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#include	"u.h"
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#include	"tos.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 VGA and APM.
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 */
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#define realmoderegs (*(Ureg*)RMUADDR)
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#define LORMBUF (RMBUF-KZERO)
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static Ureg rmu;
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static Lock rmlock;
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void
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realmode(Ureg *ureg)
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{
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	int s;
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	ulong cr3;
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	extern void realmode0(void);	/* in l.s */
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	if(getconf("*norealmode"))
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		return;
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	lock(&rmlock);
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	realmoderegs = *ureg;
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	/* copy l.s so that it can be run from 16-bit mode */
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	memmove((void*)RMCODE, (void*)KTZERO, 0x1000);
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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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	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 = realmoderegs;
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	unlock(&rmlock);
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}
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static long
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rtrapread(Chan*, void *a, long n, vlong off)
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{
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	if(off < 0)
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		error("badarg");
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	if(n+off > sizeof rmu)
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		n = sizeof rmu - off;
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	if(n <= 0)
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		return 0;
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	memmove(a, (char*)&rmu+off, n);
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	return n;
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}
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static long
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rtrapwrite(Chan*, void *a, long n, vlong off)
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{
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	if(off || n != sizeof rmu)
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		error("write a Ureg");
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	memmove(&rmu, a, sizeof rmu);
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	/*
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	 * Sanity check
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	 */
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	if(rmu.trap == 0x10){	/* VBE */
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		rmu.es = (LORMBUF>>4)&0xF000;
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		rmu.di = LORMBUF&0xFFFF;
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	}else
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		error("invalid trap arguments");
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	realmode(&rmu);
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	return n;
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}
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static long
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rmemrw(int isr, void *a, long n, vlong off)
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{
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	if(off < 0 || n < 0)
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		error("bad offset/count");
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	if(isr){
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		if(off >= MB)
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			return 0;
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		if(off+n >= MB)
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			n = MB - off;
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		memmove(a, KADDR((ulong)off), n);
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	}else{
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		/* realmode buf page ok, allow vga framebuf's access */
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		if(off >= MB || off+n > MB ||
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		    (off < LORMBUF || off+n > LORMBUF+BY2PG) &&
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		    (off < 0xA0000 || off+n > 0xB0000+0x10000))
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			error("bad offset/count in write");
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		memmove(KADDR((ulong)off), a, n);
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	}
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	return n;
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}
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static long
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rmemread(Chan*, void *a, long n, vlong off)
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{
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	return rmemrw(1, a, n, off);
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}
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static long
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rmemwrite(Chan*, void *a, long n, vlong off)
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{
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	return rmemrw(0, a, n, off);
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}
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void
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realmodelink(void)
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{
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	addarchfile("realmode", 0660, rtrapread, rtrapwrite);
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	addarchfile("realmodemem", 0660, rmemread, rmemwrite);
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}
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