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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#define MEM_ENTRY_ADDR 0x7000
13
14// These variables are set by i386_detect_memory()
15size_t npages;			// Amount of physical memory (in pages)
16static size_t npages_basemem;	// Amount of base memory (in pages)
17
18// These variables are set in mem_init()
19pde_t *kern_pgdir;		// Kernel's initial page directory
20struct PageInfo *pages;		// Physical page state array
21static struct PageInfo *page_free_list;	// Free list of physical pages
22
23
24// --------------------------------------------------------------
25// Detect machine's physical memory setup.
26// --------------------------------------------------------------
27
28static int
29nvram_read(int r)
30{
31	return mc146818_read(r) | (mc146818_read(r + 1) << 8);
32}
33
34static void
35i386_detect_memory(void)
36{
37	size_t basemem, extmem, ext16mem, totalmem;
38
39	// Use CMOS calls to measure available base & extended memory.
40	// (CMOS calls return results in kilobytes.)
41	basemem = nvram_read(NVRAM_BASELO);
42	extmem = nvram_read(NVRAM_EXTLO);
43	ext16mem = nvram_read(NVRAM_EXT16LO) * 64;
44
45	// Calculate the number of physical pages available in both base
46	// and extended memory.
47	if (ext16mem)
48		totalmem = 16 * 1024 + ext16mem;
49	else if (extmem)
50		totalmem = 1 * 1024 + extmem;
51	else
52		totalmem = basemem;
53
54	npages = totalmem / (PGSIZE / 1024);
55	npages_basemem = basemem / (PGSIZE / 1024);
56
57	cprintf("Physical memory: %uK available, base = %uK, extended = %uK\n",
58		totalmem, basemem, totalmem - basemem);
59}
60
61
62// --------------------------------------------------------------
63// Set up memory mappings above UTOP.
64// --------------------------------------------------------------
65
66static void boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm);
67static void check_page_free_list(bool only_low_memory);
68static void check_page_alloc(void);
69static void check_kern_pgdir(void);
70static physaddr_t check_va2pa(pde_t *pgdir, uintptr_t va);
71static void check_page(void);
72static void check_page_installed_pgdir(void);
73
74// This simple physical memory allocator is used only while JOS is setting
75// up its virtual memory system.  page_alloc() is the real allocator.
76//
77// If n>0, allocates enough pages of contiguous physical memory to hold 'n'
78// bytes.  Doesn't initialize the memory.  Returns a kernel virtual address.
79//
80// If n==0, returns the address of the next free page without allocating
81// anything.
82//
83// If we're out of memory, boot_alloc should panic.
84// This function may ONLY be used during initialization,
85// before the page_free_list list has been set up.
86static void *
87boot_alloc(uint32_t n)
88{
89	static char *nextfree;	// virtual address of next byte of free memory
90	char *result;
91
92	// Initialize nextfree if this is the first time.
93	// 'end' is a magic symbol automatically generated by the linker,
94	// which points to the end of the kernel's bss segment:
95	// the first virtual address that the linker did *not* assign
96	// to any kernel code or global variables.
97	if (!nextfree) {
98		extern char end[];
99		nextfree = ROUNDUP((char *) end, PGSIZE);
100	}
101
102	// Allocate a chunk large enough to hold 'n' bytes, then update
103	// nextfree.  Make sure nextfree is kept aligned
104	// to a multiple of PGSIZE.
105	//
106	// LAB 2: Your code here.
107
108	result = nextfree;  
109   	nextfree += (uint32_t)ROUNDUP((char *) n, PGSIZE);  
110	//check if we are out of memory, if yes, send an error
111	if ((uint32_t) nextfree > (npages * PGSIZE + KERNBASE)){
112        	panic("boot_alloc: we're out of memory to allocate!\n");  
113	}
114
115	return result;
116}
117
118// Set up a two-level page table:
119//    kern_pgdir is its linear (virtual) address of the root
120//
121// This function only sets up the kernel part of the address space
122// (ie. addresses >= UTOP).  The user part of the address space
123// will be set up later.
124//
125// From UTOP to ULIM, the user is allowed to read but not write.
126// Above ULIM the user cannot read or write.
127void
128mem_init(void)
129{
130	uint32_t cr0;
131	size_t n;
132
133	// Find out how much memory the machine has (npages & npages_basemem).
134	i386_detect_memory();
135
136	// Remove this line when you're ready to test this function.
137	//panic("mem_init: This function is not finished\n");
138
139	//////////////////////////////////////////////////////////////////////
140	// create initial page directory.
141	kern_pgdir = (pde_t *) boot_alloc(PGSIZE);
142	memset(kern_pgdir, 0, PGSIZE);
143
144	//////////////////////////////////////////////////////////////////////
145	// Recursively insert PD in itself as a page table, to form
146	// a virtual page table at virtual address UVPT.
