![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to memory.c CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [Early Linux] / linux / mm|
Return to memory.c CVS log | Up to [Early Linux] / linux / mm |
1.1.1.2 root 1: /*
2: * linux/mm/memory.c
3: *
4: * (C) 1991 Linus Torvalds
5: */
6:
1.1.1.3 root 7: /*
8: * demand-loading started 01.12.91 - seems it is high on the list of
9: * things wanted, and it should be easy to implement. - Linus
10: */
11:
12: /*
13: * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
14: * pages started 02.12.91, seems to work. - Linus.
15: *
16: * Tested sharing by executing about 30 /bin/sh: under the old kernel it
17: * would have taken more than the 6M I have free, but it worked well as
18: * far as I could see.
19: *
20: * Also corrected some "invalidate()"s - I wasn't doing enough of them.
21: */
22:
1.1.1.4 root 23: /*
24: * Real VM (paging to/from disk) started 18.12.91. Much more work and
25: * thought has to go into this. Oh, well..
26: * 19.12.91 - works, somewhat. Sometimes I get faults, don't know why.
27: * Found it. Everything seems to work now.
28: * 20.12.91 - Ok, making the swap-device changeable like the root.
29: */
30:
1.1 root 31: #include <signal.h>
32:
1.1.1.3 root 33: #include <asm/system.h>
34:
35: #include <linux/sched.h>
1.1 root 36: #include <linux/head.h>
37: #include <linux/kernel.h>
38:
1.1.1.3 root 39: #define CODE_SPACE(addr) ((((addr)+4095)&~4095) < \
40: current->start_code + current->end_code)
41:
1.1.1.4 root 42: unsigned long HIGH_MEMORY = 0;
1.1 root 43:
44: #define copy_page(from,to) \
45: __asm__("cld ; rep ; movsl"::"S" (from),"D" (to),"c" (1024):"cx","di","si")
46:
1.1.1.5 root 47: #define CHECK_LAST_NR 16
48:
49: static unsigned long last_pages[CHECK_LAST_NR] = { 0, };
50:
1.1.1.4 root 51: unsigned char mem_map [ PAGING_PAGES ] = {0,};
1.1 root 52:
53: /*
54: * Free a page of memory at physical address 'addr'. Used by
55: * 'free_page_tables()'
56: */
57: void free_page(unsigned long addr)
58: {
1.1.1.2 root 59: if (addr < LOW_MEM) return;
1.1.1.5 root 60: if (addr < HIGH_MEMORY) {
61: addr -= LOW_MEM;
62: addr >>= 12;
63: if (mem_map[addr]--)
64: return;
65: mem_map[addr]=0;
66: }
67: printk("trying to free free page: memory probably corrupted");
1.1 root 68: }
69:
70: /*
71: * This function frees a continuos block of page tables, as needed
72: * by 'exit()'. As does copy_page_tables(), this handles only 4Mb blocks.
73: */
74: int free_page_tables(unsigned long from,unsigned long size)
75: {
1.1.1.5 root 76: unsigned long page;
77: unsigned long page_dir;
1.1 root 78: unsigned long *pg_table;
79: unsigned long * dir, nr;
80:
81: if (from & 0x3fffff)
82: panic("free_page_tables called with wrong alignment");
83: if (!from)
84: panic("Trying to free up swapper memory space");
85: size = (size + 0x3fffff) >> 22;
86: dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
87: for ( ; size-->0 ; dir++) {
1.1.1.5 root 88: if (!(page_dir = *dir))
1.1 root 89: continue;
90: *dir = 0;
1.1.1.5 root 91: if (!(page_dir & 1)) {
92: printk("free_page_tables: bad page directory.");
93: continue;
94: }
95: pg_table = (unsigned long *) (0xfffff000 & page_dir);
96: for (nr=0 ; nr<1024 ; nr++,pg_table++) {
97: if (!(page = *pg_table))
98: continue;
99: *pg_table = 0;
100: if (1 & page)
101: free_page(0xfffff000 & page);
102: else
103: swap_free(page >> 1);
104: }
105: free_page(0xfffff000 & page_dir);
1.1 root 106: }
107: invalidate();
1.1.1.5 root 108: for (page = 0; page < CHECK_LAST_NR ; page++)
109: last_pages[page] = 0;
1.1 root 110: return 0;
111: }
112:
113: /*
114: * Well, here is one of the most complicated functions in mm. It
115: * copies a range of linerar addresses by copying only the pages.
