From: John Tsiombikas <nuclear@member.fsf.org>
Date: Sat, 25 May 2019 20:36:30 +0000 (+0300)
Subject: backported fixes from 256boss:
X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=commitdiff_plain;h=e253f9a0cad14f636a51f6211308491ab19dfbe5;hp=e253f9a0cad14f636a51f6211308491ab19dfbe5

backported fixes from 256boss:
 - moved early serial console from 1st to 2nd stage loader, to leave
   space for the partition table if needed.
 - saving boot_drive_number for later use.
 - fixed floppy motor turnoff after 2nd stage loader is done.
 - saving of carry flag before returning from int86.
 - added functions in intr.h/intr.c to manipulate the PIC IRQ masks.
 - restoring irq masks after returning from int86.
 - keyboard controller voodoo: do a single read after returning from
   int86 to clear any pending inputs that would otherwise clog the
   buffer and we'd never get an interrupt again from the keyboard.
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