pZTR5Df0

1/* See COPYRIGHT for copyright information. */
2
3#include <inc/x86.h>
4#include <inc/mmu.h>
5#include <inc/error.h>
6#include <inc/string.h>
7#include <inc/assert.h>
8
9#include <kern/pmap.h>
10#include <kern/kclock.h>
11
12// These variables are set by i386_detect_memory()
13size_t npages;			// Amount of physical memory (in pages)
14static size_t npages_basemem;	// Amount of base memory (in pages)
15
16// These variables are set in mem_init()
17pde_t *kern_pgdir;		// Kernel's initial page directory
18struct PageInfo *pages;		// Physical page state array
19static struct PageInfo *page_free_list;	// Free list of physical pages
20
21
22// --------------------------------------------------------------
23// Detect machine's physical memory setup.
24// --------------------------------------------------------------
25
26static int
27nvram_read(int r)
28{
29	return mc146818_read(r) | (mc146818_read(r + 1) << 8);
30}
31
32static void
33i386_detect_memory(void)
34{
35	size_t basemem, extmem, ext16mem, totalmem;
36
37	// Use CMOS calls to measure available base & extended memory.
38	// (CMOS calls return results in kilobytes.)
39	basemem = nvram_read(NVRAM_BASELO);
40	extmem = nvram_read(NVRAM_EXTLO);
41	ext16mem = nvram_read(NVRAM_EXT16LO) * 64;
42
43	// Calculate the number of physical pages available in both base
44	// and extended memory.
45	if (ext16mem)
46		totalmem = 16 * 1024 + ext16mem;
47	else if (extmem)
48		totalmem = 1 * 1024 + extmem;
49	else
50		totalmem = basemem;
51
52	npages = totalmem / (PGSIZE / 1024);
53	npages_basemem = basemem / (PGSIZE / 1024);
54
55	cprintf("Physical memory: %uK available, base = %uK, extended = %uK\n",
56		totalmem, basemem, totalmem - basemem);
57}
58
59
60// --------------------------------------------------------------
61// Set up memory mappings above UTOP.
62// --------------------------------------------------------------
63
64static void boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm);
65static void check_page_free_list(bool only_low_memory);
66static void check_page_alloc(void);
67static void check_kern_pgdir(void);
68static physaddr_t check_va2pa(pde_t *pgdir, uintptr_t va);
69static void check_page(void);
70static void check_page_installed_pgdir(void);
71
72// This simple physical memory allocator is used only while JOS is setting
73// up its virtual memory system.  page_alloc() is the real allocator.
74//
75// If n>0, allocates enough pages of contiguous physical memory to hold 'n'
76// bytes.  Doesn't initialize the memory.  Returns a kernel virtual address.
77//
78// If n==0, returns the address of the next free page without allocating
79// anything.
80//
81// If we're out of memory, boot_alloc should panic.
82// This function may ONLY be used during initialization,
83// before the page_free_list list has been set up.
84static void *
85boot_alloc(uint32_t n)
86{
87	static char *nextfree;	// virtual address of next byte of free memory
88	char *result;
89
90	// Initialize nextfree if this is the first time.
91	// 'end' is a magic symbol automatically generated by the linker,
92	// which points to the end of the kernel's bss segment:
93	// the first virtual address that the linker did *not* assign
94	// to any kernel code or global variables.
95	if (!nextfree) {
96		extern char end[];
97		nextfree = ROUNDUP((char *) end, PGSIZE);
98	}
99
100	// Allocate a chunk large enough to hold 'n' bytes, then update
101	// nextfree.  Make sure nextfree is kept aligned
102	// to a multiple of PGSIZE.
103	//
104	// LAB 2: Your code here.
105	result=nextfree;
106	nextfree+=ROUNDUP(n,PGSIZE);
107	if((uint32_t)nextfree-KERNBASE>(npages*PGSIZE)){
108		panic("Out of memory!\n");
109	}
110	return result;
111}
112
113// Set up a two-level page table:
114//    kern_pgdir is its linear (virtual) address of the root
115//
116// This function only sets up the kernel part of the address space
117// (ie. addresses >= UTOP).  The user part of the address space
118// will be set up later.
