pmap.c~

jos lab3代码

/* 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>
#include <kern/env.h>

// These variables are set by i386_detect_memory()
static physaddr_t maxpa;	// Maximum physical address
size_t npage;			// Amount of physical memory (in pages)
static size_t basemem;		// Amount of base memory (in bytes)
static size_t extmem;		// Amount of extended memory (in bytes)

// These variables are set in i386_vm_init()
pde_t* boot_pgdir;		// Virtual address of boot time page directory
physaddr_t boot_cr3;		// Physical address of boot time page directory
static char* boot_freemem;	// Pointer to next byte of free mem

struct Page* pages;		// Virtual address of physical page array
static struct Page_list page_free_list;	// Free list of physical pages

// Global descriptor table.
//
// The kernel and user segments are identical (except for the DPL).
// To load the SS register, the CPL must equal the DPL.  Thus,
// we must duplicate the segments for the user and the kernel.
//
struct Segdesc gdt[] =
{
	// 0x0 - unused (always faults -- for trapping NULL far pointers)
	SEG_NULL,

	// 0x8 - kernel code segment
	[GD_KT >> 3] = SEG(STA_X | STA_R, 0x0, 0xffffffff, 0),

	// 0x10 - kernel data segment
	[GD_KD >> 3] = SEG(STA_W, 0x0, 0xffffffff, 0),

	// 0x18 - user code segment
	[GD_UT >> 3] = SEG(STA_X | STA_R, 0x0, 0xffffffff, 3),

	// 0x20 - user data segment
	[GD_UD >> 3] = SEG(STA_W, 0x0, 0xffffffff, 3),

	// 0x28 - tss, initialized in idt_init()
	[GD_TSS >> 3] = SEG_NULL
};

struct Pseudodesc gdt_pd = {
	sizeof(gdt) - 1, (unsigned long) gdt
};

static int
nvram_read(int r)
{
	return mc146818_read(r) | (mc146818_read(r + 1) << 8);
}

void
i386_detect_memory(void)
{
	// CMOS tells us how many kilobytes there are
	basemem = ROUNDDOWN(nvram_read(NVRAM_BASELO)*1024, PGSIZE);
	extmem = ROUNDDOWN(nvram_read(NVRAM_EXTLO)*1024, PGSIZE);

	// Calculate the maximum physical address based on whether
	// or not there is any extended memory.  See comment in <inc/mmu.h>.
	if (extmem)
		maxpa = EXTPHYSMEM + extmem;
	else
		maxpa = basemem;

	npage = maxpa / PGSIZE;

	cprintf("Physical memory: %dK available, ", (int)(maxpa/1024));
	cprintf("base = %dK, extended = %dK\n", (int)(basemem/1024), (int)(extmem/1024));
}

// --------------------------------------------------------------
// Set up initial memory mappings and turn on MMU.
// --------------------------------------------------------------

static void check_boot_pgdir(void);
static void check_page_alloc();
static void page_check(void);
static void boot_map_segment(pde_t *pgdir, uintptr_t la, size_t size, physaddr_t pa, int perm);

//
// A simple physical memory allocator, used only a few times
// in the process of setting up the virtual memory system.
// page_alloc() is the real allocator.
//
// Allocate n bytes of physical memory aligned on an 
// align-byte boundary.  Align must be a power of two.
// Return kernel virtual address.  Returned memory is uninitialized.
//
// If we're out of memory, boot_alloc should panic.
// This function may ONLY be used during initialization,
// before the page_free_list has been set up.
// 
static void*
boot_alloc(uint32_t n, uint32_t align)
{
	
	extern char end[];
	void *v;

	// Initialize boot_freemem 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 -
	// i.e., the first virtual address that the linker
	// did _not_ assign to any kernel code or global variables.
	if (boot_freemem == 0)
		boot_freemem = end;

	
	// LAB 2: Your code here:
	//	Step 1: round boot_freemem up to be aligned properly
	//	Step 2: save current value of boot_freemem as allocated chunk
	char* temp_boot_freemem=ROUNDUP(boot_freemem,align);
	//	Step 3: increase boot_freemem to record allocation
	 boot_freemem=temp_boot_freemem+n;
	//	Step 4: return allocated chunk
	return (void *)temp_boot_freemem;
}


// Set up a two-level page table:
//    boot_pgdir is its linear (virtual) address of the root
//    boot_cr3 is the physical adresss of the root
// Then turn on paging.  Then effectively turn off segmentation.
// (i.e., the segment base addrs are set to zero).
// 
// This function only sets up the kernel part of the address space
// (ie. addresses >= UTOP).  The user part of the address space
// will be setup later.
//
// From UTOP to ULIM, the user is allowed to read but not write.
// Above ULIM the user cannot read (or write). 
void
i386_vm_init(void)
{
	pde_t* pgdir;
	uint32_t cr0;
	size_t n;

	// Delete this line:
	//panic("i386_vm_init: This function is not finished\n");

	//////////////////////////////////////////////////////////////////////
	// create initial page directory.
	pgdir = boot_alloc(PGSIZE, PGSIZE);

	memset(pgdir, 0, PGSIZE);
	boot_pgdir = pgdir;
	boot_cr3 = PADDR(pgdir);

	//////////////////////////////////////////////////////////////////////
	// Recursively insert PD in itself as a page table, to form
	// a virtual page table at virtual address VPT.
	// (For now, you don't have understand the greater purpose of the
	// following two lines.)

