plan9fox/sys/src/boot/pc/a20.s

#include "x16.h"

#undef ORB

TEXT a20(SB), $0
	CALL rmode16(SB)
	CALL16(spllo(SB))
	LWI(0x2401, rAX)
	BIOSCALL(0x15)
	JC _biosfail
	CALL16(pmode32(SB))
	RET

_biosfail:
	CALL16(pmode32(SB))

	CALL a20wait(SB)
	MOVL $0x64, DX
	MOVB $0xAD, AL
	OUTB

	CALL a20wait(SB)
	MOVL $0x64, DX
	MOVB $0xD0, AL
	OUTB

	CALL a20wait2(SB)
	MOVL $0x60, DX
	INB
	PUSHL AX

	CALL a20wait(SB)
	MOVL $0x64, DX
	MOVB $0xD1, AL
	OUTB

	CALL a20wait(SB)
	MOVL $0x60, DX
	POPL AX
	ORB $2, AL
	OUTB

	CALL a20wait(SB)
	MOVL $0x64, DX
	MOVB $0xAE, AL
	OUTB

TEXT a20wait(SB), $0
_a20wait:
	MOVL $0x64, DX
	INB
	TESTB $1, AL
	JZ _a20wait2
	RET

TEXT a20wait2(SB), $0
_a20wait2:
	MOVL $0x64, DX
	INB
	TESTB $2, AL
	JNZ _a20wait
	RET
9boot a20 gate 2011-04-12 23:43:22 +00:00			`#include "x16.h"`

			`#undef ORB`

			`TEXT a20(SB), $0`
			`CALL rmode16(SB)`
9boot: pxe/kernel memory overlap problem, add unload function 2011-04-20 10:49:54 +00:00			`CALL16(spllo(SB))`
9boot a20 gate 2011-04-12 23:43:22 +00:00			`LWI(0x2401, rAX)`
			`BIOSCALL(0x15)`
			`JC _biosfail`
			`CALL16(pmode32(SB))`
			`RET`

			`_biosfail:`
			`CALL16(pmode32(SB))`

			`CALL a20wait(SB)`
			`MOVL $0x64, DX`
			`MOVB $0xAD, AL`
			`OUTB`

			`CALL a20wait(SB)`
			`MOVL $0x64, DX`
			`MOVB $0xD0, AL`
			`OUTB`

			`CALL a20wait2(SB)`
			`MOVL $0x60, DX`
			`INB`
			`PUSHL AX`

			`CALL a20wait(SB)`
			`MOVL $0x64, DX`
			`MOVB $0xD1, AL`
			`OUTB`

			`CALL a20wait(SB)`
			`MOVL $0x60, DX`
			`POPL AX`
			`ORB $2, AL`
			`OUTB`

			`CALL a20wait(SB)`
			`MOVL $0x64, DX`
			`MOVB $0xAE, AL`
			`OUTB`

			`TEXT a20wait(SB), $0`
			`_a20wait:`
			`MOVL $0x64, DX`
			`INB`
			`TESTB $1, AL`
			`JZ _a20wait2`
			`RET`

			`TEXT a20wait2(SB), $0`
			`_a20wait2:`
			`MOVL $0x64, DX`
			`INB`
			`TESTB $2, AL`
			`JNZ _a20wait`
			`RET`