kern
view src/vm.c @ 78:251a65b62223
of course I forgot to actually add the new files... every fucking time...
| author | John Tsiombikas <nuclear@member.fsf.org> |
|---|---|
| date | Tue, 06 Dec 2011 12:56:46 +0200 |
| parents | d3601789d638 |
| children |
line source
1 #include <stdio.h>
2 #include <string.h>
3 #include <inttypes.h>
4 #include <assert.h>
5 #include "config.h"
6 #include "vm.h"
7 #include "intr.h"
8 #include "mem.h"
9 #include "panic.h"
10 #include "proc.h"
12 #define IDMAP_START 0xa0000
14 #define PGDIR_ADDR 0xfffff000
15 #define PGTBL_BASE (0xffffffff - 4096 * 1024 + 1)
16 #define PGTBL(x) ((uint32_t*)(PGTBL_BASE + PGSIZE * (x)))
18 #define ATTR_PGDIR_MASK 0x3f
19 #define ATTR_PGTBL_MASK 0x1ff
21 #define PAGEFAULT 14
24 struct page_range {
25 int start, end;
26 struct page_range *next;
27 };
29 /* defined in vm-asm.S */
30 void enable_paging(void);
31 void disable_paging(void);
32 int get_paging_status(void);
33 void set_pgdir_addr(uint32_t addr);
34 void flush_tlb(void);
35 void flush_tlb_addr(uint32_t addr);
36 #define flush_tlb_page(p) flush_tlb_addr(PAGE_TO_ADDR(p))
37 uint32_t get_fault_addr(void);
39 static void coalesce(struct page_range *low, struct page_range *mid, struct page_range *high);
40 static void pgfault(int inum);
41 static int copy_on_write(struct vm_page *page);
42 static struct page_range *alloc_node(void);
43 static void free_node(struct page_range *node);
45 /* page directory */
46 static uint32_t *pgdir;
48 /* 2 lists of free ranges, for kernel memory and user memory */
49 static struct page_range *pglist[2];
50 /* list of free page_range structures to be used in the lists */
51 static struct page_range *node_pool;
52 /* the first page range for the whole kernel address space, to get things started */
53 static struct page_range first_node;
56 void init_vm(void)
57 {
58 uint32_t idmap_end;
59 int i, kmem_start_pg, pgtbl_base_pg;
61 /* setup the page tables */
62 pgdir = (uint32_t*)alloc_phys_page();
63 memset(pgdir, 0, PGSIZE);
64 set_pgdir_addr((uint32_t)pgdir);
66 /* map the video memory and kernel code 1-1 */
67 get_kernel_mem_range(0, &idmap_end);
68 map_mem_range(IDMAP_START, idmap_end - IDMAP_START, IDMAP_START, 0);
70 /* make the last page directory entry point to the page directory */
71 pgdir[1023] = ((uint32_t)pgdir & PGENT_ADDR_MASK) | PG_PRESENT;
72 pgdir = (uint32_t*)PGDIR_ADDR;
74 /* set the page fault handler */
75 interrupt(PAGEFAULT, pgfault);
77 /* we can enable paging now */
78 enable_paging();
80 /* initialize the virtual page allocator */
81 node_pool = 0;
83 kmem_start_pg = ADDR_TO_PAGE(KMEM_START);
84 pgtbl_base_pg = ADDR_TO_PAGE(PGTBL_BASE);
86 first_node.start = kmem_start_pg;
87 first_node.end = pgtbl_base_pg;
88 first_node.next = 0;
89 pglist[MEM_KERNEL] = &first_node;
91 pglist[MEM_USER] = alloc_node();
92 pglist[MEM_USER]->start = ADDR_TO_PAGE(idmap_end);
93 pglist[MEM_USER]->end = kmem_start_pg;
94 pglist[MEM_USER]->next = 0;