147	// (For now, you don't have understand the greater purpose of the
148	// following line.)
149
150	// Permissions: kernel R, user R
151	kern_pgdir[PDX(UVPT)] = PADDR(kern_pgdir) | PTE_U | PTE_P;
152
153	//////////////////////////////////////////////////////////////////////
154	// Allocate an array of npages 'struct PageInfo's and store it in 'pages'.
155	// The kernel uses this array to keep track of physical pages: for
156	// each physical page, there is a corresponding struct PageInfo in this
157	// array.  'npages' is the number of physical pages in memory.  Use memset
158	// to initialize all fields of each struct PageInfo to 0.
159	// Your code goes here:
160	
161	uint32_t mysize = npages * sizeof(struct PageInfo);
162	pages = (struct PageInfo *) boot_alloc(mysize);
163	memset(pages, 0, mysize);  
164  
165	//////////////////////////////////////////////////////////////////////
166	// Now that we've allocated the initial kernel data structures, we set
167	// up the list of free physical pages. Once we've done so, all further
168	// memory management will go through the page_* functions. In
169	// particular, we can now map memory using boot_map_region
170	// or page_insert
171	page_init();
172
173	check_page_free_list(1);
174	check_page_alloc();
175	check_page();
176
177	//////////////////////////////////////////////////////////////////////
178	// Now we set up virtual memory
179
180	//////////////////////////////////////////////////////////////////////
181	// Map 'pages' read-only by the user at linear address UPAGES
182	// Permissions:
183	//    - the new image at UPAGES -- kernel R, user R
184	//      (ie. perm = PTE_U | PTE_P)
185	//    - pages itself -- kernel RW, user NONE
186	// Your code goes here:
187	
188	//To map paqes, we will use boot_map_region function
189	//boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm)
190	//at linear address UPAGES
191	uint32_t pa = PADDR(pages);
192	// Size is a multiple of PGSIZE, hence we use the size of page table
193	size_t custom_page_size = PTSIZE;
194	boot_map_region(kern_pgdir, UPAGES, custom_page_size, pa, (PTE_U | PTE_P));
195
196	//////////////////////////////////////////////////////////////////////
197	// Use the physical memory that 'bootstack' refers to as the kernel
198	// stack.  The kernel stack grows down from virtual address KSTACKTOP.
199	// We consider the entire range from [KSTACKTOP-PTSIZE, KSTACKTOP)
200	// to be the kernel stack, but break this into two pieces:
201	//     * [KSTACKTOP-KSTKSIZE, KSTACKTOP) -- backed by physical memory
202	//     * [KSTACKTOP-PTSIZE, KSTACKTOP-KSTKSIZE) -- not backed; so if
203	//       the kernel overflows its stack, it will fault rather than
204	//       overwrite memory.  Known as a "guard page".
205	//     Permissions: kernel RW, user NONE
206	// Your code goes here:
207	pa = PADDR(bootstack);
208	custom_page_size = KSTKSIZE; //CPU's kernel stack size
209	//[KSTACKTOP-KSTKSIZE, KSTACKTOP) -- backed by physical memory
210	boot_map_region(kern_pgdir, (KSTACKTOP-KSTKSIZE), custom_page_size, pa, (PTE_W | PTE_P));
211
212	//////////////////////////////////////////////////////////////////////
213	// Map all of physical memory at KERNBASE.
214	// Ie.  the VA range [KERNBASE, 2^32) should map to
215	//      the PA range [0, 2^32 - KERNBASE)
216	// We might not have 2^32 - KERNBASE bytes of physical memory, but
217	// we just set up the mapping anyway.
218	// Permissions: kernel RW, user NONE
219	// Your code goes here:
220
221	// Map all of physical memory at KERNBASE.
222	//2^32 is 0xFFFFFFFF in hex, so 0xFFFFFFFF-KERNBASE
223	custom_page_size = 0xFFFFFFFF-KERNBASE;
224	boot_map_region(kern_pgdir, KERNBASE, custom_page_size, 0, PTE_W | PTE_P);
225
226
227	// Check that the initial page directory has been set up correctly.
228	check_kern_pgdir();
229
230	// Switch from the minimal entry page directory to the full kern_pgdir
231	// page table we just created.	Our instruction pointer should be
232	// somewhere between KERNBASE and KERNBASE+4MB right now, which is
233	// mapped the same way by both page tables.
234	//
235	// If the machine reboots at this point, you've probably set up your
236	// kern_pgdir wrong.
237	lcr3(PADDR(kern_pgdir));
238
239	check_page_free_list(0);
240
241	// entry.S set the really important flags in cr0 (including enabling
242	// paging).  Here we configure the rest of the flags that we care about.
