1 #include "u.h"
2 #include "../port/lib.h"
3 #include "mem.h"
4 #include "dat.h"
5 #include "fns.h"
6 #include "../port/error.h"
7
8 int
fault(ulong addr,int read)9 fault(ulong addr, int read)
10 {
11 Segment *s;
12 char *sps;
13
14 if(up == nil)
15 panic("fault: nil up");
16 if(up->nlocks.ref)
17 print("fault: addr %#p: nlocks %ld\n", addr, up->nlocks.ref);
18
19 sps = up->psstate;
20 up->psstate = "Fault";
21 spllo();
22
23 m->pfault++;
24 for(;;) {
25 s = seg(up, addr, 1); /* leaves s->lk qlocked if seg != nil */
26 if(s == 0) {
27 up->psstate = sps;
28 return -1;
29 }
30
31 if(!read && (s->type&SG_RONLY)) {
32 qunlock(&s->lk);
33 up->psstate = sps;
34 return -1;
35 }
36
37 if(fixfault(s, addr, read, 1) == 0) /* qunlocks s->lk */
38 break;
39 }
40
41 up->psstate = sps;
42 return 0;
43 }
44
45 static void
faulterror(char * s,Chan * c,int freemem)46 faulterror(char *s, Chan *c, int freemem)
47 {
48 char buf[ERRMAX];
49
50 if(c && c->path){
51 snprint(buf, sizeof buf, "%s accessing %s: %s", s, c->path->s, up->errstr);
52 s = buf;
53 }
54 if(up->nerrlab) {
55 postnote(up, 1, s, NDebug);
56 error(s);
57 }
58 pexit(s, freemem);
59 }
60
61 void (*checkaddr)(ulong, Segment *, Page *);
62 ulong addr2check;
63
64 int
fixfault(Segment * s,ulong addr,int read,int doputmmu)65 fixfault(Segment *s, ulong addr, int read, int doputmmu)
66 {
67 int type;
68 int ref;
69 Pte **p, *etp;
70 ulong mmuphys=0, soff;
71 Page **pg, *lkp, *new;
72 Page *(*fn)(Segment*, ulong);
73
74 addr &= ~(BY2PG-1);
75 soff = addr-s->base;
76 p = &s->map[soff/PTEMAPMEM];
77 if(*p == 0)
78 *p = ptealloc();
79
80 etp = *p;
81 pg = &etp->pages[(soff&(PTEMAPMEM-1))/BY2PG];
82 type = s->type&SG_TYPE;
83
84 if(pg < etp->first)
85 etp->first = pg;
86 if(pg > etp->last)
87 etp->last = pg;
88
89 switch(type) {
90 default:
91 panic("fault");
92 break;
93
94 case SG_TEXT: /* Demand load */
95 if(pagedout(*pg))
96 pio(s, addr, soff, pg);
97
98 mmuphys = PPN((*pg)->pa) | PTERONLY|PTEVALID;
99 (*pg)->modref = PG_REF;
100 break;
101
102 case SG_BSS:
103 case SG_SHARED: /* Zero fill on demand */
104 case SG_STACK:
105 if(*pg == 0) {
106 new = newpage(1, &s, addr);
107 if(s == 0)
108 return -1;
109
110 *pg = new;
111 }
112 goto common;
113
114 case SG_DATA:
115 common: /* Demand load/pagein/copy on write */
116 if(pagedout(*pg))
117 pio(s, addr, soff, pg);
118
119 /*
120 * It's only possible to copy on write if
121 * we're the only user of the segment.
