[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, 7 insertions, 8 deletions

diff --git a/arch/ppc/kernel/pci.c b/arch/ppc/kernel/pci.c
index ad4ef2aaa6ab..e8f4e576750a 100644
--- a/arch/ppc/kernel/pci.c
+++ b/arch/ppc/kernel/pci.c
@@ -1594,16 +1594,17 @@ static pgprot_t __pci_mmap_set_pgprot(struct pci_dev *dev, struct resource *rp,
  * above routine
  */
 pgprot_t pci_phys_mem_access_prot(struct file *file,
-                                  unsigned long offset,
+                                  unsigned long pfn,
                                   unsigned long size,
                                   pgprot_t protection)
 {
         struct pci_dev *pdev = NULL;
         struct resource *found = NULL;
         unsigned long prot = pgprot_val(protection);
+        unsigned long offset = pfn << PAGE_SHIFT;
         int i;
 
-        if (page_is_ram(offset >> PAGE_SHIFT))
+        if (page_is_ram(pfn))
                 return prot;
 
         prot |= _PAGE_NO_CACHE | _PAGE_GUARDED;
diff --git a/arch/ppc/mm/init.c b/arch/ppc/mm/init.c
index db94efd25369..99b48abd3296 100644
--- a/arch/ppc/mm/init.c
+++ b/arch/ppc/mm/init.c
@@ -637,18 +637,16 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
  */
 int page_is_ram(unsigned long pfn)
 {
-        unsigned long paddr = (pfn << PAGE_SHIFT);
-
-        return paddr < __pa(high_memory);
+        return pfn < max_pfn;
 }
 
-pgprot_t phys_mem_access_prot(struct file *file, unsigned long addr,
+pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                               unsigned long size, pgprot_t vma_prot)
 {
         if (ppc_md.phys_mem_access_prot)
-                return ppc_md.phys_mem_access_prot(file, addr, size, vma_prot);
+                return ppc_md.phys_mem_access_prot(file, pfn, size, vma_prot);
 
-        if (!page_is_ram(addr >> PAGE_SHIFT))
+        if (!page_is_ram(pfn))
                 vma_prot = __pgprot(pgprot_val(vma_prot)
                                     | _PAGE_GUARDED | _PAGE_NO_CACHE);
         return vma_prot;