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ref: 8a01033efcdc72f8b63b5a7afcc699ca20edfdc0
dir: /sys/src/9/pc/l.s/
#include "mem.h"
#undef DELAY

#define PADDR(a)	((a) & ~KZERO)
#define KADDR(a)	(KZERO|(a))

/*
 * Some machine instructions not handled by 8[al].
 */
#define OP16		BYTE $0x66
#define DELAY		BYTE $0xEB; BYTE $0x00	/* JMP .+2 */
#define CPUID		BYTE $0x0F; BYTE $0xA2	/* CPUID, argument in AX */
#define WRMSR		BYTE $0x0F; BYTE $0x30	/* WRMSR, argument in AX/DX (lo/hi) */
#define RDTSC 		BYTE $0x0F; BYTE $0x31	/* RDTSC, result in AX/DX (lo/hi) */
#define RDMSR		BYTE $0x0F; BYTE $0x32	/* RDMSR, result in AX/DX (lo/hi) */
#define HLT		BYTE $0xF4
#define INVLPG	BYTE $0x0F; BYTE $0x01; BYTE $0x39	/* INVLPG (%ecx) */
#define WBINVD	BYTE $0x0F; BYTE $0x09

#define VectorSYSCALL	0x40

/*
 * Macros for calculating offsets within the page directory base
 * and page tables. Note that these are assembler-specific hence
 * the '<<2'.
 */
#define PDO(a)		(((((a))>>22) & 0x03FF)<<2)
#define PTO(a)		(((((a))>>12) & 0x03FF)<<2)

/*
 * For backwards compatiblity with 9load - should go away when 9load is changed
 * 9load currently sets up the mmu, however the first 16MB of memory is identity
 * mapped, so behave as if the mmu was not setup
 */
TEXT _startKADDR(SB), $0
	MOVL	$_startPADDR(SB), AX
	ANDL	$~KZERO, AX
	JMP*	AX

/*
 * Must be 4-byte aligned.
 */
TEXT _multibootheader(SB), $0
	LONG	$0x1BADB002			/* magic */
	LONG	$0x00010007			/* flags */
	LONG	$-(0x1BADB002 + 0x00010007)	/* checksum */
	LONG	$_multibootheader-KZERO(SB)	/* header_addr */
	LONG	$_startKADDR-KZERO(SB)		/* load_addr */
	LONG	$edata-KZERO(SB)		/* load_end_addr */
	LONG	$end-KZERO(SB)			/* bss_end_addr */
	LONG	$_multibootentry-KZERO(SB)		/* entry_addr */
	LONG	$0				/* mode_type */
	LONG	$0				/* width */
	LONG	$0				/* height */
	LONG	$32				/* depth */

/* 
 * the kernel expects the data segment to be page-aligned
 * multiboot bootloaders put the data segment right behind text
 */
TEXT _multibootentry(SB), $0
	MOVL	$etext-KZERO(SB), SI
	MOVL	SI, DI
	ADDL	$0xfff, DI
	ANDL	$~0xfff, DI
	MOVL	$edata-KZERO(SB), CX
	SUBL	DI, CX
	ADDL	CX, SI
	ADDL	CX, DI
	INCL	CX	/* one more for post decrement */
	STD
	REP; MOVSB
	MOVL	BX, multibootptr-KZERO(SB)
	MOVL	$_startPADDR(SB), AX
	ANDL	$~KZERO, AX
	JMP*	AX

/* multiboot structure pointer (physical address) */
TEXT multibootptr(SB), $0
	LONG	$0

/*
 * In protected mode with paging turned off and segment registers setup
 * to linear map all memory. Entered via a jump to PADDR(entry),
 * the physical address of the virtual kernel entry point of KADDR(entry).
 * Make the basic page tables for processor 0. Six pages are needed for
 * the basic set:
 *	a page directory;
 *	page tables for mapping the first 8MB of physical memory to KZERO;
 *	a page for the GDT;
 *	virtual and physical pages for mapping the Mach structure.
 * The remaining PTEs will be allocated later when memory is sized.
 * An identity mmu map is also needed for the switch to virtual mode.
 * This identity mapping is removed once the MMU is going and the JMP has
 * been made to virtual memory.
 */
TEXT _startPADDR(SB), $0
	CLI					/* make sure interrupts are off */

	/* set up the gdt so we have sane plan 9 style gdts. */
	MOVL	$tgdtptr(SB), AX
	ANDL	$~KZERO, AX
	MOVL	(AX), GDTR
	MOVW	$1, AX
	MOVW	AX, MSW

	/* clear prefetch queue (weird code to avoid optimizations) */
	DELAY

	/* set segs to something sane (avoid traps later) */
	MOVW	$(1<<3), AX
	MOVW	AX, DS
	MOVW	AX, SS
	MOVW	AX, ES
	MOVW	AX, FS
	MOVW	AX, GS

/*	JMP	$(2<<3):$mode32bit(SB) /**/
	 BYTE	$0xEA
	 LONG	$mode32bit-KZERO(SB)
	 WORD	$(2<<3)

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

/*
 *  pointer to initial gdt
 *  Note the -KZERO which puts the physical address in the gdtptr. 
 *  that's needed as we start executing in physical addresses. 
 */
TEXT tgdtptr(SB), $0
	WORD	$(3*8)
	LONG	$tgdt-KZERO(SB)

TEXT m0rgdtptr(SB), $0
	WORD	$(NGDT*8-1)
	LONG	$(CPU0GDT-KZERO)

TEXT m0gdtptr(SB), $0
	WORD	$(NGDT*8-1)
	LONG	$CPU0GDT

TEXT m0idtptr(SB), $0
	WORD $(256*8-1)
	LONG $IDTADDR

TEXT mode32bit(SB), $0
	/* At this point, the GDT setup is done. */

	MOVL	$((CPU0END-CPU0PDB)>>2), CX
	MOVL	$PADDR(CPU0PDB), DI
	XORL	AX, AX

	CLD
	REP;	STOSL

	MOVL	$PADDR(CPU0PTE), DX
	MOVL	$(PTEWRITE|PTEVALID), BX	/* page permissions */
	ORL	BX, DX

