[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 <rolandd@cisco.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 2 insertions, 4 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index f182752fe918..9df928d4f68d 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -231,9 +231,7 @@ static ssize_t write_mem(struct file * file, const char __user * buf,
 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 {
 #if defined(__HAVE_PHYS_MEM_ACCESS_PROT)
-        unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
-
-        vma->vm_page_prot = phys_mem_access_prot(file, offset,
+        vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
                                                  vma->vm_end - vma->vm_start,
                                                  vma->vm_page_prot);
 #elif defined(pgprot_noncached)
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 70be7009f8af..ca02aa2bfcec 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -918,7 +918,7 @@ fb_mmap(struct file *file, struct vm_area_struct * vma)
         }
 #endif
 #elif defined(__powerpc__)
-        vma->vm_page_prot = phys_mem_access_prot(file, off,
+        vma->vm_page_prot = phys_mem_access_prot(file, off >> PAGE_SHIFT,
                                                  vma->vm_end - vma->vm_start,
                                                  vma->vm_page_prot);
 #elif defined(__alpha__)