96 /* temporarily map something into every 1024th page of the kernel address
97 * space to force pre-allocation of all the kernel page-tables
98 */
99 for(i=kmem_start_pg; i<pgtbl_base_pg; i+=1024) {
100 /* if there's already something mapped here, leave it alone */
101 if(virt_to_phys_page(i) == -1) {
102 map_page(i, 0, 0);
103 unmap_page(i);
104 }
105 }
106 }
108 /* if ppage == -1 we allocate a physical page by calling alloc_phys_page */
109 int map_page(int vpage, int ppage, unsigned int attr)
110 {
111 uint32_t *pgtbl;
112 int diridx, pgidx, pgon, intr_state;
113 struct process *p;
115 intr_state = get_intr_state();
116 disable_intr();
118 pgon = get_paging_status();
120 if(ppage < 0) {
121 uint32_t addr = alloc_phys_page();
122 if(!addr) {
123 set_intr_state(intr_state);
124 return -1;
125 }
126 ppage = ADDR_TO_PAGE(addr);
127 }
129 diridx = PAGE_TO_PGTBL(vpage);
130 pgidx = PAGE_TO_PGTBL_PG(vpage);
132 if(!(pgdir[diridx] & PG_PRESENT)) {
133 /* no page table present, we must allocate one */
134 uint32_t addr = alloc_phys_page();
136 /* make sure all page directory entries in the below the kernel vm
137 * split have the user and writable bits set, otherwise further user
138 * mappings on the same 4mb block will be unusable in user space.
139 */
140 unsigned int pgdir_attr = attr;
141 if(vpage < ADDR_TO_PAGE(KMEM_START)) {
142 pgdir_attr |= PG_USER | PG_WRITABLE;
143 }
145 pgdir[diridx] = addr | (pgdir_attr & ATTR_PGDIR_MASK) | PG_PRESENT;
147 pgtbl = pgon ? PGTBL(diridx) : (uint32_t*)addr;
148 memset(pgtbl, 0, PGSIZE);
149 } else {
150 if(pgon) {
151 pgtbl = PGTBL(diridx);
152 } else {
153 pgtbl = (uint32_t*)(pgdir[diridx] & PGENT_ADDR_MASK);
154 }
155 }
157 pgtbl[pgidx] = PAGE_TO_ADDR(ppage) | (attr & ATTR_PGTBL_MASK) | PG_PRESENT;
158 flush_tlb_page(vpage);
160 /* if it's a new *user* mapping, and there is a current process, update the vmmap */
161 if((attr & PG_USER) && (p = get_current_proc())) {
162 struct vm_page *page;
164 if(!(page = get_vm_page_proc(p, vpage))) {
165 if(!(page = malloc(sizeof *page))) {
166 panic("map_page: failed to allocate new vm_page structure");
167 }
168 page->vpage = vpage;
169 page->ppage = ppage;
170 page->flags = (attr & ATTR_PGTBL_MASK) | PG_PRESENT;
171 page->nref = 1;
173 rb_inserti(&p->vmmap, vpage, page);
174 } else {
175 /* otherwise just update the mapping */
176 page->ppage = ppage;
178 /* XXX don't touch the flags, as that's how we implement CoW
179 * by changing the mapping without affecting the vm_page
180 */
181 }
182 }
184 set_intr_state(intr_state);
185 return 0;
186 }
188 int unmap_page(int vpage)
189 {
190 uint32_t *pgtbl;
191 int res = 0;
192 int diridx = PAGE_TO_PGTBL(vpage);
193 int pgidx = PAGE_TO_PGTBL_PG(vpage);
195 int intr_state = get_intr_state();
196 disable_intr();
198 if(!(pgdir[diridx] & PG_PRESENT)) {
199 goto err;
200 }
201 pgtbl = PGTBL(diridx);
203 if(!(pgtbl[pgidx] & PG_PRESENT)) {
204 goto err;
205 }
206 pgtbl[pgidx] = 0;
207 flush_tlb_page(vpage);
