77ddc8c654
This change makes it mandatory for programs to call segflush() on code that is not in the text segment if they want to execute it. As a side effect, this means that everything but the text segment will be non-executable by default, even without the SG_NOEXEC attribute. Segments with the SG_NOEXEC attribute never become executable, even when segflush() is called on them.
457 lines
8.1 KiB
C
457 lines
8.1 KiB
C
#include "u.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 "../port/error.h"
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static void
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faulterror(char *s, Chan *c)
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{
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char buf[ERRMAX];
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if(c != nil)
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snprint(buf, sizeof buf, "sys: %s accessing %s: %s", s, chanpath(c), up->errstr);
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else
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snprint(buf, sizeof buf, "sys: %s", s);
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if(up->nerrlab) {
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if(up->kp == 0)
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postnote(up, 1, buf, NDebug);
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error(s);
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}
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pprint("suicide: %s\n", buf);
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pexit(s, 1);
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}
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static void
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pio(Segment *s, uintptr addr, uintptr soff, Page **p)
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{
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Page *new;
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KMap *k;
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Chan *c;
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int n, ask;
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char *kaddr;
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uintptr daddr;
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Page *loadrec;
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retry:
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loadrec = *p;
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if(loadrec == nil) { /* from a text/data image */
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daddr = s->fstart+soff;
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new = lookpage(s->image, daddr);
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if(new != nil) {
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*p = new;
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return;
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}
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c = s->image->c;
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ask = BY2PG;
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if(soff >= s->flen)
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ask = 0;
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else if((soff+ask) > s->flen)
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ask = s->flen-soff;
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}
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else { /* from a swap image */
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daddr = swapaddr(loadrec);
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new = lookpage(&swapimage, daddr);
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if(new != nil) {
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putswap(loadrec);
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*p = new;
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return;
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}
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c = swapimage.c;
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ask = BY2PG;
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}
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qunlock(s);
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new = newpage(0, 0, addr);
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k = kmap(new);
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kaddr = (char*)VA(k);
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while(waserror()) {
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if(strcmp(up->errstr, Eintr) == 0)
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continue;
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kunmap(k);
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putpage(new);
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faulterror(Eioload, c);
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}
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n = devtab[c->type]->read(c, kaddr, ask, daddr);
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if(n != ask)
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error(Eshort);
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if(ask < BY2PG)
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memset(kaddr+ask, 0, BY2PG-ask);
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poperror();
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kunmap(k);
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qlock(s);
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if(loadrec == nil) { /* This is demand load */
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/*
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* race, another proc may have gotten here first while
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* s was unlocked
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*/
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if(*p == nil) {
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/*
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* check page cache again after i/o to reduce double caching
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*/
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*p = lookpage(s->image, daddr);
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if(*p == nil) {
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incref(new);
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new->daddr = daddr;
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cachepage(new, s->image);
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*p = new;
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}
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}
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}
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else { /* This is paged out */
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/*
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* race, another proc may have gotten here first
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* (and the pager may have run on that page) while
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* s was unlocked
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*/
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if(*p != loadrec) {
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if(!pagedout(*p)) {
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/* another process did it for me */
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goto done;
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} else if(*p != nil) {
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/* another process and the pager got in */
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putpage(new);
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goto retry;
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} else {
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/* another process segfreed the page */
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incref(new);
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k = kmap(new);
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memset((void*)VA(k), 0, ask);
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kunmap(k);
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*p = new;
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goto done;
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}
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}
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incref(new);
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new->daddr = daddr;
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cachepage(new, &swapimage);
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*p = new;
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putswap(loadrec);
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}
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done:
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putpage(new);
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if(s->flushme)
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(*p)->txtflush = ~0;
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}
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static int
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fixfault(Segment *s, uintptr addr, int read)
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{
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Pte **pte, *etp;
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uintptr soff, mmuphys;
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Page **pg, *old, *new;
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addr &= ~(BY2PG-1);
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soff = addr-s->base;
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pte = &s->map[soff/PTEMAPMEM];
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if((etp = *pte) == nil)
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*pte = etp = ptealloc();
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pg = &etp->pages[(soff&(PTEMAPMEM-1))/BY2PG];
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if(pg < etp->first)
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etp->first = pg;
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if(pg > etp->last)
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etp->last = pg;
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switch(s->type & SG_TYPE) {
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default:
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panic("fault");
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return -1;
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case SG_TEXT: /* Demand load */
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if(pagedout(*pg))
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pio(s, addr, soff, pg);
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mmuphys = PPN((*pg)->pa) | PTERONLY | PTECACHED | PTEVALID;
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(*pg)->modref = PG_REF;
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break;
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case SG_BSS:
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case SG_SHARED: /* Zero fill on demand */
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case SG_STACK:
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if(*pg == nil) {
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new = newpage(1, &s, addr);
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if(s == nil)
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return -1;
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*pg = new;
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}
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/* wet floor */
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case SG_DATA: /* Demand load/pagein/copy on write */
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if(pagedout(*pg))
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pio(s, addr, soff, pg);
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/*
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* It's only possible to copy on write if
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* we're the only user of the segment.