119//
120// From UTOP to ULIM, the user is allowed to read but not write.
121// Above ULIM the user cannot read or write.
122void
123mem_init(void)
124{
125	uint32_t cr0;
126	size_t n;
127
128	// Find out how much memory the machine has (npages & npages_basemem).
129	i386_detect_memory();
130
131	// Remove this line when you're ready to test this function.
132	panic("mem_init: This function is not finished\n");
133
134	//////////////////////////////////////////////////////////////////////
135	// create initial page directory.
136	kern_pgdir = (pde_t *) boot_alloc(PGSIZE);
137	memset(kern_pgdir, 0, PGSIZE);
138
139	//////////////////////////////////////////////////////////////////////
140	// Recursively insert PD in itself as a page table, to form
141	// a virtual page table at virtual address UVPT.
142	// (For now, you don't have understand the greater purpose of the
143	// following line.)
144
145	// Permissions: kernel R, user R
146	kern_pgdir[PDX(UVPT)] = PADDR(kern_pgdir) | PTE_U | PTE_P;
147
148	//////////////////////////////////////////////////////////////////////
149	// Allocate an array of npages 'struct PageInfo's and store it in 'pages'.
150	// The kernel uses this array to keep track of physical pages: for
151	// each physical page, there is a corresponding struct PageInfo in this
152	// array.  'npages' is the number of physical pages in memory.  Use memset
153	// to initialize all fields of each struct PageInfo to 0.
154	// Your code goes here:
155	pages=(struct PageInfo*)boot_alloc(npages*sizeof(struct PageInfo));
156	memset(pages,0,npages*sizeof(struct PageInfo));
157
158
159	//////////////////////////////////////////////////////////////////////
160	// Now that we've allocated the initial kernel data structures, we set
161	// up the list of free physical pages. Once we've done so, all further
162	// memory management will go through the page_* functions. In
163	// particular, we can now map memory using boot_map_region
164	// or page_insert
165	page_init();
166
167	check_page_free_list(1);
168	check_page_alloc();
169	check_page();
170
171	//////////////////////////////////////////////////////////////////////
172	// Now we set up virtual memory
173
174	//////////////////////////////////////////////////////////////////////
175	// Map 'pages' read-only by the user at linear address UPAGES
176	// Permissions:
177	//    - the new image at UPAGES -- kernel R, user R
178	//      (ie. perm = PTE_U | PTE_P)
179	//    - pages itself -- kernel RW, user NONE
180	// Your code goes here:
181
182	//////////////////////////////////////////////////////////////////////
183	// Use the physical memory that 'bootstack' refers to as the kernel
184	// stack.  The kernel stack grows down from virtual address KSTACKTOP.
185	// We consider the entire range from [KSTACKTOP-PTSIZE, KSTACKTOP)
186	// to be the kernel stack, but break this into two pieces:
187	//     * [KSTACKTOP-KSTKSIZE, KSTACKTOP) -- backed by physical memory
188	//     * [KSTACKTOP-PTSIZE, KSTACKTOP-KSTKSIZE) -- not backed; so if
189	//       the kernel overflows its stack, it will fault rather than
190	//       overwrite memory.  Known as a "guard page".
191	//     Permissions: kernel RW, user NONE
192	// Your code goes here:
193
194	//////////////////////////////////////////////////////////////////////
195	// Map all of physical memory at KERNBASE.
196	// Ie.  the VA range [KERNBASE, 2^32) should map to
197	//      the PA range [0, 2^32 - KERNBASE)
198	// We might not have 2^32 - KERNBASE bytes of physical memory, but
199	// we just set up the mapping anyway.
200	// Permissions: kernel RW, user NONE
201	// Your code goes here:
202
203	// Check that the initial page directory has been set up correctly.
204	check_kern_pgdir();
205
206	// Switch from the minimal entry page directory to the full kern_pgdir
207	// page table we just created.	Our instruction pointer should be
208	// somewhere between KERNBASE and KERNBASE+4MB right now, which is
209	// mapped the same way by both page tables.
