[PATCH 09/16] sparc64: define untagged_addr()

[Christoph Hellwig]

Add a helper to untag a user pointer.  This is needed for ADI support
in get_user_pages_fast.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 arch/sparc/include/asm/pgtable_64.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index dcf970e82262..a93eca29e85a 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -1076,6 +1076,28 @@ static inline int io_remap_pfn_range(struct vm_area_struct *vma,
 }
 #define io_remap_pfn_range io_remap_pfn_range 
 
+static inline unsigned long untagged_addr(unsigned long start)
+{
+	if (adi_capable()) {
+		long addr = start;
+
+		/* If userspace has passed a versioned address, kernel
+		 * will not find it in the VMAs since it does not store
+		 * the version tags in the list of VMAs. Storing version
+		 * tags in list of VMAs is impractical since they can be
+		 * changed any time from userspace without dropping into
+		 * kernel. Any address search in VMAs will be done with
+		 * non-versioned addresses. Ensure the ADI version bits
+		 * are dropped here by sign extending the last bit before
+		 * ADI bits. IOMMU does not implement version tags.
+		 */
+		return (addr << (long)adi_nbits()) >> (long)adi_nbits();
+	}
+
+	return start;
+}
+#define untagged_addr untagged_addr
+
 #include <asm/tlbflush.h>
 #include <asm-generic/pgtable.h>
 
-- 
2.20.1