/* Calcite, src/kernel/paging.h
 * Copyright 2025-2026 Benji Dial
 *
 * 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/>.
 */

#pragma once

#include <stdint.h>

extern uint64_t kernel_p3_physical_address;

//kernel physical and virtual bases are passed so that we can compute the
//physical addresses of the kernel's statically allocated paging structures.
void init_paging(uint64_t kernel_physical_base, void *kernel_virtual_base);

//base and length should be page-aligned
void mark_physical_memory_free(uint64_t base, uint64_t length);

//maps one page. physical and virtual bases should be page-aligned.
//virtual address should be within kernel range.
void map_in_kernel_page_table(
  uint64_t physical_base, void *virtual_base, int writable, int executable);

//virtual base should be page-aligned and within kernel range.
void create_kernel_guard_page(void *virtual_base);

//unmaps one page. base should be page-aligned and within kernel range.
void unmap_kernel_page(void *virtual_base);

//unmaps one page, and frees the corresponding physical page.
//base should be page-aligned and within kernel range.
void unmap_and_free_kernel_page(void *virtual_base);

//returns a region of contiguous pages in kernel virtual memory where nothing
//is mapped. length should be page-aligned.
void *find_free_kernel_region(uint64_t length);

uint64_t take_free_physical_page();

//implemented in paging.asm. the continuation should be noreturn.
[[noreturn]] void switch_to_kernel_page_tables(void (*continuation)());

//returns the top
void *create_syscall_stack();
void destroy_syscall_stack(void *stack_top);

//return value in bytes
uint64_t count_free_pram();

//return value in bytes
uint64_t count_free_kernel_vram();