s390/early: fix sclp_early_sccb variable lifetime

[ Upstream commit 639886b71d ]

Commit ada1da31ce ("s390/sclp: sort out physical vs
virtual pointers usage") fixed the notion of virtual
address for sclp_early_sccb pointer. However, it did
not take into account that kasan_early_init() can also
output messages and sclp_early_sccb should be adjusted
by the time kasan_early_init() is called.

Currently it is not a problem, since virtual and physical
addresses on s390 are the same. Nevertheless, should they
ever differ, this would cause an invalid pointer access.

Fixes: ada1da31ce ("s390/sclp: sort out physical vs virtual pointers usage")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/s390/kernel/early.c

@@ -288,7 +288,6 @@ static void __init sort_amode31_extable(void)
 
 void __init startup_init(void)
 {
-	sclp_early_adjust_va();
 	reset_tod_clock();
 	check_image_bootable();
 	time_early_init();

arch/s390/kernel/head64.S

@@ -25,6 +25,7 @@ ENTRY(startup_continue)
 	larl	%r14,init_task
 	stg	%r14,__LC_CURRENT
 	larl	%r15,init_thread_union+THREAD_SIZE-STACK_FRAME_OVERHEAD-__PT_SIZE
+	brasl	%r14,sclp_early_adjust_va	# allow sclp_early_printk
 #ifdef CONFIG_KASAN
 	brasl	%r14,kasan_early_init
 #endif

drivers/s390/char/sclp_early.c

@@ -161,7 +161,7 @@ static void __init sclp_early_console_detect(struct init_sccb *sccb)
 		sclp.has_linemode = 1;
 }
 
-void __init sclp_early_adjust_va(void)
+void __init __no_sanitize_address sclp_early_adjust_va(void)
 {
 	sclp_early_sccb = __va((unsigned long)sclp_early_sccb);
 }