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