/* See COPYRIGHT for copyright information. */
#include <inc/x86.h>
#include <inc/mmu.h>
#include <inc/error.h>
#include <inc/string.h>
#include <inc/assert.h>
#include <kern/pmap.h>
#include <kern/kclock.h>
// These variables are set by i386_detect_memory()
size_t npages; // Amount of physical memory (in pages)
static size_t npages_basemem; // Amount of base memory (in pages)
// These variables are set in mem_init()
pde_t *kern_pgdir; // Kernel's initial page directory
struct PageInfo *pages; // Physical page state array
static struct PageInfo *page_free_list; // Free list of physical pages
// --------------------------------------------------------------
// Detect machine's physical memory setup.
// --------------------------------------------------------------
static int
nvram_read(int r)
{
return mc146818_read(r) | (mc146818_read(r + 1) << 8);
}
static void
i386_detect_memory(void)
{
size_t basemem, extmem, ext16mem, totalmem;
// Use CMOS calls（CMOS调用） to measure（测量） available（可用的） base & extended memory.
//使用CMOS calss 来测量可用的基本内存和额外内存
// (CMOS calls return results in kilobytes.)
basemem = nvram_read(NVRAM_BASELO);
extmem = nvram_read(NVRAM_EXTLO);
ext16mem = nvram_read(NVRAM_EXT16LO) * 64;
//在32位机器上，一般有两部分可分配物理内存，一是低端的640KB内存（0~640kb)，
//二是在BIOS之后的扩展内存(1mb之后，拓展内存的大小取决于机器本身），
//BIOS存储于(640~1mb),不可修改或分配
// Calculate（计算） the number of physical pages available in both base
// and extended memory.
//计算总可分配内存
if (ext16mem)
totalmem = 16 * 1024 + ext16mem;
else if (extmem)
totalmem = 1 * 1024 + extmem;
else
totalmem = basemem;
//全部内存页数
npages = totalmem / (PGSIZE / 1024);
//0~640kb内存页数
npages_basemem = basemem / (PGSIZE / 1024);
//ps:npages-npages_basemem = 拓展内存页数
cprintf("Physical memory: %uK available, base = %uK, extended = %uK\n",
totalmem, basemem, totalmem - basemem);
}
// --------------------------------------------------------------
// Set up memory mappings above UTOP.
// --------------------------------------------------------------
static void boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm);
static void check_page_free_list(bool only_low_memory);
static void check_page_alloc(void);
static void check_kern_pgdir(void);
static physaddr_t check_va2pa(pde_t *pgdir, uintptr_t va);
static void check_page(void);
static void check_page_installed_pgdir(void);
// This simple physical memory allocator is used only while JOS is setting
// up its virtual memory system. page_alloc() is the real allocator.
//这个简单的物理内存分配器仅在JOS正在设置他的虚拟内存系统的时候使用，page_alloc()才是真正的分配器
// If n>0, allocates enough pages of contiguous physical memory to hold 'n'
// bytes. Doesn't initialize the memory. Returns a kernel virtual address.
//
// If n==0, returns the address of the next free page without allocating
// anything.
//
// If we're out of memory, boot_alloc should panic.
// This function may ONLY be used during initialization,
// before the page_free_list list has been set up.
static void *
boot_alloc(uint32_t n)
//该函数返回一个类型未定的指针
{
//静态变量，相当于全局变量
static char *nextfree; // virtual address of next byte of free memory 下一个空闲内存的虚拟地址
char *result;
// Initialize nextfree if this is the first time.
// 'end' is a magic symbol automatically generated by the linker,
// which points to the end of the kernel's bss segment:
// the first virtual address that the linker did *not* assign
// to any kernel code or global variables.
if (!nextfree) {//如果是第一次执行（nextfree为空）
extern char end[]; //外部变量，定义在kernel.ld，指向.bss段的结束地址(注意.bss后面的.comment段是一些程序的注释信息，是不进内存的)
//先将nextfree指向Kernel Code 内核代码的结束地址
//这样可以保护内核代码，使其不被分配
//这里的end为虚拟地址，使用的还是entry.S中设置的二级页表
//经过这个二级页表转换成物理地址，在kern code的后面
nextfree = ROUNDUP((char *) end, PGSIZE); //PGSIZE为4096，nextfree向上取整为4096的倍数，为
}
// Allocate a chunk large enough to hold 'n' bytes, then update
//nextfree
//分配一个足够大的块容纳n个字节，然后更新nextfree
// nextfree. Make sure nextfree is kept aligned(对齐)
// to a multiple of PGSIZE.(确保nextfree与PGSIZE的倍数保持对齐。)
//
// LAB 2: Your code here.