116: * Let's hope this is bug-free, 'cause this one I don't want to debug :-)
117: *
118: * Note! We don't copy just any chunks of memory - addresses have to
119: * be divisible by 4Mb (one page-directory entry), as this makes the
120: * function easier. It's used only by fork anyway.
121: *
122: * NOTE 2!! When from==0 we are copying kernel space for the first
123: * fork(). Then we DONT want to copy a full page-directory entry, as
124: * that would lead to some serious memory waste - we just copy the
125: * first 160 pages - 640kB. Even that is more than we need, but it
126: * doesn't take any more memory - we don't copy-on-write in the low
127: * 1 Mb-range, so the pages can be shared with the kernel. Thus the
128: * special case for nr=xxxx.
129: */
130: int copy_page_tables(unsigned long from,unsigned long to,long size)
131: {
132: unsigned long * from_page_table;
133: unsigned long * to_page_table;
134: unsigned long this_page;
135: unsigned long * from_dir, * to_dir;
1.1.1.4 root 136: unsigned long new_page;
1.1 root 137: unsigned long nr;
138:
139: if ((from&0x3fffff) || (to&0x3fffff))
140: panic("copy_page_tables called with wrong alignment");
141: from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
142: to_dir = (unsigned long *) ((to>>20) & 0xffc);
143: size = ((unsigned) (size+0x3fffff)) >> 22;
144: for( ; size-->0 ; from_dir++,to_dir++) {
1.1.1.5 root 145: if (*to_dir)
146: printk("copy_page_tables: already exist, "
147: "probable memory corruption\n");
148: if (!*from_dir)
149: continue;
150: if (!(1 & *from_dir)) {
151: printk("copy_page_tables: page table swapped out, "
152: "probable memory corruption");
153: *from_dir = 0;
1.1 root 154: continue;
1.1.1.5 root 155: }
1.1 root 156: from_page_table = (unsigned long *) (0xfffff000 & *from_dir);
157: if (!(to_page_table = (unsigned long *) get_free_page()))
158: return -1; /* Out of memory, see freeing */
159: *to_dir = ((unsigned long) to_page_table) | 7;
160: nr = (from==0)?0xA0:1024;
161: for ( ; nr-- > 0 ; from_page_table++,to_page_table++) {
162: this_page = *from_page_table;
1.1.1.4 root 163: if (!this_page)
1.1 root 164: continue;
1.1.1.4 root 165: if (!(1 & this_page)) {
166: if (!(new_page = get_free_page()))
167: return -1;
1.1.1.7 ! root 168: ++current->rss;
1.1.1.4 root 169: read_swap_page(this_page>>1, (char *) new_page);
170: *to_page_table = this_page;
171: *from_page_table = new_page | (PAGE_DIRTY | 7);
172: continue;
173: }
1.1 root 174: this_page &= ~2;
175: *to_page_table = this_page;
176: if (this_page > LOW_MEM) {
177: *from_page_table = this_page;
178: this_page -= LOW_MEM;
179: this_page >>= 12;
180: mem_map[this_page]++;
181: }
182: }
183: }
184: invalidate();
185: return 0;
186: }
187:
188: /*
189: * This function puts a page in memory at the wanted address.
190: * It returns the physical address of the page gotten, 0 if
191: * out of memory (either when trying to access page-table or
192: * page.)
