s390/switch_to: use generic header file

Move the switch_to() implementation to process.c and use the generic
switch_to.h header file instead, like some other architectures.

This addresses also the oddity that the old switch_to() implementation
assigns the return value of __switch_to() to 'prev' instead of 'last',
like it should.

Remove also all includes of switch_to.h from C files, except process.c.
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/ptrace.h

@@ -203,6 +203,10 @@ static inline int test_and_clear_pt_regs_flag(struct pt_regs *regs, int flag)
 	return ret;
 }
 
+struct task_struct;
+
+void update_cr_regs(struct task_struct *task);
+
 /*
  * These are defined as per linux/ptrace.h, which see.
  */

arch/s390/include/asm/stacktrace.h

@@ -4,7 +4,6 @@
 
 #include <linux/uaccess.h>
 #include <linux/ptrace.h>
-#include <asm/switch_to.h>
 
 struct stack_frame_user {
 	unsigned long back_chain;

arch/s390/include/asm/switch_to.h

-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright IBM Corp. 1999, 2009
- *
- * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
- */
-
-#ifndef __ASM_SWITCH_TO_H
-#define __ASM_SWITCH_TO_H
-
-#include <linux/thread_info.h>
-#include <asm/fpu/api.h>
-#include <asm/access-regs.h>
-#include <asm/ptrace.h>
-#include <asm/guarded_storage.h>
-
-extern struct task_struct *__switch_to(void *, void *);
-extern void update_cr_regs(struct task_struct *task);
-
-#define switch_to(prev, next, last) do {				\
-	/* save_fpu_regs() sets the CIF_FPU flag, which enforces	\
-	 * a restore of the floating point / vector registers as	\
-	 * soon as the next task returns to user space			\
-	 */								\
-	save_fpu_regs();						\
-	save_access_regs(&prev->thread.acrs[0]);			\
-	save_ri_cb(prev->thread.ri_cb);					\
-	save_gs_cb(prev->thread.gs_cb);					\
-	update_cr_regs(next);						\
-	restore_access_regs(&next->thread.acrs[0]);			\
-	restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb);		\
-	restore_gs_cb(next->thread.gs_cb);				\
-	prev = __switch_to(prev, next);					\
-} while (0)
-
-#endif /* __ASM_SWITCH_TO_H */

arch/s390/kernel/entry.S

@@ -171,13 +171,13 @@ _LPP_OFFSET	= __LC_LPP
 	nop	0
 
 /*
- * Scheduler resume function, called by switch_to
- *  gpr2 = (task_struct *) prev
- *  gpr3 = (task_struct *) next
+ * Scheduler resume function, called by __switch_to
+ *  gpr2 = (task_struct *)prev
+ *  gpr3 = (task_struct *)next
  * Returns:
  *  gpr2 = prev
  */
-SYM_FUNC_START(__switch_to)
+SYM_FUNC_START(__switch_to_asm)
 	stmg	%r6,%r15,__SF_GPRS(%r15)	# store gprs of prev task
 	lghi	%r4,__TASK_stack
 	lghi	%r1,__TASK_thread
@@ -193,7 +193,7 @@ SYM_FUNC_START(__switch_to)
 	lmg	%r6,%r15,__SF_GPRS(%r15)	# load gprs of next task
 	ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
 	BR_EX	%r14
-SYM_FUNC_END(__switch_to)
+SYM_FUNC_END(__switch_to_asm)
 
 #if IS_ENABLED(CONFIG_KVM)
 /*

arch/s390/kernel/entry.h

@@ -19,6 +19,7 @@ void mcck_int_handler(void);
 void restart_int_handler(void);
 void early_pgm_check_handler(void);
 
+struct task_struct *__switch_to_asm(struct task_struct *prev, struct task_struct *next);
 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);

arch/s390/kernel/machine_kexec.c

@@ -13,6 +13,7 @@
 #include <linux/reboot.h>
 #include <linux/ftrace.h>
 #include <linux/debug_locks.h>
+#include <asm/guarded_storage.h>
 #include <asm/pfault.h>
 #include <asm/cio.h>
 #include <asm/setup.h>
@@ -26,7 +27,6 @@
 #include <asm/os_info.h>
 #include <asm/set_memory.h>
 #include <asm/stacktrace.h>
-#include <asm/switch_to.h>
 #include <asm/nmi.h>
 #include <asm/sclp.h>
 

arch/s390/kernel/nmi.c

@@ -28,7 +28,6 @@
 #include <asm/cputime.h>
 #include <asm/nmi.h>
 #include <asm/crw.h>
-#include <asm/switch_to.h>
 #include <asm/asm-offsets.h>
 #include <asm/pai.h>
 #include <asm/vx-insn.h>

arch/s390/kernel/process.c

@@ -31,15 +31,18 @@
 #include <linux/init_task.h>
 #include <linux/entry-common.h>
 #include <linux/io.h>
+#include <asm/guarded_storage.h>
+#include <asm/access-regs.h>
+#include <asm/switch_to.h>
 #include <asm/cpu_mf.h>
 #include <asm/processor.h>
+#include <asm/ptrace.h>
 #include <asm/vtimer.h>
 #include <asm/exec.h>
 #include <asm/irq.h>
 #include <asm/nmi.h>
 #include <asm/smp.h>
 #include <asm/stacktrace.h>
-#include <asm/switch_to.h>
 #include <asm/runtime_instr.h>
 #include <asm/unwind.h>
 #include "entry.h"
@@ -190,6 +193,24 @@ void execve_tail(void)
 	asm volatile("sfpc %0" : : "d" (0));
 }
 
+struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next)
+{
+	/*
+	 * save_fpu_regs() sets the CIF_FPU flag, which enforces
+	 * a restore of the floating point / vector registers as
+	 * soon as the next task returns to user space.
+	 */
+	save_fpu_regs();
+	save_access_regs(&prev->thread.acrs[0]);
+	save_ri_cb(prev->thread.ri_cb);
+	save_gs_cb(prev->thread.gs_cb);
+	update_cr_regs(next);
+	restore_access_regs(&next->thread.acrs[0]);
+	restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb);
+	restore_gs_cb(next->thread.gs_cb);
+	return __switch_to_asm(prev, next);
+}
+
 unsigned long __get_wchan(struct task_struct *p)
 {
 	struct unwind_state state;

arch/s390/kernel/ptrace.c

@@ -24,11 +24,11 @@
 #include <linux/seccomp.h>
 #include <linux/compat.h>
 #include <trace/syscall.h>
+#include <asm/guarded_storage.h>
 #include <asm/access-regs.h>
 #include <asm/page.h>
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
-#include <asm/switch_to.h>
 #include <asm/runtime_instr.h>
 #include <asm/facility.h>
 #include <asm/fpu/api.h>

arch/s390/kernel/uprobes.c

@@ -12,7 +12,6 @@
 #include <linux/kdebug.h>
 #include <linux/sched/task_stack.h>
 
-#include <asm/switch_to.h>
 #include <asm/facility.h>
 #include <asm/kprobes.h>
 #include <asm/dis.h>

drivers/s390/char/zcore.c

@@ -29,7 +29,6 @@
 #include <asm/irqflags.h>
 #include <asm/checksum.h>
 #include <asm/os_info.h>
-#include <asm/switch_to.h>
 #include <asm/maccess.h>
 #include "sclp.h"