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*/
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if(read && conf.copymode == 0 && s->ref == 1) {
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mmuphys = PPN((*pg)->pa) | PTERONLY | PTECACHED | PTEVALID;
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(*pg)->modref |= PG_REF;
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break;
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}
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old = *pg;
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if(old->image == &swapimage && (old->ref + swapcount(old->daddr)) == 1)
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uncachepage(old);
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if(old->ref > 1 || old->image != nil) {
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new = newpage(0, &s, addr);
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if(s == nil)
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return -1;
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if(s->flushme)
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new->txtflush = ~0;
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*pg = new;
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copypage(old, *pg);
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putpage(old);
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}
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/* wet floor */
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case SG_STICKY: /* Never paged out */
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mmuphys = PPN((*pg)->pa) | PTEWRITE | PTECACHED | PTEVALID;
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(*pg)->modref = PG_MOD|PG_REF;
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break;
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case SG_FIXED: /* Never paged out */
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mmuphys = PPN((*pg)->pa) | PTEWRITE | PTEUNCACHED | PTEVALID;
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(*pg)->modref = PG_MOD|PG_REF;
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break;
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}
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#ifdef PTENOEXEC
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if((s->type & SG_NOEXEC) != 0 || s->flushme == 0)
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mmuphys |= PTENOEXEC;
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#endif
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qunlock(s);
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putmmu(addr, mmuphys, *pg);
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return 0;
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}
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static void
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mapphys(Segment *s, uintptr addr, int attr)
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{
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uintptr mmuphys;
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Page pg = {0};
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addr &= ~(BY2PG-1);
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pg.ref = 1;
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pg.va = addr;
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pg.pa = s->pseg->pa+(addr-s->base);
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if(s->flushme)
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pg.txtflush = ~0;
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mmuphys = PPN(pg.pa) | PTEVALID;
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if((attr & SG_RONLY) == 0)
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mmuphys |= PTEWRITE;
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else
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mmuphys |= PTERONLY;
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#ifdef PTENOEXEC
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if((attr & SG_NOEXEC) != 0 || s->flushme == 0)
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mmuphys |= PTENOEXEC;
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#endif
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#ifdef PTEDEVICE
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if((attr & SG_DEVICE) != 0)
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mmuphys |= PTEDEVICE;
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else
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#endif
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if((attr & SG_CACHED) == 0)
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mmuphys |= PTEUNCACHED;
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else
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mmuphys |= PTECACHED;
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qunlock(s);
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putmmu(addr, mmuphys, &pg);
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}
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int
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fault(uintptr addr, uintptr pc, int read)
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{
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Segment *s;
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char *sps;
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int pnd, attr;
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if(up == nil)
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panic("fault: nil up");
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if(up->nlocks){
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Lock *l = up->lastlock;
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print("fault: nlocks %d, proc %lud %s, addr %#p, lock %#p, lpc %#p\n",
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up->nlocks, up->pid, up->text, addr, l, l ? l->pc : 0);
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}
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pnd = up->notepending;
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sps = up->psstate;
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up->psstate = "Fault";
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m->pfault++;
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for(;;) {
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spllo();
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s = seg(up, addr, 1); /* leaves s locked if seg != nil */
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if(s == nil) {
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up->psstate = sps;
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return -1;
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}
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attr = s->type;
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if((attr & SG_TYPE) == SG_PHYSICAL)
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attr |= s->pseg->attr;
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if((attr & SG_FAULT) != 0
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|| read? ((attr & SG_NOEXEC) != 0 || s->flushme == 0) && (addr & -BY2PG) == (pc & -BY2PG):
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(attr & SG_RONLY) != 0) {
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qunlock(s);
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up->psstate = sps;
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if(up->kp && up->nerrlab) /* for segio */
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error(Eio);
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return -1;
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}
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if((attr & SG_TYPE) == SG_PHYSICAL){
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mapphys(s, addr, attr);
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break;
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}