243	cr0 = rcr0();
244	cr0 |= CR0_PE|CR0_PG|CR0_AM|CR0_WP|CR0_NE|CR0_MP;
245	cr0 &= ~(CR0_TS|CR0_EM);
246	lcr0(cr0);
247
248	// Some more checks, only possible after kern_pgdir is installed.
249	check_page_installed_pgdir();
250}
251
252// --------------------------------------------------------------
253// Tracking of physical pages.
254// The 'pages' array has one 'struct PageInfo' entry per physical page.
255// Pages are reference counted, and free pages are kept on a linked list.
256// --------------------------------------------------------------
257
258//
259// Initialize page structure and memory free list.
260// After this is done, NEVER use boot_alloc again.  ONLY use the page
261// allocator functions below to allocate and deallocate physical
262// memory via the page_free_list.
263//
264void
265page_init(void)
266{
267	// The example code here marks all physical pages as free.
268	// However this is not truly the case.  What memory is free?
269	//  1) Mark physical page 0 as in use.
270	//     This way we preserve the real-mode IDT and BIOS structures
271	//     in case we ever need them.  (Currently we don't, but...)
272	//  2) The rest of base memory, [PGSIZE, npages_basemem * PGSIZE)
273	//     is free.
274	//  3) Then comes the IO hole [IOPHYSMEM, EXTPHYSMEM), which must
275	//     never be allocated.
276	//  4) Then extended memory [EXTPHYSMEM, ...).
277	//     Some of it is in use, some is free. Where is the kernel
278	//     in physical memory?  Which pages are already in use for
279	//     page tables and other data structures?
280	//
281	// Change the code to reflect this.
282	// NB: DO NOT actually touch the physical memory corresponding to
283	// free pages!
284	size_t i;
285	//We will refer to memlayout to understand the layout of our memory and the bifurcations
286	uint32_t kern_size = (uint32_t)boot_alloc(0) - KERNBASE;
287	uint32_t kern_pages_cnt = kern_size/PGSIZE;
288
289	int a1 = 0, b1 = 0;
290	for (i = 0; i < npages; i++) {
291		pages[i].pp_link = NULL;
292		
293		//pages[i].pp_link = page_free_list;
294		if ((i==0) || ( i < EXTPHYSMEM/PGSIZE + kern_pages_cnt && i >= npages_basemem )){
295			a1 += 1;
296			pages[i].pp_ref = 1;
297		} else {
298			b1 += 1;
299			//cprintf("Checkpoint B, ");	
300			pages[i].pp_ref = 0;
301			pages->pp_link = page_free_list;
302			page_free_list = &pages[i];
303		}
304	}
305	cprintf("page_init succeeded, npages = %d\n", npages);
306	cprintf("a1, b1= %d | %d\n", a1, b1);
307	cprintf("Size of page_free_list = %d\n", sizeof(page_free_list));
308}
309
310
311
312struct PageInfo *
313page_alloc(int alloc_flags)
314{
315	//
316// Allocates a physical page.  If (alloc_flags & ALLOC_ZERO), fills the entire
317// returned physical page with '\0' bytes.  Does NOT increment the reference
318// count of the page - the caller must do these if necessary (either explicitly
319// or via page_insert).
320//
321// Be sure to set the pp_link field of the allocated page to NULL so
322// page_free can check for double-free bugs.
323//
324// Returns NULL if out of free memory.
325//
326// Hint: use page2kva and memset
327
328	struct PageInfo *pp = page_free_list;
329
330	if (pp)
331	{	
332		//Check if pointers to the page is 0.
333		assert (pp->pp_ref == 0);
334		//next page on the free list. transfer the value to free list and clear
335		page_free_list = pp->pp_link;
336		pp->pp_link = NULL;
337
338
339		if(alloc_flags & ALLOC_ZERO){
340		//page2kva(struct PageInfo *pp)		
341			memset (page2kva(pp), 0, PGSIZE);
342		}
343		return pp;
344
345	} else {
346		return NULL;
347	}
348}
349
350//
351// Return a page to the free list.
352// (This function should only be called when pp->pp_ref reaches 0.)
353//
354void
355page_free(struct PageInfo *pp)
356{
357	// Fill this function in
358	// Hint: You may want to panic if pp->pp_ref is nonzero or
359	// pp->pp_link is not NULL.
360
361	//assert creates panic if it is false	
362	assert (pp->pp_link == NULL);
363	assert (pp->pp_ref == 0);
364	
365	pp->pp_link = page_free_list;
366	page_free_list = pp;
367	
368}	
369
370//
371// Decrement the reference count on a page,
372// freeing it if there are no more refs.
373//
374void
375page_decref(struct PageInfo* pp)
376{
377	if (--pp->pp_ref == 0)
378		page_free(pp);
379}
380
381// Given 'pgdir', a pointer to a page directory, pgdir_walk returns
382// a pointer to the page table entry (PTE) for linear address 'va'.
