[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>

2 files changed, 5 insertions, 2 deletions

diff --git a/include/asm-sparc64/a.out.h b/include/asm-sparc64/a.out.h
index 02af289e3f46..faac321d5594 100644
--- a/include/asm-sparc64/a.out.h
+++ b/include/asm-sparc64/a.out.h
@@ -95,7 +95,9 @@ struct relocation_info /* used when header.a_machtype == M_SPARC */
 
 #ifdef __KERNEL__
 
-#define STACK_TOP (test_thread_flag(TIF_32BIT) ? 0xf0000000 : 0x80000000000L)
+#define STACK_TOP (test_thread_flag(TIF_32BIT) ? \
+                   0xf0000000 : \
+                   (0x0000080000000000UL - (1UL << 32UL)))
 
 #endif
 
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__) */