pmap.c~

jos lab3代码

	//     Some of it is in use, some is free. Where is the kernel?
	//     Which pages are used for page tables and other data structures?
	//
	// Change the code to reflect this.

	int i,con;
	LIST_INIT(&page_free_list);
	for (i = 0; i < npage; i++)
	 {	
		con=1;
		if(i!=0&&i<basemem/PGSIZE)
			con=0;
		if(i>=((int)boot_freemem-KERNBASE)/PGSIZE)
			con=0;
		pages[i].pp_ref = con;
		if(!con)
		LIST_INSERT_HEAD(&page_free_list, &pages[i], pp_link);
	}
}

//
// Initialize a Page structure.
// The result has null links and 0 refcount.
// Note that the corresponding physical page is NOT initialized!
//
static void
page_initpp(struct Page *pp)
{
	memset(pp, 0, sizeof(*pp));
}

//
// Allocates a physical page.
// Does NOT set the contents of the physical page to zero -
// the caller must do that if necessary.
//
// *pp_store -- is set to point to the Page struct of the newly allocated
// page
//
// RETURNS 
//   0 -- on success
//   -E_NO_MEM -- otherwise 
//
// Hint: use LIST_FIRST, LIST_REMOVE, and page_initpp
// Hint: pp_ref should not be incremented 
int
page_alloc(struct Page **pp_store)
{
	// Fill this function in
	struct Page *p = LIST_FIRST(&page_free_list);
    	if(p == NULL)
        	return -E_NO_MEM;
    	LIST_REMOVE(p, pp_link);
    	page_initpp(p);
    	*pp_store = p;
    	return 0;
}

//
// Return a page to the free list.
// (This function should only be called when pp->pp_ref reaches 0.)
//
void
page_free(struct Page *pp)
{
	// Fill this function in
	 LIST_INSERT_HEAD(&page_free_list, pp, pp_link);
}

//
// Decrement the reference count on a page,
// freeing it if there are no more refs.
//
void
page_decref(struct Page* pp)
{
	if (--pp->pp_ref == 0)
		page_free(pp);
}

// Given 'pgdir', a pointer to a page directory, pgdir_walk returns
// a pointer to the page table entry (PTE) for linear address 'va'.
// This requires walking the two-level page table structure.
//
// If the relevant page table doesn't exist in the page directory, then:
//    - If create == 0, pgdir_walk returns NULL.
//    - Otherwise, pgdir_walk tries to allocate a new page table
//	with page_alloc.  If this fails, pgdir_walk returns NULL.
//    - pgdir_walk sets pp_ref to 1 for the new page table.
//    - Finally, pgdir_walk returns a pointer into the new page table.
//
// Hint: you can turn a Page * into the physical address of the
// page it refers to with page2pa() from kern/pmap.h.
pte_t *
pgdir_walk(pde_t *pgdir, const void *va, int create)
{
	// Fill this function in

    pte_t *p;
    struct Page *pp;
    physaddr_t pa;
    pgdir = &pgdir[PDX(va)];
    if(!(*pgdir & PTE_P)){
        if(!create){ return NULL;}
        if(page_alloc(&pp) != 0) return NULL;
        pp->pp_ref++;
        pa = page2pa(pp);
        memset(KADDR(PTE_ADDR(pa)), 0 ,PGSIZE);
        *pgdir = pa | PTE_U | PTE_P | PTE_W;
    }
    p = (pte_t*) KADDR(PTE_ADDR((*pgdir)));
    return  &p[PTX(va)];

