[console] Avoid timer wraparound problems in getchar_timeout()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/core/getkey.c b/src/core/getkey.c
index d93ba1e6471fff7f6ed594e75767f41b8c9e14b1..5710f190002dfd99f4d7d3fc9eb80fd183f6104b 100644 (file)
--- a/src/core/getkey.c
+++ b/src/core/getkey.c
@@ -39,9 +39,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
  * @ret character      Character read from console
  */
 int getchar_timeout ( unsigned long timeout ) {
-       unsigned long expiry = ( currticks() + timeout );
+       unsigned long start = currticks();
 
-       while ( currticks() < expiry ) {
+       while ( ( currticks() - start ) < timeout ) {
                step();
                if ( iskey() )
                        return getchar();