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