cprintf("boot_alloc memory at %x\n", nextfree);
cprintf("Next memory at %x\n", ROUNDUP((char *) (nextfree+n), PGSIZE));
if(n != 0){
// nextfree = ROUNDUP(nextfree+n,PGSIZE);
// return nextfree;
//先记录当前nextfree
result = nextfree;
//n是传入参数，代表要分配n个字节的内存
//nextfree = ROUNDUP(result+n,PGSIZE);
nextfree += ROUNDUP(n, PGSIZE);
//返回偏移之前的nextfree
return result;
}else{
return nextfree;
}
}
// Set up a two-level page table（设置一个两级页表，即分为page directory 和 page table两级页表):
// kern_pgdir is its linear (virtual) address of the root(page directory的线性(虚拟)根地址是kern_pgdir)
//
// This function only sets up the kernel part of the address space
// (ie. addresses >= UTOP). The user part of the address space
// will be set up later.（这个函数只设置内核部分的地址空间，用户部分的地址空间之后再设置）
//
// From UTOP to ULIM, the user is allowed to read but not write.
// Above ULIM the user cannot read or write.
void
mem_init(void)
{
uint32_t cr0;
size_t n;
// Find out how much memory the machine has (npages & npages_basemem).
//查找机器有多大内存并输出
i386_detect_memory();
// Remove this line when you're ready to test this function.
//测试时注释这行代码
//panic("mem_init: This function is not finished\n");
//////////////////////////////////////////////////////////////////////
// create initial page directory.
//使用.bss section地址以后的空闲内存空间（即Kernel Code之后）创建页目录，页目录大小为4096kb
//boot_alloc返回一个地址并赋值给kern_pgdir，kern_pgdir将作为页目录的开头地址
kern_pgdir = (pde_t *) boot_alloc(PGSIZE);
//将kern_pgdir~kern_pgdir+4096（虚拟地址）的地址中的值全部赋为0（内存初始化）
memset(kern_pgdir, 0, PGSIZE);
//////////////////////////////////////////////////////////////////////
// Recursively insert PD in itself as a page table, to form
// a virtual page table at virtual address UVPT.
// (For now, you don't have understand the greater purpose of the
// following line.)
kern_pgdir[PDX(UVPT)] = PADDR(kern_pgdir) | PTE_U | PTE_P;
//////////////////////////////////////////////////////////////////////
// Allocate an array of npages 'struct PageInfo's and store it in 'pages'.
// The kernel uses this array to keep track of physical pages: for
// each physical page, there is a corresponding struct PageInfo in this
// array.
//'npages' is the number of physical pages in memory. Use memset
// to initialize all fields of each struct PageInfo to 0.
// Your code goes here:
//pages定义在本文件开头（struct PageInfo *pages;）
//为pages分配内存（在kern code的后面的kern_pgdir的后面）
//pages
pages = boot_alloc(npages* sizeof(struct PageInfo));
//将pages~pages+npages*sizeof(struct PageInfo)的地址中的值全部赋为0
memset(pages,0,npages*sizeof(struct PageInfo));
//////////////////////////////////////////////////////////////////////
// Now that we've allocated the initial kernel data structures, we set
// up the list of free physical pages.
//现在我们已经分配了初始的内核数据结构，我们接下来设置空闲物理页面的列表
//Once we've done so, all further memory management will go through the page_* functions.
