trap.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include	"u.h"
#include	"../port/lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"ureg.h"
#include	"../port/error.h"
#include	"tos.h"
#include	<trace.h>

static Lock vctllock;
Vctl *vctl[256];

void
intrenable(int irq, void (*f)(Ureg*, void*), void* a, char *name)
{
	int vno;
	Vctl *v;

	if(f == nil){
		print("intrenable: nil handler for %d for %s\n",
			irq, name);
		return;
	}

	v = xalloc(sizeof(Vctl));
	v->isintr = 1;
	v->irq = irq;
	v->f = f;
	v->a = a;
	strncpy(v->name, name, KNAMELEN-1);
	v->name[KNAMELEN-1] = 0;

	ilock(&vctllock);
	vno = vectorenable(v);
	if(vno == -1){
		iunlock(&vctllock);
		print("intrenable: couldn't enable irq %d for %s\n",
			irq, v->name);
		xfree(v);
		return;
	}
	v->next = vctl[vno];
	vctl[vno] = v;
	iunlock(&vctllock);
}

void
intrdisable(int irq, void (*f)(Ureg *, void *), void *a, char *name)
{
	Vctl **pv, *v;

	ilock(&vctllock);
	pv = &vctl[irq];
	while (*pv && 
		  ((*pv)->irq != irq || (*pv)->f != f || (*pv)->a != a ||
		   strcmp((*pv)->name, name)))
		pv = &((*pv)->next);

	if(*pv == nil){
		print("intrdisable: irq %d not found\n", irq);
		iunlock(&vctllock);
		return;
	}

	v = *pv;
	*pv = (*pv)->next;	/* Link out the entry */
	
	if(vctl[irq] == nil)
		vectordisable(v);
	iunlock(&vctllock);
	xfree(v);
}

void	syscall(Ureg*);
void	noted(Ureg*, ulong);
static void _dumpstack(Ureg*);

char *excname[] =
{
	"reserved 0",
	"system reset",
	"machine check",
	"data access",
	"instruction access",
	"external interrupt",
	"alignment",
	"program exception",
	"floating-point unavailable",
	"decrementer",
	"reserved A",
	"reserved B",
	"system call",
	"trace trap",
	"floating point assist",
	"reserved F",
	"reserved 10",
	"data load translation miss",
	"data store translation miss",
	"instruction address breakpoint",
	"system management interrupt",
};

char *fpcause[] =
{
	"inexact operation",
	"division by zero",
	"underflow",
	"overflow",
	"invalid operation",
};
char	*fpexcname(Ureg*, ulong, char*);
#define FPEXPMASK	0xfff80300		/* Floating exception bits in fpscr */


char *regname[]={
	"CAUSE",	"SRR1",
	"PC",		"GOK",
	"LR",		"CR",
	"XER",		"CTR",
	"R0",		"R1",
	"R2",		"R3",
	"R4",		"R5",
	"R6",		"R7",
	"R8",		"R9",
	"R10",		"R11",
	"R12",		"R13",
	"R14",		"R15",
	"R16",		"R17",
	"R18",		"R19",
	"R20",		"R21",
	"R22",		"R23",
	"R24",		"R25",
	"R26",		"R27",
	"R28",		"R29",
	"R30",		"R31",
	"DCMP",		"ICMP",
	"DMISS",	"IMISS",
	"HASH1",	"HASH2",
	"DAR",		"DSISR",
};

void
kexit(Ureg*)
{
	uvlong t;
	Tos *tos;

	/* precise time accounting, kernel exit */
	tos = (Tos*)(USTKTOP-sizeof(Tos));
	cycles(&t);
	tos->kcycles += t - up->kentry;
	tos->pcycles = up->pcycles;
	tos->pid = up->pid;
}

void
trap(Ureg *ureg)
{
	int ecode, user;
	char buf[ERRMAX], *s;
	extern FPsave initfp;

	ecode = (ureg->cause >> 8) & 0xff;
	user = (ureg->srr1 & MSR_PR) != 0;
	if(user){
		cycles(&up->kentry);
		up->dbgreg = ureg;
	}
	if(ureg->status & MSR_RI == 0)
		print("double fault?: ecode = %d\n", ecode);