	MOVL	$PADDR(CPU0PDB), AX
	ADDL	$PDO(KZERO), AX			/* page directory offset for KZERO */

	MOVL	DX, 0(AX)			/* PTE's for KZERO */
	ADDL	$BY2PG, DX
	MOVL	DX, 4(AX)			/* PTE's for KZERO+4MB */
	ADDL	$BY2PG, DX
	MOVL	DX, 8(AX)			/* PTE's for KZERO+8MB */
	ADDL	$BY2PG, DX
	MOVL	DX, 12(AX)			/* PTE's for KZERO+12MB */

	MOVL	$PADDR(CPU0PTE), AX		/* first page of page table */
	MOVL	$end-KZERO(SB), CX

	ADDL	$(16*1024), CX			/* qemu puts multiboot data after the kernel */

	ADDL	$(BY2XPG-1), CX
	ANDL	$~(BY2XPG-1), CX		/* round to 4MB */
	MOVL	CX, MemMin-KZERO(SB)		/* see memory.c */
	SHRL	$PGSHIFT, CX
	MOVL	BX, DX
_setpte:
	MOVL	DX, (AX)
	ADDL	$BY2PG, DX
	ADDL	$4, AX
	LOOP	_setpte

	MOVL	$PADDR(CPU0PTE), AX
	ADDL	$PTO(MACHADDR), AX		/* page table entry offset for MACHADDR */
	ORL	$PADDR(CPU0MACH), BX
	MOVL	BX, (AX)			/* PTE for Mach */

/*
 * Now ready to use the new map. Make sure the processor options are what is wanted.
 * It is necessary on some processors to immediately follow mode switching with a JMP instruction
 * to clear the prefetch queues.
 */
	MOVL	$PADDR(CPU0PDB), CX		/* load address of page directory */
	MOVL	(PDO(KZERO))(CX), DX		/* double-map KZERO at 0 */
	MOVL	DX, (PDO(0))(CX)
	MOVL	CX, CR3
	DELAY					/* JMP .+2 */

	MOVL	CR0, DX
	ORL	$0x80010000, DX			/* PG|WP */
	ANDL	$~0x6000000A, DX		/* ~(CD|NW|TS|MP) */

	MOVL	$_startpg(SB), AX		/* this is a virtual address */
	MOVL	DX, CR0				/* turn on paging */
	JMP*	AX				/* jump to the virtual nirvana */

/*
 * Basic machine environment set, can clear BSS and create a stack.
 * The stack starts at the top of the page containing the Mach structure.
 * The x86 architecture forces the use of the same virtual address for
 * each processor's Mach structure, so the global Mach pointer 'm' can
 * be initialised here.
 */
TEXT _startpg(SB), $0
	MOVL	$0, (PDO(0))(CX)		/* undo double-map of KZERO at 0 */
	MOVL	CX, CR3				/* load and flush the mmu */

_clearbss:
	MOVL	$edata(SB), DI
	XORL	AX, AX
	MOVL	$end(SB), CX
	SUBL	DI, CX				/* end-edata bytes */
	SHRL	$2, CX				/* end-edata doublewords */

	CLD
	REP;	STOSL				/* clear BSS */

	MOVL	$MACHADDR, SP
	MOVL	SP, m(SB)			/* initialise global Mach pointer */
	MOVL	$0, 0(SP)			/* initialise m->machno */


	ADDL	$(MACHSIZE-4), SP		/* initialise stack */

/*
 * Need to do one final thing to ensure a clean machine environment,
 * clear the EFLAGS register, which can only be done once there is a stack.
 */
	MOVL	$0, AX
	PUSHL	AX
	POPFL

	CALL	main(SB)

/*
 * Park a processor. Should never fall through a return from main to here,
 * should only be called by application processors when shutting down.
 */
TEXT idle(SB), $0
_idle:
	STI
	HLT
	JMP	_idle


TEXT load_fs(SB), $0
	MOVW fs+0(FP), AX
	MOVW AX, FS
	RET

TEXT load_gs(SB), $0
	MOVW gs+0(FP), AX
	MOVW AX, GS
	RET

/*
 * BIOS32.
 */
TEXT bios32call(SB), $0
	MOVL	ci+0(FP), BP
	MOVL	0(BP), AX
	MOVL	4(BP), BX
	MOVL	8(BP), CX
	MOVL	12(BP), DX
	MOVL	16(BP), SI
	MOVL	20(BP), DI
	PUSHL	BP

	MOVL	12(SP), BP			/* ptr */
	BYTE $0xFF; BYTE $0x5D; BYTE $0x00	/* CALL FAR 0(BP) */

	POPL	BP
	MOVL	DI, 20(BP)
	MOVL	SI, 16(BP)
	MOVL	DX, 12(BP)
	MOVL	CX, 8(BP)
	MOVL	BX, 4(BP)
	MOVL	AX, 0(BP)

	XORL	AX, AX
	JCC	_bios32xxret
	INCL	AX

_bios32xxret:
	RET

/*
 * Port I/O.
 *	in[bsl]		input a byte|short|long
 *	ins[bsl]	input a string of bytes|shorts|longs
 *	out[bsl]	output a byte|short|long
 *	outs[bsl]	output a string of bytes|shorts|longs
 */
TEXT inb(SB), $0
	MOVL	port+0(FP), DX
	XORL	AX, AX
	INB
	RET

TEXT insb(SB), $0
	MOVL	port+0(FP), DX
	MOVL	address+4(FP), DI
	MOVL	count+8(FP), CX
	CLD
	REP;	INSB
	RET

TEXT ins(SB), $0
	MOVL	port+0(FP), DX
	XORL	AX, AX
	OP16;	INL
	RET

TEXT inss(SB), $0
	MOVL	port+0(FP), DX
	MOVL	address+4(FP), DI
	MOVL	count+8(FP), CX
	CLD
	REP;	OP16; INSL
	RET

TEXT inl(SB), $0
	MOVL	port+0(FP), DX
	INL
	RET

TEXT insl(SB), $0
	MOVL	port+0(FP), DX
	MOVL	address+4(FP), DI
	MOVL	count+8(FP), CX
	CLD
	REP;	INSL
	RET

