From 44e0a832f29732b1bfbc2b657ada4ae7c9fe5e43 Mon Sep 17 00:00:00 2001
From: Eitan Adler <eadler@FreeBSD.org>
Date: Fri, 26 Jan 2018 03:30:05 +0000
Subject: [PATCH] dd(1): Use a local swapbytes() function.

swab(3) has restrict qualifiers for src and dst.
Avoid relying on undefined overlapping swab behavior.

Obtained From: OpenBSD
---
 bin/dd/dd.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/bin/dd/dd.c b/bin/dd/dd.c
index 6ccc36011ec..59066076881 100644
--- a/bin/dd/dd.c
+++ b/bin/dd/dd.c
@@ -338,6 +338,21 @@ speed_limit(void)
 	t_prev = t_now;
 }
 
+static void
+swapbytes(void *v, size_t len)
+{
+	unsigned char *p = v;
+	unsigned char t;
+
+	while (len > 1) {
+		t = p[0];
+		p[0] = p[1];
+		p[1] = t;
+		p += 2;
+		len -= 2;
+	}
+}
+
 static void
 dd_in(void)
 {
@@ -438,7 +453,7 @@ dd_in(void)
 				++st.swab;
 				--n;
 			}
-			swab(in.dbp, in.dbp, (size_t)n);
+			swapbytes(in.dbp, (size_t)n);
 		}
 
 		in.dbp += in.dbrcnt;