210	//
211	// If the machine reboots at this point, you've probably set up your
212	// kern_pgdir wrong.
213	lcr3(PADDR(kern_pgdir));
214
215	check_page_free_list(0);
216
217	// entry.S set the really important flags in cr0 (including enabling
218	// paging).  Here we configure the rest of the flags that we care about.
219	cr0 = rcr0();
220	cr0 |= CR0_PE|CR0_PG|CR0_AM|CR0_WP|CR0_NE|CR0_MP;
221	cr0 &= ~(CR0_TS|CR0_EM);
222	lcr0(cr0);
223
224	// Some more checks, only possible after kern_pgdir is installed.
225	check_page_installed_pgdir();
226}
227
228// --------------------------------------------------------------
229// Tracking of physical pages.
230// The 'pages' array has one 'struct PageInfo' entry per physical page.
231// Pages are reference counted, and free pages are kept on a linked list.
232// --------------------------------------------------------------
233
234//
235// Initialize page structure and memory free list.
236// After this is done, NEVER use boot_alloc again.  ONLY use the page
237// allocator functions below to allocate and deallocate physical
238// memory via the page_free_list.
239//
240void
241page_init(void)
242{
243	// The example code here marks all physical pages as free.
244	// However this is not truly the case.  What memory is free?
245	//  1) Mark physical page 0 as in use.
246	//     This way we preserve the real-mode IDT and BIOS structures
247	//     in case we ever need them.  (Currently we don't, but...)
248	//  2) The rest of base memory, [PGSIZE, npages_basemem * PGSIZE)
249	//     is free.
250	//  3) Then comes the IO hole [IOPHYSMEM, EXTPHYSMEM), which must
251	//     never be allocated.
252	//  4) Then extended memory [EXTPHYSMEM, ...).
253	//     Some of it is in use, some is free. Where is the kernel
254	//     in physical memory?  Which pages are already in use for
255	//     page tables and other data structures?
256	//
257	// Change the code to reflect this.
258	// NB: DO NOT actually touch the physical memory corresponding to
259	// free pages!
260	size_t i;
261	page_free_list=NULL;
262	for (i = 0; i < npages; i++) {
263		if(i==0){
264			pages[i].pp_ref=1;
265		}
266		else if(i<npages_basemem ){
267			pages[i].pp_ref=0;
268			pages[i].pp_link=page_free_list;
269			page_free_list=&pages[i];
270		}
271		else if(i>=IOPHYSMEM/PGSIZE&&i<EXTPHYSMEM/PGSIZE){
272			pages[i].pp_ref=1;
273		}
274		else{
275			pages[i].pp_ref=0;
276			pages[i].pp_link=page_free_list;
277			page_free_list=&pages[i];
278		}
279	}
280}
281
282//
283// Allocates a physical page.  If (alloc_flags & ALLOC_ZERO), fills the entire
284// returned physical page with '\0' bytes.  Does NOT increment the reference
285// count of the page - the caller must do these if necessary (either explicitly
286// or via page_insert).
287//
288// Be sure to set the pp_link field of the allocated page to NULL so
289// page_free can check for double-free bugs.
290//
291// Returns NULL if out of free memory.
292//
293// Hint: use page2kva and memset
294struct PageInfo *
295page_alloc(int alloc_flags)
296{
297	// Fill this function in
298	struct PageInfo *pp;
299	if(!page_free_list){
300		return NULL;
301	}
302	pp=page_free_list;
303	page_free_list=page_free_list->pp_link;
304	if(alloc_flags & ALLOC_ZERO)
305	{
306		memset(page2kva(pp),0,PGSIZE);
307	}
308	return pp;
309}
310
311//
312// Return a page to the free list.
313// (This function should only be called when pp->pp_ref reaches 0.)
314//
315void
316page_free(struct PageInfo *pp)
317{
318	// Fill this function in
319	// Hint: You may want to panic if pp->pp_ref is nonzero or
320	// pp->pp_link is not NULL.
