1 files changed, 32 insertions, 0 deletions

diff --git a/include/asm-m68k/shm.h b/include/asm-m68k/shm.h
new file mode 100644
index 000000000000..3fa2f368fc1a
--- /dev/null
+++ b/include/asm-m68k/shm.h
@@ -0,0 +1,32 @@
+#ifndef _M68K_SHM_H
+#define _M68K_SHM_H
+
+#include <linux/config.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 */