Initial implementation of lab 2.
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117
kern/pmap.c
117
kern/pmap.c
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@ -102,8 +102,10 @@ boot_alloc(uint32_t n)
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// to a multiple of PGSIZE.
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//
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// LAB 2: Your code here.
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result = nextfree;
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nextfree = ROUNDUP(nextfree + n, PGSIZE);
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return NULL;
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return result;
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}
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// Set up a two-level page table:
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@ -124,9 +126,6 @@ mem_init(void)
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// Find out how much memory the machine has (npages & npages_basemem).
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i386_detect_memory();
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// Remove this line when you're ready to test this function.
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panic("mem_init: This function is not finished\n");
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//////////////////////////////////////////////////////////////////////
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// create initial page directory.
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kern_pgdir = (pde_t *) boot_alloc(PGSIZE);
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@ -148,7 +147,9 @@ mem_init(void)
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// array. 'npages' is the number of physical pages in memory. Use memset
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// to initialize all fields of each struct PageInfo to 0.
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// Your code goes here:
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size_t pages_size = sizeof(struct PageInfo) * npages;
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pages = boot_alloc(pages_size);
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memset(pages, 0, pages_size);
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//////////////////////////////////////////////////////////////////////
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// Now that we've allocated the initial kernel data structures, we set
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@ -172,6 +173,11 @@ mem_init(void)
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// (ie. perm = PTE_U | PTE_P)
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// - pages itself -- kernel RW, user NONE
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// Your code goes here:
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boot_map_region(kern_pgdir,
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UPAGES, ROUNDUP(pages_size, PGSIZE),
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PADDR(pages), PTE_W);
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kern_pgdir[PDX(UPAGES)] |= PTE_U | PTE_P;
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kern_pgdir[PDX(UPAGES)] &= ~PTE_W;
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//////////////////////////////////////////////////////////////////////
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// Use the physical memory that 'bootstack' refers to as the kernel
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@ -184,6 +190,11 @@ mem_init(void)
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// overwrite memory. Known as a "guard page".
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// Permissions: kernel RW, user NONE
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// Your code goes here:
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boot_map_region(kern_pgdir,
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KSTACKTOP-KSTKSIZE, KSTKSIZE,
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PADDR(bootstack), PTE_W);
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kern_pgdir[PDX(KSTACKTOP-KSTKSIZE)] |= PTE_W | PTE_P;
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kern_pgdir[PDX(KSTACKTOP-KSTKSIZE)] &= ~PTE_U;
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//////////////////////////////////////////////////////////////////////
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// Map all of physical memory at KERNBASE.
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@ -193,6 +204,12 @@ mem_init(void)
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// we just set up the mapping anyway.
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// Permissions: kernel RW, user NONE
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// Your code goes here:
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boot_map_region(kern_pgdir,
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KERNBASE, 0x100000000 - KERNBASE,
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0, PTE_W);
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kern_pgdir[PDX(KERNBASE)] |= PTE_W | PTE_P;
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kern_pgdir[PDX(KERNBASE)] &= ~PTE_U;
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// Check that the initial page directory has been set up correctly.
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check_kern_pgdir();
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@ -224,6 +241,14 @@ mem_init(void)
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// The 'pages' array has one 'struct PageInfo' entry per physical page.
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// Pages are reference counted, and free pages are kept on a linked list.
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// --------------------------------------------------------------
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bool
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is_reserved(size_t pagenum) {
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if(pagenum == 0) return true;
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if(pagenum >= PGNUM(IOPHYSMEM) &&
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pagenum < PGNUM(PADDR(boot_alloc(0)))) return true;
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return false;
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}
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//
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// Initialize page structure and memory free list.
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@ -253,11 +278,15 @@ page_init(void)
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// free pages!
