Linux Kernel  3.7.1
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shm.h
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1 #ifndef _H8300_SHM_H
2 #define _H8300_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 /* _H8300_SHM_H */