383// This requires walking the two-level page table structure.
384//
385// The relevant page table page might not exist yet.
386// If this is true, and create == false, then pgdir_walk returns NULL.
387// Otherwise, pgdir_walk allocates a new page table page with page_alloc.
388//    - If the allocation fails, pgdir_walk returns NULL.
389//    - Otherwise, the new page's reference count is incremented,
390//	the page is cleared,
391//	and pgdir_walk returns a pointer into the new page table page.
392//
393// Hint 1: you can turn a PageInfo * into the physical address of the
394// page it refers to with page2pa() from kern/pmap.h.
395//
396// Hint 2: the x86 MMU checks permission bits in both the page directory
397// and the page table, so it's safe to leave permissions in the page
398// directory more permissive than strictly necessary.
399//
400// Hint 3: look at inc/mmu.h for useful macros that manipulate page
401// table and page directory entries.
402//
403pte_t *
404pgdir_walk(pde_t *pgdir, const void *va, int create)
405{	
406	//pde_t returns the the page directory of a pointer
407	// The PDX, PTX, PGOFF, and PGNUM macros decompose linear addresses as shown.
408// To construct a linear address la from PDX(la), PTX(la), and PGOFF(la),
409// use PGADDR(PDX(la), PTX(la), PGOFF(la)).
410	// Fill this function in
411
412	const uint32_t temp_va = PDX(va);
413	//pgdir is our page directory address
414	pte_t *entry_addr = pgdir + temp_va; 
415	struct PageInfo *pp;
416	if(*entry_addr & PTE_P){
417	} else {
418		//The directory entry does not exists
419		if(!create){
420			return NULL;
421		} else { 
422			pp = page_alloc(0); //To crate a page and memset 0, refer to page_alloc
423			if(!pp){
424				return NULL;
425			} else {
426				pp->pp_ref = pp->pp_ref+1;
427				*entry_addr = page2pa(pp); //Converting into physical address
428				//As per hint 2, we need to set the permission bits too. Executable, Valid, and Writable should be sufficient
429				*entry_addr += PTE_P + PTE_W + PTE_U;
430				//Update the if condition above now to check if the directory entry exists
431			}
432		}	
433	}
434	//pgdir_walk returns a pointer to the page table entry
435	//https://pdos.csail.mit.edu/6.828/2014/lec/l-josmem.html
436	//The PDX part of the address indexes into the page directory to give you a page table. 
437	//The PTX part indexes into the page table to give you a page, and then you add the low bits in.
438	pde_t *return_addr = KADDR(PTE_ADDR(*entry_addr))+PTX(va); //Getting the kernel address for the kernel
439	return return_addr;
440}
441
442static void
443boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm)
444{
445
446//
447// Map [va, va+size) of virtual address space to physical [pa, pa+size)
448// in the page table rooted at pgdir.  Size is a multiple of PGSIZE, and
449// va and pa are both page-aligned.
450// Use permission bits perm|PTE_P for the entries.
451//
452// This function is only intended to set up the ``static'' mappings
453// above UTOP. As such, it should *not* change the pp_ref field on the
454// mapped pages.
455//
456// Hint: the TA solution uses pgdir_walk
457
458	// Fill this function in
459	pde_t *pgdir_addr;
460	for(size_t i = 0; i < size; i += PGSIZE){
461		//create pages in the page directory
462		pgdir_addr  = pgdir_walk(pgdir, (void*)va + i, 1);
463		*pgdir_addr = (pa + i) + (perm | PTE_P); //Get the physical address along with the permission and replace the value
464	}
465
466}
467
468
469int
470page_insert(pde_t *pgdir, struct PageInfo *pp, void *va, int perm)
471{
472	//
473// Map the physical page 'pp' at virtual address 'va'.
474// The permissions (the low 12 bits) of the page table entry
475// should be set to 'perm|PTE_P'.
476//
477// Requirements
478//   - If there is already a page mapped at 'va', it should be page_remove()d.
479//   - If necessary, on demand, a page table should be allocated and inserted
480//     into 'pgdir'.
481//   - pp->pp_ref should be incremented if the insertion succeeds.
482//   - The TLB must be invalidated if a page was formerly present at 'va'.
483//
484// Corner-case hint: Make sure to consider what happens when the same
485// pp is re-inserted at the same virtual address in the same pgdir.
486// However, try not to distinguish this case in your code, as this
487// frequently leads to subtle bugs; there's an elegant way to handle
488// everything in one code path.
489//
490// RETURNS:
491//   0 on success
492//   -E_NO_MEM, if page table couldn't be allocated
493//
494// Hint: The TA solution is implemented using pgdir_walk, page_remove,
495// and page2pa.
