Subversion Repositories planix.SVN

/*

 * Bootstrap loader decompressor.  Starts at 0x10000 (where pbs puts it)

 * or 0x7c00 (where pxe puts it) and memmoves kernel (immediately following)

 * into standard kernel location.

 */

#include "mem.h"

#include "/sys/src/boot/pc/x16.h"

#undef BIOSCALL		/* we don't know what evil the bios gets up to */

#define BIOSCALL(b)	INT $(b); CLI

#define CMPL(r0, r1)	BYTE $0x66; CMP(r0, r1)

#define LLI(i, rX)	BYTE $0x66;		/* i -> rX */		\

			BYTE $(0xB8+rX);				\

			LONG $i;

#define CPUID		BYTE $0x0F; BYTE $0xA2	/* CPUID, argument in AX */

#define WBINVD		BYTE $0x0F; BYTE $0x09

TEXT origin(SB), $0

/*

 *	turn off interrupts

 */

	CLI

	/*

	 * This part of l.s is used only in the boot kernel.

	 * It assumes that we are in real address mode, i.e.,

	 * that we look like an 8086.

	 *

	 * Make sure the segments are reasonable.

	 * If we were started directly from the BIOS

	 * (i.e. no MS-DOS) then DS may not be

	 * right.

	 */

	MOVW	CS, AX

	MOVW	AX, DS

	LWI(0, rAX)			/* always put stack in first 64k */

	MTSR(rAX, rSS)

	LWI(origin(SB), rSP)		/* set the stack pointer */

	LWI(0x2401, rAX)		/* enable a20 line */

	BIOSCALL(0x15)

	XORL	AX, AX

	MOVB	$0x03, AL

//	LWI(3, rAX)

	INT	$0x10			/* set video mode in AL */

/*

 * Check for CGA mode.

 */

_cgastart:

	LWI(0x0F00, rAX)		/* get current video mode in AL */

	BIOSCALL(0x10)

	ANDI(0x007F, rAX)

	SUBI(0x0003, rAX)		/* is it mode 3? */

	JEQ	_cgamode3

	LWI(0x0003, rAX)		/* turn on text mode 3 */

	BIOSCALL(0x10)

_cgamode3:

	LWI(_hello(SB), rSI)

	CALL	_cgaputs(SB)

	LLI(BIOSTABLES, rAX)	/* tables in low memory, not after end */

	OPSIZE; ANDL $~(BY2PG-1), AX

	OPSIZE; SHRL $4, AX

	SW(rAX, _ES(SB))

	CLR(rDI)

	SW(rDI, _DI(SB))

	MTSR(rAX, rES)

/*

 * Check for APM1.2 BIOS support.

 */

	LWI(0x5304, rAX)		/* disconnect anyone else */

	CLR(rBX)

	BIOSCALL(0x15)

	JCS	_apmfail

	LWI(0x5303, rAX)		/* connect */

	CLR(rBX)

	CLC

	BIOSCALL(0x15)

	JCC	_apmpush

_apmfail:

	LW(_ES(SB), rAX)		/* no support */

	MTSR(rAX, rES)

	LW(_DI(SB), rDI)

	JCS	_apmend

_apmpush:

	OPSIZE; PUSHR(rSI)		/* save returned APM data on stack */

	OPSIZE; PUSHR(rBX)

	PUSHR(rDI)

	PUSHR(rDX)

	PUSHR(rCX)

	PUSHR(rAX)

	LW(_ES(SB), rAX)

	MTSR(rAX, rES)

	LW(_DI(SB), rDI)

	LWI(0x5041, rAX)		/* first 4 bytes are APM\0 */

	STOSW

	LWI(0x004D, rAX)

	STOSW

	LWI(8, rCX)			/* pop the saved APM data */

_apmpop:

	POPR(rAX)

	STOSW

	LOOP	_apmpop

_apmend:

/*

 * Try to retrieve the 0xE820 memory map.

 * This is weird because some BIOS do not seem to preserve

 * ES/DI on failure. Consequently they may not be valid

 * at _e820end:.

