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/*
* Far call, absolute indirect.
* The argument is the offset.
* We use a global structure for the jump params,
* so this is *not* reentrant or thread safe.
*/
#include "mem.h"
#define SSOVERRIDE BYTE $0x36
#define CSOVERRIDE BYTE $0x2E
#define RETF BYTE $0xCB
GLOBL apmjumpstruct+0(SB), $8
TEXT fortytwo(SB), $0
MOVL $42, AX
RETF
TEXT getcs(SB), $0
PUSHL CS
POPL AX
RET
TEXT apmfarcall(SB), $0
/*
* We call push and pop ourselves.
* As soon as we do the first push or pop,
* we can't use FP anymore.
*/
MOVL off+4(FP), BX
MOVL seg+0(FP), CX
MOVL BX, apmjumpstruct+0(SB)
MOVL CX, apmjumpstruct+4(SB)
/* load necessary registers from Ureg */
MOVL ureg+8(FP), DI
MOVL 28(DI), AX
MOVL 16(DI), BX
MOVL 24(DI), CX
MOVL 20(DI), DX
/* save registers, segments */
PUSHL DS
PUSHL ES
PUSHL FS
PUSHL GS
PUSHL BP
PUSHL DI
/*
* paranoia: zero the segments, since it's the
* BIOS's responsibility to initialize them.
* (trick picked up from Linux driver).
PUSHL DX
XORL DX, DX
PUSHL DX
POPL DS
PUSHL DX
POPL ES
PUSHL DX
POPL FS
PUSHL DX
POPL GS
POPL DX
*/
PUSHL $APMDSEG
POPL DS
/*
* The actual call.
*/
CSOVERRIDE; BYTE $0xFF; BYTE $0x1D
LONG $apmjumpstruct+0(SB)
/* restore segments, registers */
POPL DI
POPL BP
POPL GS
POPL FS
POPL ES
POPL DS
PUSHFL
POPL 64(DI)
/* store interesting registers back in Ureg */
MOVL AX, 28(DI)
MOVL BX, 16(DI)
MOVL CX, 24(DI)
MOVL DX, 20(DI)
MOVL SI, 4(DI)
PUSHFL
POPL AX
ANDL $1, AX /* carry flag */
RET
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