496//
497
498	// Fill this function in
499	//return 0;
500	//We will do a pgdir_walk as suggested and create a pgdir if does not exist.
501	pte_t *mypte = pgdir_walk(pgdir, va, 1); //Page directory created
502
503	//Given if this fails, we need to return -E_NO_MEM;
504	if(!mypte){
505		return -E_NO_MEM;
506	} else {
507		pp->pp_ref = pp->pp_ref+1;
508	}
509
510	//To avoid duplication we can check if the permisions are already set, if yes, then it is a duplicate.
511	if(*mypte & PTE_P){
512		page_remove(pgdir, va); //got this idea from the hint
513	}
514
515	//page_insert(pde_t *pgdir, struct PageInfo *pp, void *va, int perm)
516	// The permissions (the low 12 bits) of the page table entry
517	// should be set to 'perm|PTE_P'.
518	*mypte = page2pa(pp); //Converting to physical address, took the inspiration from pgdir_walk
519	//Changing the permission of the page table entry
520	*mypte += perm | PTE_P;
521	//Change the permission of the complete page in the directory
522	const uint32_t page_addr = PDX(va);
523	pgdir[page_addr] = pgdir[page_addr] | perm; //Set the required permissions if not already set
524	return 0;
525}
526
527
528struct PageInfo *
529page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
530{
531	//
532// Return the page mapped at virtual address 'va'.
533// If pte_store is not zero, then we store in it the address
534// of the pte for this page.  This is used by page_remove and
535// can be used to verify page permissions for syscall arguments,
536// but should not be used by most callers.
537//
538// Return NULL if there is no page mapped at va.
539//
540// Hint: the TA solution uses pgdir_walk and pa2page.
541//
542
543	// Fill this function in
544	pde_t *pgdir_addr = pgdir_walk(pgdir, va, 0);;
545
546	if (!pgdir_addr || !(*pgdir_addr & PTE_P)){
547		return NULL;
548	}
549	if (pte_store){
550		*pte_store = pgdir_addr;
551	}
552	// Address in page table or page directory entry PTE_ADDR
553	return pa2page(PTE_ADDR(*pgdir_addr));
554
555}
556
557void
558page_remove(pde_t *pgdir, void *va)
559{
560
561//
562// Unmaps the physical page at virtual address 'va'.
563// If there is no physical page at that address, silently does nothing.
564//
565// Details:
566//   - The ref count on the physical page should decrement.
567//   - The physical page should be freed if the refcount reaches 0.
568//   - The pg table entry corresponding to 'va' should be set to 0.
569//     (if such a PTE exists)
570//   - The TLB must be invalidated if you remove an entry from
571//     the page table.
572//
573// Hint: The TA solution is implemented using page_lookup,
574// 	tlb_invalidate, and page_decref.
575//
576
577	// Fill this function in
578
579	//Since we do not have a pte_store to send to page lookup, we will initiatlize one.
580	//The hints have significantly declared the answer lol.
581
582	pte_t *mypte;
583	
584	struct PageInfo *pp;
585	pp = page_lookup(pgdir, va, &mypte);
586
587	if (pp)
588	{
589		*mypte = 0;
590		page_decref(pp);
591		tlb_invalidate(pgdir, va);
592
593
594	}
595}
596
597//
598// Invalidate a TLB entry, but only if the page tables being
599// edited are the ones currently in use by the processor.
600//
601void
602tlb_invalidate(pde_t *pgdir, void *va)
603{
604	// Flush the entry only if we're modifying the current address space.
605	// For now, there is only one address space, so always invalidate.
606	invlpg(va);
607}
608
609
610// --------------------------------------------------------------
611// Checking functions.
612// --------------------------------------------------------------
613
614//
615// Check that the pages on the page_free_list are reasonable.
616//
617static void
618check_page_free_list(bool only_low_memory)
619{
620	struct PageInfo *pp;
621	unsigned pdx_limit = only_low_memory ? 1 : NPDENTRIES;
622	int nfree_basemem = 0, nfree_extmem = 0;
623	char *first_free_page;
624
625	if (!page_free_list)
626		panic("'page_free_list' is a null pointer!");
627
628	if (only_low_memory) {
629		// Move pages with lower addresses first in the free
630		// list, since entry_pgdir does not map all pages.
631		struct PageInfo *pp1, *pp2;
632		struct PageInfo **tp[2] = { &pp1, &pp2 };
633		for (pp = page_free_list; pp; pp = pp->pp_link) {
634			int pagetype = PDX(page2pa(pp)) >= pdx_limit;
635			*tp[pagetype] = pp;
636			tp[pagetype] = &pp->pp_link;
637		}
638		*tp[1] = 0;
639		*tp[0] = pp2;
640		page_free_list = pp1;
641		cprintf("only_low_memory called\n");
642	}
643	cprintf("Size of page_free_list = %d\n", sizeof(page_free_list));
644	// if there's a page that shouldn't be on the free list,
645	// try to make sure it eventually causes trouble.