209 if(0) {
210 err:
211 printf("unmap_page(%d): page already not mapped\n", vpage);
212 res = -1;
213 }
214 set_intr_state(intr_state);
215 return res;
216 }
218 /* if ppg_start is -1, we allocate physical pages to map with alloc_phys_page() */
219 int map_page_range(int vpg_start, int pgcount, int ppg_start, unsigned int attr)
220 {
221 int i, phys_pg;
223 for(i=0; i<pgcount; i++) {
224 phys_pg = ppg_start < 0 ? -1 : ppg_start + i;
225 map_page(vpg_start + i, phys_pg, attr);
226 }
227 return 0;
228 }
230 int unmap_page_range(int vpg_start, int pgcount)
231 {
232 int i, res = 0;
234 for(i=0; i<pgcount; i++) {
235 if(unmap_page(vpg_start + i) == -1) {
236 res = -1;
237 }
238 }
239 return res;
240 }
242 /* if paddr is 0, we allocate physical pages with alloc_phys_page() */
243 int map_mem_range(uint32_t vaddr, size_t sz, uint32_t paddr, unsigned int attr)
244 {
245 int vpg_start, ppg_start, num_pages;
247 if(!sz) return -1;
249 if(ADDR_TO_PGOFFS(paddr)) {
250 panic("map_mem_range called with unaligned physical address: %x\n", paddr);
251 }
253 vpg_start = ADDR_TO_PAGE(vaddr);
254 ppg_start = paddr > 0 ? ADDR_TO_PAGE(paddr) : -1;
255 num_pages = ADDR_TO_PAGE(sz) + 1;
257 return map_page_range(vpg_start, num_pages, ppg_start, attr);
258 }
260 /* translate a virtual address to a physical address using the current page table */
261 uint32_t virt_to_phys(uint32_t vaddr)
262 {
263 int pg;
264 uint32_t pgaddr;
266 if((pg = virt_to_phys_page(ADDR_TO_PAGE(vaddr))) == -1) {
267 return 0;
268 }
269 pgaddr = PAGE_TO_ADDR(pg);
271 return pgaddr | ADDR_TO_PGOFFS(vaddr);
272 }
274 /* translate a virtual page number to a physical page number using the current page table */
275 int virt_to_phys_page(int vpg)
276 {
277 uint32_t pgaddr, *pgtbl;
278 int diridx, pgidx;
280 if(vpg < 0 || vpg >= PAGE_COUNT) {
281 return -1;
282 }
284 diridx = PAGE_TO_PGTBL(vpg);
285 pgidx = PAGE_TO_PGTBL_PG(vpg);
287 if(!(pgdir[diridx] & PG_PRESENT)) {
288 return -1;
289 }
290 pgtbl = PGTBL(diridx);
292 if(!(pgtbl[pgidx] & PG_PRESENT)) {
293 return -1;
294 }
295 pgaddr = pgtbl[pgidx] & PGENT_ADDR_MASK;
296 return ADDR_TO_PAGE(pgaddr);
297 }
299 /* same as virt_to_phys, but uses the vm_page tree instead of the actual page table */
300 uint32_t virt_to_phys_proc(struct process *p, uint32_t vaddr)
301 {
302 int pg;
303 uint32_t pgaddr;
305 if((pg = virt_to_phys_page_proc(p, ADDR_TO_PAGE(vaddr))) == -1) {
306 return 0;
307 }
308 pgaddr = PAGE_TO_ADDR(pg);
310 return pgaddr | ADDR_TO_PGOFFS(vaddr);
311 }
313 /* same virt_to_phys_page, but uses the vm_page tree instead of the actual page table */
314 int virt_to_phys_page_proc(struct process *p, int vpg)
315 {
316 struct rbnode *node;
317 assert(p);
319 if(!(node = rb_findi(&p->vmmap, vpg))) {
320 return -1;
321 }
322 return ((struct vm_page*)node->data)->ppage;
323 }
325 /* allocate a contiguous block of virtual memory pages along with
326 * backing physical memory for them, and update the page table.
