s390/base: pass pt_regs to early program check handler

Pass pt_regs to early program check handler like it is done for every
other interrupt and exception handler.

Also the passed pt_regs can be changed by the called function and the
changes register contents and psw contents will be taken into account
when returning. In addition the return psw will not be copied to the
program check old psw in lowcore, but to the usual return psw
location, like it is also done by the regular program check handler.
This allows also to get rid of the code that disabled lowcore
protection when changing the return address.

Reviewed-by: Alexander Gordeev <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Vasily Gorbik <[e-mail]>

arch/s390/include/asm/processor.h

···
  * Basic Program Check Handler.
  */
 extern void s390_base_pgm_handler(void);
-extern void (*s390_base_pgm_handler_fn)(void);
+extern void (*s390_base_pgm_handler_fn)(struct pt_regs *regs);
 
 #define ARCH_LOW_ADDRESS_LIMIT	0x7fffffffUL
 

arch/s390/kernel/base.S

···
 	GEN_BR_THUNK %r9
 	GEN_BR_THUNK %r14
 
+__PT_R0 = __PT_GPRS
+__PT_R8 = __PT_GPRS + 64
+
 ENTRY(s390_base_pgm_handler)
-	stmg	%r0,%r15,__LC_SAVE_AREA_SYNC
-	basr	%r13,0
-0:	aghi	%r15,-STACK_FRAME_OVERHEAD
+	stmg	%r8,%r15,__LC_SAVE_AREA_SYNC
+	aghi	%r15,-(STACK_FRAME_OVERHEAD+__PT_SIZE)
+	la	%r11,STACK_FRAME_OVERHEAD(%r15)
+	xc	__SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
+	stmg	%r0,%r7,__PT_R0(%r11)
+	mvc	__PT_PSW(16,%r11),__LC_PGM_OLD_PSW
+	mvc	__PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
+	lgr	%r2,%r11
 	larl	%r1,s390_base_pgm_handler_fn
 	lg	%r9,0(%r1)
 	ltgr	%r9,%r9
 	jz	1f
 	BASR_EX	%r14,%r9
-	lmg	%r0,%r15,__LC_SAVE_AREA_SYNC
-	lpswe	__LC_PGM_OLD_PSW
-1:	lpswe	disabled_wait_psw-0b(%r13)
+	mvc	__LC_RETURN_PSW(16),STACK_FRAME_OVERHEAD+__PT_PSW(%r15)
+	lmg	%r0,%r15,STACK_FRAME_OVERHEAD+__PT_R0(%r15)
+	lpswe	__LC_RETURN_PSW
+1:	larl	%r13,disabled_wait_psw
+	lpswe	0(%r13)
 ENDPROC(s390_base_pgm_handler)
 
 	.align	8

arch/s390/kernel/early.c

···
 	topology_max_mnest = max_mnest;
 }
 
-static void early_pgm_check_handler(void)
+static void early_pgm_check_handler(struct pt_regs *regs)
 {
 	const struct exception_table_entry *fixup;
-	unsigned long cr0, cr0_new;
-	unsigned long addr;
 
-	addr = S390_lowcore.program_old_psw.addr;
-	fixup = s390_search_extables(addr);
+	fixup = s390_search_extables(regs->psw.addr);
 	if (!fixup)
 		disabled_wait();
-	/* Disable low address protection before storing into lowcore. */
-	__ctl_store(cr0, 0, 0);
-	cr0_new = cr0 & ~(1UL << 28);
-	__ctl_load(cr0_new, 0, 0);
-	S390_lowcore.program_old_psw.addr = extable_fixup(fixup);
-	__ctl_load(cr0, 0, 0);
+	regs->psw.addr = extable_fixup(fixup);
 }
 
 static noinline __init void setup_lowcore_early(void)