646	for (pp = page_free_list; pp; pp = pp->pp_link)
647		if (PDX(page2pa(pp)) < pdx_limit)
648			memset(page2kva(pp), 0x97, 128);
649
650	first_free_page = (char *) boot_alloc(0);
651	for (pp = page_free_list; pp; pp = pp->pp_link) {
652		cprintf("Size of pp = %d, page_free_list = %d\n", sizeof(pp), sizeof(page_free_list));
653		// check that we didn't corrupt the free list itself
654		assert(pp >= pages);
655		assert(pp < pages + npages);
656		assert(((char *) pp - (char *) pages) % sizeof(*pp) == 0);
657
658		// check a few pages that shouldn't be on the free list
659		assert(page2pa(pp) != 0);
660		assert(page2pa(pp) != IOPHYSMEM);
661		assert(page2pa(pp) != EXTPHYSMEM - PGSIZE);
662		assert(page2pa(pp) != EXTPHYSMEM);
663		assert(page2pa(pp) < EXTPHYSMEM || (char *) page2kva(pp) >= first_free_page);
664
665		cprintf("value of EXTPHYSMEM and page2pa(pp): %08x | %08x | %08x\n", EXTPHYSMEM, page2pa(pp));
666		if (page2pa(pp) < EXTPHYSMEM)
667			++nfree_basemem;
668		else
669			++nfree_extmem;
670	}
671	cprintf("value of nfree_basemem and nfree_extmem: %d | %d\n", nfree_basemem, nfree_extmem);
672	assert(nfree_basemem > 0);
673	assert(nfree_extmem > 0);
674
675
676	cprintf("check_page_free_list() succeeded!\n");
677}
678
679//
680// Check the physical page allocator (page_alloc(), page_free(),
681// and page_init()).
682//
683static void
684check_page_alloc(void)
685{
686	struct PageInfo *pp, *pp0, *pp1, *pp2;
687	int nfree;
688	struct PageInfo *fl;
689	char *c;
690	int i;
691
692	if (!pages)
693		panic("'pages' is a null pointer!");
694
695	// check number of free pages
696	for (pp = page_free_list, nfree = 0; pp; pp = pp->pp_link)
697		++nfree;
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	assert(page2pa(pp0) < npages*PGSIZE);
709	assert(page2pa(pp1) < npages*PGSIZE);
710	assert(page2pa(pp2) < npages*PGSIZE);
711
712	// temporarily steal the rest of the free pages
713	fl = page_free_list;
714	page_free_list = 0;
715
716	// should be no free memory
717	assert(!page_alloc(0));
718
719	// free and re-allocate?
720	page_free(pp0);
721	page_free(pp1);
722	page_free(pp2);
723	pp0 = pp1 = pp2 = 0;
724	assert((pp0 = page_alloc(0)));
725	assert((pp1 = page_alloc(0)));
726	assert((pp2 = page_alloc(0)));
727	assert(pp0);
728	assert(pp1 && pp1 != pp0);
729	assert(pp2 && pp2 != pp1 && pp2 != pp0);
730	assert(!page_alloc(0));
731
732	// test flags
733	memset(page2kva(pp0), 1, PGSIZE);
734	page_free(pp0);
735	assert((pp = page_alloc(ALLOC_ZERO)));
736	assert(pp && pp0 == pp);
737	c = page2kva(pp);
738	for (i = 0; i < PGSIZE; i++)
739		assert(c[i] == 0);
740
741	// give free list back
742	page_free_list = fl;
743
744	// free the pages we took
745	page_free(pp0);
746	page_free(pp1);
747	page_free(pp2);
748
749	// number of free pages should be the same
750	for (pp = page_free_list; pp; pp = pp->pp_link)
751		--nfree;
752	assert(nfree == 0);
753
754	cprintf("check_page_alloc() succeeded!\n");
755}
756
757//
758// Checks that the kernel part of virtual address space
759// has been set up roughly correctly (by mem_init()).
760//
761// This function doesn't test every corner case,
762// but it is a pretty good sanity check.
