hfQ8FEs6

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