From: Heiko Carstens <hca@linux.ibm.com>
Date: Tue, 9 Jun 2026 10:33:40 +0000 (+0200)
Subject: s390/string: Convert memcpy() to C
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=611b5c1f60f90f2cbe4d328cbd4d4a625abc32b4;p=thirdparty%2Flinux.git

s390/string: Convert memcpy() to C

Convert memcpy() 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 a27b103d7450c..d2e1ca87a5680 100644
--- a/arch/s390/lib/mem.S
+++ b/arch/s390/lib/mem.S
@@ -11,37 +11,6 @@
 
 	GEN_BR_THUNK %r14
 
-/*
- * memcpy implementation
- *
- * void *memcpy(void *dest, const void *src, size_t n)
- */
-SYM_FUNC_START(__memcpy)
-	ltgr	%r4,%r4
-	jz	.Lmemcpy_exit
-	aghi	%r4,-1
-	srlg	%r5,%r4,8
-	ltgr	%r5,%r5
-	lgr	%r1,%r2
-	jnz	.Lmemcpy_loop
-.Lmemcpy_remainder:
-	exrl	%r4,.Lmemcpy_mvc
-.Lmemcpy_exit:
-	BR_EX	%r14
-.Lmemcpy_loop:
-	mvc	0(256,%r1),0(%r3)
-	la	%r1,256(%r1)
-	la	%r3,256(%r3)
-	brctg	%r5,.Lmemcpy_loop
-	j	.Lmemcpy_remainder
-.Lmemcpy_mvc:
-	mvc	0(1,%r1),0(%r3)
-SYM_FUNC_END(__memcpy)
-EXPORT_SYMBOL(__memcpy)
-
-SYM_FUNC_ALIAS(memcpy, __memcpy)
-EXPORT_SYMBOL(memcpy)
-
 /*
  * __memset16/32/64
  *
diff --git a/arch/s390/lib/string.c b/arch/s390/lib/string.c
index f59d67925e772..056ea2027ddd2 100644
--- a/arch/s390/lib/string.c
+++ b/arch/s390/lib/string.c
@@ -124,6 +124,40 @@ EXPORT_SYMBOL(__memset);
 EXPORT_SYMBOL(memset);
 #endif
 
+#ifdef __HAVE_ARCH_MEMCPY
+noinstr void *__memcpy(void *dest, const void *src, size_t n)
+{
+	void *d = dest;
+
+	if (!n)
+		return d;
+	while (n >= 256) {
+		asm volatile(
+			"	mvc	0(256,%[dest]),0(%[src])"
+			:
+			: [dest] "a" (dest), [src] "a" (src)
+			: "memory");
+		dest += 256;
+		src += 256;
+		n -= 256;
+	}
+	if (!n)
+		return d;
+	asm volatile(
+		"	exrl	%[n],1f\n"
+		"	j	2f\n"
+		"1:	mvc	0(1,%[dest]),0(%[src])\n"
+		"2:"
+		:
+		: [dest] "a" (dest), [src] "a" (src), [n] "a" (n - 1)
+		: "memory");
+	return d;
+}
+SYMBOL_FUNCTION_ALIAS(memcpy, __memcpy);
+EXPORT_SYMBOL(__memcpy);
+EXPORT_SYMBOL(memcpy);
+#endif
+
 /*
  * Helper functions to find the end of a string
  */