REALEMU(8) REALEMU(8)
NAME
realemu - software emulation of /dev/realmode
SYNOPSIS
aux/realemu [ -Dpt ] [ -s srvname ] [ -m mntpt ]
DESCRIPTION
Originally, the kernel provided /dev/realmode and
/dev/realmodemem files via arch(3). These devices provided
access to real mode memory and BIOS calls.
Interrupts were disabled and the processor switched to 16-
bit "real mode" to fit the BIOS api. If BIOS reprograms
hardware in use or reenables interrupts or crashes, the sys-
tem may freeze or reboot with little ability for diagnosis
or recovery. To avoid this, realemu emulates BIOS by inter-
preting the code intercepting dangerous actions that could
compromise the system.
With no arguments, realemu mounts itself before /dev and
serves /dev/realmode. Flag D will enable 9P debugging; flag
p traces i/o port access; t traces instructions. The -s
flag causes realemu to post its channel on /srv/mntpt and
the default mntpt is ignored. If mntpt is given before
srvname argument then it is ignored, otherwise it will be
used.
EXAMPLES
Realemu is only needed when accessing /dev/realmode. To
invoke a subshell so that realemu exits normally after
aux/vga completes:
; @{rfork n; aux/realemu; aux/vga -m vesa -l $vgasize}
SOURCE
/sys/src/cmd/aux/realemu
SEE ALSO
vga(8), arch(3)
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