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/*
* 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
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