sparc64: define untagged_addr()

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

Link: http://lkml.kernel.org/r/20190625143715.1689-9-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 439129a..8358ba0 100644 (file)
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -1078,6 +1078,28 @@ 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>