/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include	"u.h"#include	"../port/lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"io.h"#include	"ureg.h"#include	"../port/error.h" /* * Back the processor into real mode to run a BIOS call, * then return.  This must be used carefully, since it  * completely disables hardware interrupts (e.g., the i8259) * while running.  It is *not* using VM86 mode.  * Maybe that's really the right answer, but real mode * is fine for now.  We don't expect to use this very much -- * just for BIOS INT 13 disk i/o. */ void realmode0(void);		/* in realmode0.s */void realmodeintrinst(void);	/* in realmode0.s */void realmodeend(void);		/* in realmode0.s */ extern ushort rmseg;		/* in realmode0.s */ static Ureg rmu;static QLock rmlock;static int beenhere; voidrealmode(Ureg *ureg){	int s, sz;	ulong cr3;	uchar *ip; 	qlock(&rmlock);	if (!beenhere)		iprint("into bios in real mode...");	*(Ureg *)RMUADDR = *ureg; 	/*	 * in pxe-loaded bootstraps, the l.s real-mode code is already	 * below 64K, but for pbs-loaded bootstraps, we need to copy it there.	 */	ip = (void *)realmodeintrinst;		/* the INT instruction */	ip[1] = ureg->trap;			/* insert INT number */	coherence();	if ((uintptr)KTZERO == KZERO+PXEBASE)	/* pxe-loaded? */		rmseg = 0;			/* into JMPFAR instr. */	else {		/* copy l.s so that it can be run from 16-bit mode */		sz = (char *)realmodeend - (char *)KTZERO;		if (sz > RMSIZE)			panic("real mode code %d bytes > %d", sz, RMSIZE);		rmseg = (RMCODE - KZERO) >> 4;	/* into JMPFAR instr. */		memmove((void*)RMCODE, (void*)KTZERO, sz);	}	coherence(); 	s = splhi();	m->pdb[PDX(0)] = m->pdb[PDX(KZERO)];	/* identity map low */	cr3 = getcr3();	putcr3(PADDR(m->pdb));	if (arch)		arch->introff();	else		i8259off(); 	realmode0();	splhi();				/* who knows what the bios did */ 	if(m->tss){		/*		 * Called from memory.c before initialization of mmu.		 * Don't turn interrupts on before the kernel is ready!		 */		if (arch)			arch->intron();		else			i8259on();	}	m->pdb[PDX(0)] = 0;	/* remove low mapping */	putcr3(cr3);	splx(s); 	*ureg = *(Ureg *)RMUADDR;	if (!beenhere) {		beenhere = 1;		iprint("and back\n");	}	qunlock(&rmlock);}