//In particular, we can now map memory using boot_map_region or page_insert
//一旦我们这么做了，所有剩下的内存都会被page_*函数处理，实际上我们现在以使用boot_map_region或page_insert来映射内存
page_init();
check_page_free_list(1);
check_page_alloc();
check_page();
//////////////////////////////////////////////////////////////////////
// Now we set up virtual memory
//现在我们开始设置虚拟内存
//////////////////////////////////////////////////////////////////////
// Map 'pages' read-only by the user at linear address UPAGES
// Permissions:
// - the new image at UPAGES -- kernel R, user R
// (ie. perm = PTE_U | PTE_P)
// - pages itself -- kernel RW, user NONE
// Your code goes here:
boot_map_region(kern_pgdir, UPAGES, npages * sizeof(struct PageInfo), PADDR(pages), PTE_U);
//////////////////////////////////////////////////////////////////////
// Use the physical memory that 'bootstack' refers to as the kernel
// stack. The kernel stack grows down from virtual address KSTACKTOP.
// We consider the entire range from [KSTACKTOP-PTSIZE, KSTACKTOP)
// to be the kernel stack, but break this into two pieces:
// * [KSTACKTOP-KSTKSIZE, KSTACKTOP) -- backed by physical memory
// * [KSTACKTOP-PTSIZE, KSTACKTOP-KSTKSIZE) -- not backed; so if
// the kernel overflows its stack, it will fault rather than
// overwrite memory. Known as a "guard page".
// Permissions: kernel RW, user NONE
// Your code goes here:
boot_map_region(kern_pgdir, KERNBASE, 0xffffffff - KERNBASE, 0, PTE_W);
//////////////////////////////////////////////////////////////////////
// Map all of physical memory at KERNBASE.
// Ie. the VA range [KERNBASE, 2^32) should map to
// the PA range [0, 2^32 - KERNBASE)
// We might not have 2^32 - KERNBASE bytes of physical memory, but
// we just set up the mapping anyway.
// Permissions: kernel RW, user NONE
// Your code goes here:
boot_map_region(kern_pgdir, KSTACKTOP - KSTKSIZE, KSTKSIZE, PADDR(bootstack), PTE_W);
// Check that the initial page directory has been set up correctly.
check_kern_pgdir();
// Switch from the minimal entry page directory to the full kern_pgdir
// page table we just created. Our instruction pointer should be
// somewhere between KERNBASE and KERNBASE+4MB right now, which is
// mapped the same way by both page tables.
//
// If the machine reboots at this point, you've probably set up your
// kern_pgdir wrong.
lcr3(PADDR(kern_pgdir));
check_page_free_list(0);
// entry.S set the really important flags in cr0 (including enabling
// paging). Here we configure the rest of the flags that we care about.
cr0 = rcr0();
cr0 |= CR0_PE|CR0_PG|CR0_AM|CR0_WP|CR0_NE|CR0_MP;
cr0 &= ~(CR0_TS|CR0_EM);
lcr0(cr0);
// Some more checks, only possible after kern_pgdir is installed.
check_page_installed_pgdir();
}
// --------------------------------------------------------------
// Tracking of physical pages.
// The 'pages' array has one 'struct PageInfo' entry per physical page.
// Pages are reference counted, and free pages are kept on a linked list.
// --------------------------------------------------------------
//
// Initialize page structure and memory free list.
// 初始化 page structure 和 memory free list。
// After this is done, NEVER use boot_alloc again. ONLY use the page
// allocator functions below to allocate and deallocate physical
// memory via the page_free_list.
//在这之后，不要再使用boot_alloc。仅使用下面的页面分配器函数通过page_free_list分配和释放物理内存。
void
page_init(void)
{
// The example code here marks all physical pages as free.
// However this is not truly the case. What memory is free?
// 1) Mark physical page 0 as in use.
// This way we preserve(保存) the real-mode IDT and BIOS structures
// in case we ever need them. (Currently we don't, but...)
// 2) The rest of base memory, [PGSIZE, npages_basemem * PGSIZE)
// is free. (npages_basemem：Amount of base memory (in pages)， PGSIZE:每页的大小)
// 3) Then comes the IO hole [IOPHYSMEM, EXTPHYSMEM), which must
// never be allocated.
// 4) Then extended memory [EXTPHYSMEM, ...).
// Some of it is in use, some is free. Where is the kernel
// in physical memory? Which pages are already in use for
// page tables and other data structures?
//
// Change the code to reflect this.