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size_t i;
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for (i = 0; i < npages; i++) {
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if(is_reserved(i)) {
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pages[i].pp_ref = 1;
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} else {
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pages[i].pp_ref = 0;
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pages[i].pp_link = page_free_list;
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page_free_list = &pages[i];
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}
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}
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}
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//
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// Allocates a physical page. If (alloc_flags & ALLOC_ZERO), fills the entire
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@ -274,8 +303,17 @@ page_init(void)
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struct PageInfo *
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page_alloc(int alloc_flags)
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{
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// Fill this function in
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return 0;
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struct PageInfo* to_return = page_free_list;
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if(to_return == 0) return NULL;
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page_free_list = to_return->pp_link;
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to_return->pp_link = NULL;
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if(alloc_flags & ALLOC_ZERO) {
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memset(page2kva(to_return), 0, PGSIZE);
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}
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return to_return;
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}
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//
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@ -285,9 +323,10 @@ page_alloc(int alloc_flags)
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void
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page_free(struct PageInfo *pp)
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{
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// Fill this function in
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// Hint: You may want to panic if pp->pp_ref is nonzero or
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// pp->pp_link is not NULL.
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if(pp->pp_ref || pp->pp_link != NULL)
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panic("Freeing page with nonzero reference count!");
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pp->pp_link = page_free_list;
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page_free_list = pp;
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}
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//
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@ -326,8 +365,25 @@ page_decref(struct PageInfo* pp)
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pte_t *
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pgdir_walk(pde_t *pgdir, const void *va, int create)
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{
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pte_t* base_table = NULL;
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if(pgdir[PDX(va)] & PTE_P) {
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// We have a valid page table; awesome!
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base_table = KADDR(PTE_ADDR(pgdir[PDX(va)]));
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} else {
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if(!create) return NULL;
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struct PageInfo* page = page_alloc(ALLOC_ZERO);
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if(!page) return NULL;
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page->pp_ref++;
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physaddr_t ppa = page2pa(page);
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pgdir[PDX(va)] = ppa | PTE_P | PTE_U | PTE_W;
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base_table = KADDR(ppa);
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}
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// Fill this function in
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return NULL;
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return &base_table[PTX(va)];
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}
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//
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@ -344,7 +400,16 @@ pgdir_walk(pde_t *pgdir, const void *va, int create)
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static void
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boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm)
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{
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// Fill this function in
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size_t count = size / PGSIZE;
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uintptr_t start_va = va;
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physaddr_t start_pa = pa;
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while(count-- && start_va <= va && start_pa <= pa) {
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pte_t* pte = pgdir_walk(pgdir, (void*) va, true);
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*pte = pa | perm | PTE_P;
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va += PGSIZE;
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pa += PGSIZE;
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}
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}
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//
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@ -375,7 +440,14 @@ boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm
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int
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page_insert(pde_t *pgdir, struct PageInfo *pp, void *va, int perm)
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{
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// Fill this function in
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pte_t* pte;
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if(!(pte = pgdir_walk(pgdir, va, true))) return -E_NO_MEM;
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pp->pp_ref++;
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if(*pte & PTE_P) page_remove(pgdir, va);
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*pte = page2pa(pp) | PTE_P | perm;
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tlb_invalidate(pgdir, va);
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return 0;
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}
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@ -393,10 +465,17 @@ page_insert(pde_t *pgdir, struct PageInfo *pp, void *va, int perm)
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struct PageInfo *
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page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
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{
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// Fill this function in
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pte_t* pte;
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if(!(pte = pgdir_walk(pgdir, va, false))) {
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if(pte_store) *pte_store = NULL;
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return NULL;
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}
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struct PageInfo* pp = pa2page(PTE_ADDR(*pte));
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if(pte_store) *pte_store = pte;
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return pp;
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}
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//
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// Unmaps the physical page at virtual address 'va'.
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// If there is no physical page at that address, silently does nothing.
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@ -415,7 +494,15 @@ page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
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void
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page_remove(pde_t *pgdir, void *va)
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{
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// Fill this function in
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pte_t* pte;
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struct PageInfo* pp;
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pp = page_lookup(pgdir, va, &pte);
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if(!(*pte & PTE_P)) return;
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if(!(--(pp->pp_ref))) page_free(pp);
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*pte = 0;
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tlb_invalidate(pgdir, va);
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}
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//
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