[PATCH v4 02/16] x86/asm: Introduce inline memcpy and memset

[Alexander Shishkin]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Provide inline memcpy and memset functions that can be used instead of
the GCC builtins whenever necessary.

Code posted by Peter Zijlstra <peterz@xxxxxxxxxxxxx>.
Link: https://lore.kernel.org/lkml/Y759AJ%2F0N9fqwDED@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
[Missing Signed-off-by from PeterZ]
Signed-off-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>
Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/string.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/x86/include/asm/string.h b/arch/x86/include/asm/string.h
index c3c2c1914d65..9cb5aae7fba9 100644
--- a/arch/x86/include/asm/string.h
+++ b/arch/x86/include/asm/string.h
@@ -1,6 +1,32 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_STRING_H
+#define _ASM_X86_STRING_H
+
 #ifdef CONFIG_X86_32
 # include <asm/string_32.h>
 #else
 # include <asm/string_64.h>
 #endif
+
+static __always_inline void *__inline_memcpy(void *to, const void *from, size_t len)
+{
+	void *ret = to;
+
+	asm volatile("rep movsb"
+		     : "+D" (to), "+S" (from), "+c" (len)
+		     : : "memory");
+	return ret;
+}
+
+static __always_inline void *__inline_memset(void *s, int v, size_t n)
+{
+	void *ret = s;
+
+	asm volatile("rep stosb"
+		     : "+D" (s), "+c" (n)
+		     : "a" ((uint8_t)v)
+		     : "memory");
+	return ret;
+}
+
+#endif /* _ASM_X86_STRING_H */
-- 
2.43.0