// NB: DO NOT actually touch the physical memory corresponding（相应的） to
// free pages!
size_t i;
// 1 Mark physical page 0 as in use
pages[0].pp_ref = 1;
// 2. [PGSIZE, npages_basemem * PGSIZE] is free
for(i = 1; i < npages_basemem; i++) {
pages[i].pp_ref = 0;
pages[i].pp_link = page_free_list;
page_free_list = &pages[i];
}
// 3. IO hole([IOPHYSMEM, EXTPHYSMEM]) never be allocated
for(i = (IOPHYSMEM >> PGSHIFT); i < (EXTPHYSMEM >> PGSHIFT); i++) {
pages[i].pp_ref = 1;
}
// 4. extended memory, some is free, some is used
size_t first_free_page = (PADDR(boot_alloc(0))) >> PGSHIFT;
for(i = (EXTPHYSMEM >> PGSHIFT); i < first_free_page; i++) {
pages[i].pp_ref = 1;
}
for(i = first_free_page; i < npages; i++) {
pages[i].pp_ref = 0;
pages[i].pp_link = page_free_list;
page_free_list = &pages[i];
}
}
//分配物理页
// Allocates a physical page. If (alloc_flags & ALLOC_ZERO), fills the entire
// returned physical page with '\0' bytes. Does NOT increment the reference
// count of the page - the caller must do these if necessary (either explicitly
// or via page_insert).
//
// Be sure to set the pp_link field of the allocated page to NULL so
// page_free can check for double-free bugs.
//
// Returns NULL if out of free memory.
//
// Hint: use page2kva and memset
//我们不在page_alloc中增加pp_ref（若在这里处理应该也可以），由它的调用者如page_insert或者pgdir_walk来处理
struct PageInfo *
page_alloc(int alloc_flags)
{
// Fill this function in
//page_free_list=NULL 说明没有内存可供分配
if (page_free_list == NULL) {
cprintf("page_alloc: 暂无空闲内存\n");
return NULL;
}
struct PageInfo *addr = page_free_list;
//摘下那一页
page_free_list = page_free_list->pp_link;
//将被摘下的那一页的pp_link设置为NULL，即设置为非空闲页
addr->pp_link = NULL;
//如果ALLOC_ZERO为0，则分配内存后还要对内存进行初始化
if(alloc_flags & ALLOC_ZERO){
//page2kva 参数:struct PageInfo 作用：通过空闲页结构得到这一页起始位置的虚拟地址
memset(page2kva(addr),0,PGSIZE);
}
cprintf("page_alloc:第%d页已被分配,对应的物理地址为:%x,对应的虚拟地址为:%x\n",addr-pages,page2pa(addr),page2kva(addr));
//返回这个空闲页首地址
return addr;
}
//
// Return a page to the free list.
// (This function should only be called when pp->pp_ref reaches 0.)
//
void
page_free(struct PageInfo *pp)
{
if (pp->pp_ref != 0 || pp->pp_link != NULL) {
panic("page_free failed. pp->pp_ref is nonzero or pp->pp_link is not NULL!");
return;
}
// Fill this function in
// Hint: You may want to panic if pp->pp_ref is nonzero or
// pp->pp_link is not NULL.
pp->pp_link = page_free_list;
page_free_list = pp;
}
//
// Decrement the reference count on a page,
// freeing it if there are no more refs.
//减少页面上的引用计数，如果没有更多的引用，则释放它
void
page_decref(struct PageInfo* 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.
//
// The relevant(有关的) page table page might not exist yet.
// If this is true, and create == false, then pgdir_walk returns NULL.
// Otherwise, pgdir_walk allocates a new page table page with page_alloc.
// - If the allocation fails, pgdir_walk returns NULL.
// - Otherwise, the new page's reference count（引用计数） is incremented（增加）,
// the page is cleared,
// and pgdir_walk returns a pointer into the new page table page.
//
// 提示
// Hint 1: you can turn a PageInfo * into the physical address of the
// page it refers to with page2pa() from kern/pmap.h.
//
// Hint 2: the x86 MMU checks permission bits in both the page directory
// and the page table, so it's safe to leave permissions in the page
// directory more permissive than strictly necessary.
//
// Hint 3: look at inc/mmu.h for useful macros（宏） that manipulate（操作） page
// table and page directory entries.