327 */
328 int pgalloc(int num, int area)
329 {
330 int intr_state, ret = -1;
331 struct page_range *node, *prev, dummy;
333 intr_state = get_intr_state();
334 disable_intr();
336 dummy.next = pglist[area];
337 node = pglist[area];
338 prev = &dummy;
340 while(node) {
341 if(node->end - node->start >= num) {
342 ret = node->start;
343 node->start += num;
345 if(node->start == node->end) {
346 prev->next = node->next;
347 node->next = 0;
349 if(node == pglist[area]) {
350 pglist[area] = 0;
351 }
352 free_node(node);
353 }
354 break;
355 }
357 prev = node;
358 node = node->next;
359 }
361 if(ret >= 0) {
362 /*unsigned int attr = (area == MEM_USER) ? (PG_USER | PG_WRITABLE) : PG_GLOBAL;*/
363 unsigned int attr = (area == MEM_USER) ? (PG_USER | PG_WRITABLE) : 0;
365 /* allocate physical storage and map */
366 if(map_page_range(ret, num, -1, attr) == -1) {
367 ret = -1;
368 }
369 }
371 set_intr_state(intr_state);
372 return ret;
373 }
375 int pgalloc_vrange(int start, int num)
376 {
377 struct page_range *node, *prev, dummy;
378 int area, intr_state, ret = -1;
380 area = (start >= ADDR_TO_PAGE(KMEM_START)) ? MEM_KERNEL : MEM_USER;
381 if(area == MEM_USER && start + num > ADDR_TO_PAGE(KMEM_START)) {
382 printf("pgalloc_vrange: invalid range request crossing user/kernel split\n");
383 return -1;
384 }
386 intr_state = get_intr_state();
387 disable_intr();
389 dummy.next = pglist[area];
390 node = pglist[area];
391 prev = &dummy;
393 /* check to see if the requested VM range is available */
394 node = pglist[area];
395 while(node) {
396 if(start >= node->start && start + num <= node->end) {
397 ret = start; /* can do .. */
399 if(start == node->start) {
400 /* adjacent to the start of the range */
401 node->start += num;
402 } else if(start + num == node->end) {
403 /* adjacent to the end of the range */
404 node->end = start;
405 } else {
406 /* somewhere in the middle, which means we need
407 * to allocate a new page_range
408 */
409 struct page_range *newnode;
411 if(!(newnode = alloc_node())) {
412 panic("pgalloc_vrange failed to allocate new page_range while splitting a range in half... bummer\n");
413 }
414 newnode->start = start + num;
415 newnode->end = node->end;
416 newnode->next = node->next;
418 node->end = start;
419 node->next = newnode;
420 /* no need to check for null nodes at this point, there's
421 * certainly stuff at the begining and the end, otherwise we
422 * wouldn't be here. so break out of it.
423 */
424 break;
425 }
427 if(node->start == node->end) {
428 prev->next = node->next;
429 node->next = 0;
431 if(node == pglist[area]) {
432 pglist[area] = 0;
433 }
434 free_node(node);
435 }
436 break;
437 }
439 prev = node;
440 node = node->next;
441 }
443 if(ret >= 0) {
444 /*unsigned int attr = (area == MEM_USER) ? (PG_USER | PG_WRITABLE) : PG_GLOBAL;*/
445 unsigned int attr = (area == MEM_USER) ? (PG_USER | PG_WRITABLE) : 0;
447 /* allocate physical storage and map */
448 if(map_page_range(ret, num, -1, attr) == -1) {
449 ret = -1;
450 }
451 }
453 set_intr_state(intr_state);
454 return ret;
455 }
457 void pgfree(int start, int num)
458 {
459 int i, area, intr_state;
460 struct page_range *node, *new, *prev, *next;
462 intr_state = get_intr_state();
463 disable_intr();
465 for(i=0; i<num; i++) {
466 int phys_pg = virt_to_phys_page(start + i);
467 if(phys_pg != -1) {
468 free_phys_page(phys_pg);
469 }
470 }
472 if(!(new = alloc_node())) {
473 panic("pgfree: can't allocate new page_range node to add the freed pages\n");
474 }
475 new->start = start;
476 new->end = start + num;
478 area = PAGE_TO_ADDR(start) >= KMEM_START ? MEM_KERNEL : MEM_USER;
480 if(!pglist[area] || pglist[area]->start > start) {
481 next = new->next = pglist[area];
482 pglist[area] = new;
483 prev = 0;