193: */
1.1.1.4 root 194: static unsigned long put_page(unsigned long page,unsigned long address)
1.1 root 195: {
196: unsigned long tmp, *page_table;
197:
198: /* NOTE !!! This uses the fact that _pg_dir=0 */
199:
1.1.1.5 root 200: if (page < LOW_MEM || page >= HIGH_MEMORY) {
201: printk("put_page: trying to put page %p at %p\n",page,address);
202: return 0;
203: }
204: if (mem_map[(page-LOW_MEM)>>12] != 1) {
1.1 root 205: printk("mem_map disagrees with %p at %p\n",page,address);
1.1.1.5 root 206: return 0;
207: }
1.1 root 208: page_table = (unsigned long *) ((address>>20) & 0xffc);
209: if ((*page_table)&1)
210: page_table = (unsigned long *) (0xfffff000 & *page_table);
211: else {
212: if (!(tmp=get_free_page()))
213: return 0;
1.1.1.4 root 214: *page_table = tmp | 7;
1.1 root 215: page_table = (unsigned long *) tmp;
216: }
1.1.1.6 root 217: page_table += (address>>12) & 0x3ff;
218: if (*page_table) {
219: printk("put_page: page already exists\n");
220: *page_table = 0;
221: invalidate();
222: }
223: *page_table = page | 7;
1.1.1.3 root 224: /* no need for invalidate */
1.1 root 225: return page;
226: }
227:
1.1.1.4 root 228: /*
229: * The previous function doesn't work very well if you also want to mark
230: * the page dirty: exec.c wants this, as it has earlier changed the page,
231: * and we want the dirty-status to be correct (for VM). Thus the same
232: * routine, but this time we mark it dirty too.
233: */
234: unsigned long put_dirty_page(unsigned long page, unsigned long address)
235: {
236: unsigned long tmp, *page_table;
237:
238: /* NOTE !!! This uses the fact that _pg_dir=0 */
239:
240: if (page < LOW_MEM || page >= HIGH_MEMORY)
1.1.1.5 root 241: printk("put_dirty_page: trying to put page %p at %p\n",page,address);
1.1.1.4 root 242: if (mem_map[(page-LOW_MEM)>>12] != 1)
243: printk("mem_map disagrees with %p at %p\n",page,address);
244: page_table = (unsigned long *) ((address>>20) & 0xffc);
245: if ((*page_table)&1)
246: page_table = (unsigned long *) (0xfffff000 & *page_table);
247: else {
248: if (!(tmp=get_free_page()))
249: return 0;
250: *page_table = tmp|7;
251: page_table = (unsigned long *) tmp;
252: }
1.1.1.6 root 253: page_table += (address>>12) & 0x3ff;
254: if (*page_table) {
255: printk("put_dirty_page: page already exists\n");
256: *page_table = 0;
257: invalidate();
258: }
259: *page_table = page | (PAGE_DIRTY | 7);
1.1.1.4 root 260: /* no need for invalidate */
261: return page;
262: }
263:
1.1 root 264: void un_wp_page(unsigned long * table_entry)
265: {
1.1.1.5 root 266: unsigned long old_page;
267: unsigned long new_page = 0;
268: unsigned long dirty;
269:
270: repeat:
271: old_page = *table_entry;
272: dirty = old_page & PAGE_DIRTY;
273: if (!(old_page & 1)) {
274: if (new_page)
275: free_page(new_page);
276: return;
277: }
278: old_page &= 0xfffff000;
279: if (old_page >= HIGH_MEMORY) {
280: if (new_page)
281: free_page(new_page);
282: printk("bad page address\n\r");
283: do_exit(SIGSEGV);
284: }
1.1 root 285: if (old_page >= LOW_MEM && mem_map[MAP_NR(old_page)]==1) {
286: *table_entry |= 2;
1.1.1.3 root 287: invalidate();
1.1.1.5 root 288: if (new_page)
289: free_page(new_page);
1.1 root 290: return;
291: }
1.1.1.5 root 292: if (!new_page) {
293: if (!(new_page=get_free_page()))
294: oom();
295: goto repeat;
296: }
1.1.1.4 root 297: copy_page(old_page,new_page);
1.1.1.5 root 298: *table_entry = new_page | dirty | 7;
299: free_page(old_page);
1.1.1.3 root 300: invalidate();
1.1 root 301: }
302:
303: /*
304: * This routine handles present pages, when users try to write
305: * to a shared page. It is done by copying the page to a new address
306: * and decrementing the shared-page counter for the old page.
1.1.1.3 root 307: *
308: * If it's in code space we exit with a segment error.