//
//pgdir_walk这个函数接受一个page directory和一个虚拟地址，
//要求得到虚拟地址在这个page directory下对应的page table entry。
//对应的页表不一定存在，如果create参数为false则直接返回NULL否则，该函数申请新的一页来做页表，并增加页的引用计数值
pte_t *
pgdir_walk(pde_t *pgdir, const void *va, int create)
{
// pde 即 page directory entry
pde_t* pde = &pgdir[PDX(va)];
pte_t* pgtab; // 指向pg table的指针
if (*pde & PTE_P) {
// 先获取page table的地址
pgtab = KADDR(PTE_ADDR(*pde));
} else { // 如果相关page table不存在，就考虑alloc一个pgtab
// 如果不创建那就直接返回NULL
if (!create) {
return NULL;
}
// 创建时将页面内容置0
struct PageInfo* pp = page_alloc(ALLOC_ZERO);
if (pp == NULL) {
return NULL;
}
pp->pp_ref++;
pgtab = (pte_t*)page2kva(pp);
*pde = PADDR(pgtab) | PTE_P | PTE_W | PTE_U;
}
return &pgtab[PTX(va)];
}
//
// Map [va, va+size) of virtual address space to physical [pa, pa+size)
// in the page table rooted（扎根） at pgdir. Size is a multiple of PGSIZE, and
// va and pa are both page-aligned（页面对齐）.
// Use permission bits perm|PTE_P for the entries.
//
// This function is only intended（打算） to set up the ``static'' mappings（静态映射）
// above UTOP. As such, it should *not* change the pp_ref field on the
// mapped pages.
//
// Hint: the TA solution uses pgdir_walk
//将虚拟地址 va~va+size 映射到物理地址 pa~pa+size
static void
boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm)
{
pte_t* pte;
uintptr_t last = ROUNDDOWN(va + size - 1, PGSIZE);
va = ROUNDDOWN(va, PGSIZE);
pa = ROUNDDOWN(pa, PGSIZE);
for (;;) {
if ((pte = pgdir_walk(pgdir, (void*)va, 1)) == NULL) {
return;
}
*pte = pa | perm | PTE_P;
if (va == last) {
return;
}
va += PGSIZE;
pa += PGSIZE;
}
}
//
// 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'.
//
// Requirements
// - If there is already a page mapped at 'va', it should be page_remove()d.
// - If necessary, on demand, a page table should be allocated and inserted
// 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'.
//
// Corner-case hint: Make sure to consider what happens when the same
// pp is re-inserted at the same virtual address in the same pgdir.
// However, try not to distinguish this case in your code, as this
// frequently leads to subtle bugs; there's an elegant way to handle
// everything in one code path.
//
// 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 PageInfo *pp, void *va, int perm)
{
pte_t* pte = pgdir_walk(pgdir, va, 1);
if (pte == NULL) {
return -E_NO_MEM; // 没有空间了
}
// 一定要在page_remove之前增加引用，否则可能被加入page_free_list
pp->pp_ref++;
if (*pte & PTE_P) { // 如果该页表项已经存在
// 否则移除另一个va的映射
page_remove(pgdir, va);
}
*pte = page2pa(pp) | perm | PTE_P;
// Fill this function in
return 0;
}
//
// 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 and
// can be used to verify page permissions for syscall arguments,
// but should not be used by most callers.
//
// Return NULL if there is no page mapped at va.
//
// Hint: the TA solution uses pgdir_walk and pa2page.
//
struct PageInfo *
page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
{
pte_t* pte;
if ((pte = pgdir_walk(pgdir, va, 0)) == NULL) {
return NULL;
}
// pte_store 是指向一个 pte 的指针
if (pte_store) {
*pte_store = pte;
}
// Fill this function in
return pa2page(PTE_ADDR(*pte));
}
//
// Unmaps（取消映射） the physical page at virtual address 'va'.
// If there is no physical page at that address, silently（默默地） 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 page table.
//
// Hint: The TA solution is implemented using page_lookup,
// tlb_invalidate, and page_decref.
