85 lines
1.1 KiB
ArmAsm
85 lines
1.1 KiB
ArmAsm
#include "x16.h"
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#undef ORB
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TEXT a20test(SB), $0
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LONG $1234567
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TEXT a20check(SB), $0
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MOVL $10000, CX
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_loop:
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LEAL a20test(SB), AX
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MOVL (AX), BX
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ADDL $12345, BX
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MOVL BX, (AX)
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ORL $(1<<20), AX
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MOVL (AX), AX
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CMPL AX, BX
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JNZ _done
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LOOP _loop
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RET
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_done:
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/* return directly to caller of a20() */
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ADDL $4, SP
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XORL AX, AX
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RET
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TEXT a20(SB), $0
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CALL a20check(SB)
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/* try bios */
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CALL rmode16(SB)
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STI
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LWI(0x2401, rAX)
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BIOSCALL(0x15)
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CALL16(pmode32(SB))
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CALL a20check(SB)
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/* try fast a20 */
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MOVL $0x92, DX
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INB
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TESTB $2, AL
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JNZ _no92
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ORB $2, AL
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ANDB $0xfe, AL
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OUTB
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_no92:
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CALL a20check(SB)
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/* try keyboard */
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CALL kbdempty(SB)
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MOVL $0x64, DX
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MOVB $0xd1, AL /* command write */
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OUTB
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CALL kbdempty(SB)
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MOVL $0x60, DX
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MOVB $0xdf, AL /* a20 on */
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OUTB
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CALL kbdempty(SB)
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MOVL $0x64, DX
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MOVB $0xff, AL /* magic */
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OUTB
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CALL kbdempty(SB)
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CALL a20check(SB)
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/* fail */
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XORL AX, AX
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DECL AX
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RET
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TEXT kbdempty(SB), $0
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_kbdwait:
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MOVL $0x64, DX
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INB
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TESTB $1, AL
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JZ _kbdempty
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MOVL $0x60, DX
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INB
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JMP _kbdwait
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_kbdempty:
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TESTB $2, AL
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JNZ _kbdwait
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RET
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