ref: c1fd7c210bdafe97e7b8d07dc256f4b089df9342
dir: /sys/src/9/port/fault.c/
#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
int
fault(uintptr addr, int read)
{
Segment *s;
char *sps;
int pnd, attr;
if(up == nil)
panic("fault: nil up");
if(up->nlocks){
Lock *l = up->lastlock;
print("fault: nlocks %d, proc %lud %s, addr %#p, lock %#p, lpc %#p\n",
up->nlocks, up->pid, up->text, addr, l, l ? l->pc : 0);
}
pnd = up->notepending;
sps = up->psstate;
up->psstate = "Fault";
m->pfault++;
for(;;) {
spllo();
s = seg(up, addr, 1); /* leaves s locked if seg != nil */
if(s == nil) {
up->psstate = sps;
return -1;
}
attr = s->type;
if((attr & SG_TYPE) == SG_PHYSICAL)
attr |= s->pseg->attr;
if((attr & SG_FAULT) != 0 || !read && (attr & SG_RONLY) != 0) {
qunlock(s);
up->psstate = sps;
return -1;
}
if(fixfault(s, addr, read) == 0)
break;
splhi();
switch(up->procctl){
case Proc_exitme:
case Proc_exitbig:
procctl();
}
}
up->psstate = sps;
up->notepending |= pnd;
return 0;
}
static void
faulterror(char *s, Chan *c)
{
char buf[ERRMAX];
if(c != nil)
snprint(buf, sizeof buf, "sys: %s accessing %s: %s", s, chanpath(c), up->errstr);
else
snprint(buf, sizeof buf, "sys: %s", s);
if(up->nerrlab) {
if(up->kp == 0)
postnote(up, 1, buf, NDebug);
error(s);
}
pprint("suicide: %s\n", buf);
pexit(s, 1);
}
static void
pio(Segment *s, uintptr addr, uintptr soff, Page **p)
{
Page *new;
KMap *k;
Chan *c;
int n, ask;
char *kaddr;
uintptr daddr;
Page *loadrec;
retry:
loadrec = *p;
if(loadrec == nil) { /* from a text/data image */
daddr = s->fstart+soff;
new = lookpage(s->image, daddr);
if(new != nil) {
*p = new;
return;
}
c = s->image->c;
ask = BY2PG;
if(soff >= s->flen)
ask = 0;
else if((soff+ask) > s->flen)
ask = s->flen-soff;
}
else { /* from a swap image */
daddr = swapaddr(loadrec);
new = lookpage(&swapimage, daddr);
if(new != nil) {
putswap(loadrec);
*p = new;
return;
}
c = swapimage.c;
ask = BY2PG;
}
qunlock(s);
new = newpage(0, 0, addr);
k = kmap(new);
kaddr = (char*)VA(k);
while(waserror()) {
if(strcmp(up->errstr, Eintr) == 0)
continue;
kunmap(k);
putpage(new);
faulterror(Eioload, c);
}
n = devtab[c->type]->read(c, kaddr, ask, daddr);
if(n != ask)
error(Eshort);
if(ask < BY2PG)
memset(kaddr+ask, 0, BY2PG-ask);
poperror();
kunmap(k);
qlock(s);
if(loadrec == nil) { /* This is demand load */
/*
* race, another proc may have gotten here first while
* s was unlocked
*/
if(*p == nil) {
/*
* check page cache again after i/o to reduce double caching
*/
*p = lookpage(s->image, daddr);
if(*p == nil) {
incref(new);
new->daddr = daddr;
cachepage(new, s->image);
*p = new;
}
}
}
else { /* This is paged out */
/*
* race, another proc may have gotten here first
* (and the pager may have run on that page) while
* s was unlocked
*/
if(*p != loadrec) {
if(!pagedout(*p)) {
/* another process did it for me */
goto done;
} else if(*p != nil) {
/* another process and the pager got in */
putpage(new);
goto retry;
} else {
/* another process segfreed the page */
incref(new);
k = kmap(new);
memset((void*)VA(k), 0, ask);
kunmap(k);
*p = new;
goto done;
}
}
incref(new);
new->daddr = daddr;
cachepage(new, &swapimage);
*p = new;
putswap(loadrec);
}
done:
putpage(new);
if(s->flushme)
(*p)->txtflush = ~0;
}
void (*checkaddr)(uintptr, Segment *, Page *);
uintptr addr2check;
int
fixfault(Segment *s, uintptr addr, int read)
{
int type;
Pte **pte, *etp;
uintptr soff, mmuphys;
Page **pg, *old, *new;
addr &= ~(BY2PG-1);
soff = addr-s->base;
pte = &s->map[soff/PTEMAPMEM];
if((etp = *pte) == nil)
*pte = etp = ptealloc();
pg = &etp->pages[(soff&(PTEMAPMEM-1))/BY2PG];
if(pg < etp->first)
etp->first = pg;
if(pg > etp->last)
etp->last = pg;
type = s->type & SG_TYPE;
switch(type) {
default:
panic("fault");
return -1;
case SG_TEXT: /* Demand load */
if(pagedout(*pg))
pio(s, addr, soff, pg);
mmuphys = PPN((*pg)->pa) | PTERONLY|PTEVALID;
(*pg)->modref = PG_REF;
break;
case SG_BSS:
case SG_SHARED: /* Zero fill on demand */
case SG_STACK:
if(*pg == nil) {
new = newpage(1, &s, addr);
if(s == nil)
return -1;
*pg = new;
}
/* wet floor */
case SG_DATA: /* Demand load/pagein/copy on write */
if(pagedout(*pg))
pio(s, addr, soff, pg);
/*
* It's only possible to copy on write if
* we're the only user of the segment.
