[S390] Cleanup struct _lowcore usage and defines.

Use asm offsets to make sure the offset defines to struct _lowcore and
its layout don't get out of sync.
Also add a BUILD_BUG_ON() which checks that the size of the structure
is sane.
And while being at it change those sites which use odd casts to access
the current lowcore. These should use S390_lowcore instead.

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

1 files changed, 2 insertions, 5 deletions

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index d9fb98cde0fa..77a63ae419f0 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -396,15 +396,12 @@ static void __init
 setup_lowcore(void)
 {
         struct _lowcore *lc;
-        int lc_pages;
 
         /*
          * Setup lowcore for boot cpu
          */
-        lc_pages = sizeof(void *) == 8 ? 2 : 1;
-        lc = (struct _lowcore *)
-                __alloc_bootmem(lc_pages * PAGE_SIZE, lc_pages * PAGE_SIZE, 0);
-        memset(lc, 0, lc_pages * PAGE_SIZE);
+        BUILD_BUG_ON(sizeof(struct _lowcore) != LC_PAGES * 4096);
+        lc = __alloc_bootmem(LC_PAGES * PAGE_SIZE, LC_PAGES * PAGE_SIZE, 0);
         lc->restart_psw.mask = PSW_BASE_BITS | PSW_DEFAULT_KEY;
         lc->restart_psw.addr =
                 PSW_ADDR_AMODE | (unsigned long) restart_int_handler;