321	if(pp->pp_link!=NULL){
322		panic("pp->pp_link is not NULL.\n");
323		//不是一个单独的页面
324	}
325	if(pp->pp_ref!=0){
326		panic("pp->pp_ref is nonzero");
327		//这个页面还在使用中
328	}
329	pp->pp_link=page_free_list;
330	page_free_list=pp;
331}
332
333//
334// Decrement the reference count on a page,
335// freeing it if there are no more refs.
336//
337void
338page_decref(struct PageInfo* pp)
339{
340	if (--pp->pp_ref == 0)
341		page_free(pp);
342}
343
344// Given 'pgdir', a pointer to a page directory, pgdir_walk returns
345// a pointer to the page table entry (PTE) for linear address 'va'.
346// This requires walking the two-level page table structure.
347//
348// The relevant page table page might not exist yet.
349// If this is true, and create == false, then pgdir_walk returns NULL.
350// Otherwise, pgdir_walk allocates a new page table page with page_alloc.
351//    - If the allocation fails, pgdir_walk returns NULL.
352//    - Otherwise, the new page's reference count is incremented,
353//	the page is cleared,
354//	and pgdir_walk returns a pointer into the new page table page.
355//
356// Hint 1: you can turn a PageInfo * into the physical address of the
357// page it refers to with page2pa() from kern/pmap.h.
358//
359// Hint 2: the x86 MMU checks permission bits in both the page directory
360// and the page table, so it's safe to leave permissions in the page
361// directory more permissive than strictly necessary.
362//
363// Hint 3: look at inc/mmu.h for useful macros that manipulate page
364// table and page directory entries.
365//
366pte_t *
367pgdir_walk(pde_t *pgdir, const void *va, int create)
368{
369	// Fill this function in
370	return NULL;
371}
372
373//
374// Map [va, va+size) of virtual address space to physical [pa, pa+size)
375// in the page table rooted at pgdir.  Size is a multiple of PGSIZE, and
376// va and pa are both page-aligned.
377// Use permission bits perm|PTE_P for the entries.
378//
379// This function is only intended to set up the ``static'' mappings
380// above UTOP. As such, it should *not* change the pp_ref field on the
381// mapped pages.
382//
383// Hint: the TA solution uses pgdir_walk
384static void
385boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm)
386{
387	// Fill this function in
388}
389
390//
391// Map the physical page 'pp' at virtual address 'va'.
392// The permissions (the low 12 bits) of the page table entry
393// should be set to 'perm|PTE_P'.
394//
395// Requirements
396//   - If there is already a page mapped at 'va', it should be page_remove()d.
397//   - If necessary, on demand, a page table should be allocated and inserted
398//     into 'pgdir'.
399//   - pp->pp_ref should be incremented if the insertion succeeds.
400//   - The TLB must be invalidated if a page was formerly present at 'va'.
401//
402// Corner-case hint: Make sure to consider what happens when the same
403// pp is re-inserted at the same virtual address in the same pgdir.
404// However, try not to distinguish this case in your code, as this
405// frequently leads to subtle bugs; there's an elegant way to handle
406// everything in one code path.
407//
408// RETURNS:
409//   0 on success
410//   -E_NO_MEM, if page table couldn't be allocated
411//
412// Hint: The TA solution is implemented using pgdir_walk, page_remove,
413// and page2pa.
414//
415int
416page_insert(pde_t *pgdir, struct PageInfo *pp, void *va, int perm)
417{
418	// Fill this function in
419	return 0;
420}
421
422//
423// Return the page mapped at virtual address 'va'.
424// If pte_store is not zero, then we store in it the address
425// of the pte for this page.  This is used by page_remove and
426// can be used to verify page permissions for syscall arguments,
427// but should not be used by most callers.
428//
429// Return NULL if there is no page mapped at va.
430//
431// Hint: the TA solution uses pgdir_walk and pa2page.
432//
433struct PageInfo *
434page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
435{
436	// Fill this function in
437	return NULL;
438}
439
440//
441// Unmaps the physical page at virtual address 'va'.
442// If there is no physical page at that address, silently does nothing.