}

//
// Map the physical page 'pp' at virtual address 'va'.
// The permissions (the low 12 bits) of the page table
//  entry should be set to 'perm|PTE_P'.
//
// Details
//   - If there is already a page mapped at 'va', it is page_remove()d.
//   - If necessary, on demand, allocates a page table and inserts it into
//     'pgdir'.
//   - pp->pp_ref should be incremented if the insertion succeeds.
//   - The TLB must be invalidated if a page was formerly present at 'va'.
//
// RETURNS: 
//   0 on success
//   -E_NO_MEM, if page table couldn't be allocated
//
// Hint: The TA solution is implemented using pgdir_walk, page_remove,
// and page2pa.
//
int
page_insert(pde_t *pgdir, struct Page *pp, void *va, int perm) 
{
// Fill this function in
	pte_t * p;
	if((p=pgdir_walk(pgdir,va,1))==0)
		return -E_NO_MEM;
	if(*p&PTE_P)
	{
		if(pa2page(PTE_ADDR(*p))!=pp)
		{
			page_remove(pgdir,va);
			pp->pp_ref++;
		}
		*p=page2pa(pp)|perm|PTE_P;
	}
	else
	{
		*p=page2pa(pp)|perm|PTE_P;
		pp->pp_ref++;
	}

    return 0;
}

//
// Map [la, la+size) of linear address space to physical [pa, pa+size)
// in the page table rooted at pgdir.  Size is a multiple of PGSIZE.
// Use permission bits perm|PTE_P for the entries.
//
// This function is only intended to set up the ``static'' mappings
// above UTOP. As such, it should *not* change the pp_ref field on the
// mapped pages.
//
// Hint: the TA solution uses pgdir_walk
static void
boot_map_segment(pde_t *pgdir, uintptr_t la, size_t size, physaddr_t pa, int perm)
{
	int i=0;
	for(i=0;i<size;i+=PGSIZE)
	{
		*(pgdir_walk(pgdir,(void *)(la+i),1))=PTE_ADDR(pa+i)|perm|PTE_P;
	}
	// Fill this function in
}

//
// Return the page mapped at virtual address 'va'.
// If pte_store is not zero, then we store in it the address
// of the pte for this page.  This is used by page_remove
// but should not be used by other callers.
//
// Return 0 if there is no page mapped at va.
//
// Hint: the TA solution uses pgdir_walk and pa2page.
//
struct Page *
page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
{
	// Fill this function in
	*pte_store=pgdir_walk(pgdir,va,0);
	if(*pte_store != 0&&(**pte_store&PTE_P) )
		return pa2page(PTE_ADDR(**pte_store));
	return NULL;
}

//
// Unmaps the physical page at virtual address 'va'.
// If there is no physical page at that address, silently does nothing.
//
// Details:
//   - The ref count on the physical page should decrement.
//   - The physical page should be freed if the refcount reaches 0.
//   - The pg table entry corresponding to 'va' should be set to 0.
//     (if such a PTE exists)
//   - The TLB must be invalidated if you remove an entry from
//     the pg dir/pg table.
//
// Hint: The TA solution is implemented using page_lookup,
// 	tlb_invalidate, and page_decref.
//
void
page_remove(pde_t *pgdir, void *va)
{
	// Fill this function in
	pte_t* pp;
	struct Page *p=page_lookup(pgdir,va,&pp);
	if( p!=NULL){
		page_decref(p);
		*pp=0;
		tlb_invalidate(pgdir,va);
	} 
}

//
// Invalidate a TLB entry, but only if the page tables being
// edited are the ones currently in use by the processor.
//
void
tlb_invalidate(pde_t *pgdir, void *va)
{
	// Flush the entry only if we're modifying the current address space.
	// For now, there is only one address space, so always invalidate.
	invlpg(va);
}

static uintptr_t user_mem_check_addr;

//
// Check that an environment is allowed to access the range of memory
// [va, va+len) with permissions 'perm | PTE_P'.
// Normally 'perm' will contain PTE_U at least, but this is not required.
// 'va' and 'len' need not be page-aligned; you must test every page that
// contains any of that range.  You will test either 'len/PGSIZE',
// 'len/PGSIZE + 1', or 'len/PGSIZE + 2' pages.
//
// A user program can access a virtual address if (1) the address is below
// ULIM, and (2) the page table gives it permission.  These are exactly
// the tests you should implement here.
//
// If there is an error, set the 'user_mem_check_addr' variable to the first
// erroneous virtual address.
//
// Returns 0 if the user program can access this range of addresses,
// and -E_FAULT otherwise.
//
int
user_mem_check(struct Env *env, const void *va, size_t len, int perm)
{
	// LAB 3: Your code here. 
 // LAB 3: Your code here.
 uintptr_t va_start = (uintptr_t) va;
 uintptr_t va_end = va_start + len;