	switch(ecode) {
	case CEI:
		m->intr++;
		intr(ureg);
		break;
	case CDEC:
		clockintr(ureg);
		break;
	case CDSI:
		m->pfault++;
		if (up == nil){
			dumpregs(ureg);
			panic("kernel fault");
		}
		up->mmureg = ureg;
		faultpower(ureg, ureg->dar, (ureg->dsisr & BIT(6)) == 0);
		break;
	case CISI:
		m->pfault++;
		if (up == nil){
			dumpregs(ureg);
			panic("kernel fault");
		}
		up->mmureg = ureg;
		faultpower(ureg, ureg->pc, 1);
		break;
	case CIMISS:	/* instruction miss */
		if (up == nil){
			dumpregs(ureg);
			panic("kernel fault");
		}
		up->mmureg = ureg;
		faultpower(ureg, ureg->imiss, 1);
		break;
	case CLMISS:	/* data load miss */
		if (up == nil){
			dumpregs(ureg);
			panic("kernel fault");
		}
		up->mmureg = ureg;
		faultpower(ureg, ureg->dmiss, 1);
		break;
	case CSMISS:	/* data store miss */
		if (up == nil){
			dumpregs(ureg);
			panic("kernel fault");
		}
		up->mmureg = ureg;
		faultpower(ureg, ureg->dmiss, 0);
		break;

	case CSYSCALL:
		if(!user)
			panic("syscall in kernel: srr1 0x%4.4luX\n", ureg->srr1);
		syscall(ureg);
		if (up->delaysched){
			sched();
			splhi();
		}
		kexit(ureg);
		return;		/* syscall() calls notify itself, don't do it again */

	case CFPU:
		if(!user || up == nil) {
			dumpregs(ureg);
			panic("floating point in kernel");
		}
		switch(up->fpstate){
		case FPinit:
			fprestore(&initfp);
			up->fpstate = FPactive;
			break;
		case FPinactive:
			fprestore(&up->fpsave);
			up->fpstate = FPactive;
			break;
		case FPactive:
			print("up->fpstate %d\n", up->fpstate);
			delay(100);
			dumpregs(ureg);
			delay(200);
			panic("fpstate");
			break;
		default:
			if(user){
				spllo();
				sprint(buf, "sys: floating point in note handler:");
				postnote(up, 1, buf, NDebug);
				break;
			}
			panic("kernel fpstate illegal");
		}
		ureg->srr1 |= MSR_FP;
		break;
	case CPROG:
		if(ureg->status & (1<<19))
			s = "floating point exception";
		else if(ureg->status & (1<<18))
			s = "illegal instruction";
		else if(ureg->status & (1<<17))
			s = "privileged instruction";
		else
			s = "undefined program exception";
		if(user){
			spllo();
			sprint(buf, "sys: trap: %s", s);
			postnote(up, 1, buf, NDebug);
			break;
		}
		dumpregs(ureg);
		panic(s);
		break;
	default:
		if(ecode <= nelem(excname) && user){
			spllo();
			sprint(buf, "sys: trap: %s", excname[ecode]);
			postnote(up, 1, buf, NDebug);
			break;
		}
		dumpregs(ureg);
		if(ecode < nelem(excname))
			panic("%s", excname[ecode]);
		panic("unknown trap/intr: %d\n", ecode);
	}

	/* restoreureg must execute at high IPL */
	splhi();

	/* delaysched set because we held a lock or because our quantum ended */
	if(up && up->delaysched && ecode == CDEC){
		sched();
		splhi();
	}

	if(user) {
		if (up->fpstate == FPactive && (ureg->srr1 & MSR_FP) == 0){
			postnote(up, 1, buf, NDebug);
		}
		notify(ureg);
		if(up->fpstate != FPactive)
			ureg->srr1 &= ~MSR_FP;
		kexit(ureg);
	}
}

void
faultpower(Ureg *ureg, ulong addr, int read)
{
	int user, insyscall, n;
	char buf[ERRMAX];