	// Permissions: kernel RW, user NONE
	pgdir[PDX(VPT)] = PADDR(pgdir)|PTE_W|PTE_P;

	// same for UVPT
	// Permissions: kernel R, user R 
	pgdir[PDX(UVPT)] = PADDR(pgdir)|PTE_U|PTE_P;

	//////////////////////////////////////////////////////////////////////
	// Make 'pages' point to an array of size 'npage' of 'struct Page'.
	// The kernel uses this structure to keep track of physical pages;
	// 'npage' equals the number of physical pages in memory.  User-level
	// programs will get read-only access to the array as well.
	// You must allocate the array yourself.
	// Your code goes here: 

	 pages = boot_alloc(npage * sizeof(struct Page), PGSIZE);
	
	

	//////////////////////////////////////////////////////////////////////
	// Make 'envs' point to an array of size 'NENV' of 'struct Env'.
	// LAB 3: Your code here.
	envs=boot_alloc(NENV*sizeof(struct Env),PGSIZE);

	//////////////////////////////////////////////////////////////////////
	// Now that we've allocated the initial kernel data structures, we set
	// up the list of free physical pages. 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_segment or page_insert
	page_init();

        check_page_alloc();
	
	page_check();

	//////////////////////////////////////////////////////////////////////
	// Now we set up virtual memory 
	
	//////////////////////////////////////////////////////////////////////
	// Map 'pages' read-only by the user at linear address UPAGES
	// (ie. perm = PTE_U | PTE_P)
	// Permissions:
	//    - pages -- kernel RW, user NONE
	//    - the read-only version mapped at UPAGES -- kernel R, user R
	// Your code goes here:
//<<<<<<< pmap.c
 	boot_map_segment(pgdir, UPAGES, npage * sizeof(struct Page), PADDR(pages), PTE_U | PTE_P);
//=======

	//////////////////////////////////////////////////////////////////////
	// Map the 'envs' array read-only by the user at linear address UENVS
	// (ie. perm = PTE_U | PTE_P).
	// Permissions:
	//    - envs itself -- kernel RW, user NONE
	//    - the image of envs mapped at UENVS  -- kernel R, user R
//>>>>>>> 1.1.1.3
	boot_map_segment(pgdir,UENVS,NENV*sizeof(struct Env),PADDR(envs),PTE_U|PTE_P);

	//////////////////////////////////////////////////////////////////////
	// Map the kernel stack (symbol name "bootstack").  The complete VA
	// range of the stack, [KSTACKTOP-PTSIZE, KSTACKTOP), breaks into two
	// pieces:
	//     * [KSTACKTOP-KSTKSIZE, KSTACKTOP) -- backed by physical memory
	//     * [KSTACKTOP-PTSIZE, KSTACKTOP-KSTKSIZE) -- not backed => faults
	//     Permissions: kernel RW, user NONE
	// Your code goes here:
	boot_map_segment(pgdir, KSTACKTOP - KSTKSIZE, KSTKSIZE, PADDR(bootstack), PTE_W|PTE_P);
	//////////////////////////////////////////////////////////////////////
	// 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 amapping anyway.
	// Permissions: kernel RW, user NONE
	// Your code goes here: 
	 boot_map_segment(pgdir, KERNBASE, (0xFFFFFFFF)-KERNBASE + 1, 0, PTE_W|PTE_P);
	// Check that the initial page directory has been set up correctly.
	check_boot_pgdir();

	//////////////////////////////////////////////////////////////////////
	// On x86, segmentation maps a VA to a LA (linear addr) and
	// paging maps the LA to a PA.  I.e. VA => LA => PA.  If paging is
	// turned off the LA is used as the PA.  Note: there is no way to
	// turn off segmentation.  The closest thing is to set the base
	// address to 0, so the VA => LA mapping is the identity.

	// Current mapping: VA KERNBASE+x => PA x.
	//     (segmentation base=-KERNBASE and paging is off)

	// From here on down we must maintain this VA KERNBASE + x => PA x
	// mapping, even though we are turning on paging and reconfiguring
	// segmentation.

