mm/nommu.c: fix remap_pfn_range()

remap_pfn_range() means map physical address pfn<<PAGE_SHIFT to user addr.

For nommu arch it's implemented by vma->vm_start = pfn << PAGE_SHIFT which
is wrong acroding the original meaning of this function.  And some driver
developer using remap_pfn_range() with correct parameter will get
unexpected result because vm_start is changed.  It should be implementd
like addr = pfn << PAGE_SHIFT but which is meanless on nommu arch, this
patch just make it simply return.

Parameter name and setting of vma->vm_flags also be fixed.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: David Howells <dhowells@redhat.com>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Bob Liu <lliubbo@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
index 1fd0c51b10a6..9edc897a3970 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1813,10 +1813,13 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
         return NULL;
 }
 
-int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
-                unsigned long to, unsigned long size, pgprot_t prot)
+int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
+                unsigned long pfn, unsigned long size, pgprot_t prot)
 {
-        vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
+        if (addr != (pfn << PAGE_SHIFT))
+                return -EINVAL;
+
+        vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
         return 0;
 }
 EXPORT_SYMBOL(remap_pfn_range);