TEXT outb(SB), $0
	MOVL	port+0(FP), DX
	MOVL	byte+4(FP), AX
	OUTB
	RET

TEXT outsb(SB), $0
	MOVL	port+0(FP), DX
	MOVL	address+4(FP), SI
	MOVL	count+8(FP), CX
	CLD
	REP;	OUTSB
	RET

TEXT outs(SB), $0
	MOVL	port+0(FP), DX
	MOVL	short+4(FP), AX
	OP16;	OUTL
	RET

TEXT outss(SB), $0
	MOVL	port+0(FP), DX
	MOVL	address+4(FP), SI
	MOVL	count+8(FP), CX
	CLD
	REP;	OP16; OUTSL
	RET

TEXT outl(SB), $0
	MOVL	port+0(FP), DX
	MOVL	long+4(FP), AX
	OUTL
	RET

TEXT outsl(SB), $0
	MOVL	port+0(FP), DX
	MOVL	address+4(FP), SI
	MOVL	count+8(FP), CX
	CLD
	REP;	OUTSL
	RET

/*
 * Read/write various system registers.
 * CR4 and the 'model specific registers' should only be read/written
 * after it has been determined the processor supports them
 */
TEXT lgdt(SB), $0				/* GDTR - global descriptor table */
	MOVL	gdtptr+0(FP), AX
	MOVL	(AX), GDTR
	RET

TEXT lldt(SB), $0				/* LDTR - local descriptor table */
	MOVL	sel+0(FP), AX
	BYTE $0x0F; BYTE $0x00; BYTE $0xD0	/* LLDT AX */
	RET

TEXT lidt(SB), $0				/* IDTR - interrupt descriptor table */
	MOVL	idtptr+0(FP), AX
	MOVL	(AX), IDTR
	RET

TEXT ltr(SB), $0				/* TR - task register */
	MOVL	tptr+0(FP), AX
	MOVW	AX, TASK
	RET

TEXT getcr0(SB), $0				/* CR0 - processor control */
	MOVL	CR0, AX
	RET

TEXT getcr2(SB), $0				/* CR2 - page fault linear address */
	MOVL	CR2, AX
	RET

TEXT putcr2(SB), $0
	MOVL	cr2+0(FP), AX
	MOVL	AX, CR2
	RET

TEXT getcr3(SB), $0				/* CR3 - page directory base */
	MOVL	CR3, AX
	RET

TEXT putcr0(SB), $0
	MOVL	cr0+0(FP), AX
	MOVL	AX, CR0
	RET

TEXT putcr3(SB), $0
	MOVL	cr3+0(FP), AX
	MOVL	AX, CR3
	RET

TEXT getcr4(SB), $0				/* CR4 - extensions */
	MOVL	CR4, AX
	RET

TEXT putcr4(SB), $0
	MOVL	cr4+0(FP), AX
	MOVL	AX, CR4
	RET

TEXT invlpg(SB), $0
	/* 486+ only */
	MOVL	va+0(FP), CX
	INVLPG
	RET

TEXT wbinvd(SB), $0
	WBINVD
	RET

TEXT _cycles(SB), $0				/* time stamp counter */
	RDTSC
	MOVL	vlong+0(FP), CX			/* &vlong */
	MOVL	AX, 0(CX)			/* lo */
	MOVL	DX, 4(CX)			/* hi */
	RET

/*
 * stub for:
 * time stamp counter; low-order 32 bits of 64-bit cycle counter
 * Runs at fasthz/4 cycles per second (m->clkin>>3)
 */
TEXT lcycles(SB),1,$0
	RDTSC
	RET

TEXT rdmsr(SB), $0				/* model-specific register */
	MOVL	$0, BP
	MOVL	index+0(FP), CX
TEXT _rdmsrinst(SB), $0
	RDMSR
	MOVL	vlong+4(FP), CX			/* &vlong */
	MOVL	AX, 0(CX)			/* lo */
	MOVL	DX, 4(CX)			/* hi */
	MOVL	BP, AX				/* BP set to -1 if traped */
	RET
	
TEXT wrmsr(SB), $0
	MOVL	$0, BP
	MOVL	index+0(FP), CX
	MOVL	lo+4(FP), AX
	MOVL	hi+8(FP), DX
TEXT _wrmsrinst(SB), $0
	WRMSR
	MOVL	BP, AX				/* BP set to -1 if traped */
	RET

/*
 * Try to determine the CPU type which requires fiddling with EFLAGS.
 * If the Id bit can be toggled then the CPUID instruction can be used
 * to determine CPU identity and features. First have to check if it's
 * a 386 (Ac bit can't be set). If it's not a 386 and the Id bit can't be
 * toggled then it's an older 486 of some kind.
 *
 *	cpuid(fun, regs[4]);
 */
TEXT cpuid(SB), $0
	MOVL	$0x240000, AX
	PUSHL	AX
	POPFL					/* set Id|Ac */
	PUSHFL
	POPL	BX				/* retrieve value */
	MOVL	$0, AX
	PUSHL	AX
	POPFL					/* clear Id|Ac, EFLAGS initialised */
	PUSHFL
	POPL	AX				/* retrieve value */
	XORL	BX, AX
	TESTL	$0x040000, AX			/* Ac */
	JZ	_cpu386				/* can't set this bit on 386 */
	TESTL	$0x200000, AX			/* Id */
	JZ	_cpu486				/* can't toggle this bit on some 486 */
	MOVL	fn+0(FP), AX
	CPUID
	JMP	_cpuid
_cpu486:
	MOVL	$0x400, AX
	JMP	_maybezapax
_cpu386:
	MOVL	$0x300, AX
_maybezapax:
	CMPL	fn+0(FP), $1
	JE	_zaprest
	XORL	AX, AX
_zaprest:
	XORL	BX, BX
	XORL	CX, CX
	XORL	DX, DX
_cpuid:
	MOVL	regs+4(FP), BP
	MOVL	AX, 0(BP)
	MOVL	BX, 4(BP)
	MOVL	CX, 8(BP)
	MOVL	DX, 12(BP)
	RET

/*
 * Basic timing loop to determine CPU frequency.
 */
TEXT aamloop(SB), $0
	MOVL	count+0(FP), CX
_aamloop:
	AAM
	LOOP	_aamloop
	RET

