Subversion Repositories planix.SVN

/*
 * 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