443//
444// Details:
445//   - The ref count on the physical page should decrement.
446//   - The physical page should be freed if the refcount reaches 0.
447//   - The pg table entry corresponding to 'va' should be set to 0.
448//     (if such a PTE exists)
449//   - The TLB must be invalidated if you remove an entry from
450//     the page table.
451//
452// Hint: The TA solution is implemented using page_lookup,
453// 	tlb_invalidate, and page_decref.
454//
455void
456page_remove(pde_t *pgdir, void *va)
457{
458	// Fill this function in
459}
460
461//
462// Invalidate a TLB entry, but only if the page tables being
463// edited are the ones currently in use by the processor.
464//
465void
466tlb_invalidate(pde_t *pgdir, void *va)
467{
468	// Flush the entry only if we're modifying the current address space.
469	// For now, there is only one address space, so always invalidate.
470	invlpg(va);
471}
472
473
474// --------------------------------------------------------------
475// Checking functions.
476// --------------------------------------------------------------
477
478//
479// Check that the pages on the page_free_list are reasonable.
480//
481static void
482check_page_free_list(bool only_low_memory)
483{
484	struct PageInfo *pp;
485	unsigned pdx_limit = only_low_memory ? 1 : NPDENTRIES;
486	int nfree_basemem = 0, nfree_extmem = 0;
487	char *first_free_page;
488
489	if (!page_free_list)
490		panic("'page_free_list' is a null pointer!");
491
492	if (only_low_memory) {
493		// Move pages with lower addresses first in the free
494		// list, since entry_pgdir does not map all pages.
495		struct PageInfo *pp1, *pp2;
496		struct PageInfo **tp[2] = { &pp1, &pp2 };
497		for (pp = page_free_list; pp; pp = pp->pp_link) {
498			int pagetype = PDX(page2pa(pp)) >= pdx_limit;
499			*tp[pagetype] = pp;
500			tp[pagetype] = &pp->pp_link;
501		}
502		*tp[1] = 0;
503		*tp[0] = pp2;
504		page_free_list = pp1;
505	}
506
507	// if there's a page that shouldn't be on the free list,
508	// try to make sure it eventually causes trouble.
509	for (pp = page_free_list; pp; pp = pp->pp_link)
510		if (PDX(page2pa(pp)) < pdx_limit)
511			memset(page2kva(pp), 0x97, 128);
512
513	first_free_page = (char *) boot_alloc(0);
514	for (pp = page_free_list; pp; pp = pp->pp_link) {
515		// check that we didn't corrupt the free list itself
516		assert(pp >= pages);
517		assert(pp < pages + npages);
518		assert(((char *) pp - (char *) pages) % sizeof(*pp) == 0);
519
520		// check a few pages that shouldn't be on the free list
521		assert(page2pa(pp) != 0);
522		assert(page2pa(pp) != IOPHYSMEM);
523		assert(page2pa(pp) != EXTPHYSMEM - PGSIZE);
524		assert(page2pa(pp) != EXTPHYSMEM);
525		assert(page2pa(pp) < EXTPHYSMEM || (char *) page2kva(pp) >= first_free_page);
526
527		if (page2pa(pp) < EXTPHYSMEM)
528			++nfree_basemem;
529		else
530			++nfree_extmem;
531	}
532
533	assert(nfree_basemem > 0);
534	assert(nfree_extmem > 0);
535
536	cprintf("check_page_free_list() succeeded!\n");
537}
538
539//
540// Check the physical page allocator (page_alloc(), page_free(),
541// and page_init()).