1.1 root 309: */
310: void do_wp_page(unsigned long error_code,unsigned long address)
311: {
1.1.1.6 root 312: if (address < TASK_SIZE) {
1.1.1.4 root 313: printk("\n\rBAD! KERNEL MEMORY WP-ERR!\n\r");
1.1.1.6 root 314: do_exit(SIGSEGV);
315: }
1.1.1.5 root 316: if (address - current->start_code >= TASK_SIZE) {
1.1.1.4 root 317: printk("Bad things happen: page error in do_wp_page\n\r");
318: do_exit(SIGSEGV);
319: }
1.1.1.7 ! root 320: ++current->min_flt;
1.1 root 321: un_wp_page((unsigned long *)
322: (((address>>10) & 0xffc) + (0xfffff000 &
323: *((unsigned long *) ((address>>20) &0xffc)))));
324: }
325:
326: void write_verify(unsigned long address)
327: {
328: unsigned long page;
329:
330: if (!( (page = *((unsigned long *) ((address>>20) & 0xffc)) )&1))
331: return;
332: page &= 0xfffff000;
333: page += ((address>>10) & 0xffc);
334: if ((3 & *(unsigned long *) page) == 1) /* non-writeable, present */
335: un_wp_page((unsigned long *) page);
336: return;
337: }
338:
1.1.1.3 root 339: void get_empty_page(unsigned long address)
340: {
341: unsigned long tmp;
342:
343: if (!(tmp=get_free_page()) || !put_page(tmp,address)) {
344: free_page(tmp); /* 0 is ok - ignored */
345: oom();
346: }
347: }
348:
349: /*
350: * try_to_share() checks the page at address "address" in the task "p",
351: * to see if it exists, and if it is clean. If so, share it with the current
352: * task.
353: *
354: * NOTE! This assumes we have checked that p != current, and that they
1.1.1.4 root 355: * share the same executable or library.
1.1.1.3 root 356: */
357: static int try_to_share(unsigned long address, struct task_struct * p)
358: {
359: unsigned long from;
360: unsigned long to;
361: unsigned long from_page;
362: unsigned long to_page;
363: unsigned long phys_addr;
364:
365: from_page = to_page = ((address>>20) & 0xffc);
366: from_page += ((p->start_code>>20) & 0xffc);
367: to_page += ((current->start_code>>20) & 0xffc);
368: /* is there a page-directory at from? */
369: from = *(unsigned long *) from_page;
370: if (!(from & 1))
371: return 0;
372: from &= 0xfffff000;
373: from_page = from + ((address>>10) & 0xffc);
374: phys_addr = *(unsigned long *) from_page;
375: /* is the page clean and present? */
376: if ((phys_addr & 0x41) != 0x01)
377: return 0;
378: phys_addr &= 0xfffff000;
379: if (phys_addr >= HIGH_MEMORY || phys_addr < LOW_MEM)
380: return 0;
381: to = *(unsigned long *) to_page;
1.1.1.5 root 382: if (!(to & 1)) {
1.1.1.3 root 383: if (to = get_free_page())
384: *(unsigned long *) to_page = to | 7;
385: else
386: oom();
1.1.1.5 root 387: }
1.1.1.3 root 388: to &= 0xfffff000;
389: to_page = to + ((address>>10) & 0xffc);
390: if (1 & *(unsigned long *) to_page)
391: panic("try_to_share: to_page already exists");
392: /* share them: write-protect */
393: *(unsigned long *) from_page &= ~2;
394: *(unsigned long *) to_page = *(unsigned long *) from_page;
395: invalidate();
396: phys_addr -= LOW_MEM;
397: phys_addr >>= 12;
398: mem_map[phys_addr]++;
399: return 1;
400: }
401:
402: /*
403: * share_page() tries to find a process that could share a page with
404: * the current one. Address is the address of the wanted page relative
405: * to the current data space.
406: *
407: * We first check if it is at all feasible by checking executable->i_count.
408: * It should be >1 if there are other tasks sharing this inode.