763//
764
765static void
766check_kern_pgdir(void)
767{
768	uint32_t i, n;
769	pde_t *pgdir;
770
771	pgdir = kern_pgdir;
772
773	// check pages array
774	n = ROUNDUP(npages*sizeof(struct PageInfo), PGSIZE);
775	for (i = 0; i < n; i += PGSIZE)
776		assert(check_va2pa(pgdir, UPAGES + i) == PADDR(pages) + i);
777
778
779	// check phys mem
780	for (i = 0; i < npages * PGSIZE; i += PGSIZE)
781		assert(check_va2pa(pgdir, KERNBASE + i) == i);
782
783	// check kernel stack
784	for (i = 0; i < KSTKSIZE; i += PGSIZE)
785		assert(check_va2pa(pgdir, KSTACKTOP - KSTKSIZE + i) == PADDR(bootstack) + i);
786	assert(check_va2pa(pgdir, KSTACKTOP - PTSIZE) == ~0);
787
788	// check PDE permissions
789	for (i = 0; i < NPDENTRIES; i++) {
790		switch (i) {
791		case PDX(UVPT):
792		case PDX(KSTACKTOP-1):
793		case PDX(UPAGES):
794			assert(pgdir[i] & PTE_P);
795			break;
796		default:
797			if (i >= PDX(KERNBASE)) {
798				assert(pgdir[i] & PTE_P);
799				assert(pgdir[i] & PTE_W);
800			} else
801				assert(pgdir[i] == 0);
802			break;
803		}
804	}
805	cprintf("check_kern_pgdir() succeeded!\n");
806}
807
808// This function returns the physical address of the page containing 'va',
809// defined by the page directory 'pgdir'.  The hardware normally performs
810// this functionality for us!  We define our own version to help check
811// the check_kern_pgdir() function; it shouldn't be used elsewhere.
812
813static physaddr_t
814check_va2pa(pde_t *pgdir, uintptr_t va)
815{
816	pte_t *p;
817
818	pgdir = &pgdir[PDX(va)];
819	if (!(*pgdir & PTE_P))
820		return ~0;
821	p = (pte_t*) KADDR(PTE_ADDR(*pgdir));
822	if (!(p[PTX(va)] & PTE_P))
823		return ~0;
824	return PTE_ADDR(p[PTX(va)]);
825}
826
827
828// check page_insert, page_remove, &c
829static void
830check_page(void)
831{
832	struct PageInfo *pp, *pp0, *pp1, *pp2;
833	struct PageInfo *fl;
834	pte_t *ptep, *ptep1;
835	void *va;
836	int i;
837	extern pde_t entry_pgdir[];
838
839	// should be able to allocate three pages
840	pp0 = pp1 = pp2 = 0;
841	assert((pp0 = page_alloc(0)));
842	assert((pp1 = page_alloc(0)));
843	assert((pp2 = page_alloc(0)));
844
845	assert(pp0);
846	assert(pp1 && pp1 != pp0);
847	assert(pp2 && pp2 != pp1 && pp2 != pp0);
848
849	// temporarily steal the rest of the free pages
850	fl = page_free_list;
851	page_free_list = 0;
852
853	// should be no free memory
854	assert(!page_alloc(0));
855
856	// there is no page allocated at address 0
857	assert(page_lookup(kern_pgdir, (void *) 0x0, &ptep) == NULL);
858
859	// there is no free memory, so we can't allocate a page table
860	assert(page_insert(kern_pgdir, pp1, 0x0, PTE_W) < 0);
861
862	// free pp0 and try again: pp0 should be used for page table
863	page_free(pp0);
864	assert(page_insert(kern_pgdir, pp1, 0x0, PTE_W) == 0);
865	assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
866	assert(check_va2pa(kern_pgdir, 0x0) == page2pa(pp1));
867	assert(pp1->pp_ref == 1);
868	assert(pp0->pp_ref == 1);
869
870	// should be able to map pp2 at PGSIZE because pp0 is already allocated for page table
871	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
872	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
873	assert(pp2->pp_ref == 1);
874
875	// should be no free memory
876	assert(!page_alloc(0));
877
878	// should be able to map pp2 at PGSIZE because it's already there
879	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
880	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
881	assert(pp2->pp_ref == 1);
882
883	// pp2 should NOT be on the free list
884	// could happen in ref counts are handled sloppily in page_insert
885	assert(!page_alloc(0));
886
887	// check that pgdir_walk returns a pointer to the pte
888	ptep = (pte_t *) KADDR(PTE_ADDR(kern_pgdir[PDX(PGSIZE)]));
889	assert(pgdir_walk(kern_pgdir, (void*)PGSIZE, 0) == ptep+PTX(PGSIZE));
890
891	// should be able to change permissions too.
892	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W|PTE_U) == 0);
893	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
894	assert(pp2->pp_ref == 1);
895	assert(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U);
896	assert(kern_pgdir[0] & PTE_U);
897
898	// should be able to remap with fewer permissions
899	assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
900	assert(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_W);
901	assert(!(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U));
902
903	// should not be able to map at PTSIZE because need free page for page table
904	assert(page_insert(kern_pgdir, pp0, (void*) PTSIZE, PTE_W) < 0);
905
906	// insert pp1 at PGSIZE (replacing pp2)
907	assert(page_insert(kern_pgdir, pp1, (void*) PGSIZE, PTE_W) == 0);
908	assert(!(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U));
909
910	// should have pp1 at both 0 and PGSIZE, pp2 nowhere, ...