542//
543static void
544check_page_alloc(void)
545{
546	struct PageInfo *pp, *pp0, *pp1, *pp2;
547	int nfree;
548	struct PageInfo *fl;
549	char *c;
550	int i;
551
552	if (!pages)
553		panic("'pages' is a null pointer!");
554
555	// check number of free pages
556	for (pp = page_free_list, nfree = 0; pp; pp = pp->pp_link)
557		++nfree;
558
559	// should be able to allocate three pages
560	pp0 = pp1 = pp2 = 0;
561	assert((pp0 = page_alloc(0)));
562	assert((pp1 = page_alloc(0)));
563	assert((pp2 = page_alloc(0)));
564
565	assert(pp0);
566	assert(pp1 && pp1 != pp0);
567	assert(pp2 && pp2 != pp1 && pp2 != pp0);
568	assert(page2pa(pp0) < npages*PGSIZE);
569	assert(page2pa(pp1) < npages*PGSIZE);
570	assert(page2pa(pp2) < npages*PGSIZE);
571
572	// temporarily steal the rest of the free pages
573	fl = page_free_list;
574	page_free_list = 0;
575
576	// should be no free memory
577	assert(!page_alloc(0));
578
579	// free and re-allocate?
580	page_free(pp0);
581	page_free(pp1);
582	page_free(pp2);
583	pp0 = pp1 = pp2 = 0;
584	assert((pp0 = page_alloc(0)));
585	assert((pp1 = page_alloc(0)));
586	assert((pp2 = page_alloc(0)));
587	assert(pp0);
588	assert(pp1 && pp1 != pp0);
589	assert(pp2 && pp2 != pp1 && pp2 != pp0);
590	assert(!page_alloc(0));
591
592	// test flags
593	memset(page2kva(pp0), 1, PGSIZE);
594	page_free(pp0);
595	assert((pp = page_alloc(ALLOC_ZERO)));
596	assert(pp && pp0 == pp);
597	c = page2kva(pp);
598	for (i = 0; i < PGSIZE; i++)
599		assert(c[i] == 0);
600
601	// give free list back
602	page_free_list = fl;
603
604	// free the pages we took
605	page_free(pp0);
606	page_free(pp1);
607	page_free(pp2);
608
609	// number of free pages should be the same
610	for (pp = page_free_list; pp; pp = pp->pp_link)
611		--nfree;
612	assert(nfree == 0);
613
614	cprintf("check_page_alloc() succeeded!\n");
615}
616
617//
618// Checks that the kernel part of virtual address space
619// has been set up roughly correctly (by mem_init()).
620//
621// This function doesn't test every corner case,
622// but it is a pretty good sanity check.
623//
624
625static void
626check_kern_pgdir(void)
627{
628	uint32_t i, n;
629	pde_t *pgdir;
630
631	pgdir = kern_pgdir;
632
633	// check pages array
634	n = ROUNDUP(npages*sizeof(struct PageInfo), PGSIZE);
635	for (i = 0; i < n; i += PGSIZE)
636		assert(check_va2pa(pgdir, UPAGES + i) == PADDR(pages) + i);
637
638
639	// check phys mem
640	for (i = 0; i < npages * PGSIZE; i += PGSIZE)
641		assert(check_va2pa(pgdir, KERNBASE + i) == i);
642
643	// check kernel stack
644	for (i = 0; i < KSTKSIZE; i += PGSIZE)
645		assert(check_va2pa(pgdir, KSTACKTOP - KSTKSIZE + i) == PADDR(bootstack) + i);
646	assert(check_va2pa(pgdir, KSTACKTOP - PTSIZE) == ~0);
647
648	// check PDE permissions
649	for (i = 0; i < NPDENTRIES; i++) {
650		switch (i) {
651		case PDX(UVPT):
652		case PDX(KSTACKTOP-1):
653		case PDX(UPAGES):
654			assert(pgdir[i] & PTE_P);
655			break;
656		default:
657			if (i >= PDX(KERNBASE)) {
658				assert(pgdir[i] & PTE_P);
659				assert(pgdir[i] & PTE_W);
660			} else
661				assert(pgdir[i] == 0);
662			break;
663		}
664	}
665	cprintf("check_kern_pgdir() succeeded!\n");
666}
667
668// This function returns the physical address of the page containing 'va',
669// defined by the page directory 'pgdir'.  The hardware normally performs
670// this functionality for us!  We define our own version to help check
671// the check_kern_pgdir() function; it shouldn't be used elsewhere.
