os/kernel/cpu/i386/paging.c

245 lines
7.1 KiB
C

/**
* \file
*/
#include "../../pmem.h"
#include "../../vga_err.h"
#include "../halt.h"
#include "../paging.h"
#include "arch_consts.h"
#include <stdint.h>
#include <stdlib.h>
/**
* Represents an entry in a page table/directory.
* \note Privlege bits in the page directory and page table entries for a page are ANDed together, so the most restrictive privlege between the page directory and the page table wins.
*/
typedef struct {
int pres:1; //!< Whether the page is present
int wr:1; //!< Whether the page is writeable
int usr:1; //!< Whether the page is accessible by user mode
int cachetype:1; //!< Cache type for the page. Write-through caching when 1, write-back caching when 0.
int cachedisable:1; //!< Whether caching is disabled
int accessed:1; //!< Whether the page has been accessed
int dirty:1; //!< Whether the page is dirty (has been written to)
int sz:1; //!< Page size
int osavail:4; //!< Availible for OS use
int pgno:20; //!< Physical page number this page maps to
} pg_struct_entry;
static pg_struct_entry page_directory[1024] __attribute__((aligned(4096))); //!< The kernel process's page directory
static pg_struct_entry kern_page_tables[NUM_KERN_FRAMES] __attribute__((aligned(4096))); //!< The page tables where the kernel binary is mapped in
static pg_struct_entry kstack_page_tables[218*1024] __attribute__((aligned(4096))); //!< Page tables for thread kernel stacks
static pg_struct_entry kmalloc_page_tables[4*1024] __attribute__((aligned(4096))); //!< Page tables for the kmalloc heap
static pg_struct_entry* pagdirmap=(pg_struct_entry*)0xFFFFF000; //!< Pointer to the page directory entries in the recursive mapping
static pg_struct_entry* page_table_map=(pg_struct_entry*)0xFFC00000; //!< Pointer to the page table entries in the recursive mapping
/**
* Checks whether a page is present
* \param page The page number to check
* \return Whether the page is present
*/
static char is_page_present(size_t page) {
int table=page>>10;
page=page&0x3FF;
if (!pagdirmap[table].pres) {
return 0;
}
return page_table_map[page+1024*table].pres;
}
void map_pages(void* virt_addr_ptr,void* phys_addr_ptr,int num_pages,char usr,char wr) {
uint32_t virt_addr=(uint32_t)virt_addr_ptr;
uint32_t phys_addr=(uint32_t)phys_addr_ptr;
int dir_entry=(virt_addr&0xFFC00000)>>22;
int table_entry=(virt_addr&0x3FF000)>>12;
for (int i=0;i<num_pages;i++) {
if (!pagdirmap[dir_entry].pres) {
pg_struct_entry* entry=&pagdirmap[dir_entry];
entry->pgno=(uint32_t)pmem_alloc(1)>>12;
entry->pres=1;
entry->usr=usr;
entry->wr=wr;
}
pg_struct_entry* entry=&page_table_map[table_entry+1024*dir_entry];
if (phys_addr_ptr==NULL) {
phys_addr=(uint32_t)pmem_alloc(1);
}
entry->pgno=phys_addr>>12;
entry->pres=1;
entry->usr=usr;
entry->wr=wr;
table_entry++;
if (table_entry==1024) {
table_entry=0;
dir_entry++;
}
phys_addr+=0x1000;
}
}
void* find_free_pages(int num_pages) {
size_t bmap_index;
size_t remaining_blks;
for(size_t i=1;i<131072;i++) {
char got_0=0;
remaining_blks=num_pages;
size_t old_j;
for (size_t j=i*8;;j++) {
char bit=is_page_present(j);
if (got_0) {
if (bit) {
if (remaining_blks==0) {
bmap_index=old_j;
break;
} else {
i+=j/8;
i--;
break;
}
} else {
remaining_blks--;
}
} else {
if (!bit) {
got_0=1;
old_j=j;
remaining_blks--;
}
}
if (remaining_blks==0) {
bmap_index=old_j;
break;
}
}
if (remaining_blks==0) {
break;
}
}
if (remaining_blks!=0) {
vga_write_string("[PANIC] Out of memory");
halt();
}
return (void*)(bmap_index<<12);
}
void* alloc_pages(int num_pages) {
void* addr=find_free_pages(num_pages);
map_pages(addr,NULL,num_pages,1,1);
return addr;
}
void* virt_to_phys(void* virt_addr_arg) {
uint32_t virt_addr=(uint32_t)virt_addr_arg;
int offset=virt_addr&0x3FF;
virt_addr=virt_addr&0xFFFFFC00;
if (!is_page_present(virt_addr>>12)) return NULL;
int dir_idx=(virt_addr&0xFFC00000)>>22;
int tbl_idx=(virt_addr&0x3FFC00)>>12;
if (!pagdirmap[dir_idx].pres) {
return 0;
}
return (void*)(((page_table_map[tbl_idx+1024*dir_idx].pgno)<<12)+offset);
}
void alloc_pages_virt(int num_pages,void* addr) {
map_pages(addr,NULL,num_pages,1,1);
}
/**
* Invalidates a page in the TLB,
* \param addr The address of the page to invalidate.
