ref: 4308f6e7e6586e3a27aa46c4d54c434b8533b16d
dir: /sys/src/boot/pc/l.s/
#include "x16.h"
#include "mem.h"
#undef ORB
#define DATA32SEL SELECTOR(1, SELGDT, 0)
#define EXEC32SEL SELECTOR(2, SELGDT, 0)
#define DATA16SEL SELECTOR(3, SELGDT, 0)
#define EXEC16SEL SELECTOR(4, SELGDT, 0)
#define SEGSS BYTE $0x36
#define SEGES BYTE $0x26
#define FARRET BYTE $0xCB
TEXT origin(SB), $0
CLI
CLR(rCX)
MTSR(rCX, rSS)
OPSIZE; MOVL $origin(SB), SP
PUSHA
OPSIZE; ADSIZE; PUSHL SP
OPSIZE; ADSIZE; PUSHL CX
PUSHI(start(SB))
TEXT pmode32(SB), $0
CLI
/* get return pc */
POPR(rDI)
/* make sure stack is at 0000: */
CLR(rCX)
MTSR(rCX, rSS)
OPSIZE; ANDL $0xFFFF, SP
/* convert 16-bit return pc to far pointer */
PUSHI(EXEC32SEL)
PUSHR(rDI)
/* load gdt */
SEGSS; LGDT(tgdtptr(SB))
/* enable protected mode */
MFCR(rCR0, rCX)
ORB $1, CL
MTCR(rCX, rCR0)
/* flush */
FARJUMP16(EXEC16SEL, pmode32flush(SB));
TEXT pmode32flush(SB), $0
/* load 32-bit protected mode data selector */
LWI(DATA32SEL, rCX)
_segret:
/* load all data segments */
MTSR(rCX, rDS)
MTSR(rCX, rES)
MTSR(rCX, rFS)
MTSR(rCX, rGS)
MTSR(rCX, rSS)
FARRET
TEXT rmode16(SB), $0
/* setup farret to rmode16x */
PUSHL $EXEC16SEL
PUSHL $rmode16x(SB)
/* load 16-bit protected mode data selector */
MOVL $DATA16SEL, CX
JMP _segret
TEXT rmode16x(SB), $0
/* disable protected mode */
MFCR(rCR0, rCX)
ANDB $0xfe, CL
MTCR(rCX, rCR0)
/* flush */
FARJUMP16(0, rmode16flush(SB));
TEXT rmode16flush(SB), $0
/*
* load 16-bit realmode data segment 0000: and
* return to 32 bit return pc interpreted
* as 16 bit far pointer.
*/
CLR(rCX)
JMP _segret
TEXT tgdt(SB), $0
/* null descriptor */
LONG $0
LONG $0
/* data segment descriptor for 4 gigabytes (PL 0) */
LONG $(0xFFFF)
LONG $(SEGG|SEGB|(0xF<<16)|SEGP|SEGPL(0)|SEGDATA|SEGW)
/* exec segment descriptor for 4 gigabytes (PL 0) */
LONG $(0xFFFF)
LONG $(SEGG|SEGD|(0xF<<16)|SEGP|SEGPL(0)|SEGEXEC|SEGR)
/* data segment descriptor for (PL 0) 16-bit */
LONG $(0xFFFF)
LONG $((0xF<<16)|SEGP|SEGPL(0)|SEGDATA|SEGW)
/* exec segment descriptor for (PL 0) 16-bit */
LONG $(0xFFFF)
LONG $((0xF<<16)|SEGP|SEGPL(0)|SEGEXEC|SEGR)
TEXT tgdtptr(SB), $0
WORD $(5*8)
LONG $tgdt(SB)
TEXT jump(SB), $0
MOVL 4(SP), AX
JMP *AX
TEXT halt(SB), $0
_halt:
JMP _halt
TEXT kbdgetc(SB), $0
CALL rmode16(SB)
STI
MOVB $0x01, AH