/*
 * Floating point.
 * Note: the encodings for the FCLEX, FINIT, FSAVE, FSTCW, FSENV and FSTSW
 * instructions do NOT have the WAIT prefix byte (i.e. they act like their
 * FNxxx variations) so WAIT instructions must be explicitly placed in the
 * code as necessary.
 */
#define FPOFF							 ;\
	MOVL	CR0, AX						 ;\
	ORL	$0x28, AX			/* NE=1, TS=1 */ ;\
	MOVL	AX, CR0

#define	FPON							 ;\
	MOVL	CR0, AX						 ;\
	ANDL	$~0xC, AX			/* EM=0, TS=0 */ ;\
	MOVL	AX, CR0

TEXT fpoff(SB), $0				/* disable */
	FPOFF
	RET

TEXT fpinit(SB), $0				/* enable and init */
	FPON
	FINIT
	WAIT
	/* setfcr(FPPDBL|FPRNR|FPINVAL|FPZDIV|FPOVFL) */
	/* note that low 6 bits are masks, not enables, on this chip */
	PUSHW	$0x0232
	FLDCW	0(SP)
	POPW	AX
	WAIT
	RET

TEXT fpx87save0(SB), $0				/* save state and disable */
	MOVL	p+0(FP), AX
	FSAVE	0(AX)				/* no WAIT */
	FPOFF
	RET

TEXT fpx87restore0(SB), $0			/* enable and restore state */
	FPON
	MOVL	p+0(FP), AX
	FRSTOR	0(AX)
	WAIT
	RET

TEXT fpclear(SB), $0				/* clear pending exceptions */
	FPON
	FCLEX					/* no WAIT */
	FPOFF
	RET

TEXT fpssesave(SB), $0				/* save state and disable */
	MOVL	p+0(FP), AX
	FXSAVE	0(AX)				/* no WAIT */
	FPOFF
	RET

TEXT fpsserestore(SB), $0			/* enable and restore state */
	FPON
	MOVL	p+0(FP), AX
	FXRSTOR	0(AX)
	WAIT
	RET

TEXT ldmxcsr(SB), $0				/* Load MXCSR */
	LDMXCSR	mxcsr+0(FP)
	RET

/*
 */
TEXT splhi(SB), $0
shi:
	PUSHFL
	POPL	AX
	TESTL	$0x200, AX
	JZ	alreadyhi
	MOVL	$(MACHADDR+0x04), CX 		/* save PC in m->splpc */
	MOVL	(SP), BX
	MOVL	BX, (CX)
alreadyhi:
	CLI
	RET

TEXT spllo(SB), $0
slo:
	PUSHFL
	POPL	AX
	TESTL	$0x200, AX
	JNZ	alreadylo
	MOVL	$(MACHADDR+0x04), CX		/* clear m->splpc */
	MOVL	$0, (CX)
alreadylo:
	STI
	RET

TEXT splx(SB), $0
	MOVL	s+0(FP), AX
	TESTL	$0x200, AX
	JNZ	slo
	JMP	shi

TEXT spldone(SB), $0
	RET

TEXT islo(SB), $0
	PUSHFL
	POPL	AX
	ANDL	$0x200, AX			/* interrupt enable flag */
	RET

/*
 * Test-And-Set
 */
TEXT tas(SB), $0
TEXT _tas(SB), $0
	MOVL	$0xDEADDEAD, AX
	MOVL	lock+0(FP), BX
	XCHGL	AX, (BX)			/* lock->key */
	RET

TEXT mb386(SB), $0
	POPL	AX				/* return PC */
	PUSHFL
	PUSHL	CS
	PUSHL	AX
	IRETL

TEXT mb586(SB), $0
	XORL	AX, AX
	CPUID
	RET

TEXT sfence(SB), $0
	BYTE $0x0f
	BYTE $0xae
	BYTE $0xf8
	RET

TEXT lfence(SB), $0
	BYTE $0x0f
	BYTE $0xae
	BYTE $0xe8
	RET

TEXT mfence(SB), $0
	BYTE $0x0f
	BYTE $0xae
	BYTE $0xf0
	RET

TEXT xchgw(SB), $0
	MOVL	v+4(FP), AX
	MOVL	p+0(FP), BX
	XCHGW	AX, (BX)
	RET

TEXT cmpswap486(SB), $0
	MOVL	addr+0(FP), BX
	MOVL	old+4(FP), AX
	MOVL	new+8(FP), CX
	LOCK
	BYTE $0x0F; BYTE $0xB1; BYTE $0x0B	/* CMPXCHGL CX, (BX) */
	JNZ didnt
	MOVL	$1, AX
	RET
didnt:
	XORL	AX,AX
	RET

TEXT mul64fract(SB), $0
/*
 * Multiply two 64-bit number s and keep the middle 64 bits from the 128-bit result
 * See ../port/tod.c for motivation.
 */
	MOVL	r+0(FP), CX
	XORL	BX, BX				/* BX = 0 */

	MOVL	a+8(FP), AX
	MULL	b+16(FP)			/* a1*b1 */
	MOVL	AX, 4(CX)			/* r2 = lo(a1*b1) */

	MOVL	a+8(FP), AX
	MULL	b+12(FP)			/* a1*b0 */
	MOVL	AX, 0(CX)			/* r1 = lo(a1*b0) */
	ADDL	DX, 4(CX)			/* r2 += hi(a1*b0) */

	MOVL	a+4(FP), AX
	MULL	b+16(FP)			/* a0*b1 */
	ADDL	AX, 0(CX)			/* r1 += lo(a0*b1) */
	ADCL	DX, 4(CX)			/* r2 += hi(a0*b1) + carry */

	MOVL	a+4(FP), AX
	MULL	b+12(FP)			/* a0*b0 */
	ADDL	DX, 0(CX)			/* r1 += hi(a0*b0) */
	ADCL	BX, 4(CX)			/* r2 += carry */
	RET

/*
 *  label consists of a stack pointer and a PC
 */
TEXT gotolabel(SB), $0
	MOVL	label+0(FP), AX
	MOVL	0(AX), SP			/* restore sp */
	MOVL	4(AX), AX			/* put return pc on the stack */
	MOVL	AX, 0(SP)
	MOVL	$1, AX				/* return 1 */
	RET