*/
static void invl_page(void* addr) {
asm volatile("invlpg (%0)"::"r"(addr):"memory");
}
void* paging_new_address_space() {
void* dir=pmem_alloc(1);
pg_struct_entry* freepg=find_free_pages(1);
map_pages(freepg,dir,1,0,1);
for (size_t i=0;i<1024;i++) {
freepg[i]=page_directory[i];
}
pg_struct_entry* entry=&freepg[1023];
entry->pres=1;
entry->wr=1;
entry->pgno=(uint32_t)dir>>12;
unmap_pages(freepg,1,0);
return dir;
}
void load_address_space(void* address_space) {
asm volatile("movl %0, %%eax; movl %%eax, %%cr3;":"=m"(address_space)::"%eax");
}
void unmap_pages(void* start_virt,int num_pages,int free_phys) {
uint32_t virt_addr=(uint32_t)start_virt;
int dir_entry=(virt_addr&0xFFC00000)>>22;
int table_entry=(virt_addr&0x3FF000)>>12;
for (int i=0;i<=num_pages;i++) {
if (page_table_map[dir_entry].pres) {
pg_struct_entry* entry=&page_table_map[table_entry+1024*dir_entry];
entry->pres=0;
if (free_phys) {
pmem_free((void*)(entry->pgno<<12),1);
}
invl_page(start_virt+(i*4096));
table_entry++;
if (table_entry==1024) {
dir_entry++;
table_entry=0;
}
}
}
}
void paging_init() {
for (size_t i=0;i<NUM_KERN_FRAMES;i++) {
pg_struct_entry* entry=&kern_page_tables[i];
entry->pres=1;
entry->wr=1;
entry->pgno=i;
}
for (size_t i=0;i<218*1024;i++) {
pg_struct_entry* entry=&kstack_page_tables[i];
entry->pres=0;
}
for (size_t i=0;i<4*1024;i++) {
pg_struct_entry* entry=&kmalloc_page_tables[i];
entry->pres=1;
entry->wr=1;
entry->pgno=(uint32_t)pmem_alloc(1)>>12;
}
for (size_t i=0;i<NUM_KERN_FRAMES/1024;i++) {
uint32_t entry_virt=(uint32_t)&(kern_page_tables[i*1024]);
pg_struct_entry* entry=&page_directory[i+768];
entry->pres=1;
entry->wr=1;
entry->pgno=((uint32_t)entry_virt-0xC0000000)>>12;
}
for (size_t i=0;i<4;i++) {
uint32_t entry_virt=(uint32_t)&(kmalloc_page_tables[i*1024]);
pg_struct_entry* entry=&page_directory[i+1018];
entry->pres=1;
entry->wr=1;
entry->pgno=((uint32_t)entry_virt-0xC0000000)>>12;
}
pg_struct_entry* entry=&page_directory[1023];
entry->pres=1;
entry->wr=1;
entry->pgno=((uint32_t)page_directory-0xC0000000)>>12;
load_address_space((uint32_t*)((uint32_t)page_directory-0xC0000000));
}
void* get_address_space() {
void* address_space;
asm volatile("movl %%cr3, %%eax; movl %%eax, %0;":"=m"(address_space)::"%eax");
return address_space;
}
void dealloc_pages(int num_pages,void* addr) {
pmem_free((void*)((uint32_t)virt_to_phys(addr)>>12),num_pages);
unmap_pages(addr,num_pages,1);
}