KVM: Add memcmp() helper function

Link: https://lore.kernel.org/ltp/[email protected]/
Reviewed-by: Petr Vorel <[email protected]>
Signed-off-by: Martin Doucha <[email protected]>

Author: mdoucha

testcases/kernel/kvm/include/kvm_guest.h

@@ -48,6 +48,8 @@ void *memset(void *dest, int val, size_t size);
 void *memzero(void *dest, size_t size);
 void *memcpy(void *dest, const void *src, size_t size);
 
+int memcmp(const void *a, const void *b, size_t length);
+
 char *strcpy(char *dest, const char *src);
 char *strcat(char *dest, const char *src);
 size_t strlen(const char *str);

testcases/kernel/kvm/lib_guest.c

@@ -45,6 +45,18 @@ void *memcpy(void *dest, const void *src, size_t size)
 	return dest;
 }
 
+int memcmp(const void *a, const void *b, size_t length)
+{
+	const unsigned char *x = a, *y = b;
+
+	for (; length; x++, y++, length--) {
+		if (*x != *y)
+			return (int)*x - (int)*y;
+	}
+
+	return 0;
+}
+
 char *strcpy(char *dest, const char *src)
 {
 	char *ret = dest;