TEXT setlabel(SB), $0
	MOVL	label+0(FP), AX
	MOVL	SP, 0(AX)			/* store sp */
	MOVL	0(SP), BX			/* store return pc */
	MOVL	BX, 4(AX)
	MOVL	$0, AX				/* return 0 */
	RET

/*
 * Attempt at power saving. -rsc
 */
TEXT halt(SB), $0
	CLI
	CMPL	nrdy(SB), $0
	JEQ	_nothingready
	STI
	RET

_nothingready:
	STI
	HLT
	RET

TEXT mwait(SB), $0
	MOVL	addr+0(FP), AX
	MOVL	(AX), CX
	ORL	CX, CX
	JNZ	_mwaitdone
	XORL	DX, DX
	BYTE $0x0f; BYTE $0x01; BYTE $0xc8	/* MONITOR */
	MOVL	(AX), CX
	ORL	CX, CX
	JNZ	_mwaitdone
	XORL	AX, AX
	BYTE $0x0f; BYTE $0x01; BYTE $0xc9	/* MWAIT */
_mwaitdone:
	RET

#define RDRANDAX	BYTE $0x0f; BYTE $0xc7; BYTE $0xf0

TEXT rdrand32(SB), $-4
_rloop32:
	RDRANDAX
	JCC	_rloop32
	RET

TEXT rdrandbuf(SB), $0
	MOVL	buf+0(FP), DI
	MOVL	cnt+4(FP), CX
	CLD
	MOVL	CX, DX
	SHRL	$2, CX
	CMPL	CX, $0
	JE	_rndleft
_rnddwords:
	CALL	rdrand32(SB)
	STOSL
	LOOP _rnddwords
_rndleft:
	MOVL	DX, CX
	ANDL	$3, CX
	CMPL	CX, $0
	JE	_rnddone
_rndbytes:
	CALL rdrand32(SB)
	STOSB
	LOOP _rndbytes
_rnddone:
	RET

/* debug register access */

TEXT putdr(SB), $0
	MOVL	p+0(FP), SI
	MOVL	28(SI), AX
	MOVL	AX, DR7
_putdr01236:
	MOVL	0(SI), AX
	MOVL	AX, DR0
	MOVL	4(SI), AX
	MOVL	AX, DR1
	MOVL	8(SI), AX
	MOVL	AX, DR2
	MOVL	12(SI), AX
	MOVL	AX, DR3
	MOVL	24(SI), AX
	MOVL	AX, DR6
	RET

TEXT putdr01236(SB), $0
	MOVL p+0(FP), SI
	JMP _putdr01236

TEXT getdr6(SB), $0
	MOVL	DR6, AX
	RET

TEXT putdr6(SB), $0
	MOVL	p+0(FP), AX
	MOVL	AX, DR6
	RET
	
TEXT putdr7(SB), $0
	MOVL	p+0(FP), AX
	MOVL	AX, DR7
	RET

/* VMX instructions */
TEXT vmxon(SB), $0
	/* VMXON 4(SP) */
	BYTE	$0xf3; BYTE $0x0f; BYTE $0xc7; BYTE $0x74; BYTE $0x24; BYTE $0x04
	JMP	_vmout

TEXT vmxoff(SB), $0
	BYTE	$0x0f; BYTE $0x01; BYTE $0xc4
	JMP	_vmout

TEXT vmclear(SB), $0
	/* VMCLEAR 4(SP) */
	BYTE	$0x66; BYTE $0x0f; BYTE $0xc7; BYTE $0x74; BYTE $0x24; BYTE $0x04
	JMP	_vmout

TEXT vmlaunch(SB), $0
	MOVL	$0x6C14, DI
	MOVL	SP, DX
	BYTE	$0x0f; BYTE $0x79; BYTE $0xfa /* VMWRITE DX, DI */
	JBE	_vmout
	MOVL	$0x6C16, DI
	MOVL	$vmrestore(SB), DX
	BYTE	$0x0f; BYTE $0x79; BYTE $0xfa /* VMWRITE DX, DI */
	JBE	_vmout
	
	MOVL	resume+4(FP), AX
	TESTL	AX, AX
	MOVL	ureg+0(FP), DI
	MOVL	4(DI), SI
	MOVL	8(DI), BP
	MOVL	16(DI), BX
	MOVL	20(DI), DX
	MOVL	24(DI), CX
	MOVL	28(DI), AX
	MOVL	0(DI), DI
	JNE	_vmresume
	BYTE	$0x0f; BYTE $0x01; BYTE	$0xc2 /* VMLAUNCH */
	JMP	_vmout
_vmresume:
	BYTE	$0x0f; BYTE $0x01; BYTE $0xc3 /* VMRESUME */
	JMP _vmout

TEXT vmrestore(SB), $0
	PUSHL	DI
	MOVL	ureg+0(FP), DI
	POPL	0(DI)
	MOVL	SI, 4(DI)
	MOVL	BP, 8(DI)
	MOVL	BX, 16(DI)
	MOVL	DX, 20(DI)
	MOVL	CX, 24(DI)
	MOVL	AX, 28(DI)
	XORL	AX, AX
	RET

TEXT vmptrld(SB), $0
	/* VMPTRLD 4(SP) */
	BYTE $0x0f; BYTE $0xc7; BYTE $0x74; BYTE $0x24; BYTE $0x04
	JMP _vmout

TEXT vmwrite(SB), $0
	MOVL addr+0(FP),DI
	MOVL val+4(FP),DX
	/* VMWRITE DX, DI */
	BYTE $0x0f; BYTE $0x79; BYTE $0xfa
	JMP _vmout

TEXT vmread(SB), $0
	MOVL addr+0(FP),DI
	MOVL valp+4(FP),SI
	/* VMREAD (SI), DI */
	BYTE $0x0f; BYTE $0x78; BYTE $0x3e
	JMP _vmout

TEXT invept(SB), $0
	MOVL type+0(FP), AX
	/* INVEPT AX, 8(SP) */
	BYTE $0x66; BYTE $0x0f; BYTE $0x38; BYTE $0x80; BYTE $0x44; BYTE $0x24; BYTE $0x08
	JMP _vmout

