dos: vacuous ADV support

Vacuous ADV support: install an empty ADV.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/dos/memmove.S b/dos/memmove.S
new file mode 100644
index 00000000..1ab2cb23
--- /dev/null
+++ b/dos/memmove.S
@@ -0,0 +1,36 @@
+#
+# memmove.S
+#
+# Simple 16-bit memmove() implementation
+#
+
+	.text
+	.code16gcc
+	.globl memmove
+	.type memmove, @function
+memmove:
+	pushw %di
+	pushw %si
+	movw %ax,%di
+	movw %dx,%si
+	cmpw %si,%di
+	ja 1f
+	# The third argument is already in cx
+	cld
+	rep ; movsb
+2:
+	popw %si
+	popw %di
+	ret
+
+1:	/* si <= di, need reverse copy */
+	add %cx,%di
+	add %cx,%si
+	dec %di
+	dec %si
+	std
+	rep ; movsb
+	cld
+	jmp 2b
+
+	.size memmove,.-memmove