s390/acrs: cleanup access register handling

save_access_regs() and restore_access_regs() are only available by
including switch_to.h. This is done by a couple of C files, which have
nothing to do with switch_to(), but only need these functions.

Move both functions to a new header file and improve the implementation:

- Get rid of typedef

- Add memory access instrumentation support

- Use long displacement instructions lamy/stamy instead of lam/stam - all
  current users end up with better code because of this

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/access-regs.h

@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright IBM Corp. 1999, 2024
+ */
+
+#ifndef __ASM_S390_ACCESS_REGS_H
+#define __ASM_S390_ACCESS_REGS_H
+
+#include <linux/instrumented.h>
+#include <asm/sigcontext.h>
+
+struct access_regs {
+	unsigned int regs[NUM_ACRS];
+};
+
+static inline void save_access_regs(unsigned int *acrs)
+{
+	struct access_regs *regs = (struct access_regs *)acrs;
+
+	instrument_write(regs, sizeof(*regs));
+	asm volatile("stamy	0,15,%[regs]"
+		     : [regs] "=QS" (*regs)
+		     :
+		     : "memory");
+}
+
+static inline void restore_access_regs(unsigned int *acrs)
+{
+	struct access_regs *regs = (struct access_regs *)acrs;
+
+	instrument_read(regs, sizeof(*regs));
+	asm volatile("lamy	0,15,%[regs]"
+		     :
+		     : [regs] "QS" (*regs)
+		     : "memory");
+}
+
+#endif /* __ASM_S390_ACCESS_REGS_H */

arch/s390/include/asm/switch_to.h

@@ -10,26 +10,13 @@
 
 #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);
 
-static inline void save_access_regs(unsigned int *acrs)
-{
-	typedef struct { int _[NUM_ACRS]; } acrstype;
-
-	asm volatile("stam 0,15,%0" : "=Q" (*(acrstype *)acrs));
-}
-
-static inline void restore_access_regs(unsigned int *acrs)
-{
-	typedef struct { int _[NUM_ACRS]; } acrstype;
-
-	asm volatile("lam 0,15,%0" : : "Q" (*(acrstype *)acrs));
-}
-
 #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	\

arch/s390/kernel/compat_signal.c

@@ -24,10 +24,10 @@
 #include <linux/tty.h>
 #include <linux/personality.h>
 #include <linux/binfmts.h>
+#include <asm/access-regs.h>
 #include <asm/ucontext.h>
 #include <linux/uaccess.h>
 #include <asm/lowcore.h>
-#include <asm/switch_to.h>
 #include <asm/vdso.h>
 #include <asm/fpu/api.h>
 #include "compat_linux.h"

arch/s390/kernel/early.c

@@ -19,6 +19,8 @@
 #include <linux/kernel.h>
 #include <asm/asm-extable.h>
 #include <linux/memblock.h>
+#include <asm/access-regs.h>
+#include <asm/fpu/api.h>
 #include <asm/diag.h>
 #include <asm/ebcdic.h>
 #include <asm/ipl.h>
@@ -31,7 +33,6 @@
 #include <asm/sclp.h>
 #include <asm/facility.h>
 #include <asm/boot_data.h>
-#include <asm/switch_to.h>
 #include "entry.h"
 
 #define decompressor_handled_param(param)			\

arch/s390/kernel/ptrace.c

@@ -24,6 +24,7 @@
 #include <linux/seccomp.h>
 #include <linux/compat.h>
 #include <trace/syscall.h>
+#include <asm/access-regs.h>
 #include <asm/page.h>
 #include <linux/uaccess.h>
 #include <asm/unistd.h>

arch/s390/kernel/signal.c

@@ -30,8 +30,8 @@
 #include <linux/compat.h>
 #include <asm/ucontext.h>
 #include <linux/uaccess.h>
+#include <asm/access-regs.h>
 #include <asm/lowcore.h>
-#include <asm/switch_to.h>
 #include <asm/vdso.h>
 #include "entry.h"
 

arch/s390/kernel/smp.c

@@ -36,11 +36,11 @@
 #include <linux/sched/task_stack.h>
 #include <linux/crash_dump.h>
 #include <linux/kprobes.h>
+#include <asm/access-regs.h>
 #include <asm/asm-offsets.h>
 #include <asm/ctlreg.h>
 #include <asm/pfault.h>
 #include <asm/diag.h>
-#include <asm/switch_to.h>
 #include <asm/facility.h>
 #include <asm/ipl.h>
 #include <asm/setup.h>

arch/s390/kvm/gaccess.c

@@ -11,11 +11,11 @@
 #include <linux/err.h>
 #include <linux/pgtable.h>
 #include <linux/bitfield.h>
+#include <asm/access-regs.h>
 #include <asm/fault.h>
 #include <asm/gmap.h>
 #include "kvm-s390.h"
 #include "gaccess.h"
-#include <asm/switch_to.h>
 
 union asce {
 	unsigned long val;

arch/s390/kvm/interrupt.c

@@ -19,13 +19,13 @@
 #include <linux/slab.h>
 #include <linux/bitmap.h>
 #include <linux/vmalloc.h>
+#include <asm/access-regs.h>
 #include <asm/asm-offsets.h>
 #include <asm/dis.h>
 #include <linux/uaccess.h>
 #include <asm/sclp.h>
 #include <asm/isc.h>
 #include <asm/gmap.h>
-#include <asm/switch_to.h>
 #include <asm/nmi.h>
 #include <asm/airq.h>
 #include <asm/tpi.h>

arch/s390/kvm/kvm-s390.c

@@ -33,12 +33,12 @@
 #include <linux/pgtable.h>
 #include <linux/mmu_notifier.h>
 
+#include <asm/access-regs.h>
 #include <asm/asm-offsets.h>
 #include <asm/lowcore.h>
 #include <asm/stp.h>
 #include <asm/gmap.h>
 #include <asm/nmi.h>
-#include <asm/switch_to.h>
 #include <asm/isc.h>
 #include <asm/sclp.h>
 #include <asm/cpacf.h>