485 } else {
487 prev = 0;
488 node = pglist[area];
489 next = node ? node->next : 0;
491 while(node) {
492 if(!next || next->start > start) {
493 /* place here, after node */
494 new->next = next;
495 node->next = new;
496 prev = node; /* needed by coalesce after the loop */
497 break;
498 }
500 prev = node;
501 node = next;
502 next = node ? node->next : 0;
503 }
504 }
506 coalesce(prev, new, next);
507 set_intr_state(intr_state);
508 }
510 static void coalesce(struct page_range *low, struct page_range *mid, struct page_range *high)
511 {
512 if(high) {
513 if(mid->end == high->start) {
514 mid->end = high->end;
515 mid->next = high->next;
516 free_node(high);
517 }
518 }
520 if(low) {
521 if(low->end == mid->start) {
522 low->end += mid->end;
523 low->next = mid->next;
524 free_node(mid);
525 }
526 }
527 }
529 static void pgfault(int inum)
530 {
531 struct intr_frame *frm = get_intr_frame();
532 uint32_t fault_addr = get_fault_addr();
534 /* the fault occured in user space */
535 if(frm->err & PG_USER) {
536 int fault_page = ADDR_TO_PAGE(fault_addr);
537 struct process *proc = get_current_proc();
538 printf("DBG: page fault in user space (pid: %d)\n", proc->id);
539 assert(proc);
541 if(frm->err & PG_PRESENT) {
542 /* it's not due to a missing page fetch the attributes */
543 int pgnum = ADDR_TO_PAGE(fault_addr);
545 if((frm->err & PG_WRITABLE) && (get_page_bit(pgnum, PG_WRITABLE, 0) == 0)) {
546 /* write permission fault might be a CoW fault or just an error
547 * fetch the vm_page permissions to check if this is suppoosed to be
548 * a writable page (which means we should CoW).
549 */
550 struct vm_page *page = get_vm_page_proc(proc, pgnum);
552 if(page->flags & PG_WRITABLE) {
553 /* ok this is a CoW fault */
554 if(copy_on_write(page) == -1) {
555 panic("copy on write failed!");
556 }
557 return; /* done, allow the process to restart the instruction and continue */
558 } else {
559 /* TODO eventually we'll SIGSEGV the process, for now just panic.
560 */
561 goto unhandled;
562 }
563 }
564 goto unhandled;
565 }
567 /* so it's a missing page... ok */
569 /* detect if it's an automatic stack growth deal */
570 if(fault_page < proc->user_stack_pg && proc->user_stack_pg - fault_page < USTACK_MAXGROW) {
571 int num_pages = proc->user_stack_pg - fault_page;
572 printf("growing user (%d) stack by %d pages\n", proc->id, num_pages);
574 if(pgalloc_vrange(fault_page, num_pages) != fault_page) {
575 printf("failed to allocate VM for stack growth\n");
576 /* TODO: in the future we'd SIGSEGV the process here, for now just panic */
577 goto unhandled;
578 }
579 proc->user_stack_pg = fault_page;
580 return;
581 }
583 /* it's not a stack growth fault. since we don't do swapping yet, just
584 * fall to unhandled and panic
585 */
586 }
588 unhandled:
589 printf("~~~~ PAGE FAULT ~~~~\n");
590 printf("fault address: %x\n", fault_addr);
591 printf("error code: %x\n", frm->err);
593 if(frm->err & PG_PRESENT) {
594 if(frm->err & 8) {
595 printf("reserved bit set in some paging structure\n");
596 } else {
597 printf("%s protection violation ", (frm->err & PG_WRITABLE) ? "WRITE" : "READ");
598 printf("in %s mode\n", (frm->err & PG_USER) ? "user" : "kernel");
599 }
600 } else {
601 printf("page not present\n");
602 }
604 panic("unhandled page fault\n");
605 }
607 /* copy-on-write handler, called from pgfault above */
608 static int copy_on_write(struct vm_page *page)
609 {
610 int tmpvpg;
611 struct vm_page *newpage;
612 struct rbnode *vmnode;
613 struct process *p = get_current_proc();
615 assert(page->nref > 0);
617 /* first of all check the refcount. If it's 1 then we don't need to copy
618 * anything. This will happen when all forked processes except one have
619 * marked this read-write again after faulting.
