#include "paging.h"
#include <bitset.h>
#include <stdlib.h>
#include <core/monitor.h>
#include "mem.h"
#include "seg.h"
#include <core/sys.h>
#include <task/task.h>
static struct bitset frames;
struct page_directory *kernel_pagedir, *current_pagedir;
/************************** PHYSICAL MEMORY ALLOCATION ************************/
/* Allocates a page of physical memory. */
uint32_t frame_alloc() {
uint32_t free = bitset_firstFree(&frames);
bitset_set(&frames, free);
return free;
}
void frame_free(uint32_t id) {
bitset_clear(&frames, id);
}
/************************* PAGING INITIALIZATION *****************************/
/* This function creates the kernel page directory. It must be called before the GDT is loaded.
It maps 0xE0000000+ to the corresponding physical kernel code, but it also maps
0x00000000+ to that code because with the false GDT we set up in loader_.asm,
the code will be looked for at the beginning of the memory. Only when the real GDT is loaded
we can de-allocate pages at 0x00000000 ; this is done by paging_cleanup. */
void paging_init(size_t totalRam) {
uint32_t i;
frames.size = totalRam / 0x1000;
frames.bits = kmalloc(INDEX_FROM_BIT(frames.size));
kernel_pagedir = kmalloc(sizeof(struct page_directory));
kernel_pagedir->mappedSegs = 0;
kernel_pagedir->tablesPhysical = kmalloc_page(&kernel_pagedir->physicalAddr);
for (i = 0; i < 1024; i++) {
kernel_pagedir->tables[i] = 0;
kernel_pagedir->tablesPhysical[i] = 0;
}
for (i = 0xE0000000; i < mem_placementAddr; i += 0x1000) {
page_map(pagedir_getPage(kernel_pagedir, i, 1), frame_alloc(), 0, 0);
}
for (i = 0; i < (mem_placementAddr - 0xE0000000) / 0x100000; i++) {
kernel_pagedir->tablesPhysical[i] = kernel_pagedir->tablesPhysical[i + 896];
kernel_pagedir->tables[i] = kernel_pagedir->tables[i + 896];
}
monitor_write("{PD: ");
monitor_writeHex(kernel_pagedir->physicalAddr);
pagedir_switch(kernel_pagedir);
monitor_write("} [Paging] ");
}
/* De-allocates pages at 0x00000000 where kernel code was read from with the GDT from loader_.asm. */
void paging_cleanup() {
uint32_t i;
for (i = 0; i < (mem_placementAddr - 0xE0000000) / 0x100000; i++) {
kernel_pagedir->tablesPhysical[i] = 0;
kernel_pagedir->tables[i] = 0;
}
monitor_write("[PD Cleanup] ");
}
/************************* PAGING EVERYDAY USE *****************************/
/* Switch to a page directory. Can be done if we are sure not to be interrupted by a task switch.
Example use for cross-memory space writing in linker/elf.c */
void pagedir_switch(struct page_directory *pd) {
current_pagedir = pd;
asm volatile("mov %0, %%cr3" : : "r"(pd->physicalAddr));
uint32_t cr0;
asm volatile("mov %%cr0, %0" : "=r"(cr0));
cr0 |= 0x80000000;
asm volatile("mov %0, %%cr0" : : "r"(cr0));
}
/* Creates a new page directory for a process, and maps the kernel page tables on it. */
struct page_directory *pagedir_new() {
uint32_t i;
struct page_directory *pd = kmalloc(sizeof(struct page_directory));
pd->tablesPhysical = kmalloc_page(&pd->physicalAddr);
pd->mappedSegs = 0;
for (i = 0; i < 1024; i++) {
pd->tables[i] = 0; pd->tablesPhysical[i] = 0;
}
for (i = 896; i < 1024; i++) {
pd->tables[i] = kernel_pagedir->tables[i];
pd->tablesPhysical[i] = kernel_pagedir->tablesPhysical[i];
}
return pd;
}
/* Deletes a page directory, cleaning it up. */
void pagedir_delete(struct page_directory *pd) {
uint32_t i;
//Unmap segments
while (pd->mappedSegs != 0) seg_unmap(pd->mappedSegs);
//Cleanup page tables
for (i = 0; i < 896; i++) {
kfree_page(pd->tables[i]);
}
kfree_page(pd->tablesPhysical);
kfree(pd);
}
/* Handle a paging fault. First, looks for the corresponding segment.
If the segment was found and it handles the fault, return normally.
Else, display informatinos and return an error. */
uint32_t paging_fault(struct registers *regs) {
size_t addr;
struct segment_map *seg = 0;
asm volatile("mov %%cr2, %0" : "=r"(addr));
seg = current_pagedir->mappedSegs;
while (seg) {
if (seg->start <= addr && seg->start + seg->len > addr) break;
seg = seg->next;
}
if (seg != 0) {
if (seg->seg->handle_fault(seg, addr, (regs->err_code & 0x2) && (regs->eip < 0xE0000000)) != 0) seg = 0;
}
if (seg == 0) {
WHERE; monitor_write("Unhandled Page Fault ");
if (regs->err_code & 0x1) monitor_write("present ");
if (regs->err_code & 0x2) monitor_write("write ");
if (regs->err_code & 0x4) monitor_write("user ");
if (regs->err_code & 0x8) monitor_write("rsvd ");
if (regs->err_code & 0x10) monitor_write("instructionfetch ");
monitor_write("cr2:"); monitor_writeHex(addr); monitor_write("\n");
return 1;
}
return 0;
}
/* Gets the corresponding page in a page directory for a given address.
If make is set, the necessary page table can be created.
Can return 0 if make is not set. */
struct page *pagedir_getPage(struct page_directory *pd, uint32_t address, int make) {
address /= 0x1000;
uint32_t table_idx = address / 1024;
if (pd->tables[table_idx]) {
return &pd->tables[table_idx]->pages[address % 1024];
} else if (make) {
pd->tables[table_idx] = kmalloc_page(pd->tablesPhysical + table_idx);
if (table_idx >= 896)
tasking_updateKernelPagetable(table_idx, pd->tables[table_idx], pd->tablesPhysical[table_idx]);
memset((uint8_t*)pd->tables[table_idx], 0, 0x1000);
pd->tablesPhysical[table_idx] |= 0x07;
return &pd->tables[table_idx]->pages[address % 1024];
} else {
return 0;
}
}
/* Modifies a page structure so that it is mapped to a frame. */
void page_map(struct page *page, uint32_t frame, uint32_t user, uint32_t rw) {
if (page != 0 && page->frame == 0 && page->present == 0) {
page->present = 1;
page->rw = (rw ? 1 : 0);
page->user = (user ? 1 : 0);
page->frame = frame;
}
}
/* Modifies a page structure so that it is no longer mapped to a frame. */
void page_unmap(struct page *page) {
if (page != 0) {
page->frame = 0;
page->present = 0;
}
}
/* Same as above but also frees the frame. */
void page_unmapFree(struct page *page) {
if (page != 0) {
if (page->frame != 0) frame_free(page->frame);
page->frame = 0;
page->present = 0;
}
}