911	assert(check_va2pa(kern_pgdir, 0) == page2pa(pp1));
912	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp1));
913	// ... and ref counts should reflect this
914	assert(pp1->pp_ref == 2);
915	assert(pp2->pp_ref == 0);
916
917	// pp2 should be returned by page_alloc
918	assert((pp = page_alloc(0)) && pp == pp2);
919
920	// unmapping pp1 at 0 should keep pp1 at PGSIZE
921	page_remove(kern_pgdir, 0x0);
922	assert(check_va2pa(kern_pgdir, 0x0) == ~0);
923	assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp1));
924	assert(pp1->pp_ref == 1);
925	assert(pp2->pp_ref == 0);
926
927	// test re-inserting pp1 at PGSIZE
928	assert(page_insert(kern_pgdir, pp1, (void*) PGSIZE, 0) == 0);
929	assert(pp1->pp_ref);
930	assert(pp1->pp_link == NULL);
931
932	// unmapping pp1 at PGSIZE should free it
933	page_remove(kern_pgdir, (void*) PGSIZE);
934	assert(check_va2pa(kern_pgdir, 0x0) == ~0);
935	assert(check_va2pa(kern_pgdir, PGSIZE) == ~0);
936	assert(pp1->pp_ref == 0);
937	assert(pp2->pp_ref == 0);
938
939	// so it should be returned by page_alloc
940	assert((pp = page_alloc(0)) && pp == pp1);
941
942	// should be no free memory
943	assert(!page_alloc(0));
944
945	// forcibly take pp0 back
946	assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
947	kern_pgdir[0] = 0;
948	assert(pp0->pp_ref == 1);
949	pp0->pp_ref = 0;
950
951	// check pointer arithmetic in pgdir_walk
952	page_free(pp0);
953	va = (void*)(PGSIZE * NPDENTRIES + PGSIZE);
954	ptep = pgdir_walk(kern_pgdir, va, 1);
955	ptep1 = (pte_t *) KADDR(PTE_ADDR(kern_pgdir[PDX(va)]));
956	assert(ptep == ptep1 + PTX(va));
957	kern_pgdir[PDX(va)] = 0;
958	pp0->pp_ref = 0;
959
960	// check that new page tables get cleared
961	memset(page2kva(pp0), 0xFF, PGSIZE);
962	page_free(pp0);
963	pgdir_walk(kern_pgdir, 0x0, 1);
964	ptep = (pte_t *) page2kva(pp0);
965	for(i=0; i<NPTENTRIES; i++)
966		assert((ptep[i] & PTE_P) == 0);
967	kern_pgdir[0] = 0;
968	pp0->pp_ref = 0;
969
970	// give free list back
971	page_free_list = fl;
972
973	// free the pages we took
974	page_free(pp0);
975	page_free(pp1);
976	page_free(pp2);
977
978	cprintf("check_page() succeeded!\n");
979}
980
981// check page_insert, page_remove, &c, with an installed kern_pgdir
982static void
983check_page_installed_pgdir(void)
984{
985	struct PageInfo *pp, *pp0, *pp1, *pp2;
986	struct PageInfo *fl;
987	pte_t *ptep, *ptep1;
988	uintptr_t va;
989	int i;
990
991	// check that we can read and write installed pages
992	pp1 = pp2 = 0;
993	assert((pp0 = page_alloc(0)));
994	assert((pp1 = page_alloc(0)));
995	assert((pp2 = page_alloc(0)));
996	page_free(pp0);
997	memset(page2kva(pp1), 1, PGSIZE);
998	memset(page2kva(pp2), 2, PGSIZE);
999	page_insert(kern_pgdir, pp1, (void*) PGSIZE, PTE_W);
1000	assert(pp1->pp_ref == 1);
1001	assert(*(uint32_t *)PGSIZE == 0x01010101U);
1002	page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W);
1003	assert(*(uint32_t *)PGSIZE == 0x02020202U);
1004	assert(pp2->pp_ref == 1);
1005	assert(pp1->pp_ref == 0);
1006	*(uint32_t *)PGSIZE = 0x03030303U;
1007	assert(*(uint32_t *)page2kva(pp2) == 0x03030303U);
1008	page_remove(kern_pgdir, (void*) PGSIZE);
1009	assert(pp2->pp_ref == 0);
1010
1011	// forcibly take pp0 back
1012	assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
1013	kern_pgdir[0] = 0;
1014	assert(pp0->pp_ref == 1);
1015	pp0->pp_ref = 0;
1016
1017	// free the pages we took
1018	page_free(pp0);
1019
1020	cprintf("check_page_installed_pgdir() succeeded!\n");
1021}