TEXT invvpid(SB), $0
	MOVL type+0(FP), AX
	/* INVVPID AX, 8(SP) */
	BYTE $0x66; BYTE $0x0f; BYTE $0x38; BYTE $0x81; BYTE $0x44; BYTE $0x24; BYTE $0x08
	JMP _vmout

_vmout:
	JC _vmout1
	JZ _vmout2
	XORL AX, AX
	RET
_vmout1:
	MOVL $-1, AX
	RET
_vmout2:
	MOVL $-2, AX
	RET

/*
 *  Used to get to the first process:
 * 	set up an interrupt return frame and IRET to user level.
 */
TEXT touser(SB), $0
	PUSHL	$(UDSEL)			/* old ss */
	MOVL	sp+0(FP), AX			/* old sp */
	PUSHL	AX
	MOVL	$0x200, AX			/* interrupt enable flag */
	PUSHL	AX				/* old flags */
	PUSHL	$(UESEL)			/* old cs */
	PUSHL	$(UTZERO+32)			/* old pc */
	MOVL	$(UDSEL), AX
	MOVW	AX, DS
	MOVW	AX, ES
	MOVW	AX, GS
	MOVW	AX, FS
	IRETL

/*
 * Interrupt/exception handling.
 * Each entry in the vector table calls either _strayintr or _strayintrx depending
 * on whether an error code has been automatically pushed onto the stack
 * (_strayintrx) or not, in which case a dummy entry must be pushed before retrieving
 * the trap type from the vector table entry and placing it on the stack as part
 * of the Ureg structure.
 * The size of each entry in the vector table (6 bytes) is known in trapinit().
 */
TEXT _strayintr(SB), $0
	PUSHL	AX			/* save AX */
	MOVL	4(SP), AX		/* return PC from vectortable(SB) */
	JMP	intrcommon

TEXT _strayintrx(SB), $0
	XCHGL	AX, (SP)		/* swap AX with vectortable CALL PC */
intrcommon:
	PUSHL	DS			/* save DS */
	PUSHL	$(KDSEL)
	POPL	DS			/* fix up DS */
	MOVBLZX	(AX), AX		/* trap type -> AX */
	XCHGL	AX, 4(SP)		/* exchange trap type with saved AX */

	PUSHL	ES			/* save ES */
	PUSHL	$(KDSEL)
	POPL	ES			/* fix up ES */

	PUSHL	FS			/* save the rest of the Ureg struct */
	PUSHL	GS
	PUSHAL

	PUSHL	SP			/* Ureg* argument to trap */
	CALL	trap(SB)

TEXT forkret(SB), $0
	POPL	AX
	POPAL
TEXT _forkretpopgs(SB), $0
	POPL	GS
TEXT _forkretpopfs(SB), $0
	POPL	FS
TEXT _forkretpopes(SB), $0
	POPL	ES
TEXT _forkretpopds(SB), $0
	POPL	DS
	ADDL	$8, SP			/* pop error code and trap type */
TEXT _forkretiret(SB), $0
	IRETL

/*
 * This is merely _strayintr optimised to vector
 * to syscall() without going through trap().
 */
TEXT _syscallintr(SB), $0
	PUSHL	$VectorSYSCALL		/* trap type */

	PUSHL	DS
	PUSHL	ES
	PUSHL	FS
	PUSHL	GS
	PUSHAL
	MOVL	$(KDSEL), AX
	MOVW	AX, DS
	MOVW	AX, ES

	MOVL	$syscall(SB), AX

	PUSHL	SP			/* Ureg* argument to syscall */
	PUSHL	$forkret(SB)		/* return pc */
	JMP	*AX