620 */
621 if(page->nref == 1) {
622 set_page_bit(page->vpage, PG_WRITABLE, PAGE_ONLY);
623 return 0;
624 }
626 /* ok let's make a copy and mark it read-write */
627 if(!(newpage = malloc(sizeof *newpage))) {
628 printf("copy_on_write: failed to allocate new vm_page\n");
629 return -1;
630 }
631 newpage->vpage = page->vpage;
632 newpage->flags = page->flags;
634 if(!(tmpvpg = pgalloc(1, MEM_KERNEL))) {
635 printf("copy_on_write: failed to allocate physical page\n");
636 /* XXX proper action: SIGSEGV */
637 return -1;
638 }
639 newpage->ppage = virt_to_phys_page(tmpvpg);
640 newpage->nref = 1;
642 /* do the copy */
643 memcpy((void*)PAGE_TO_ADDR(tmpvpg), (void*)PAGE_TO_ADDR(page->vpage), PGSIZE);
644 unmap_page(tmpvpg);
645 pgfree(tmpvpg, 1);
647 /* set the new vm_page in the process vmmap */
648 vmnode = rb_findi(&p->vmmap, newpage->vpage);
649 assert(vmnode && vmnode->data == page); /* shouldn't be able to fail */
650 vmnode->data = newpage;
652 /* also update tha page table */
653 map_page(newpage->vpage, newpage->ppage, newpage->flags);
655 /* finally decrease the refcount at the original vm_page struct */
656 page->nref--;
657 return 0;
658 }
660 /* --- page range list node management --- */
661 #define NODES_IN_PAGE (PGSIZE / sizeof(struct page_range))
663 static struct page_range *alloc_node(void)
664 {
665 struct page_range *node;
666 int pg, i;
668 if(node_pool) {
669 node = node_pool;
670 node_pool = node_pool->next;
671 /*printf("alloc_node -> %x\n", (unsigned int)node);*/
672 return node;
673 }
675 /* no node structures in the pool, we need to allocate a new page,
676 * split it up into node structures, add them in the pool, and
677 * allocate one of them.
678 */
679 if(!(pg = pgalloc(1, MEM_KERNEL))) {
680 panic("ran out of physical memory while allocating VM range structures\n");
681 }
682 node_pool = (struct page_range*)PAGE_TO_ADDR(pg);
684 /* link them up, skip the first as we'll just allocate it anyway */
685 for(i=2; i<NODES_IN_PAGE; i++) {
686 node_pool[i - 1].next = node_pool + i;
687 }
688 node_pool[NODES_IN_PAGE - 1].next = 0;
690 /* grab the first and return it */
691 node = node_pool++;
692 /*printf("alloc_node -> %x\n", (unsigned int)node);*/
693 return node;
694 }
696 static void free_node(struct page_range *node)
697 {
698 node->next = node_pool;
699 node_pool = node;
700 /*printf("free_node\n");*/
701 }
703 /* clone_vm makes a copy of the current page tables, thus duplicating the
704 * virtual address space.
705 *
706 * For the kernel part of the address space (last 256 page directory entries)
707 * we don't want to diplicate the page tables, just point all page directory
708 * entries to the same set of page tables.
709 *
710 * If "cow" is non-zero it also marks the shared user-space pages as
711 * read-only, to implement copy-on-write.
712 */
713 void clone_vm(struct process *pdest, struct process *psrc, int cow)
714 {
715 int i, j, dirpg, tblpg, kstart_dirent;
716 uint32_t paddr;
717 uint32_t *ndir, *ntbl;
718 struct rbnode *vmnode;
720 /* allocate the new page directory */
721 if((dirpg = pgalloc(1, MEM_KERNEL)) == -1) {
722 panic("clone_vmem: failed to allocate page directory page\n");
723 }
724 ndir = (uint32_t*)PAGE_TO_ADDR(dirpg);
726 /* allocate a virtual page for temporarily mapping all new
727 * page tables while we populate them.