 */

	SW(rDI, _DI(SB))		/* save DI */

	CLR(rAX)			/* write terminator */

	STOSW

	STOSW

	CLR(rBX)

	PUSHR(rBX)			/* keep loop count on stack */

					/* BX is the continuation value */

_e820loop:

	POPR(rAX)

	INC(rAX)

	PUSHR(rAX)			/* doesn't affect FLAGS */

	CMPI(32, rAX)			/* mmap[32+1] in C code */

	JGT	_e820pop

	LLI(20, rCX)			/* buffer size */

	LLI(0x534D4150, rDX)		/* signature - ASCII "SMAP" */

	LLI(0x0000E820, rAX)		/* function code */

	BIOSCALL(0x15)			/* writes 20 bytes at (es,di) */

	JCS	_e820pop		/* some kind of error */

	LLI(0x534D4150, rDX)

	CMPL(rDX, rAX)			/* verify correct BIOS version */

	JNE	_e820pop

	LLI(20, rDX)

	CMPL(rDX, rCX)			/* verify correct count */

	JNE	_e820pop

	SUBI(4, rDI)			/* overwrite terminator */

	LWI(0x414D, rAX)		/* first 4 bytes are "MAP\0" */

	STOSW

	LWI(0x0050, rAX)

	STOSW

	ADDI(20, rDI)			/* bump to next entry */

	SW(rDI, _DI(SB))		/* save DI */

	CLR(rAX)			/* write terminator */

	STOSW

	STOSW

	OR(rBX, rBX)			/* zero if last entry */

	JNE	_e820loop

_e820pop:

	POPR(rAX)			/* loop count */

	LW(_DI(SB), rDI)

	CLR(rAX)

	MTSR(rAX, rES)

_e820end:

/*

 * 	goto protected mode

 */

/*	MOVL	loadgdtptr(SB),GDTR /**/

	 BYTE	$0x0f

	 BYTE	$0x01

	 BYTE	$0x16

	 WORD	$loadgdtptr(SB)

	DELAY

	LWI(1, rAX)

	/* MOV AX,MSW */

	BYTE $0x0F; BYTE $0x01; BYTE $0xF0

/*

 *	clear prefetch queue (weird code to avoid optimizations)

 */

	DELAY

/*

 *	set all segs

 */

/*	MOVW	$KDSEL,AX	/**/

	 BYTE	$0xc7

	 BYTE	$0xc0

	 WORD	$KDSEL

	MOVW	AX,DS

	MOVW	AX,SS

	MOVW	AX,ES

	MOVW	AX,FS

	MOVW	AX,GS

	MOVW	$(20*1024*1024-4), SP		/* new stack pointer */

	DELAY

	/* god only knows what the damned bios has been up to... */

	CLI

	/* jump to C (main) */

/*	JMPFAR	KESEL:$main(SB) /**/

	 BYTE	$0x66

	 BYTE	$0xEA

	 LONG	$_main(SB)

	 WORD	$KESEL

/* output a cheery wee message (rSI) */

TEXT _cgaputs(SB), $0

//_cgaputs:

	CLR(rBX)

_cgaputsloop:

	LODSB

	ORB(rAL, rAL)

	JEQ	_cgaend

	LBI(0x0E,rAH)

	BIOSCALL(0x10)

	JMP	_cgaputsloop

_cgaend:

	RET

TEXT _hello(SB), $0

	BYTE $'\r'; BYTE $'\n'

	BYTE $'9'; BYTE $'b'; BYTE $'o'; BYTE $'o'

	BYTE $'t'; BYTE $' '

	BYTE $'\z'

/* offset into bios tables using segment ES.  stos? use (es,di) */

TEXT _DI(SB), $0

	LONG	$0

/* segment address of bios tables (BIOSTABLES >> 4) */

TEXT _ES(SB), $0

	LONG	$0

/*

 *  pointer to initial gdt

 */

TEXT	loadgdtptr(SB),$0

	WORD	$(4*8)

	LONG	$loadgdt(SB)

/*

 *  gdt to get us to 32-bit/segmented/unpaged mode

 */

TEXT	loadgdt(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)

	/* exec segment descriptor for 4 gigabytes (PL 0) 16-bit */

	LONG	$(0xFFFF)

	LONG	$(SEGG|(0xF<<16)|SEGP|SEGPL(0)|SEGEXEC|SEGR)

/*

 *  output a byte

 */

TEXT	outb(SB),$0

	MOVL	p+0(FP),DX

	MOVL	b+4(FP),AX

	OUTB

	RET

/*

 *  input a byte

 */

TEXT	inb(SB),$0

	MOVL	p+0(FP),DX

	XORL	AX,AX

	INB

	RET

TEXT mb586(SB), $0

	XORL	AX, AX

	CPUID

	RET

TEXT wbinvd(SB), $0

	WBINVD

	RET

TEXT	splhi(SB),$0

	PUSHFL

	POPL	AX

	CLI

	RET