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/*
* bubbl
* Copyright (C) 2025 Raghuram Subramani <raghus2247@gmail.com>
*
* 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 <http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
#include <kernel/halt.h>
#include <libk/stdio.h>
#include <mm/physical_mm.h>
#include <mm/virtual_mm.h>
extern uint32_t kernel_start;
extern uint32_t kernel_end;
uint32_t *current_page_directory = 0;
ALWAYS_INLINE void
virtual_mm_load_page_directory(uint32_t *page_directory)
{
__asm__("movl %0, %%eax" ::"r"(page_directory));
}
bool
virtual_mm_switch_page_directory(uint32_t *page_directory)
{
if (!page_directory)
return false;
current_page_directory = page_directory;
virtual_mm_load_page_directory(page_directory);
return true;
}
ALWAYS_INLINE static void
virtual_mm_enable_paging(void)
{
__asm__("movl %%cr0, %%eax;"
"orl $0x80000000, %%eax;"
"movl %%eax, %%cr0" ::
: "eax");
}
void
virtual_mm_initialize(void)
{
uint32_t *table = physical_mm_allocate_block();
if (!table)
ASSERT_NOT_REACHED();
for (uint32_t i = 0; i < 1024; i++)
table[i] = 0;
/* Identity map the first 4MiB (maps 4KiB 1024 times) */
for (uint32_t i = 0, physical_addr = 0, virtual_addr = 0; i < 1024;
i++, physical_addr += 4096, virtual_addr += 4096) {
uint32_t pt_entry = 0;
ADD_ATTRIB(&pt_entry, SET_PTE_PRESENT(1));
ADD_ATTRIB(&pt_entry, SET_PTE_WRITABLE(1));
ADD_ATTRIB(&pt_entry, SET_PTE_FRAME(physical_addr));
table[PAGE_TABLE_INDEX(virtual_addr)] = pt_entry;
}
printk("debug", "Page table is at: 0x%x", table);
uint32_t *page_directory = physical_mm_allocate_block();
if (!page_directory)
ASSERT_NOT_REACHED();
for (uint32_t i = 0; i < 1024; i++)
page_directory[i] = 0;
uint32_t *pd_entry = &page_directory[PAGE_DIRECTORY_INDEX(0)];
ADD_ATTRIB(pd_entry, SET_PDE_PRESENT(1));
ADD_ATTRIB(pd_entry, SET_PDE_WRITABLE(1));
ADD_ATTRIB(pd_entry, SET_PDE_FRAME((uint32_t) table));
printk("debug", "Page directory is at: 0x%x", page_directory);
printk("debug", "pd_entry: 0x%x", pd_entry);
virtual_mm_switch_page_directory(page_directory);
virtual_mm_enable_paging();
}
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