728 */
729 if((tblpg = pgalloc(1, MEM_KERNEL)) == -1) {
730 panic("clone_vmem: failed to allocate page table page\n");
731 }
732 ntbl = (uint32_t*)PAGE_TO_ADDR(tblpg);
734 /* we will allocate physical pages and map them to this virtual page
735 * as needed in the loop below. we don't need the physical page allocated
736 * by pgalloc.
737 */
738 free_phys_page(virt_to_phys((uint32_t)ntbl));
740 kstart_dirent = ADDR_TO_PAGE(KMEM_START) / 1024;
742 /* user space */
743 for(i=0; i<kstart_dirent; i++) {
744 if(pgdir[i] & PG_PRESENT) {
745 if(cow) {
746 /* first go through all the entries of the existing
747 * page table and unset the writable bits.
748 */
749 for(j=0; j<1024; j++) {
750 if(PGTBL(i)[j] & PG_PRESENT) {
751 clear_page_bit(i * 1024 + j, PG_WRITABLE, PAGE_ONLY);
752 /*PGTBL(i)[j] &= ~(uint32_t)PG_WRITABLE;*/
753 }
754 }
755 }
757 /* allocate a page table for the clone */
758 paddr = alloc_phys_page();
760 /* copy the page table */
761 map_page(tblpg, ADDR_TO_PAGE(paddr), 0);
762 memcpy(ntbl, PGTBL(i), PGSIZE);
764 /* set the new page directory entry */
765 ndir[i] = paddr | (pgdir[i] & PGOFFS_MASK);
766 } else {
767 ndir[i] = 0;
768 }
769 }
771 /* make a copy of the parent's vmmap tree pointing to the same vm_pages
772 * and increase the reference counters for all vm_pages.
773 */
774 rb_init(&pdest->vmmap, RB_KEY_INT);
775 rb_begin(&psrc->vmmap);
776 while((vmnode = rb_next(&psrc->vmmap))) {
777 struct vm_page *pg = vmnode->data;
778 pg->nref++;
780 /* insert the same vm_page to the new tree */
781 rb_inserti(&pdest->vmmap, pg->vpage, pg);
782 }
784 /* for the kernel space we'll just use the same page tables */
785 for(i=kstart_dirent; i<1023; i++) {
786 ndir[i] = pgdir[i];
787 }
789 /* also point the last page directory entry to the page directory address
790 * since we're relying on recursive page tables
791 */
792 paddr = virt_to_phys((uint32_t)ndir);
793 ndir[1023] = paddr | PG_PRESENT;
795 if(cow) {
796 /* we just changed all the page protection bits, so we need to flush the TLB */
797 flush_tlb();
798 }
800 /* unmap before freeing the virtual pages, to avoid deallocating the physical pages */
801 unmap_page(dirpg);
802 unmap_page(tblpg);
804 pgfree(dirpg, 1);
805 pgfree(tblpg, 1);
807 /* set the new page directory pointer */
808 pdest->ctx.pgtbl_paddr = paddr;
809 }
811 /* cleanup_vm called by exit to clean up any memory used by the process */
812 void cleanup_vm(struct process *p)
813 {
814 struct rbnode *vmnode;
816 /* go through the vm map and reduce refcounts all around
817 * when a ref goes to 0, free the physical page
818 */
819 rb_begin(&p->vmmap);
820 while((vmnode = rb_next(&p->vmmap))) {
821 struct vm_page *page = vmnode->data;
823 /* skip kernel pages obviously */
824 if(!(page->flags & PG_USER)) {
825 continue;
826 }
828 if(--page->nref <= 0) {