 uintptr_t vp = PPN(va_start) << PGSHIFT;
 uintptr_t vp_end = PPN(va_end) << PGSHIFT;
 perm |= PTE_P;

 for (; vp <= vp_end; vp += PGSIZE)
 {
  pte_t *ppte = pgdir_walk(env->env_pgdir, (void *) vp, 0);
  if ((ppte != NULL) && ((*ppte & perm) == perm))
   continue;

  user_mem_check_addr = (vp < va_start) ? va_start : vp;
  return -E_FAULT;
 }

 return 0;
}

//
// Checks that environment 'env' is allowed to access the range
// of memory [va, va+len) with permissions 'perm | PTE_U'.
// If it can, then the function simply returns.
// If it cannot, 'env' is destroyed.
//
void
user_mem_assert(struct Env *env, const void *va, size_t len, int perm)
{
	if (user_mem_check(env, va, len, perm | PTE_U) < 0) {
		cprintf("[%08x] user_mem_check assertion failure for "
			"va %08x\n", curenv->env_id, user_mem_check_addr);
		env_destroy(env);	// may not return
	}
}

// check page_insert, page_remove, &c
static void
page_check(void)
{
	struct Page *pp, *pp0, *pp1, *pp2;
	struct Page_list fl;
	pte_t *ptep, *ptep1;
	void *va;
	int i;

	// should be able to allocate three pages
	pp0 = pp1 = pp2 = 0;
	assert(page_alloc(&pp0) == 0);
	assert(page_alloc(&pp1) == 0);
	assert(page_alloc(&pp2) == 0);

	assert(pp0);
	assert(pp1 && pp1 != pp0);
	assert(pp2 && pp2 != pp1 && pp2 != pp0);

	// temporarily steal the rest of the free pages
	fl = page_free_list;
	LIST_INIT(&page_free_list);

	// should be no free memory
	assert(page_alloc(&pp) == -E_NO_MEM);

	// there is no page allocated at address 0
	assert(page_lookup(boot_pgdir, (void *) 0x0, &ptep) == NULL);

	// there is no free memory, so we can't allocate a page table 
	assert(page_insert(boot_pgdir, pp1, 0x0, 0) < 0);

	// free pp0 and try again: pp0 should be used for page table
	page_free(pp0);
	assert(page_insert(boot_pgdir, pp1, 0x0, 0) == 0);
	assert(PTE_ADDR(boot_pgdir[0]) == page2pa(pp0));
	assert(check_va2pa(boot_pgdir, 0x0) == page2pa(pp1));
	assert(pp1->pp_ref == 1);
	assert(pp0->pp_ref == 1);

	// should be able to map pp2 at PGSIZE because pp0 is already allocated for page table
	assert(page_insert(boot_pgdir, pp2, (void*) PGSIZE, 0) == 0);
	assert(check_va2pa(boot_pgdir, PGSIZE) == page2pa(pp2));
	assert(pp2->pp_ref == 1);

	// should be no free memory
	assert(page_alloc(&pp) == -E_NO_MEM);

	// should be able to map pp2 at PGSIZE because it's already there
	assert(page_insert(boot_pgdir, pp2, (void*) PGSIZE, 0) == 0);
	assert(check_va2pa(boot_pgdir, PGSIZE) == page2pa(pp2));
	assert(pp2->pp_ref == 1);

	// pp2 should NOT be on the free list
	// could happen in ref counts are handled sloppily in page_insert
	assert(page_alloc(&pp) == -E_NO_MEM);

	// check that pgdir_walk returns a pointer to the pte
	ptep = KADDR(PTE_ADDR(boot_pgdir[PDX(PGSIZE)]));
	assert(pgdir_walk(boot_pgdir, (void*)PGSIZE, 0) == ptep+PTX(PGSIZE));

