within the shared memory segment
12                    (actually only bits 25..16 get used since SHMMAX is so low)
13   bit 31 (SHM_READ_ONLY) flag whether the page belongs to a read-only attach
14*/
15/* on the m68k both bits 0 and 1 must be zero */
16/* format on the sun3 is similar, but bits 30, 31 are set to zero and all
17   others are reduced by 2. --m */
18
19#ifndef CONFIG_SUN3
20#define SHM_ID_SHIFT	9
21#else
22#define SHM_ID_SHIFT	7
23#endif
24#define _SHM_ID_BITS	7
25#define SHM_ID_MASK	((1<<_SHM_ID_BITS)-1)
26
27#define SHM_IDX_SHIFT	(SHM_ID_SHIFT+_SHM_ID_BITS)
28#define _SHM_IDX_BITS	15
29#define SHM_IDX_MASK	((1<<_SHM_IDX_BITS)-1)
30
31#endif /* _M68K_SHM_H */
32