122 */
123 if(read && conf.copymode == 0 && s->ref == 1) {
124 mmuphys = PPN((*pg)->pa)|PTERONLY|PTEVALID;
125 (*pg)->modref |= PG_REF;
126 break;
127 }
128
129 lkp = *pg;
130 lock(lkp);
131
132 if(lkp->image == &swapimage)
133 ref = lkp->ref + swapcount(lkp->daddr);
134 else
135 ref = lkp->ref;
136 if(ref == 1 && lkp->image){
137 /* save a copy of the original for the image cache */
138 duppage(lkp);
139 ref = lkp->ref;
140 }
141 unlock(lkp);
142 if(ref > 1){
143 new = newpage(0, &s, addr);
144 if(s == 0)
145 return -1;
146 *pg = new;
147 copypage(lkp, *pg);
148 putpage(lkp);
149 }
150 mmuphys = PPN((*pg)->pa) | PTEWRITE | PTEVALID;
151 (*pg)->modref = PG_MOD|PG_REF;
152 break;
153
154 case SG_PHYSICAL:
155 if(*pg == 0) {
156 fn = s->pseg->pgalloc;
157 if(fn)
158 *pg = (*fn)(s, addr);
159 else {
160 new = smalloc(sizeof(Page));
161 new->va = addr;
162 new->pa = s->pseg->pa+(addr-s->base);
163 new->ref = 1;
164 *pg = new;
165 }
166 }
167
168 if (checkaddr && addr == addr2check)
169 (*checkaddr)(addr, s, *pg);
170 mmuphys = PPN((*pg)->pa) |PTEWRITE|PTEUNCACHED|PTEVALID;
171 (*pg)->modref = PG_MOD|PG_REF;
172 break;
173 }
174 qunlock(&s->lk);
175
176 if(doputmmu)
177 putmmu(addr, mmuphys, *pg);
178
179 return 0;
180 }
181
182 void
pio(Segment * s,ulong addr,ulong soff,Page ** p)183 pio(Segment *s, ulong addr, ulong soff, Page **p)
184 {
185 Page *new;
186 KMap *k;
187 Chan *c;
188 int n, ask;
189 char *kaddr;
190 ulong daddr;
191 Page *loadrec;
192
193 retry:
194 loadrec = *p;
195 if(loadrec == 0) { /* from a text/data image */
196 daddr = s->fstart+soff;
197 new = lookpage(s->image, daddr);
198 if(new != nil) {
199 *p = new;
200 return;
201 }
202
203 c = s->image->c;
204 ask = s->flen-soff;
205 if(ask > BY2PG)
206 ask = BY2PG;
207 }
208 else { /* from a swap image */
209 daddr = swapaddr(loadrec);
210 new = lookpage(&swapimage, daddr);
211 if(new != nil) {
212 putswap(loadrec);
213 *p = new;
214 return;
215 }
216
217 c = swapimage.c;
218 ask = BY2PG;
219 }
220 qunlock(&s->lk);
221
222 new = newpage(0, 0, addr);
223 k = kmap(new);
224 kaddr = (char*)VA(k);
225
226 while(waserror()) {
227 if(strcmp(up->errstr, Eintr) == 0)
228 continue;
229 kunmap(k);
230 putpage(new);
231 faulterror(Eioload, c, 0);
232 }
233
234 n = devtab[c->type]->read(c, kaddr, ask, daddr);
235 if(n != ask)
236 faulterror(Eioload, c, 0);
237 if(ask < BY2PG)
238 memset(kaddr+ask, 0, BY2PG-ask);
239
240 poperror();
241 kunmap(k);
242 qlock(&s->lk);
243 if(loadrec == 0) { /* This is demand load */
244 /*
245 * race, another proc may have gotten here first while
246 * s->lk was unlocked
247 */
248 if(*p == 0) {
249 new->daddr = daddr;
250 cachepage(new, s->image);
251 *p = new;
252 }
253 else
254 putpage(new);
255 }
256 else { /* This is paged out */
257 /*
258 * race, another proc may have gotten here first
259 * (and the pager may have run on that page) while
260 * s->lk was unlocked
261 */