409: */
1.1.1.5 root 410: static int share_page(struct inode * inode, unsigned long address)
1.1.1.3 root 411: {
412: struct task_struct ** p;
413:
1.1.1.4 root 414: if (inode->i_count < 2 || !inode)
1.1.1.3 root 415: return 0;
416: for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
417: if (!*p)
418: continue;
419: if (current == *p)
420: continue;
1.1.1.4 root 421: if (address < LIBRARY_OFFSET) {
422: if (inode != (*p)->executable)
423: continue;
424: } else {
425: if (inode != (*p)->library)
426: continue;
427: }
1.1.1.3 root 428: if (try_to_share(address,*p))
429: return 1;
430: }
431: return 0;
432: }
433:
1.1.1.7 ! root 434: void do_no_page(unsigned long error_code, unsigned long address,
! 435: struct task_struct *tsk)
1.1 root 436: {
1.1.1.5 root 437: static unsigned int last_checked = 0;
1.1.1.3 root 438: int nr[4];
1.1 root 439: unsigned long tmp;
1.1.1.3 root 440: unsigned long page;
441: int block,i;
1.1.1.5 root 442: struct inode * inode;
1.1 root 443:
1.1.1.7 ! root 444: /* Thrashing ? Make it interruptible, but don't penalize otherwise */
1.1.1.5 root 445: for (i = 0; i < CHECK_LAST_NR; i++)
446: if ((address & 0xfffff000) == last_pages[i]) {
447: current->counter = 0;
448: schedule();
449: }
450: last_checked++;
451: if (last_checked >= CHECK_LAST_NR)
452: last_checked = 0;
453: last_pages[last_checked] = address & 0xfffff000;
1.1.1.6 root 454: if (address < TASK_SIZE) {
1.1.1.4 root 455: printk("\n\rBAD!! KERNEL PAGE MISSING\n\r");
1.1.1.6 root 456: do_exit(SIGSEGV);
457: }
1.1.1.5 root 458: if (address - tsk->start_code >= TASK_SIZE) {
1.1.1.4 root 459: printk("Bad things happen: nonexistent page error in do_no_page\n\r");
460: do_exit(SIGSEGV);
461: }
1.1.1.7 ! root 462: ++tsk->rss;
1.1.1.4 root 463: page = *(unsigned long *) ((address >> 20) & 0xffc);
1.1.1.5 root 464: /* check the page directory: make a page dir entry if no such exists */
1.1.1.4 root 465: if (page & 1) {
466: page &= 0xfffff000;
467: page += (address >> 10) & 0xffc;
468: tmp = *(unsigned long *) page;
469: if (tmp && !(1 & tmp)) {
1.1.1.7 ! root 470: ++tsk->maj_flt;
1.1.1.4 root 471: swap_in((unsigned long *) page);
472: return;
473: }
1.1.1.5 root 474: } else {
475: if (page)
476: printk("do_no_page: bad page directory\n");
477: if (!(page = get_free_page()))
478: oom();
479: page |= 7;
480: *(unsigned long *) ((address >> 20) & 0xffc) = page;
1.1.1.4 root 481: }
1.1.1.3 root 482: address &= 0xfffff000;
1.1.1.5 root 483: tmp = address - tsk->start_code;
1.1.1.4 root 484: if (tmp >= LIBRARY_OFFSET ) {
1.1.1.5 root 485: inode = tsk->library;
1.1.1.4 root 486: block = 1 + (tmp-LIBRARY_OFFSET) / BLOCK_SIZE;
1.1.1.5 root 487: } else if (tmp < tsk->end_data) {
488: inode = tsk->executable;
1.1.1.4 root 489: block = 1 + tmp / BLOCK_SIZE;
490: } else {
491: inode = NULL;
492: block = 0;
493: }
494: if (!inode) {
1.1.1.7 ! root 495: ++tsk->min_flt;
! 496: if (tmp > tsk->brk && tsk == current &&
! 497: LIBRARY_OFFSET - tmp > tsk->rlim[RLIMIT_STACK].rlim_max)
! 498: do_exit(SIGSEGV);
1.1.1.3 root 499: get_empty_page(address);
500: return;
501: }
1.1.1.5 root 502: if (tsk == current)