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if(fixfault(s, addr, read) == 0)
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break;
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splhi();
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switch(up->procctl){
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case Proc_exitme:
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case Proc_exitbig:
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procctl();
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}
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}
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up->psstate = sps;
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up->notepending |= pnd;
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return 0;
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}
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/*
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* Called only in a system call
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*/
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int
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okaddr(uintptr addr, ulong len, int write)
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{
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Segment *s;
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if((long)len >= 0 && len <= -addr) {
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for(;;) {
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s = seg(up, addr, 0);
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if(s == nil || (write && (s->type&SG_RONLY)))
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break;
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if(addr+len > s->top) {
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len -= s->top - addr;
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addr = s->top;
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continue;
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}
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return 1;
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}
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}
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return 0;
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}
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void
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validaddr(uintptr addr, ulong len, int write)
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{
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if(!okaddr(addr, len, write)){
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pprint("suicide: invalid address %#p/%lud in sys call pc=%#p\n", addr, len, userpc());
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postnote(up, 1, "sys: bad address in syscall", NDebug);
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error(Ebadarg);
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}
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}
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/*
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* &s[0] is known to be a valid address.
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*/
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void*
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vmemchr(void *s, int c, ulong n)
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{
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uintptr a;
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ulong m;
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void *t;
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a = (uintptr)s;
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for(;;){
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m = BY2PG - (a & (BY2PG-1));
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if(n <= m)
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break;
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/* spans pages; handle this page */
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t = memchr((void*)a, c, m);
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if(t != nil)
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return t;
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a += m;
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n -= m;
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if(a < KZERO)
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validaddr(a, 1, 0);
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}
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/* fits in one page */
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return memchr((void*)a, c, n);
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}
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Segment*
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seg(Proc *p, uintptr addr, int dolock)
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{
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Segment **s, **et, *n;
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et = &p->seg[NSEG];
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for(s = p->seg; s < et; s++) {
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if((n = *s) == nil)
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continue;
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if(addr >= n->base && addr < n->top) {
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if(dolock == 0)
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return n;
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qlock(n);
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if(addr >= n->base && addr < n->top)
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return n;
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qunlock(n);
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}
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}
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return nil;
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}
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extern void checkmmu(uintptr, uintptr);
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void
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checkpages(void)
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{
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uintptr addr, off;
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Pte *p;
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Page *pg;
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Segment **sp, **ep, *s;
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if(up == nil)
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return;
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for(sp=up->seg, ep=&up->seg[NSEG]; sp<ep; sp++){
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if((s = *sp) == nil)
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continue;
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qlock(s);
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if(s->mapsize > 0){
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for(addr=s->base; addr<s->top; addr+=BY2PG){
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off = addr - s->base;
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if((p = s->map[off/PTEMAPMEM]) == nil)
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continue;
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pg = p->pages[(off&(PTEMAPMEM-1))/BY2PG];
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if(pagedout(pg))
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continue;
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checkmmu(addr, pg->pa);
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}
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}
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qunlock(s);
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}
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}
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