//
void
page_remove(pde_t *pgdir, void *va)
{
pte_t* pte;
struct PageInfo* page = page_lookup(pgdir, va, &pte);
if (page == NULL) {
return;
}
page_decref(page);
tlb_invalidate(pgdir, va);
*pte = 0;
// Fill this function in
}
//
// 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);
}
// --------------------------------------------------------------
// Checking functions.
// --------------------------------------------------------------
//
// Check that the pages on the page_free_list are reasonable.
//
static void
check_page_free_list(bool only_low_memory)
{
struct PageInfo *pp;
unsigned pdx_limit = only_low_memory ? 1 : NPDENTRIES;
int nfree_basemem = 0, nfree_extmem = 0;
char *first_free_page;
if (!page_free_list)
panic("'page_free_list' is a null pointer!");
if (only_low_memory) {
// Move pages with lower addresses first in the free
// list, since entry_pgdir does not map all pages.
struct PageInfo *pp1, *pp2;
struct PageInfo **tp[2] = { &pp1, &pp2 };
for (pp = page_free_list; pp; pp = pp->pp_link) {
int pagetype = PDX(page2pa(pp)) >= pdx_limit;
*tp[pagetype] = pp;
tp[pagetype] = &pp->pp_link;
}
*tp[1] = 0;
*tp[0] = pp2;
page_free_list = pp1;
}
// if there's a page that shouldn't be on the free list,
// try to make sure it eventually causes trouble.
for (pp = page_free_list; pp; pp = pp->pp_link)
if (PDX(page2pa(pp)) < pdx_limit)
memset(page2kva(pp), 0x97, 128);
first_free_page = (char *) boot_alloc(0);
for (pp = page_free_list; pp; pp = pp->pp_link) {
// check that we didn't corrupt the free list itself
assert(pp >= pages);
assert(pp < pages + npages);
assert(((char *) pp - (char *) pages) % sizeof(*pp) == 0);
// check a few pages that shouldn't be on the free list
assert(page2pa(pp) != 0);
assert(page2pa(pp) != IOPHYSMEM);
assert(page2pa(pp) != EXTPHYSMEM - PGSIZE);
assert(page2pa(pp) != EXTPHYSMEM);
assert(page2pa(pp) < EXTPHYSMEM || (char *) page2kva(pp) >= first_free_page);
if (page2pa(pp) < EXTPHYSMEM)
++nfree_basemem;
else
++nfree_extmem;
}
assert(nfree_basemem > 0);
assert(nfree_extmem > 0);
cprintf("check_page_free_list() succeeded!\n");
}
//
// Check the physical page allocator (page_alloc(), page_free(),
// and page_init()).
//
static void
check_page_alloc(void)
{
struct PageInfo *pp, *pp0, *pp1, *pp2;
int nfree;
struct PageInfo *fl;
char *c;
int i;
if (!pages)
panic("'pages' is a null pointer!");
// check number of free pages
for (pp = page_free_list, nfree = 0; pp; pp = pp->pp_link)
++nfree;
// should be able to allocate three pages
pp0 = pp1 = pp2 = 0;
assert((pp0 = page_alloc(0)));
assert((pp1 = page_alloc(0)));
assert((pp2 = page_alloc(0)));
assert(pp0);
assert(pp1 && pp1 != pp0);
assert(pp2 && pp2 != pp1 && pp2 != pp0);
assert(page2pa(pp0) < npages*PGSIZE);
assert(page2pa(pp1) < npages*PGSIZE);
assert(page2pa(pp2) < npages*PGSIZE);
// temporarily steal the rest of the free pages
fl = page_free_list;
page_free_list = 0;
// should be no free memory
assert(!page_alloc(0));
// free and re-allocate?
page_free(pp0);
page_free(pp1);
page_free(pp2);
pp0 = pp1 = pp2 = 0;
assert((pp0 = page_alloc(0)));
assert((pp1 = page_alloc(0)));
assert((pp2 = page_alloc(0)));
assert(pp0);
assert(pp1 && pp1 != pp0);
assert(pp2 && pp2 != pp1 && pp2 != pp0);
assert(!page_alloc(0));
// test flags
memset(page2kva(pp0), 1, PGSIZE);
page_free(pp0);
assert((pp = page_alloc(ALLOC_ZERO)));
assert(pp && pp0 == pp);
c = page2kva(pp);
for (i = 0; i < PGSIZE; i++)
assert(c[i] == 0);
// give free list back
page_free_list = fl;
// free the pages we took
page_free(pp0);
page_free(pp1);
page_free(pp2);
// number of free pages should be the same
for (pp = page_free_list; pp; pp = pp->pp_link)
--nfree;
assert(nfree == 0);
cprintf("check_page_alloc() succeeded!\n");
}
//
// Checks that the kernel part of virtual address space
// has been set up roughly correctly (by mem_init()).
