[SPARC64]: Do not allow mapping pages within 4GB of 64-bit VA hole.

The UltraSPARC T1 manual recommends this because the chip
could instruction prefetch into the VA hole, and this would
also make decoding  certain kinds of memory access traps
more difficult (because the chip sign extends certain pieces
of trap state).

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/asm-sparc64/page.h b/include/asm-sparc64/page.h
index 5426bb28a993..c277ac56b9d7 100644
--- a/include/asm-sparc64/page.h
+++ b/include/asm-sparc64/page.h
@@ -107,7 +107,8 @@ typedef unsigned long pgprot_t;
 #endif
 
 #define TASK_UNMAPPED_BASE      (test_thread_flag(TIF_32BIT) ? \
-                                 (_AC(0x0000000070000000,UL)) : (PAGE_OFFSET))
+                                 (_AC(0x0000000070000000,UL)) : \
+                                 (_AC(0xfffff80000000000,UL) + (1UL << 32UL)))
 
 #endif /* !(__ASSEMBLY__) */