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rockOS/kernel/rockos/paging.c

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/**
* Paging section of rockOS
* Copyright (C) 2022 Furkan Mudanyali
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, _either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
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#include <rockos/paging.h>
#include <rockos/kheap.h>
#include <rockos/rockos.h>
#include <string.h>
#define INDEX_FROM_BIT(x) (x/(8*4))
#define OFFSET_FROM_BIT(x) (x%(8*4))
PageDirectory* kernel_dir = 0;
PageDirectory* current_dir = 0;
uint32_t* frames;
uint32_t nframes;
extern uint32_t start_addr;
extern Heap* kheap;
void FrameSet(uint32_t frame_addr) {
uint32_t frame = frame_addr / 0x1000;
frames[INDEX_FROM_BIT(frame)] |= (1 << OFFSET_FROM_BIT(frame));
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}
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void FrameClear(uint32_t frame_addr) {
uint32_t frame = frame_addr / 0x1000;
frames[INDEX_FROM_BIT(frame)] &= ~(1 << OFFSET_FROM_BIT(frame));
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}
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uint32_t FrameTest(uint32_t frame_addr) {
uint32_t frame = frame_addr / 0x1000;
return (frames[INDEX_FROM_BIT(frame)] & (1 << OFFSET_FROM_BIT(frame)));
}
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uint32_t FrameFirst() {
for(uint32_t i = 0; i < INDEX_FROM_BIT(nframes); ++i) {
if(frames[i] != 0xFFFFFFFF) {
for(uint32_t j = 0; j < 32; ++j) {
uint32_t test = 1 << j;
if(!(frames[i]&test)) {
return i*4*8 + j;
}
}
}
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}
return 0;
}
void FrameAlloc(Page* page, char kernel, char writeable) {
if (page->frame) {
return;
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}
uint32_t i = FrameFirst();
if(i == (uint32_t)-1) {
panic("NO FREE FRAMES LEFT!");
}
FrameSet(i * 0x1000);
page->present = 1;
page->rw = writeable;
page->user = !kernel;
page->frame = i;
}
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void FrameFree(Page* page) {
uint32_t frame;
if(!(frame = page->frame)) {
return;
}
FrameClear(frame);
page->frame = 0;
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}
Page* PageGet(uint32_t addr, int32_t make, PageDirectory* dir) {
addr /= 0x1000;
uint32_t table_i = addr / 1024;
if(dir->tables[table_i]) {
return &dir->tables[table_i]->pages[addr%1024];
}
if(make) {
uint32_t temp;
dir->tables[table_i] = (PageTable*)kmalloc_int(sizeof(PageTable), 1, &temp);
memset(dir->tables[table_i], 0, 0x1000);
dir->tablesPhys[table_i] = temp | 0x7;
return &dir->tables[table_i]->pages[addr%1024];
}
return 0;
}
void paging_switch_dir(PageDirectory* dir) {
current_dir = dir;
asm volatile("mov %0, %%cr3":: "r"(&dir->tablesPhys));
uint32_t cr0;
asm volatile("mov %%cr0, %0": "=r"(cr0));
cr0 |= 0x80000000;
asm volatile("mov %0, %%cr0":: "r"(cr0));
}
void paging_init() {
printf("Initializing paging.\n");
uint32_t page_end_mem = 0x1000000;
nframes = page_end_mem / 0x1000;
frames = (uint32_t*)kmalloc(INDEX_FROM_BIT(nframes));
memset(frames, 0, INDEX_FROM_BIT(nframes));
kernel_dir = (PageDirectory*)kmalloc_int(sizeof(PageDirectory), 1, 0);
memset(kernel_dir, 0, sizeof(PageDirectory));
current_dir = kernel_dir;
for(uint32_t i = KHEAP_START; i < KHEAP_START + KHEAP_INITIAL_SIZE; i += 0x1000) {
PageGet(i, 1, kernel_dir);
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}
for(uint32_t i = 0; i < start_addr + 0x1000; i += 0x1000) {
FrameAlloc(PageGet(i, 1, kernel_dir), 0, 0);
}
for(uint32_t i = KHEAP_START; i < KHEAP_START + KHEAP_INITIAL_SIZE; i += 0x1000) {
FrameAlloc(PageGet(i, 1, kernel_dir), 0, 0);
}
paging_switch_dir(kernel_dir);
kheap = HeapCreate(KHEAP_START, KHEAP_START + KHEAP_INITIAL_SIZE, 0xCFFFF000, 0, 0);
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}