	// should be able to change permissions too.
	assert(page_insert(boot_pgdir, pp2, (void*) PGSIZE, PTE_U) == 0);
	assert(check_va2pa(boot_pgdir, PGSIZE) == page2pa(pp2));
	assert(pp2->pp_ref == 1);
	assert(*pgdir_walk(boot_pgdir, (void*) PGSIZE, 0) & PTE_U);


	// should not be able to map at PTSIZE because need free page for page table
	assert(page_insert(boot_pgdir, pp0, (void*) PTSIZE, 0) < 0);

	// insert pp1 at PGSIZE (replacing pp2)
	assert(page_insert(boot_pgdir, pp1, (void*) PGSIZE, 0) == 0);

	// should have pp1 at both 0 and PGSIZE, pp2 nowhere, ...
	assert(check_va2pa(boot_pgdir, 0) == page2pa(pp1));
	assert(check_va2pa(boot_pgdir, PGSIZE) == page2pa(pp1));
	// ... and ref counts should reflect this
	
	assert(pp1->pp_ref == 2);
	assert(pp2->pp_ref == 0);

	// pp2 should be returned by page_alloc
	assert(page_alloc(&pp) == 0 && pp == pp2);

	// unmapping pp1 at 0 should keep pp1 at PGSIZE
	page_remove(boot_pgdir, 0x0);
	assert(check_va2pa(boot_pgdir, 0x0) == ~0);
	assert(check_va2pa(boot_pgdir, PGSIZE) == page2pa(pp1));
	assert(pp1->pp_ref == 1);
	assert(pp2->pp_ref == 0);

	// unmapping pp1 at PGSIZE should free it
	page_remove(boot_pgdir, (void*) PGSIZE);
	assert(check_va2pa(boot_pgdir, 0x0) == ~0);
	assert(check_va2pa(boot_pgdir, PGSIZE) == ~0);
	assert(pp1->pp_ref == 0);
	assert(pp2->pp_ref == 0);

	// so it should be returned by page_alloc
	assert(page_alloc(&pp) == 0 && pp == pp1);

	// should be no free memory
	assert(page_alloc(&pp) == -E_NO_MEM);
	
#if 0
	// should be able to page_insert to change a page
	// and see the new data immediately.
	memset(page2kva(pp1), 1, PGSIZE);
	memset(page2kva(pp2), 2, PGSIZE);
	page_insert(boot_pgdir, pp1, 0x0, 0);
	assert(pp1->pp_ref == 1);
	assert(*(int*)0 == 0x01010101);
	page_insert(boot_pgdir, pp2, 0x0, 0);
	assert(*(int*)0 == 0x02020202);
	assert(pp2->pp_ref == 1);
	assert(pp1->pp_ref == 0);
	page_remove(boot_pgdir, 0x0);
	assert(pp2->pp_ref == 0);
#endif

	// forcibly take pp0 back
	assert(PTE_ADDR(boot_pgdir[0]) == page2pa(pp0));
	boot_pgdir[0] = 0;
	assert(pp0->pp_ref == 1);
	pp0->pp_ref = 0;
	
	// check pointer arithmetic in pgdir_walk
	page_free(pp0);
	va = (void*)(PGSIZE * NPDENTRIES + PGSIZE);
	ptep = pgdir_walk(boot_pgdir, va, 1);
	ptep1 = KADDR(PTE_ADDR(boot_pgdir[PDX(va)]));
	assert(ptep == ptep1 + PTX(va));
	boot_pgdir[PDX(va)] = 0;
	pp0->pp_ref = 0;
	
	// check that new page tables get cleared
	memset(page2kva(pp0), 0xFF, PGSIZE);
	page_free(pp0);
	pgdir_walk(boot_pgdir, 0x0, 1);
	ptep = page2kva(pp0);
	for(i=0; i<NPTENTRIES; i++)
		assert((ptep[i] & PTE_P) == 0);
	boot_pgdir[0] = 0;
	pp0->pp_ref = 0;

	// give free list back
	page_free_list = fl;

	// free the pages we took
	page_free(pp0);
	page_free(pp1);
	page_free(pp2);
	
	cprintf("page_check() succeeded!\n");
}