TEXT vectortable(SB), $0
	CALL _strayintr(SB); BYTE $0x00		/* divide error */
	CALL _strayintr(SB); BYTE $0x01		/* debug exception */
	CALL _strayintr(SB); BYTE $0x02		/* NMI interrupt */
	CALL _strayintr(SB); BYTE $0x03		/* breakpoint */
	CALL _strayintr(SB); BYTE $0x04		/* overflow */
	CALL _strayintr(SB); BYTE $0x05		/* bound */
	CALL _strayintr(SB); BYTE $0x06		/* invalid opcode */
	CALL _strayintr(SB); BYTE $0x07		/* no coprocessor available */
	CALL _strayintrx(SB); BYTE $0x08	/* double fault */
	CALL _strayintr(SB); BYTE $0x09		/* coprocessor segment overflow */
	CALL _strayintrx(SB); BYTE $0x0A	/* invalid TSS */
	CALL _strayintrx(SB); BYTE $0x0B	/* segment not available */
	CALL _strayintrx(SB); BYTE $0x0C	/* stack exception */
	CALL _strayintrx(SB); BYTE $0x0D	/* general protection error */
	CALL _strayintrx(SB); BYTE $0x0E	/* page fault */
	CALL _strayintr(SB); BYTE $0x0F		/*  */
	CALL _strayintr(SB); BYTE $0x10		/* coprocessor error */
	CALL _strayintrx(SB); BYTE $0x11	/* alignment check */
	CALL _strayintr(SB); BYTE $0x12		/* machine check */
	CALL _strayintr(SB); BYTE $0x13		/* simd error */
	CALL _strayintr(SB); BYTE $0x14
	CALL _strayintr(SB); BYTE $0x15
	CALL _strayintr(SB); BYTE $0x16
	CALL _strayintr(SB); BYTE $0x17
	CALL _strayintr(SB); BYTE $0x18
	CALL _strayintr(SB); BYTE $0x19
	CALL _strayintr(SB); BYTE $0x1A
	CALL _strayintr(SB); BYTE $0x1B
	CALL _strayintr(SB); BYTE $0x1C
	CALL _strayintr(SB); BYTE $0x1D
	CALL _strayintr(SB); BYTE $0x1E
	CALL _strayintr(SB); BYTE $0x1F
	CALL _strayintr(SB); BYTE $0x20		/* VectorLAPIC */
	CALL _strayintr(SB); BYTE $0x21
	CALL _strayintr(SB); BYTE $0x22
	CALL _strayintr(SB); BYTE $0x23
	CALL _strayintr(SB); BYTE $0x24
	CALL _strayintr(SB); BYTE $0x25
	CALL _strayintr(SB); BYTE $0x26
	CALL _strayintr(SB); BYTE $0x27
	CALL _strayintr(SB); BYTE $0x28
	CALL _strayintr(SB); BYTE $0x29
	CALL _strayintr(SB); BYTE $0x2A
	CALL _strayintr(SB); BYTE $0x2B
	CALL _strayintr(SB); BYTE $0x2C
	CALL _strayintr(SB); BYTE $0x2D
	CALL _strayintr(SB); BYTE $0x2E
	CALL _strayintr(SB); BYTE $0x2F
	CALL _strayintr(SB); BYTE $0x30
	CALL _strayintr(SB); BYTE $0x31
	CALL _strayintr(SB); BYTE $0x32
	CALL _strayintr(SB); BYTE $0x33
	CALL _strayintr(SB); BYTE $0x34
	CALL _strayintr(SB); BYTE $0x35
	CALL _strayintr(SB); BYTE $0x36
	CALL _strayintr(SB); BYTE $0x37
	CALL _strayintr(SB); BYTE $0x38
	CALL _strayintr(SB); BYTE $0x39
	CALL _strayintr(SB); BYTE $0x3A
	CALL _strayintr(SB); BYTE $0x3B
	CALL _strayintr(SB); BYTE $0x3C
	CALL _strayintr(SB); BYTE $0x3D
	CALL _strayintr(SB); BYTE $0x3E
	CALL _strayintr(SB); BYTE $0x3F
	CALL _syscallintr(SB); BYTE $0x40	/* VectorSYSCALL */
	CALL _strayintr(SB); BYTE $0x41
	CALL _strayintr(SB); BYTE $0x42
	CALL _strayintr(SB); BYTE $0x43
	CALL _strayintr(SB); BYTE $0x44
	CALL _strayintr(SB); BYTE $0x45
	CALL _strayintr(SB); BYTE $0x46
	CALL _strayintr(SB); BYTE $0x47
	CALL _strayintr(SB); BYTE $0x48
	CALL _strayintr(SB); BYTE $0x49
	CALL _strayintr(SB); BYTE $0x4A
	CALL _strayintr(SB); BYTE $0x4B
	CALL _strayintr(SB); BYTE $0x4C
	CALL _strayintr(SB); BYTE $0x4D
	CALL _strayintr(SB); BYTE $0x4E
	CALL _strayintr(SB); BYTE $0x4F
	CALL _strayintr(SB); BYTE $0x50
	CALL _strayintr(SB); BYTE $0x51
	CALL _strayintr(SB); BYTE $0x52
	CALL _strayintr(SB); BYTE $0x53
	CALL _strayintr(SB); BYTE $0x54
	CALL _strayintr(SB); BYTE $0x55
	CALL _strayintr(SB); BYTE $0x56
	CALL _strayintr(SB); BYTE $0x57
	CALL _strayintr(SB); BYTE $0x58
	CALL _strayintr(SB); BYTE $0x59
	CALL _strayintr(SB); BYTE $0x5A
	CALL _strayintr(SB); BYTE $0x5B
	CALL _strayintr(SB); BYTE $0x5C
	CALL _strayintr(SB); BYTE $0x5D
	CALL _strayintr(SB); BYTE $0x5E
	CALL _strayintr(SB); BYTE $0x5F
	CALL _strayintr(SB); BYTE $0x60
	CALL _strayintr(SB); BYTE $0x61
	CALL _strayintr(SB); BYTE $0x62
	CALL _strayintr(SB); BYTE $0x63
	CALL _strayintr(SB); BYTE $0x64
	CALL _strayintr(SB); BYTE $0x65
	CALL _strayintr(SB); BYTE $0x66
	CALL _strayintr(SB); BYTE $0x67
	CALL _strayintr(SB); BYTE $0x68
	CALL _strayintr(SB); BYTE $0x69
	CALL _strayintr(SB); BYTE $0x6A
	CALL _strayintr(SB); BYTE $0x6B
	CALL _strayintr(SB); BYTE $0x6C
	CALL _strayintr(SB); BYTE $0x6D
	CALL _strayintr(SB); BYTE $0x6E
	CALL _strayintr(SB); BYTE $0x6F
	CALL _strayintr(SB); BYTE $0x70
	CALL _strayintr(SB); BYTE $0x71
	CALL _strayintr(SB); BYTE $0x72
	CALL _strayintr(SB); BYTE $0x73
	CALL _strayintr(SB); BYTE $0x74
	CALL _strayintr(SB); BYTE $0x75
	CALL _strayintr(SB); BYTE $0x76
	CALL _strayintr(SB); BYTE $0x77
	CALL _strayintr(SB); BYTE $0x78