	user = (ureg->srr1 & MSR_PR) != 0;
	insyscall = up->insyscall;
	up->insyscall = 1;
	n = fault(addr, read);
	if(n < 0){
		if(!user){
			dumpregs(ureg);
			panic("fault: 0x%lux", addr);
		}
		sprint(buf, "sys: trap: fault %s addr=0x%lux", read? "read" : "write", addr);
		postnote(up, 1, buf, NDebug);
	}
	up->insyscall = insyscall;
}

void
sethvec(int v, void (*r)(void))
{
	ulong *vp, pa, o;

	vp = KADDR(v);
	vp[0] = 0x7c1043a6;			/* MOVW R0, SPR(SPRG0) */
	vp[1] = 0x7c0802a6;			/* MOVW LR, R0 */
	vp[2] = 0x7c1243a6;			/* MOVW R0, SPR(SPRG2) */
	pa = PADDR(r);
	o = pa >> 25;
	if(o != 0 && o != 0x7F){
		/* a branch too far */
		vp[3] = (15<<26)|(pa>>16);	/* MOVW $r&~0xFFFF, R0 */
		vp[4] = (24<<26)|(pa&0xFFFF);	/* OR $r&0xFFFF, R0 */
		vp[5] = 0x7c0803a6;		/* MOVW	R0, LR */
		vp[6] = 0x4e800021;		/* BL (LR) */
	}else
		vp[3] = (18<<26)|(pa&0x3FFFFFC)|3;	/* bla */
}

void
setmvec(int v, void (*r)(void), void (*t)(void))
{
	ulong *vp, pa, o, n;

	vp = KADDR(v);
	n = 0;
	vp[n++] = 0x7c1043a6;			/* MOVW R0, SPR(SPRG0) */
	vp[n++] = 0x7c0802a6;			/* MOVW LR, R0 */
	vp[n++] = 0x7c1243a6;			/* MOVW R0, SPR(SPRG2) */
	pa = PADDR(r);
	o = pa >> 25;
	if(o != 0 && o != 0x7F){
		/* a branch too far */
		vp[n++] = (15<<26)|(pa>>16);	/* MOVW $r&~0xFFFF, R0 */
		vp[n++] = (24<<26)|(pa&0xFFFF);	/* OR $r&0xFFFF, R0 */
		vp[n++] = 0x7c0803a6;		/* MOVW	R0, LR */
		vp[n++] = 0x4e800021;		/* BL (LR) */
	}else
		vp[n++] = (18<<26)|(pa&0x3FFFFFC)|3;	/* bla */
	pa = PADDR(t);
	o = pa >> 25;
	if(o != 0 && o != 0x7F){
		/* a branch too far */
		vp[n++] = (15<<26)|(pa>>16);	/* MOVW $r&~0xFFFF, R0 */
		vp[n++] = (24<<26)|(pa&0xFFFF);	/* OR $r&0xFFFF, R0 */
		vp[n++] = 0x7c0803a6;		/* MOVW	R0, LR */
		vp[n] = 0x4e800021;		/* BL (LR) */
	}else
		vp[n] = (18<<26)|(pa&0x3FFFFFC)|3;	/* bla */
}

char*
fpexcname(Ureg *ur, ulong fpscr, char *buf)
{
	int i;
	char *s;
	ulong fppc;

	fppc = ur->pc;
	s = 0;
	fpscr >>= 3;		/* trap enable bits */
	fpscr &= (fpscr>>22);	/* anded with exceptions */
	for(i=0; i<5; i++)
		if(fpscr & (1<<i))
			s = fpcause[i];
	if(s == 0)
		return "no floating point exception";
	sprint(buf, "%s fppc=0x%lux", s, fppc);
	return buf;
}

/*
 * Fill in enough of Ureg to get a stack trace, and call a function.
 * Used by debugging interface rdb.
 */

static void
getpcsp(ulong *pc, ulong *sp)
{
	*pc = getcallerpc(&pc);
	*sp = (ulong)&pc-4;
}

void
callwithureg(void (*fn)(Ureg*))
{
	Ureg ureg;

	getpcsp((ulong*)&ureg.pc, (ulong*)&ureg.sp);