[IA64] Rationalize kernel mode alignment checking

Itanium processors can handle some misaligned data accesses. They
also provide a mode where all such accesses are forced to trap. The
kernel was schizophrenic about use of this mode:

* Base kernel code ran in permissive mode where the only traps
  generated were from those cases that the h/w could not handle.
* Interrupt, syscall and trap code ran in strict mode where all
  unaligned accesses caused traps to the 0x5a00 unaligned reference
  vector.

Use strict alignment checking throughout the kernel, but make
sure that we continue to let user mode use more relaxed mode
as the default.

Signed-off-by: Tony Luck <tony.luck@intel.com>

2 files changed, 2 insertions, 1 deletions

diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index 7ef0c594f5ed..d435f4a7a96c 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -499,6 +499,7 @@ GLOBAL_ENTRY(prefetch_stack)
 END(prefetch_stack)
 
 GLOBAL_ENTRY(kernel_execve)
+        rum psr.ac
         mov r15=__NR_execve                     // put syscall number in place
         break __BREAK_SYSCALL
         br.ret.sptk.many rp
diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
index 66e491d8baac..59301c472800 100644
--- a/arch/ia64/kernel/head.S
+++ b/arch/ia64/kernel/head.S
@@ -260,7 +260,7 @@ start_ap:
          * Switch into virtual mode:
          */
         movl r16=(IA64_PSR_IT|IA64_PSR_IC|IA64_PSR_DT|IA64_PSR_RT|IA64_PSR_DFH|IA64_PSR_BN \
-                  |IA64_PSR_DI)
+                  |IA64_PSR_DI|IA64_PSR_AC)
         ;;
         mov cr.ipsr=r16
         movl r17=1f