powerpc/hugetlb: Add ABI defines for supported HugeTLB page sizes

Add user space exported API definitions for 512KB, 1MB, 2MB, 8MB, 16MB,
1GB, 16GB non default huge page sizes to be used with mmap() system
call.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
[mpe: Reword the comment to emphasise that these are only needed to use
 the non-default huge page size, and updated the change log.]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/uapi/asm/mman.h

@@ -29,4 +29,20 @@
 #define MAP_STACK	0x20000		/* give out an address that is best suited for process/thread stacks */
 #define MAP_HUGETLB	0x40000		/* create a huge page mapping */
 
+/*
+ * When MAP_HUGETLB is set, bits [26:31] of the flags argument to mmap(2),
+ * encode the log2 of the huge page size. A value of zero indicates that the
+ * default huge page size should be used. To use a non-default huge page size,
+ * one of these defines can be used, or the size can be encoded by hand. Note
+ * that on most systems only a subset, or possibly none, of these sizes will be
+ * available.
+ */
+#define MAP_HUGE_512KB	(19 << MAP_HUGE_SHIFT)	/* 512KB HugeTLB Page */
+#define MAP_HUGE_1MB	(20 << MAP_HUGE_SHIFT)	/* 1MB   HugeTLB Page */
+#define MAP_HUGE_2MB	(21 << MAP_HUGE_SHIFT)	/* 2MB   HugeTLB Page */
+#define MAP_HUGE_8MB	(23 << MAP_HUGE_SHIFT)	/* 8MB   HugeTLB Page */
+#define MAP_HUGE_16MB	(24 << MAP_HUGE_SHIFT)	/* 16MB  HugeTLB Page */
+#define MAP_HUGE_1GB	(30 << MAP_HUGE_SHIFT)	/* 1GB   HugeTLB Page */
+#define MAP_HUGE_16GB	(34 << MAP_HUGE_SHIFT)	/* 16GB  HugeTLB Page */
+
 #endif /* _UAPI_ASM_POWERPC_MMAN_H */