bootsect.inc: make sure the $PnP header can fit inside the segment

Terminate the search as soon as the $PnP header would fall outside the
segment, not just the $PnP signature itself.

diff --git a/bootsect.inc b/bootsect.inc
index 6989956..715100a 100644 (file)
--- a/bootsect.inc
+++ b/bootsect.inc
@@ -150,8 +150,8 @@ replace_bootstrap:
                cmp dword [fs:bx], "$PnP"
                jz .foundpnp
                inc bx
-               cmp bx,-3               ; Don't get a segment overflow error!
-               jb .findpnp
+               cmp bx,-21h             ; Don't get a segment overflow error!
+               jbe .findpnp
                jmp .donepnp            ; No $PnP header found
 .foundpnp:
                movzx cx,byte [fs:bx+5] ; Size of $PnP header