[syslinux] memdisk.asm patch

[Andy Polyakov]

While getting pqmagic(*) working off memdisk under [pxe|iso]linux I
noticed that the the whole thing freezes whenever the mouse moves under
I/O against memdisk [most notably when you open help index]. Attached
patch [relative to 1.67] cured the problem.

Cheers. Andy.

(*) real-mode [yet] GUI application running under DR-DOS.

*** ./memdisk/memdisk.asm.orig  Sun Feb  3 22:37:55 2002
--- ./memdisk/memdisk.asm       Thu Mar 28 17:45:51 2002
***************
*** 386,391 ****
--- 386,398 ----
                push ebx
                push edx
                push ebp
+               ; apparently cli after int 15h below is not
sufficient:-(
+               ; we've got to mask hardware interrupts in PIC as well!
+               xor  eax,eax
+               in   al,21h
+               push eax
+               or   al,0xfe    ; leave timer on
+               out  21h,al
  .copy_loop:
                push esi
                push edi
***************
*** 420,425 ****
--- 427,434 ----
                jnz .copy_loop
                ; CF = 0
  .error:
+               pop eax
+               out 21h,al      ; restore hardware interrupt mask
                pop ebp
                pop edx
                pop ebx