1 #ifndef _M68K_SHM_H
2 #define _M68K_SHM_H
3
4 #include <linux/config.h>
5
6 /* format of page table entries that correspond to shared memory pages
7 currently out in swap space (see also mm/swap.c):
8 bits 0-1 (PAGE_PRESENT) is = 0
9 bits 8..2 (SWP_TYPE) are = SHM_SWP_TYPE
10 bits 31..9 are used like this:
11 bits 15..9 (SHM_ID) the id of the shared memory segment
12 bits 30..16 (SHM_IDX) the index of the page within the shared memory segment
13 (actually only bits 25..16 get used since SHMMAX is so low)
14 bit 31 (SHM_READ_ONLY) flag whether the page belongs to a read-only attach
15 */
16 /* on the m68k both bits 0 and 1 must be zero */
17 /* format on the sun3 is similar, but bits 30, 31 are set to zero and all
18 others are reduced by 2. --m */
19
20 #ifndef CONFIG_SUN3
21 #define SHM_ID_SHIFT 9
22 #else
23 #define SHM_ID_SHIFT 7
24 #endif
25 #define _SHM_ID_BITS 7
26 #define SHM_ID_MASK ((1<<_SHM_ID_BITS)-1)
27
28 #define SHM_IDX_SHIFT (SHM_ID_SHIFT+_SHM_ID_BITS)
29 #define _SHM_IDX_BITS 15
30 #define SHM_IDX_MASK ((1<<_SHM_IDX_BITS)-1)
31
32 #endif /* _M68K_SHM_H */
33
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