[PATCH v2] nommu: fix remap_pfn_range()implemention

[Bob Liu <lliubbo@gmail.com>]

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.

Reported-by: Scott Jiang <scott.jiang.linux@gmail.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
---
 mm/nommu.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 1fd0c51..9edc897 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);
-- 
1.6.3.3


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