672
673static physaddr_t
674check_va2pa(pde_t *pgdir, uintptr_t va)
675{
676	pte_t *p;
677
678	pgdir = &pgdir[PDX(va)];
679	if (!(*pgdir & PTE_P))
680		return ~0;
681	p = (pte_t*) KADDR(PTE_ADDR(*pgdir));
682	if (!(p[PTX(va)] & PTE_P))
683		return ~0;
684	return PTE_ADDR(p[PTX(va)]);
685}
686
687
688// check page_insert, page_remove, &c
689static void
690check_page(void)
691{
692	struct PageInfo *pp, *pp0, *pp1, *pp2;
693	struct PageInfo *fl;
694	pte_t *ptep, *ptep1;
695	void *va;
696	int i;
697	extern pde_t entry_pgdir[];
698
699	// should be able to allocate three pages
700	pp0 = pp1 = pp2 = 0;
701	assert((pp0 = page_alloc(0)));
702	assert((pp1 = page_alloc(0)));
703	assert((pp2 = page_alloc(0)));
704
705	assert(pp0);
706	assert(pp1 && pp1 != pp0);
707	assert(pp2 && pp2 != pp1 && pp2 != pp0);
708
709	// temporarily steal the rest of the free pages
710	fl = page_free_list;
711	page_free_list = 0;
712
713	// should be no free memory
714	assert(!page_alloc(0));
715
716	// there is no page allocated at address 0
717	assert(page_lookup(kern_pgdir, (void *) 0x0, &ptep) == NULL);
718
719	// there is no free memory, so we can't allocate a page table
720	assert(page_insert(kern_pgdir, pp1, 0x0, PTE_W) < 0);
721
722	// free pp0 and try again: pp0 should be used for page table
723	page_free(pp0);
724	assert(page_insert(kern_pgdir, pp1, 0x0, PTE_W) == 0);
725	assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
726	assert(check_va2pa(kern_pgdir, 0x0) == page2pa(pp1));
727	assert(pp1->pp_ref == 1);
728	assert(pp0->pp_ref == 1);
729
730	// should be able to map pp2 at PGSIZE because pp0 is already allocated for page table
731	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
732	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
733	assert(pp2->pp_ref == 1);
734
735	// should be no free memory
736	assert(!page_alloc(0));
737
738	// should be able to map pp2 at PGSIZE because it's already there
739	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
740	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
741	assert(pp2->pp_ref == 1);
742
743	// pp2 should NOT be on the free list
744	// could happen in ref counts are handled sloppily in page_insert
745	assert(!page_alloc(0));
746
747	// check that pgdir_walk returns a pointer to the pte
748	ptep = (pte_t *) KADDR(PTE_ADDR(kern_pgdir[PDX(PGSIZE)]));
749	assert(pgdir_walk(kern_pgdir, (void*)PGSIZE, 0) == ptep+PTX(PGSIZE));
750
751	// should be able to change permissions too.
752	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W|PTE_U) == 0);
753	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
754	assert(pp2->pp_ref == 1);
755	assert(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U);
756	assert(kern_pgdir[0] & PTE_U);
757
758	// should be able to remap with fewer permissions
759	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
760	assert(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_W);
761	assert(!(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U));
762
763	// should not be able to map at PTSIZE because need free page for page table
764	assert(page_insert(kern_pgdir, pp0, (void*) PTSIZE, PTE_W) < 0);
765
766	// insert pp1 at PGSIZE (replacing pp2)
767	assert(page_insert(kern_pgdir, pp1, (void*) PGSIZE, PTE_W) == 0);
768	assert(!(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U));
769
770	// should have pp1 at both 0 and PGSIZE, pp2 nowhere, ...