BIOSCALL(0x16)
JNZ _gotkey
CLR(rAX)
JMP _pret32
_gotkey:
CLR(rAX)
BIOSCALL(0x16)
JMP _pret32
TEXT cgaputc(SB), $0
MOVL 4(SP),AX
CALL rmode16(SB)
STI
MOVB $0x0E, AH
BIOSCALL(0x10)
_pret32:
CALL16(pmode32(SB))
ANDL $0xFFFF, AX
RET
TEXT usleep(SB), $0
MOVL t+4(SP), AX
PUSHL AX
CALL rmode16(SB)
STI
POPR(rDX)
POPR(rCX)
MOVB $0x86, AH
BIOSCALL(0x15)
JMP _pret32
#ifdef PXE
TEXT pxeinit(SB), $0
CALL rmode16(SB)
/* get pxe env structure in ES:BX */
LWI(0x5650, rAX)
BIOSCALL(0x1A)
JC _pret32
/* !PXE or PXEENV+ signature */
SEGES; LXW(0, xBX, rAX)
CMPI((('!'<<0)|('P'<<8)), rAX)
JEQ _getentry
CMPI((('P'<<0)|('X'<<8)), rAX)
JNE _pret32
SEGES; LXW(0x2A, xBX, rAX)
SEGES; LXW(0x28, xBX, rBX)
MTSR(rAX, rES)
_getentry:
SEGES; LXW(0x12, xBX, rAX)
SW(rAX, pxepseg(SB))
SEGES; LXW(0x10, xBX, rAX)
SW(rAX, pxepoff(SB))
CLR(rAX)
JMP _pret32
TEXT pxecallret(SB), $0
ADDI(6, rSP)
JMP _pret32
TEXT pxecall(SB), $0
MOVL op+4(SP),AX
MOVL buf+8(SP),SI
CALL rmode16(SB)
CLR(rCX)
PUSHR(rCX)
PUSHR(rSI)
/* opcode */
PUSHR(rAX)
/* farcall */
PUSHR(rCX)
PUSHI(pxecallret(SB))
LW(pxepseg(SB), rAX)
PUSHR(rAX)
LW(pxepoff(SB), rAX)
PUSHR(rAX)
STI
CLR(rAX)
CLR(rBX)
CLR(rCX)
CLR(rDX)
CLR(rDI)
CLR(rSI)
FARRET
TEXT pxepseg(SB), $0
WORD $0
TEXT pxepoff(SB), $0
WORD $0
#else /* PXE */
/*
* in:
* DL drive
* AX:BX lba32,
* 0000:SI buffer
*/
TEXT readsect16(SB), $0
PUSHA
CLR(rCX)
PUSHR(rCX) /* qword lba */
PUSHR(rCX)
PUSHR(rBX)
PUSHR(rAX)
PUSHR(rCX) /* dword buffer */
PUSHR(rSI)
INC(rCX)
PUSHR(rCX) /* word # of sectors */
PUSHI(0x0010) /* byte reserved, byte packet size */
MW(rSP, rSI)
LWI(0x4200, rAX)
BIOSCALL(0x13)
JCC _readok
ADDI(0x10, rSP)
POPA
CLR(rAX)
DEC(rAX)
RET
_readok:
ADDI(0x10, rSP)
POPA
CLR(rAX)
RET
TEXT readsect(SB), $0
MOVL 4(SP), DX
MOVW 8(SP), AX
MOVW 10(SP), BX
MOVL 12(SP), SI
CALL rmode16(SB)
STI
CALL16(readsect16(SB))
CALL16(pmode32(SB))
ANDL $0xFFFF, AX
RET
#endif
#ifdef ISO
TEXT bootname(SB), $0
BYTE $'3'; BYTE $'8'; BYTE $'6'; BYTE $'/';
BYTE $'9'; BYTE $'b'; BYTE $'o'; BYTE $'o';
BYTE $'t'; BYTE $'i'; BYTE $'s'; BYTE $'o';
BYTE $0
#endif
TEXT uart(SB), $0
BYTE $0xff
TEXT hex(SB), $0
BYTE $'0'; BYTE $'1'; BYTE $'2'; BYTE $'3';
BYTE $'4'; BYTE $'5'; BYTE $'6'; BYTE $'7';
BYTE $'8'; BYTE $'9'; BYTE $'a'; BYTE $'b';
BYTE $'c'; BYTE $'d'; BYTE $'e'; BYTE $'f'