*/
if(read && conf.copymode == 0 && s->ref == 1) {
mmuphys = PPN((*pg)->pa)|PTERONLY|PTEVALID;
(*pg)->modref |= PG_REF;
break;
}
old = *pg;
if(old->image == &swapimage && (old->ref + swapcount(old->daddr)) == 1)
uncachepage(old);
if(old->ref > 1 || old->image != nil) {
new = newpage(0, &s, addr);
if(s == nil)
return -1;
if(s->flushme)
new->txtflush = ~0;
*pg = new;
copypage(old, *pg);
putpage(old);
}
mmuphys = PPN((*pg)->pa) | PTEWRITE | PTEVALID;
(*pg)->modref = PG_MOD|PG_REF;
break;
case SG_PHYSICAL:
if(*pg == nil){
new = smalloc(sizeof(Page));
new->va = addr;
new->pa = s->pseg->pa+(addr-s->base);
new->ref = 1;
*pg = new;
}
/* wet floor */
case SG_FIXED: /* Never paged out */
if (checkaddr && addr == addr2check)
(*checkaddr)(addr, s, *pg);
mmuphys = PPN((*pg)->pa) |PTEWRITE|PTEUNCACHED|PTEVALID;
(*pg)->modref = PG_MOD|PG_REF;
break;
}
qunlock(s);
putmmu(addr, mmuphys, *pg);
return 0;
}
/*
* Called only in a system call
*/
int
okaddr(uintptr addr, ulong len, int write)
{
Segment *s;
if((long)len >= 0 && len <= -addr) {
for(;;) {
s = seg(up, addr, 0);
if(s == nil || (write && (s->type&SG_RONLY)))
break;
if(addr+len > s->top) {
len -= s->top - addr;
addr = s->top;
continue;
}
return 1;
}
}
return 0;
}
void
validaddr(uintptr addr, ulong len, int write)
{
if(!okaddr(addr, len, write)){
pprint("suicide: invalid address %#p/%lud in sys call pc=%#p\n", addr, len, userpc());
postnote(up, 1, "sys: bad address in syscall", NDebug);
error(Ebadarg);
}
}
/*
* &s[0] is known to be a valid address.
*/
void*
vmemchr(void *s, int c, ulong n)
{
uintptr a;
ulong m;
void *t;
a = (uintptr)s;
for(;;){
m = BY2PG - (a & (BY2PG-1));
if(n <= m)
break;
/* spans pages; handle this page */
t = memchr((void*)a, c, m);
if(t != nil)
return t;
a += m;
n -= m;
if(a < KZERO)
validaddr(a, 1, 0);
}
/* fits in one page */
return memchr((void*)a, c, n);
}
Segment*
seg(Proc *p, uintptr addr, int dolock)
{
Segment **s, **et, *n;
et = &p->seg[NSEG];
for(s = p->seg; s < et; s++) {
if((n = *s) == nil)
continue;
if(addr >= n->base && addr < n->top) {
if(dolock == 0)
return n;
qlock(n);
if(addr >= n->base && addr < n->top)
return n;
qunlock(n);
}
}
return nil;
}
extern void checkmmu(uintptr, uintptr);
void
checkpages(void)
{
uintptr addr, off;
Pte *p;
Page *pg;
Segment **sp, **ep, *s;
if(up == nil)
return;
for(sp=up->seg, ep=&up->seg[NSEG]; sp<ep; sp++){
if((s = *sp) == nil)
continue;
qlock(s);
for(addr=s->base; addr<s->top; addr+=BY2PG){
off = addr - s->base;
if((p = s->map[off/PTEMAPMEM]) == nil)
continue;
pg = p->pages[(off&(PTEMAPMEM-1))/BY2PG];
if(pagedout(pg))
continue;
checkmmu(addr, pg->pa);
}
qunlock(s);
}
}