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#include	"u.h"
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#include	"../port/lib.h"
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#include	"mem.h"
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#include	"dat.h"
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#include	"fns.h"
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#include	"io.h"
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#include	"ureg.h"
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#include	"../port/error.h"
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/*
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 * Back the processor into real mode to run a BIOS call,
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 * then return.  This must be used carefully, since it
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 * completely disables hardware interrupts (e.g., the i8259)
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 * while running.  It is *not* using VM86 mode.
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 * Maybe that's really the right answer, but real mode
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 * is fine for now.  We don't expect to use this very much --
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 * just for BIOS INT 13 disk i/o.
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 */
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void realmode0(void);		/* in realmode0.s */
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void realmodeintrinst(void);	/* in realmode0.s */
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void realmodeend(void);		/* in realmode0.s */
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extern ushort rmseg;		/* in realmode0.s */
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static Ureg rmu;
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static QLock rmlock;
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static int beenhere;
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void
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realmode(Ureg *ureg)
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{
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	int s, sz;
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	ulong cr3;
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	uchar *ip;
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	qlock(&rmlock);
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	if (!beenhere)
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		iprint("into bios in real mode...");
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	*(Ureg *)RMUADDR = *ureg;
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	/*
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	 * in pxe-loaded bootstraps, the l.s real-mode code is already
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	 * below 64K, but for pbs-loaded bootstraps, we need to copy it there.
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	 */
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	ip = (void *)realmodeintrinst;		/* the INT instruction */
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	ip[1] = ureg->trap;			/* insert INT number */
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	coherence();
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	if ((uintptr)KTZERO == KZERO+PXEBASE)	/* pxe-loaded? */
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		rmseg = 0;			/* into JMPFAR instr. */
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	else {
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		/* copy l.s so that it can be run from 16-bit mode */
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		sz = (char *)realmodeend - (char *)KTZERO;
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		if (sz > RMSIZE)
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			panic("real mode code %d bytes > %d", sz, RMSIZE);
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		rmseg = (RMCODE - KZERO) >> 4;	/* into JMPFAR instr. */
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		memmove((void*)RMCODE, (void*)KTZERO, sz);
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	}
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	coherence();
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	s = splhi();
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	m->pdb[PDX(0)] = m->pdb[PDX(KZERO)];	/* identity map low */
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	cr3 = getcr3();
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	putcr3(PADDR(m->pdb));
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	if (arch)
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		arch->introff();
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	else
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		i8259off();
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	realmode0();
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	splhi();				/* who knows what the bios did */
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	if(m->tss){
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		/*
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		 * Called from memory.c before initialization of mmu.
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		 * Don't turn interrupts on before the kernel is ready!
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		 */
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		if (arch)
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			arch->intron();
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		else
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			i8259on();
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	}
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	m->pdb[PDX(0)] = 0;	/* remove low mapping */
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	putcr3(cr3);
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	splx(s);
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	*ureg = *(Ureg *)RMUADDR;
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	if (!beenhere) {
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		beenhere = 1;
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		iprint("and back\n");
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	}
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	qunlock(&rmlock);
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}