	CALL _strayintr(SB); BYTE $0x79
	CALL _strayintr(SB); BYTE $0x7A
	CALL _strayintr(SB); BYTE $0x7B
	CALL _strayintr(SB); BYTE $0x7C
	CALL _strayintr(SB); BYTE $0x7D
	CALL _strayintr(SB); BYTE $0x7E
	CALL _strayintr(SB); BYTE $0x7F
	CALL _strayintr(SB); BYTE $0x80		/* Vector[A]PIC */
	CALL _strayintr(SB); BYTE $0x81
	CALL _strayintr(SB); BYTE $0x82
	CALL _strayintr(SB); BYTE $0x83
	CALL _strayintr(SB); BYTE $0x84
	CALL _strayintr(SB); BYTE $0x85
	CALL _strayintr(SB); BYTE $0x86
	CALL _strayintr(SB); BYTE $0x87
	CALL _strayintr(SB); BYTE $0x88
	CALL _strayintr(SB); BYTE $0x89
	CALL _strayintr(SB); BYTE $0x8A
	CALL _strayintr(SB); BYTE $0x8B
	CALL _strayintr(SB); BYTE $0x8C
	CALL _strayintr(SB); BYTE $0x8D
	CALL _strayintr(SB); BYTE $0x8E
	CALL _strayintr(SB); BYTE $0x8F
	CALL _strayintr(SB); BYTE $0x90
	CALL _strayintr(SB); BYTE $0x91
	CALL _strayintr(SB); BYTE $0x92
	CALL _strayintr(SB); BYTE $0x93
	CALL _strayintr(SB); BYTE $0x94
	CALL _strayintr(SB); BYTE $0x95
	CALL _strayintr(SB); BYTE $0x96
	CALL _strayintr(SB); BYTE $0x97
	CALL _strayintr(SB); BYTE $0x98
	CALL _strayintr(SB); BYTE $0x99
	CALL _strayintr(SB); BYTE $0x9A
	CALL _strayintr(SB); BYTE $0x9B
	CALL _strayintr(SB); BYTE $0x9C
	CALL _strayintr(SB); BYTE $0x9D
	CALL _strayintr(SB); BYTE $0x9E
	CALL _strayintr(SB); BYTE $0x9F
	CALL _strayintr(SB); BYTE $0xA0
	CALL _strayintr(SB); BYTE $0xA1
	CALL _strayintr(SB); BYTE $0xA2
	CALL _strayintr(SB); BYTE $0xA3
	CALL _strayintr(SB); BYTE $0xA4
	CALL _strayintr(SB); BYTE $0xA5
	CALL _strayintr(SB); BYTE $0xA6
	CALL _strayintr(SB); BYTE $0xA7
	CALL _strayintr(SB); BYTE $0xA8
	CALL _strayintr(SB); BYTE $0xA9
	CALL _strayintr(SB); BYTE $0xAA
	CALL _strayintr(SB); BYTE $0xAB
	CALL _strayintr(SB); BYTE $0xAC
	CALL _strayintr(SB); BYTE $0xAD
	CALL _strayintr(SB); BYTE $0xAE
	CALL _strayintr(SB); BYTE $0xAF
	CALL _strayintr(SB); BYTE $0xB0
	CALL _strayintr(SB); BYTE $0xB1
	CALL _strayintr(SB); BYTE $0xB2
	CALL _strayintr(SB); BYTE $0xB3
	CALL _strayintr(SB); BYTE $0xB4
	CALL _strayintr(SB); BYTE $0xB5
	CALL _strayintr(SB); BYTE $0xB6
	CALL _strayintr(SB); BYTE $0xB7
	CALL _strayintr(SB); BYTE $0xB8
	CALL _strayintr(SB); BYTE $0xB9
	CALL _strayintr(SB); BYTE $0xBA
	CALL _strayintr(SB); BYTE $0xBB
	CALL _strayintr(SB); BYTE $0xBC
	CALL _strayintr(SB); BYTE $0xBD
	CALL _strayintr(SB); BYTE $0xBE
	CALL _strayintr(SB); BYTE $0xBF
	CALL _strayintr(SB); BYTE $0xC0
	CALL _strayintr(SB); BYTE $0xC1
	CALL _strayintr(SB); BYTE $0xC2
	CALL _strayintr(SB); BYTE $0xC3
	CALL _strayintr(SB); BYTE $0xC4
	CALL _strayintr(SB); BYTE $0xC5
	CALL _strayintr(SB); BYTE $0xC6
	CALL _strayintr(SB); BYTE $0xC7
	CALL _strayintr(SB); BYTE $0xC8
	CALL _strayintr(SB); BYTE $0xC9
	CALL _strayintr(SB); BYTE $0xCA
	CALL _strayintr(SB); BYTE $0xCB
	CALL _strayintr(SB); BYTE $0xCC
	CALL _strayintr(SB); BYTE $0xCD
	CALL _strayintr(SB); BYTE $0xCE
	CALL _strayintr(SB); BYTE $0xCF
	CALL _strayintr(SB); BYTE $0xD0
	CALL _strayintr(SB); BYTE $0xD1
	CALL _strayintr(SB); BYTE $0xD2
	CALL _strayintr(SB); BYTE $0xD3
	CALL _strayintr(SB); BYTE $0xD4
	CALL _strayintr(SB); BYTE $0xD5
	CALL _strayintr(SB); BYTE $0xD6
	CALL _strayintr(SB); BYTE $0xD7
	CALL _strayintr(SB); BYTE $0xD8
	CALL _strayintr(SB); BYTE $0xD9
	CALL _strayintr(SB); BYTE $0xDA
	CALL _strayintr(SB); BYTE $0xDB
	CALL _strayintr(SB); BYTE $0xDC
	CALL _strayintr(SB); BYTE $0xDD
	CALL _strayintr(SB); BYTE $0xDE
	CALL _strayintr(SB); BYTE $0xDF
	CALL _strayintr(SB); BYTE $0xE0
	CALL _strayintr(SB); BYTE $0xE1
	CALL _strayintr(SB); BYTE $0xE2
	CALL _strayintr(SB); BYTE $0xE3
	CALL _strayintr(SB); BYTE $0xE4
	CALL _strayintr(SB); BYTE $0xE5
	CALL _strayintr(SB); BYTE $0xE6
	CALL _strayintr(SB); BYTE $0xE7
	CALL _strayintr(SB); BYTE $0xE8
	CALL _strayintr(SB); BYTE $0xE9
	CALL _strayintr(SB); BYTE $0xEA
	CALL _strayintr(SB); BYTE $0xEB
	CALL _strayintr(SB); BYTE $0xEC
	CALL _strayintr(SB); BYTE $0xED
	CALL _strayintr(SB); BYTE $0xEE
	CALL _strayintr(SB); BYTE $0xEF
	CALL _strayintr(SB); BYTE $0xF0
	CALL _strayintr(SB); BYTE $0xF1
	CALL _strayintr(SB); BYTE $0xF2
	CALL _strayintr(SB); BYTE $0xF3
	CALL _strayintr(SB); BYTE $0xF4
	CALL _strayintr(SB); BYTE $0xF5
	CALL _strayintr(SB); BYTE $0xF6
	CALL _strayintr(SB); BYTE $0xF7
	CALL _strayintr(SB); BYTE $0xF8
	CALL _strayintr(SB); BYTE $0xF9
	CALL _strayintr(SB); BYTE $0xFA
	CALL _strayintr(SB); BYTE $0xFB
	CALL _strayintr(SB); BYTE $0xFC
	CALL _strayintr(SB); BYTE $0xFD
	CALL _strayintr(SB); BYTE $0xFE
	CALL _strayintr(SB); BYTE $0xFF