262 if(*p != loadrec){
263 if(!pagedout(*p)){
264 /* another process did it for me */
265 putpage(new);
266 goto done;
267 } else {
268 /* another process and the pager got in */
269 putpage(new);
270 goto retry;
271 }
272 }
273
274 new->daddr = daddr;
275 cachepage(new, &swapimage);
276 *p = new;
277 putswap(loadrec);
278 }
279
280 done:
281 if(s->flushme)
282 memset((*p)->cachectl, PG_TXTFLUSH, sizeof((*p)->cachectl));
283 }
284
285 /*
286 * Called only in a system call
287 */
288 int
okaddr(ulong addr,ulong len,int write)289 okaddr(ulong addr, ulong len, int write)
290 {
291 Segment *s;
292
293 if((long)len >= 0) {
294 for(;;) {
295 s = seg(up, addr, 0);
296 if(s == 0 || (write && (s->type&SG_RONLY)))
297 break;
298
299 if(addr+len > s->top) {
300 len -= s->top - addr;
301 addr = s->top;
302 continue;
303 }
304 return 1;
305 }
306 }
307 pprint("suicide: invalid address %#lux/%lud in sys call pc=%#lux\n", addr, len, userpc());
308 return 0;
309 }
310
311 void
validaddr(ulong addr,ulong len,int write)312 validaddr(ulong addr, ulong len, int write)
313 {
314 if(!okaddr(addr, len, write)){
315 postnote(up, 1, "sys: bad address in syscall", NDebug);
316 error(Ebadarg);
317 }
318 }
319
320 /*
321 * &s[0] is known to be a valid address.
322 */
323 void*
vmemchr(void * s,int c,int n)324 vmemchr(void *s, int c, int n)
325 {
326 int m;
327 ulong a;
328 void *t;
329
330 a = (ulong)s;
331 while(PGROUND(a) != PGROUND(a+n-1)){
332 /* spans pages; handle this page */
333 m = BY2PG - (a & (BY2PG-1));
334 t = memchr((void*)a, c, m);
335 if(t)
336 return t;
337 a += m;
338 n -= m;
339 if(a < KZERO)
340 validaddr(a, 1, 0);
341 }
342
343 /* fits in one page */
344 return memchr((void*)a, c, n);
345 }
346
347 Segment*
seg(Proc * p,ulong addr,int dolock)348 seg(Proc *p, ulong addr, int dolock)
349 {
350 Segment **s, **et, *n;
351
352 et = &p->seg[NSEG];
353 for(s = p->seg; s < et; s++) {
354 n = *s;
355 if(n == 0)
356 continue;
357 if(addr >= n->base && addr < n->top) {
358 if(dolock == 0)
359 return n;
360
361 qlock(&n->lk);
362 if(addr >= n->base && addr < n->top)
363 return n;
364 qunlock(&n->lk);
365 }
366 }
367
368 return 0;
369 }
370
371 extern void checkmmu(ulong, ulong);
372 void
checkpages(void)373 checkpages(void)
374 {
375 int checked;
376 ulong addr, off;
377 Pte *p;
378 Page *pg;
379 Segment **sp, **ep, *s;
380
381 if(up == nil)
382 return;
383
384 checked = 0;
385 for(sp=up->seg, ep=&up->seg[NSEG]; sp<ep; sp++){
386 s = *sp;
387 if(s == nil)
388 continue;
389 qlock(&s->lk);
390 for(addr=s->base; addr<s->top; addr+=BY2PG){
391 off = addr - s->base;
392 p = s->map[off/PTEMAPMEM];
393 if(p == 0)
394 continue;
395 pg = p->pages[(off&(PTEMAPMEM-1))/BY2PG];
396 if(pg == 0 || pagedout(pg))
397 continue;
398 checkmmu(addr, pg->pa);
399 checked++;
400 }
401 qunlock(&s->lk);
402 }
403 print("%ld %s: checked %d page table entries\n", up->pid, up->text, checked);
404 }
405