From: Heiko Carstens <hca@linux.ibm.com>
Date: Tue, 9 Jun 2026 10:33:38 +0000 (+0200)
Subject: s390/string: Convert memmove() to C
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c3e4b7eb1b981712ebd128825d4ef3b4e9e0ee8b;p=thirdparty%2Flinux.git

s390/string: Convert memmove() to C

Convert memmove() from assembler to C, which should make it easier to
read and change, if required. And it allows the compiler to optimize
the code, and use different instructions, except for the used inline
assemblies.

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

diff --git a/arch/s390/lib/mem.S b/arch/s390/lib/mem.S
index d026debf250c7..712b955ea9b4a 100644
--- a/arch/s390/lib/mem.S
+++ b/arch/s390/lib/mem.S
@@ -11,47 +11,6 @@
 
 	GEN_BR_THUNK %r14
 
-/*
- * void *memmove(void *dest, const void *src, size_t n)
- */
-SYM_FUNC_START(__memmove)
-	ltgr	%r4,%r4
-	lgr	%r1,%r2
-	jz	.Lmemmove_exit
-	aghi	%r4,-1
-	clgr	%r2,%r3
-	jnh	.Lmemmove_forward
-	la	%r5,1(%r4,%r3)
-	clgr	%r2,%r5
-	jl	.Lmemmove_reverse
-.Lmemmove_forward:
-	srlg	%r0,%r4,8
-	ltgr	%r0,%r0
-	jz	.Lmemmove_forward_remainder
-.Lmemmove_forward_loop:
-	mvc	0(256,%r1),0(%r3)
-	la	%r1,256(%r1)
-	la	%r3,256(%r3)
-	brctg	%r0,.Lmemmove_forward_loop
-.Lmemmove_forward_remainder:
-	exrl	%r4,.Lmemmove_mvc
-.Lmemmove_exit:
-	BR_EX	%r14
-.Lmemmove_reverse:
-	ic	%r0,0(%r4,%r3)
-	stc	%r0,0(%r4,%r1)
-	brctg	%r4,.Lmemmove_reverse
-	ic	%r0,0(%r4,%r3)
-	stc	%r0,0(%r4,%r1)
-	BR_EX	%r14
-.Lmemmove_mvc:
-	mvc	0(1,%r1),0(%r3)
-SYM_FUNC_END(__memmove)
-EXPORT_SYMBOL(__memmove)
-
-SYM_FUNC_ALIAS(memmove, __memmove)
-EXPORT_SYMBOL(memmove)
-
 /*
  * memset implementation
  *
diff --git a/arch/s390/lib/string.c b/arch/s390/lib/string.c
index a48e5bb3c15f9..648d5a66484d8 100644
--- a/arch/s390/lib/string.c
+++ b/arch/s390/lib/string.c
@@ -17,6 +17,52 @@
 #include <linux/export.h>
 #include <asm/asm.h>
 
+#define SYMBOL_FUNCTION_ALIAS(alias, name)		\
+asm(".globl " __stringify(alias) "\n\t"			\
+    ".set   " __stringify(alias) "," __stringify(name))
+
+#ifdef __HAVE_ARCH_MEMMOVE
+noinstr void *__memmove(void *dest, const void *src, size_t n)
+{
+	const char *s = src;
+	char *d = dest;
+
+	if (!n)
+		return dest;
+	if ((d <= s || d >= s + n)) {
+		/* Forward copy */
+		while (n >= 256) {
+			asm volatile(
+				"	mvc	0(256,%[d]),0(%[s])\n"
+				:
+				: [d] "a" (d), [s] "a" (s)
+				: "memory");
+			d += 256;
+			s += 256;
+			n -= 256;
+		}
+		if (n) {
+			asm volatile(
+				"	exrl	%[n],0f\n"
+				"	j	1f\n"
+				"0:	mvc	0(1,%[d]),0(%[s])\n"
+				"1:"
+				:
+				: [d] "a" (d), [s] "a" (s), [n] "a" (n - 1)
+				: "memory");
+		}
+	} else {
+		/* Backward copy */
+		while (n--)
+			d[n] = s[n];
+	}
+	return dest;
+}
+SYMBOL_FUNCTION_ALIAS(memmove, __memmove);
+EXPORT_SYMBOL(__memmove);
+EXPORT_SYMBOL(memmove);
+#endif
+
 /*
  * Helper functions to find the end of a string
  */