Restructering Kernel folder before moving to higher half kernel
The boot up process will be changed somewhat dramatically, therefor a restructering of the kernel seems as a good starting point.
This commit is contained in:
170
src/kernel/Memory/paging.cpp
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170
src/kernel/Memory/paging.cpp
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#include "paging.h"
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PageDirectoryEntry kernel_directory[MAX_DIRECTORY_ENTRIES]__attribute__((aligned(4096)));
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PageTableEntry first_page_table[MAX_PAGE_TABLE_ENTRIES]__attribute__((aligned(4096)));
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void IdentityMap (){
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printf("\nInit paging\n");
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// The basics as explained by wiki.osdev.org
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// Set all page_directories to not present
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int i = 0;
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while ( i < 1024)
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{
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kernel_directory[i] = 0x2;
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i++;
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}
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// map 4 megabytes
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unsigned int j ;
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for( j = 0; j < 1024; j++ )
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{
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first_page_table[j] = (j * 0x1000) | 3 ;
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//Attributes:
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//Supervisor Level ,
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//read/write,
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//present,
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}
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// Put the page table in the page directory
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// attributes: supervisor level, read/write, present;
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kernel_directory[0] = ((unsigned int)first_page_table) | 3;
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printf("Init paging DONE\n");
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}
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void InitializePaging()
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{
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/*
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Initial kernel page directory
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set all page tables to not present
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*/
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for (int i = 0; i < MAX_DIRECTORY_ENTRIES; i++)
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{
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kernel_directory[i] = 0x2;
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}
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// BIOS Address Identity mapping
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// Identity map the first 8MiB ... Physical addresses 0x00000000 to 0x007A1200
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PHYSICAL_ADDRESS BIOSAddr = 0x00000000;
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PHYSICAL_ADDRESS BIOSAddr_Max = 0x800000;
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// How many PDE's do we need
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uint8_t NUM_PDE = BIOSAddr_Max / (4 * 1024 * 1024);
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printf("The first 8MiB require %d Page Directory Entries\n", NUM_PDE);
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/*
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for( int i = 0; i < NUM_PDE; i++)
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{
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// setup a page table
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PageTableEntry pagetable[MAX_PAGE_TABLE_ENTRIES] = PhysicalMemory::allocate_block(); // TODO :: Physical memory manager functions should be available here.
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for(int j = 0; j < MAX_PAGE_TABLE_ENTRIES; j++)
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{
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pagetable[j] = ( j * 4096 ) | 3;
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}
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// add page table as page directory entry
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kernel_directory[i] = ( (unsigned int) pagetable ) | 3;
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}
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*/
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// map the kernel space
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VIRTUAL_ADDRESS Vaddr = KERNEL_VRT_MEMORY_BEGIN;
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PHYSICAL_ADDRESS KernelAddr = kernel_begin;
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PHYSICAL_ADDRESS KernelEndAddr = kernel_end;
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uint32_t KernelSizeInBytes = (KernelEndAddr - KernelAddr);
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printf("Kernel is 0x%x bytes\n", KernelSizeInBytes);
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NUM_PDE = KernelSizeInBytes / (4 * 1024* 1024);
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printf("Kernel requires %d Page Directory Entries\n", NUM_PDE);
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/*
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for(int i = 0; i < NUM_PDE; i++)
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{
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PageTableEntry pageTable [MAX_PAGE_TABLE_ENTRIES] = PhysicalMemory::allocate_block();
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for(int j = 0; j < MAX_PAGE_TABLE_ENTRIES; j++)
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{
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pageTable[j] = ( j * 4096) | 3; // NOTE: Check if page is actually supposed to be present
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}
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// TODO: Calculate Page Directory index
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}
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*/
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// Identity map VGA memory
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// Calc which PDE adn
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}
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void AllocatePage(VIRTUAL_ADDRESS vaddr, PageDirectoryEntry& page_directory)
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{
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}
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void FreePage(VIRTUAL_ADDRESS vaddr , PageDirectoryEntry& page_directory)
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{
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}
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void Map ( PHYSICAL_ADDRESS paddr, VIRTUAL_ADDRESS vaddr, PageDirectoryEntry& page_directory)
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{
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}
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void Unmap(VIRTUAL_ADDRESS vaddr, PageDirectoryEntry& page_directory)
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{
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// NOTE: I will implement lazy unmapping for now
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}
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void Enable()
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{
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//TODO: Write protect will not be turned on
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// for the moment altough according to the intel
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// developer manual this should happen.
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uint32_t CR0;
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CR0 = GetCR0();
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printf("PG bit = %d \n" , GET_PG_BIT(CR0));
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printf("Load into CR3 address: 0x%x\n", (uint32_t)(&kernel_directory[0]));
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loadPageDirectory(&kernel_directory[0]);
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enablePaging();
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printf("Paging enabled!\n");
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CR0 = GetCR0();
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uint32_t CR4 = GetCR4();
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printf("PG bit = %d\n" , GET_PG_BIT(CR0) );
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printf("PAE bit = %d\n", GET_PAE_BIT(CR4));
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if(GET_PAE_BIT(CR4) == 0){
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printf("Using 32bit paging\n");
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if(GET_PSE_BIT(CR4) == 0 ){
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printf("Page size is 4KiB\n");
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} else {
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printf("Page size is 4MiB\n");
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}
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} else {
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printf("Using some extended version for paging\n");
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}
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}
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