harvey/sys/src/9/rb/faultmips.c

#include	"u.h"
#include	"../port/lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"ureg.h"
#include	"../port/error.h"
#include	"io.h"

enum {
	Debug = 0,
};

typedef struct Fault Fault;
struct Fault {
	uintptr	va;
	ulong	pid;
	uintptr	pc;
	int	cnt;
	char	*prog;
	int	code;
};

extern char *excname[];

static Fault lflt, maxflt;

/*
 * Ask if the instruction at EPC could have cause this badvaddr
 */
int
tstbadvaddr(Ureg *ur)
{
	int rn;
	ulong iw, off, ea;

	iw = ur->pc;
	if(ur->cause & BD)
		iw += 4;

	if(seg(up, iw, 0) == 0)
		return 0;

	iw = *(ulong*)iw;

/*	print("iw: %#lux\n", iw);	/**/

	switch((iw>>26) & 0x3f) {
	default:
		return 1;
	case 0x20:	/* LB */
	case 0x24:	/* LBU */
			/* LD */
	case 0x35:
	case 0x36:
	case 0x37:	/* LDCz */
	case 0x1A:	/* LDL */
	case 0x1B:	/* LDR */
	case 0x21:	/* LH */
	case 0x25:	/* LHU */
	case 0x30:	/* LL */
	case 0x34:	/* LLD */
	case 0x23:	/* LW */
	case 0x31:
	case 0x32:	/* LWCz possible 0x33 */
	case 0x27:	/* LWU */
	case 0x22:	/* LWL */
	case 0x26:	/* LWR */
		break;

	case 0x28:	/* SB */
	case 0x38:	/* SC */
	case 0x3C:	/* SCD */
	case 0x3D:
	case 0x3E:
	case 0x3F:	/* SDCz */
	case 0x2C:	/* SDL */
	case 0x2D:	/* SDR */
	case 0x29:	/* SH */
	case 0x2B:	/* SW */
	case 0x39:
	case 0x3A:	/* SWCz */
	case 0x2A:	/* SWL */
	case 0x2E:	/* SWR */
		break;
	}

	off = iw & 0xffff;
	if(off & 0x8000)
		off |= ~0xffff;

	rn = (iw>>21) & 0x1f;
	ea = *reg(ur, rn);
	if(rn == 0)
		ea = 0;
	ea += off;

	/* print("ea %#lux %#lux(R%d) bv %#lux pc %#lux\n", ea, off, rn, ur->badvaddr, ur->pc); /**/

	if(ur->badvaddr == ea)
		return 0;

	return 1;
}

/*
 * we think we get consecutive page faults from unlucky combinations of
 * scheduling and stlb hashes, and they only happen with 16K pages.
 * however, we also get page faults while servicing the exact same fault.
 * more than 5 consecutive faults is unusual, now that we have a better
 * hash function.
 *
 * this can be helpful during mmu and cache debugging.
 */
static int
ckfaultstuck(Ureg *ur, int read, int code)
{
	uintptr pc, va;

	va = ur->badvaddr;
	pc = ur->pc;
	if (va != lflt.va || up->pid != lflt.pid || pc != lflt.pc ||
	    code != lflt.code) {
		/* at least one address or cause is different from last time */
		lflt.cnt = 1;
		lflt.va = va;
		lflt.pid = up->pid;
		lflt.pc = pc;
		lflt.code = code;
		return 0;
	}
	++lflt.cnt;
	if (lflt.cnt >= 1000)	/* fixfault() isn't fixing underlying cause? */
		panic("fault: %d consecutive faults for va %#p", lflt.cnt, va);
	if (lflt.cnt > maxflt.cnt) {
		maxflt.cnt = lflt.cnt;
		maxflt.va = va;
		maxflt.pid = up->pid;
		maxflt.pc = pc;
		kstrdup(&maxflt.prog, up->text);
	}

	/* we're servicing that fault now! */
	/* adjust the threshold and program name to suit */
	if (lflt.cnt < 5 || strncmp(up->text, "8l", 2) != 0)
		return 0;
	iprint("%d consecutive faults for va %#p at pc %#p in %s "
		"pid %ld\n", lflt.cnt, lflt.va, pc, up->text, lflt.pid);
	iprint("\t%s: %s%s r31 %#lux tlbvirt %#lux\n",
		excname[code], va == pc? "[instruction] ": "",
		(read? "read": "write"), ur->r31, tlbvirt());
	return 0;
}

char *
faultsprint(char *p, char *ep)
{
	if (Debug)
		p = seprint(p, ep,
			"max consecutive faults %d for va %#p in %s\n",
			maxflt.cnt, maxflt.va, maxflt.prog);
	return p;
}

/*
 *  find out fault address and type of access.
 *  Call common fault handler.
 */
void
faultmips(Ureg *ur, int user, int code)
{
	int read;
	ulong addr;
	char *p, buf[ERRMAX];
	static int infault, printed;

	if (0 && infault && !printed) {
		printed = 1;
		print("fault: recursive fault (%d deep) pc %#p va %#p\n",
			infault+1, ur->pc, ur->badvaddr);
	}
	infault++;
	if(waserror()){
		infault--;
		nexterror();
	}

	addr = ur->badvaddr;
	addr &= ~(BY2PG-1);

	read = !(code==CTLBM || code==CTLBS);

/*	print("fault: %s code %d va %#p pc %#p r31 %#lux tlbvirt %#lux\n",
		up->text, code, ur->badvaddr, ur->pc, ur->r31, tlbvirt());/**/

	if (Debug && ckfaultstuck(ur, read, code) || fault(addr, read) == 0){
		infault--;
		poperror();
		return;
	}

	infault--;
	poperror();

	if(tstbadvaddr(ur)) {
		print("fault: spurious badvaddr %#lux in %s at pc %#lux\n",
			ur->badvaddr, up->text, ur->pc);/**/
		return;
	}

	if(user) {
		p = "store";
		if(read)
			p = "load";
		snprint(buf, sizeof buf, "sys: trap: fault %s addr=%#lux r31=%#lux",
			p, ur->badvaddr, ur->r31);
		postnote(up, 1, buf, NDebug);
		return;
	}

	print("kernel %s vaddr=%#lux\n", excname[code], ur->badvaddr);
	print("st=%#lux pc=%#lux r31=%#lux sp=%#lux\n",
		ur->status, ur->pc, ur->r31, ur->sp);
	dumpregs(ur);
	panic("fault");
}

/*
 * called in sysfile.c
 */
void
evenaddr(ulong addr)
{
	if(addr & 3){
		postnote(up, 1, "sys: odd address", NDebug);
		error(Ebadarg);
	}
}