s390: simplify early program check handler

Due to historic reasons the base program check handler calls a
configurable function. Given that there is only the early program
check handler left, simplify the code by directly calling that
function.

The only other user was removed with commit d485235b ("s390:
assume diag308 set always works").

Also rename all functions and the asm file to reflect this.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/processor.h

@@ -304,12 +304,6 @@ static __always_inline void __noreturn disabled_wait(void)
 	while (1);
 }
 
-/*
- * Basic Program Check Handler.
- */
-extern void s390_base_pgm_handler(void);
-extern void (*s390_base_pgm_handler_fn)(struct pt_regs *regs);
-
 #define ARCH_LOW_ADDRESS_LIMIT	0x7fffffffUL
 
 extern int memcpy_real(void *, unsigned long, size_t);

arch/s390/kernel/Makefile

@@ -33,7 +33,7 @@ CFLAGS_stacktrace.o	+= -fno-optimize-sibling-calls
 CFLAGS_dumpstack.o	+= -fno-optimize-sibling-calls
 CFLAGS_unwind_bc.o	+= -fno-optimize-sibling-calls
 
-obj-y	:= traps.o time.o process.o base.o early.o setup.o idle.o vtime.o
+obj-y	:= traps.o time.o process.o earlypgm.o early.o setup.o idle.o vtime.o
 obj-y	+= processor.o syscall.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
 obj-y	+= debug.o irq.o ipl.o dis.o diag.o vdso.o
 obj-y	+= sysinfo.o lgr.o os_info.o machine_kexec.o

arch/s390/kernel/early.c

@@ -149,7 +149,7 @@ static __init void setup_topology(void)
 	topology_max_mnest = max_mnest;
 }
 
-static void early_pgm_check_handler(struct pt_regs *regs)
+void __do_early_pgm_check(struct pt_regs *regs)
 {
 	if (!fixup_exception(regs))
 		disabled_wait();
@@ -159,12 +159,11 @@ static noinline __init void setup_lowcore_early(void)
 {
 	psw_t psw;
 
-	psw.addr = (unsigned long)s390_base_pgm_handler;
+	psw.addr = (unsigned long)early_pgm_check_handler;
 	psw.mask = PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA;
 	if (IS_ENABLED(CONFIG_KASAN))
 		psw.mask |= PSW_MASK_DAT;
 	S390_lowcore.program_new_psw = psw;
-	s390_base_pgm_handler_fn = early_pgm_check_handler;
 	S390_lowcore.preempt_count = INIT_PREEMPT_COUNT;
 }
 

arch/s390/kernel/base.S → arch/s390/kernel/earlypgm.S

 /* SPDX-License-Identifier: GPL-2.0 */
 /*
- *  arch/s390/kernel/base.S
- *
  *    Copyright IBM Corp. 2006, 2007
  *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
  */
 
 #include <linux/linkage.h>
 #include <asm/asm-offsets.h>
-#include <asm/nospec-insn.h>
-#include <asm/ptrace.h>
-
-	GEN_BR_THUNK %r9
-	GEN_BR_THUNK %r14
 
 __PT_R0 = __PT_GPRS
 __PT_R8 = __PT_GPRS + 64
 
-ENTRY(s390_base_pgm_handler)
+ENTRY(early_pgm_check_handler)
 	stmg	%r8,%r15,__LC_SAVE_AREA_SYNC
 	aghi	%r15,-(STACK_FRAME_OVERHEAD+__PT_SIZE)
 	la	%r11,STACK_FRAME_OVERHEAD(%r15)
@@ -26,25 +19,8 @@ ENTRY(s390_base_pgm_handler)
 	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
+	brasl	%r14,__do_early_pgm_check
 	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
-disabled_wait_psw:
-	.quad	0x0002000180000000,0x0000000000000000 + s390_base_pgm_handler
-
-	.section .bss
-	.align 8
-	.globl s390_base_pgm_handler_fn
-s390_base_pgm_handler_fn:
-	.quad	0
-	.previous
+ENDPROC(early_pgm_check_handler)

arch/s390/kernel/entry.h

@@ -17,10 +17,12 @@ void ext_int_handler(void);
 void io_int_handler(void);
 void mcck_int_handler(void);
 void restart_int_handler(void);
+void early_pgm_check_handler(void);
 
 void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs);
 void __do_pgm_check(struct pt_regs *regs);
 void __do_syscall(struct pt_regs *regs, int per_trap);
+void __do_early_pgm_check(struct pt_regs *regs);
 
 void do_protection_exception(struct pt_regs *regs);
 void do_dat_exception(struct pt_regs *regs);