| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | #ifndef _M68K_SHM_H |
| 2 | #define _M68K_SHM_H |
| 3 | |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 */ |