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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 <>
Cc: Geert Uytterhoeven <>
Cc: David Howells <>
Acked-by: Greg Ungerer <>
Cc: Mike Frysinger <>
Cc: Bob Liu <>
Cc: <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
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commit 8f3b1327aa454bc8283e96bca7669c3c88b83f79 1 parent f607e7f
@lliubbo lliubbo authored torvalds committed
Showing with 6 additions and 3 deletions.
  1. +6 −3 mm/nommu.c
9 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;
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