771	assert(check_va2pa(kern_pgdir, 0) == page2pa(pp1));
772	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp1));
773	// ... and ref counts should reflect this
774	assert(pp1->pp_ref == 2);
775	assert(pp2->pp_ref == 0);
776
777	// pp2 should be returned by page_alloc
778	assert((pp = page_alloc(0)) && pp == pp2);
779
780	// unmapping pp1 at 0 should keep pp1 at PGSIZE
781	page_remove(kern_pgdir, 0x0);
782	assert(check_va2pa(kern_pgdir, 0x0) == ~0);
783	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp1));
784	assert(pp1->pp_ref == 1);
785	assert(pp2->pp_ref == 0);
786
787	// test re-inserting pp1 at PGSIZE
788	assert(page_insert(kern_pgdir, pp1, (void*) PGSIZE, 0) == 0);
789	assert(pp1->pp_ref);
790	assert(pp1->pp_link == NULL);
791
792	// unmapping pp1 at PGSIZE should free it
793	page_remove(kern_pgdir, (void*) PGSIZE);
794	assert(check_va2pa(kern_pgdir, 0x0) == ~0);
795	assert(check_va2pa(kern_pgdir, PGSIZE) == ~0);
796	assert(pp1->pp_ref == 0);
797	assert(pp2->pp_ref == 0);
798
799	// so it should be returned by page_alloc
800	assert((pp = page_alloc(0)) && pp == pp1);
801
802	// should be no free memory
803	assert(!page_alloc(0));
804
805	// forcibly take pp0 back
806	assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
807	kern_pgdir[0] = 0;
808	assert(pp0->pp_ref == 1);
809	pp0->pp_ref = 0;
810
811	// check pointer arithmetic in pgdir_walk
812	page_free(pp0);
813	va = (void*)(PGSIZE * NPDENTRIES + PGSIZE);
814	ptep = pgdir_walk(kern_pgdir, va, 1);
815	ptep1 = (pte_t *) KADDR(PTE_ADDR(kern_pgdir[PDX(va)]));
816	assert(ptep == ptep1 + PTX(va));
817	kern_pgdir[PDX(va)] = 0;
818	pp0->pp_ref = 0;
819
820	// check that new page tables get cleared
821	memset(page2kva(pp0), 0xFF, PGSIZE);
822	page_free(pp0);
823	pgdir_walk(kern_pgdir, 0x0, 1);
824	ptep = (pte_t *) page2kva(pp0);
825	for(i=0; i<NPTENTRIES; i++)
826		assert((ptep[i] & PTE_P) == 0);
827	kern_pgdir[0] = 0;
828	pp0->pp_ref = 0;
829
830	// give free list back
831	page_free_list = fl;
832
833	// free the pages we took
834	page_free(pp0);
835	page_free(pp1);
836	page_free(pp2);
837
838	cprintf("check_page() succeeded!\n");
839}
840
841// check page_insert, page_remove, &c, with an installed kern_pgdir
842static void
843check_page_installed_pgdir(void)
844{
845	struct PageInfo *pp, *pp0, *pp1, *pp2;
846	struct PageInfo *fl;
847	pte_t *ptep, *ptep1;
848	uintptr_t va;
849	int i;
850
851	// check that we can read and write installed pages
852	pp1 = pp2 = 0;
853	assert((pp0 = page_alloc(0)));
854	assert((pp1 = page_alloc(0)));
855	assert((pp2 = page_alloc(0)));
856	page_free(pp0);
857	memset(page2kva(pp1), 1, PGSIZE);
858	memset(page2kva(pp2), 2, PGSIZE);
859	page_insert(kern_pgdir, pp1, (void*) PGSIZE, PTE_W);
860	assert(pp1->pp_ref == 1);
861	assert(*(uint32_t *)PGSIZE == 0x01010101U);
862	page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W);
863	assert(*(uint32_t *)PGSIZE == 0x02020202U);
864	assert(pp2->pp_ref == 1);
865	assert(pp1->pp_ref == 0);
866	*(uint32_t *)PGSIZE = 0x03030303U;
867	assert(*(uint32_t *)page2kva(pp2) == 0x03030303U);
868	page_remove(kern_pgdir, (void*) PGSIZE);
869	assert(pp2->pp_ref == 0);
870
871	// forcibly take pp0 back
872	assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
873	kern_pgdir[0] = 0;
874	assert(pp0->pp_ref == 1);
875	pp0->pp_ref = 0;
876
877	// free the pages we took
878	page_free(pp0);
879
880	cprintf("check_page_installed_pgdir() succeeded!\n");
881}