//
// This function doesn't test every corner case,
// but it is a pretty good sanity check.
//
static void
check_kern_pgdir(void)
{
uint32_t i, n;
pde_t *pgdir;
pgdir = kern_pgdir;
// check pages array
n = ROUNDUP(npages*sizeof(struct PageInfo), PGSIZE);
for (i = 0; i < n; i += PGSIZE)
assert(check_va2pa(pgdir, UPAGES + i) == PADDR(pages) + i);
// check phys mem
for (i = 0; i < npages * PGSIZE; i += PGSIZE)
assert(check_va2pa(pgdir, KERNBASE + i) == i);
// check kernel stack
for (i = 0; i < KSTKSIZE; i += PGSIZE)
assert(check_va2pa(pgdir, KSTACKTOP - KSTKSIZE + i) == PADDR(bootstack) + i);
assert(check_va2pa(pgdir, KSTACKTOP - PTSIZE) == ~0);
// check PDE permissions
for (i = 0; i < NPDENTRIES; i++) {
switch (i) {
case PDX(UVPT):
case PDX(KSTACKTOP-1):
case PDX(UPAGES):
assert(pgdir[i] & PTE_P);
break;
default:
if (i >= PDX(KERNBASE)) {
assert(pgdir[i] & PTE_P);
assert(pgdir[i] & PTE_W);
} else
assert(pgdir[i] == 0);
break;
}
}
cprintf("check_kern_pgdir() succeeded!\n");
}
// This function returns the physical address of the page containing 'va',
// defined by the page directory 'pgdir'. The hardware normally performs
// this functionality for us! We define our own version to help check
// the check_kern_pgdir() function; it shouldn't be used elsewhere.
static physaddr_t
check_va2pa(pde_t *pgdir, uintptr_t va)
{
pte_t *p;
pgdir = &pgdir[PDX(va)];
if (!(*pgdir & PTE_P))
return ~0;
p = (pte_t*) KADDR(PTE_ADDR(*pgdir));
if (!(p[PTX(va)] & PTE_P))
return ~0;
return PTE_ADDR(p[PTX(va)]);
}
// check page_insert, page_remove, &c
static void
check_page(void)
{
struct PageInfo *pp, *pp0, *pp1, *pp2;
struct PageInfo *fl;
pte_t *ptep, *ptep1;
void *va;
int i;
extern pde_t entry_pgdir[];
// should be able to allocate three pages
pp0 = pp1 = pp2 = 0;
assert((pp0 = page_alloc(0)));
assert((pp1 = page_alloc(0)));
assert((pp2 = page_alloc(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;
page_free_list = 0;
// should be no free memory
assert(!page_alloc(0));
// there is no page allocated at address 0
assert(page_lookup(kern_pgdir, (void *) 0x0, &ptep) == NULL);
// there is no free memory, so we can't allocate a page table
assert(page_insert(kern_pgdir, pp1, 0x0, PTE_W) < 0);
// free pp0 and try again: pp0 should be used for page table
page_free(pp0);
assert(page_insert(kern_pgdir, pp1, 0x0, PTE_W) == 0);
assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
assert(check_va2pa(kern_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(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
assert(pp2->pp_ref == 1);
// should be no free memory
assert(!page_alloc(0));
// should be able to map pp2 at PGSIZE because it's already there
assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
assert(check_va2pa(kern_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(0));
// check that pgdir_walk returns a pointer to the pte
ptep = (pte_t *) KADDR(PTE_ADDR(kern_pgdir[PDX(PGSIZE)]));
assert(pgdir_walk(kern_pgdir, (void*)PGSIZE, 0) == ptep+PTX(PGSIZE));
// should be able to change permissions too.
assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W|PTE_U) == 0);
assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp2));
assert(pp2->pp_ref == 1);
assert(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U);
assert(kern_pgdir[0] & PTE_U);
// should be able to remap with fewer permissions
assert(page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W) == 0);
assert(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_W);
assert(!(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U));
// should not be able to map at PTSIZE because need free page for page table
assert(page_insert(kern_pgdir, pp0, (void*) PTSIZE, PTE_W) < 0);
// insert pp1 at PGSIZE (replacing pp2)
assert(page_insert(kern_pgdir, pp1, (void*) PGSIZE, PTE_W) == 0);
assert(!(*pgdir_walk(kern_pgdir, (void*) PGSIZE, 0) & PTE_U));
// should have pp1 at both 0 and PGSIZE, pp2 nowhere, ...
assert(check_va2pa(kern_pgdir, 0) == page2pa(pp1));
assert(check_va2pa(kern_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((pp = page_alloc(0)) && pp == pp2);
// unmapping pp1 at 0 should keep pp1 at PGSIZE
page_remove(kern_pgdir, 0x0);
assert(check_va2pa(kern_pgdir, 0x0) == ~0);
assert(check_va2pa(kern_pgdir, PGSIZE) == page2pa(pp1));
assert(pp1->pp_ref == 1);
assert(pp2->pp_ref == 0);
// test re-inserting pp1 at PGSIZE
assert(page_insert(kern_pgdir, pp1, (void*) PGSIZE, 0) == 0);
assert(pp1->pp_ref);
assert(pp1->pp_link == NULL);
// unmapping pp1 at PGSIZE should free it
page_remove(kern_pgdir, (void*) PGSIZE);
assert(check_va2pa(kern_pgdir, 0x0) == ~0);
assert(check_va2pa(kern_pgdir, PGSIZE) == ~0);
assert(pp1->pp_ref == 0);
assert(pp2->pp_ref == 0);
// so it should be returned by page_alloc
assert((pp = page_alloc(0)) && pp == pp1);
// should be no free memory
assert(!page_alloc(0));
// forcibly take pp0 back
assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
kern_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(kern_pgdir, va, 1);
ptep1 = (pte_t *) KADDR(PTE_ADDR(kern_pgdir[PDX(va)]));
assert(ptep == ptep1 + PTX(va));
kern_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(kern_pgdir, 0x0, 1);
ptep = (pte_t *) page2kva(pp0);
for(i=0; i<NPTENTRIES; i++)
assert((ptep[i] & PTE_P) == 0);
kern_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("check_page() succeeded!\n");
}
// check page_insert, page_remove, &c, with an installed kern_pgdir
static void
check_page_installed_pgdir(void)
{
struct PageInfo *pp, *pp0, *pp1, *pp2;
struct PageInfo *fl;
pte_t *ptep, *ptep1;
uintptr_t va;
int i;
// check that we can read and write installed pages
pp1 = pp2 = 0;
assert((pp0 = page_alloc(0)));
assert((pp1 = page_alloc(0)));
assert((pp2 = page_alloc(0)));
page_free(pp0);
memset(page2kva(pp1), 1, PGSIZE);
memset(page2kva(pp2), 2, PGSIZE);
page_insert(kern_pgdir, pp1, (void*) PGSIZE, PTE_W);
assert(pp1->pp_ref == 1);
assert(*(uint32_t *)PGSIZE == 0x01010101U);
page_insert(kern_pgdir, pp2, (void*) PGSIZE, PTE_W);
assert(*(uint32_t *)PGSIZE == 0x02020202U);
assert(pp2->pp_ref == 1);
assert(pp1->pp_ref == 0);
*(uint32_t *)PGSIZE = 0x03030303U;
assert(*(uint32_t *)page2kva(pp2) == 0x03030303U);
page_remove(kern_pgdir, (void*) PGSIZE);
assert(pp2->pp_ref == 0);
// forcibly take pp0 back
assert(PTE_ADDR(kern_pgdir[0]) == page2pa(pp0));
kern_pgdir[0] = 0;
assert(pp0->pp_ref == 1);
pp0->pp_ref = 0;
// free the pages we took
page_free(pp0);
cprintf("check_page_installed_pgdir() succeeded!\n");
}
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