1.1.1.7 ! root 503: if (share_page(inode,tmp)) {
! 504: ++tsk->min_flt;
! 505: return;
! 506: }
! 507: ++tsk->maj_flt;
1.1.1.3 root 508: if (!(page = get_free_page()))
509: oom();
510: /* remember that 1 block is used for header */
511: for (i=0 ; i<4 ; block++,i++)
1.1.1.4 root 512: nr[i] = bmap(inode,block);
513: bread_page(page,inode->i_dev,nr);
1.1.1.5 root 514: i = tmp + 4096 - tsk->end_data;
1.1.1.4 root 515: if (i>4095)
516: i = 0;
1.1.1.3 root 517: tmp = page + 4096;
518: while (i-- > 0) {
519: tmp--;
520: *(char *)tmp = 0;
521: }
522: if (put_page(page,address))
523: return;
524: free_page(page);
525: oom();
1.1 root 526: }
527:
1.1.1.2 root 528: void mem_init(long start_mem, long end_mem)
529: {
530: int i;
531:
1.1.1.5 root 532: swap_device = 0;
533: swap_file = NULL;
1.1.1.2 root 534: HIGH_MEMORY = end_mem;
535: for (i=0 ; i<PAGING_PAGES ; i++)
536: mem_map[i] = USED;
537: i = MAP_NR(start_mem);
538: end_mem -= start_mem;
539: end_mem >>= 12;
540: while (end_mem-->0)
541: mem_map[i++]=0;
542: }
543:
1.1.1.4 root 544: void show_mem(void)
1.1 root 545: {
1.1.1.4 root 546: int i,j,k,free=0,total=0;
1.1.1.7 ! root 547: int shared = 0;
1.1.1.4 root 548: unsigned long * pg_tbl;
1.1.1.7 ! root 549: static int lock = 0;
1.1.1.4 root 550:
1.1.1.7 ! root 551: cli();
! 552: if (lock) {
! 553: sti();
! 554: return;
! 555: }
! 556: lock = 1;
! 557: sti();
1.1.1.4 root 558: printk("Mem-info:\n\r");
559: for(i=0 ; i<PAGING_PAGES ; i++) {
560: if (mem_map[i] == USED)
561: continue;
562: total++;
563: if (!mem_map[i])
564: free++;
565: else
566: shared += mem_map[i]-1;
567: }
568: printk("%d free pages of %d\n\r",free,total);
569: printk("%d pages shared\n\r",shared);
570: k = 0;
571: for(i=4 ; i<1024 ;) {
1.1 root 572: if (1&pg_dir[i]) {
1.1.1.4 root 573: if (pg_dir[i]>HIGH_MEMORY) {
574: printk("page directory[%d]: %08X\n\r",
575: i,pg_dir[i]);
1.1.1.5 root 576: i++;
1.1.1.4 root 577: continue;
578: }
579: if (pg_dir[i]>LOW_MEM)
580: free++,k++;
581: pg_tbl=(unsigned long *) (0xfffff000 & pg_dir[i]);
582: for(j=0 ; j<1024 ; j++)
583: if ((pg_tbl[j]&1) && pg_tbl[j]>LOW_MEM)
584: if (pg_tbl[j]>HIGH_MEMORY)
585: printk("page_dir[%d][%d]: %08X\n\r",
586: i,j, pg_tbl[j]);
587: else
588: k++,free++;
589: }
590: i++;
591: if (!(i&15) && k) {
592: k++,free++; /* one page/process for task_struct */
593: printk("Process %d: %d pages\n\r",(i>>4)-1,k);
594: k = 0;
1.1 root 595: }
596: }
1.1.1.4 root 597: printk("Memory found: %d (%d)\n\r",free-shared,total);
1.1.1.7 ! root 598: lock = 0;
1.1 root 599: }
1.1.1.5 root 600:
601:
602: /* This routine handles page faults. It determines the address,
603: and the problem then passes it off to one of the appropriate
604: routines. */
1.1.1.6 root 605: void do_page_fault(unsigned long *esp, unsigned long error_code)
1.1.1.5 root 606: {
607: unsigned long address;
608: /* get the address */
609:
1.1.1.6 root 610: __asm__("movl %%cr2,%0":"=r" (address));
1.1.1.5 root 611: if (!(error_code & 1)) {
612: do_no_page(error_code, address, current);
613: return;
614: } else {
615: do_wp_page(error_code, address);
616: return;
617: }
618: }
This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.