[PATCH] ppc: make phys_mem_access_prot() work with pfns instead of addresses

Change the phys_mem_access_prot() function to take a pfn instead of an
address.  This allows mmap64() to work on /dev/mem for addresses above 4G
on 32-bit architectures.  We start with a pfn in mmap_mem(), so there's no
need to convert to an address; in fact, it's actively bad, since the
conversion can overflow when the address is above 4G.

Similarly fix the ppc32 page_is_ram() function to avoid a conversion to an
address by directly comparing to max_pfn.  Working with max_pfn instead of
high_memory fixes page_is_ram() to give the right answer for highmem pages.

Signed-off-by: Roland Dreier <[email protected]>
Cc: Anton Blanchard <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Paul Mackerras <[email protected]>

include/asm-powerpc/machdep.h

@@ -144,7 +144,7 @@ struct machdep_calls {
 	
 	/* Get access protection for /dev/mem */
 	pgprot_t	(*phys_mem_access_prot)(struct file *file,
-						unsigned long offset,
+						unsigned long pfn,
 						unsigned long size,
 						pgprot_t vma_prot);