s390/smp: make absolute lowcore / cpu restart parameter accesses more robust

Setting the cpu restart parameters is done in three different fashions:
- directly setting the four parameters individually
- copying the four parameters with memcpy (using 4 * sizeof(long))
- copying the four parameters using a private structure

In addition code in entry*.S relies on a certain order of the restart
members of struct _lowcore.

Make all of this more robust to future changes by adding a
mem_absolute_assign(dest, val) define, which assigns val to dest
using absolute addressing mode. Also the load multiple instructions
in entry*.S have been split into separate load instruction so the
order of the struct _lowcore members doesn't matter anymore.

In addition move the prototypes of memcpy_real/absolute from uaccess.h
to processor.h. These memcpy* variants are not related to uaccess at all.
string.h doesn't seem to match as well, so lets use processor.h.

Also replace the eight byte array in struct _lowcore which represents a
misaliged u64 with a u64. The compiler will always create code that
handles the misaligned u64 correctly.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index d5f02e480e51..2813e831ba32 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -751,7 +751,9 @@ ENTRY(restart_int_handler)
 	mvc	__PT_PSW(16,%r15),__LC_RST_OLD_PSW # store restart old psw
 	aghi	%r15,-STACK_FRAME_OVERHEAD	# create stack frame on stack
 	xc	0(STACK_FRAME_OVERHEAD,%r15),0(%r15)
-	lmg	%r1,%r3,__LC_RESTART_FN		# load fn, parm & source cpu
+	lg	%r1,__LC_RESTART_FN		# load fn, parm & source cpu
+	lg	%r2,__LC_RESTART_DATA
+	lg	%r3,__LC_RESTART_SOURCE
 	ltgr	%r3,%r3				# test source cpu address
 	jm	1f				# negative -> skip source stop
 0:	sigp	%r4,%r3,SIGP_SENSE		# sigp sense to source cpu