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Diffstat (limited to 'arch/m68k/include/asm/shm.h')
-rw-r--r--arch/m68k/include/asm/shm.h31
1 files changed, 31 insertions, 0 deletions
diff --git a/arch/m68k/include/asm/shm.h b/arch/m68k/include/asm/shm.h
new file mode 100644
index 00000000000..fa56ec84a12
--- /dev/null
+++ b/arch/m68k/include/asm/shm.h
@@ -0,0 +1,31 @@
+#ifndef _M68K_SHM_H
+#define _M68K_SHM_H
+
+
+/* format of page table entries that correspond to shared memory pages
+ currently out in swap space (see also mm/swap.c):
+ bits 0-1 (PAGE_PRESENT) is = 0
+ bits 8..2 (SWP_TYPE) are = SHM_SWP_TYPE
+ bits 31..9 are used like this:
+ bits 15..9 (SHM_ID) the id of the shared memory segment
+ bits 30..16 (SHM_IDX) the index of the page within the shared memory segment
+ (actually only bits 25..16 get used since SHMMAX is so low)
+ bit 31 (SHM_READ_ONLY) flag whether the page belongs to a read-only attach
+*/
+/* on the m68k both bits 0 and 1 must be zero */
+/* format on the sun3 is similar, but bits 30, 31 are set to zero and all
+ others are reduced by 2. --m */
+
+#ifndef CONFIG_SUN3
+#define SHM_ID_SHIFT 9
+#else
+#define SHM_ID_SHIFT 7
+#endif
+#define _SHM_ID_BITS 7
+#define SHM_ID_MASK ((1<<_SHM_ID_BITS)-1)
+
+#define SHM_IDX_SHIFT (SHM_ID_SHIFT+_SHM_ID_BITS)
+#define _SHM_IDX_BITS 15
+#define SHM_IDX_MASK ((1<<_SHM_IDX_BITS)-1)
+
+#endif /* _M68K_SHM_H */