829 /* free the physical page if nref goes to 0 */
830 free_phys_page(PAGE_TO_ADDR(page->ppage));
831 }
832 }
834 /* destroying the tree will free the nodes */
835 rb_destroy(&p->vmmap);
836 }
839 int get_page_bit(int pgnum, uint32_t bit, int wholepath)
840 {
841 int tidx = PAGE_TO_PGTBL(pgnum);
842 int tent = PAGE_TO_PGTBL_PG(pgnum);
843 uint32_t *pgtbl = PGTBL(tidx);
845 if(wholepath) {
846 if((pgdir[tidx] & bit) == 0) {
847 return 0;
848 }
849 }
851 return pgtbl[tent] & bit;
852 }
854 void set_page_bit(int pgnum, uint32_t bit, int wholepath)
855 {
856 int tidx = PAGE_TO_PGTBL(pgnum);
857 int tent = PAGE_TO_PGTBL_PG(pgnum);
858 uint32_t *pgtbl = PGTBL(tidx);
860 if(wholepath) {
861 pgdir[tidx] |= bit;
862 }
863 pgtbl[tent] |= bit;
865 flush_tlb_page(pgnum);
866 }
868 void clear_page_bit(int pgnum, uint32_t bit, int wholepath)
869 {
870 int tidx = PAGE_TO_PGTBL(pgnum);
871 int tent = PAGE_TO_PGTBL_PG(pgnum);
872 uint32_t *pgtbl = PGTBL(tidx);
874 if(wholepath) {
875 pgdir[tidx] &= ~bit;
876 }
878 pgtbl[tent] &= ~bit;
880 flush_tlb_page(pgnum);
881 }
884 #define USER_PGDIR_ENTRIES PAGE_TO_PGTBL(KMEM_START_PAGE)
885 int cons_vmmap(struct rbtree *vmmap)
886 {
887 int i, j;
889 rb_init(vmmap, RB_KEY_INT);
891 for(i=0; i<USER_PGDIR_ENTRIES; i++) {
892 if(pgdir[i] & PG_PRESENT) {
893 /* page table is present, iterate through its 1024 pages */
894 uint32_t *pgtbl = PGTBL(i);
896 for(j=0; j<1024; j++) {
897 if(pgtbl[j] & PG_PRESENT) {
898 struct vm_page *vmp;
900 if(!(vmp = malloc(sizeof *vmp))) {
901 panic("cons_vmap failed to allocate memory");
902 }
903 vmp->vpage = i * 1024 + j;
904 vmp->ppage = ADDR_TO_PAGE(pgtbl[j] & PGENT_ADDR_MASK);
905 vmp->flags = pgtbl[j] & ATTR_PGTBL_MASK;
906 vmp->nref = 1; /* when first created assume no sharing */
908 rb_inserti(vmmap, vmp->vpage, vmp);
909 }
910 }
911 }
912 }
914 return 0;
915 }
917 struct vm_page *get_vm_page(int vpg)
918 {
919 return get_vm_page_proc(get_current_proc(), vpg);
920 }
922 struct vm_page *get_vm_page_proc(struct process *p, int vpg)
923 {
924 struct rbnode *node;
926 if(!p || !(node = rb_findi(&p->vmmap, vpg))) {
927 return 0;
928 }
929 return node->data;
930 }
933 void dbg_print_vm(int area)
934 {
935 struct page_range *node;
936 int last, intr_state;
938 intr_state = get_intr_state();
939 disable_intr();
941 node = pglist[area];
942 last = area == MEM_USER ? 0 : ADDR_TO_PAGE(KMEM_START);
944 printf("%s vm space\n", area == MEM_USER ? "user" : "kernel");
946 while(node) {
947 if(node->start > last) {
948 printf(" vm-used: %x -> %x\n", PAGE_TO_ADDR(last), PAGE_TO_ADDR(node->start));
949 }
951 printf(" vm-free: %x -> ", PAGE_TO_ADDR(node->start));
952 if(node->end >= PAGE_COUNT) {
953 printf("END\n");
954 } else {
955 printf("%x\n", PAGE_TO_ADDR(node->end));
956 }
958 last = node->end;
959 node = node->next;
960 }
962 set_intr_state(intr_state);
963 }