	// Map VA 0:4MB same as VA KERNBASE, i.e. to PA 0:4MB.
	// (Limits our kernel to <4MB)
	pgdir[0] = pgdir[PDX(KERNBASE)];

	// Install page table.
	lcr3(boot_cr3);

	// Turn on paging.
	cr0 = rcr0();
	cr0 |= CR0_PE|CR0_PG|CR0_AM|CR0_WP|CR0_NE|CR0_TS|CR0_EM|CR0_MP;
	cr0 &= ~(CR0_TS|CR0_EM);
	lcr0(cr0);

	// Current mapping: KERNBASE+x => x => x.
	// (x < 4MB so uses paging pgdir[0])

	// Reload all segment registers.
	asm volatile("lgdt gdt_pd");
	asm volatile("movw %%ax,%%gs" :: "a" (GD_UD|3));
	asm volatile("movw %%ax,%%fs" :: "a" (GD_UD|3));
	asm volatile("movw %%ax,%%es" :: "a" (GD_KD));
	asm volatile("movw %%ax,%%ds" :: "a" (GD_KD));
	asm volatile("movw %%ax,%%ss" :: "a" (GD_KD));
	asm volatile("ljmp %0,$1f\n 1:\n" :: "i" (GD_KT));  // reload cs
	asm volatile("lldt %%ax" :: "a" (0));

	// Final mapping: KERNBASE+x => KERNBASE+x => x.

	// This mapping was only used after paging was turned on but
	// before the segment registers were reloaded.
	pgdir[0] = 0;

	// Flush the TLB for good measure, to kill the pgdir[0] mapping.
	lcr3(boot_cr3);
}

//
// Check the physical page allocator (page_alloc(), page_free(),
// and page_init()).
//
static void
check_page_alloc()
{
	struct Page *pp, *pp0, *pp1, *pp2;
	struct Page_list fl;
			
        // if there's a page that shouldn't be on
        // the free list, try to make sure it
        // eventually causes trouble.
	LIST_FOREACH(pp0, &page_free_list, pp_link)
		memset(page2kva(pp0), 0x97, 128);
	
	// 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);
        assert(page2pa(pp0) < npage*PGSIZE);
        assert(page2pa(pp1) < npage*PGSIZE);
        assert(page2pa(pp2) < npage*PGSIZE);

	// 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);

        // free and re-allocate?
        page_free(pp0);
        page_free(pp1);
        page_free(pp2);
	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);
	assert(page_alloc(&pp) == -E_NO_MEM);
	
	// 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_alloc() succeeded!\n");
}

//
// Checks that the kernel part of virtual address space
// has been setup roughly correctly(by i386_vm_init()).
//
// This function doesn't test every corner case,
// in fact it doesn't test the permission bits at all,
// but it is a pretty good sanity check. 
//
static physaddr_t check_va2pa(pde_t *pgdir, uintptr_t va);

static void
check_boot_pgdir(void)
{
	uint32_t i, n;
	pde_t *pgdir;

	pgdir = boot_pgdir;

	// check pages array
	n = ROUNDUP(npage*sizeof(struct Page), PGSIZE);
	for (i = 0; i < n; i += PGSIZE)
		assert(check_va2pa(pgdir, UPAGES + i) == PADDR(pages) + i);
	
	// check envs array (new test for lab 3)
	n = ROUNDUP(NENV*sizeof(struct Env), PGSIZE);
	for (i = 0; i < n; i += PGSIZE)
		assert(check_va2pa(pgdir, UENVS + i) == PADDR(envs) + i);

	// check phys mem
	for (i = 0; i < npage; 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);

	// check for zero/non-zero in PDEs
	for (i = 0; i < NPDENTRIES; i++) {
		switch (i) {
		case PDX(VPT):
		case PDX(UVPT):
		case PDX(KSTACKTOP-1):
		case PDX(UPAGES):
		case PDX(UENVS):
			assert(pgdir[i]);
			break;
		default:
			if (i >= PDX(KERNBASE))
				assert(pgdir[i]);
			else
				assert(pgdir[i] == 0);
			break;
		}
	}
	cprintf("check_boot_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_boot_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)]);
}
		
// --------------------------------------------------------------
// Tracking of physical pages.
// The 'pages' array has one 'struct Page' entry per physical page.
// Pages are reference counted, and free pages are kept on a linked list.
// --------------------------------------------------------------

//  
// Initialize page structure and memory free list.
// After this point, ONLY use the functions below
// to allocate and deallocate physical memory via the page_free_list,
// and NEVER use boot_alloc()
//
void
page_init(void)
{
	// The example code here marks all pages as free.
	// However this is not truly the case.  What memory is free?
	//  1) Mark page 0 as in use.
	//     This way we preserve the real-mode IDT and BIOS structures
	//     in case we ever need them.  (Currently we don't, but...)
	//  2) Mark the rest of base memory as free.
	//  3) Then comes the IO hole [IOPHYSMEM, EXTPHYSMEM).
	//     Mark it as in use so that it can never be allocated.      
	//  4) Then extended memory [EXTPHYSMEM, ...).