Merge pull request #8 from AbleTheAbove/paging

Paging

ableos/.cargo/config.toml

@@ -3,7 +3,8 @@ target = "./json_targets/x86_64-ableos.json"
 
 [unstable]
 build-std-features = ["compiler-builtins-mem"]
-build-std = ["core","alloc", "compiler_builtins"]
+build-std = ["core", "compiler_builtins", "alloc"]
+
 
 
 [target.'cfg(target_arch = "x86_64")']

ableos/Cargo.toml

@@ -36,7 +36,7 @@ psp = "0.1.5"
 
 [target.'cfg(target_arch = "x86_64")'.dependencies]
 volatile = "0.2.6"
-bootloader = "0.9.8"
+bootloader = {version = "0.9.8", features = ["map_physical_memory"]}
 cpuio = { git = "https://github.com/anyusernameworks/cpuio.git" }
 x86_64 = "*"
 uart_16550 = "0.2.0"

ableos/src/arch/x86_64/memory.rs

@@ -0,0 +1,112 @@
+use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
+use x86_64::{
+	structures::paging::{
+		FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
+	},
+	PhysAddr, VirtAddr,
+};
+
+pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
+	let level_4_table = active_level_4_table(physical_memory_offset);
+	OffsetPageTable::new(level_4_table, physical_memory_offset)
+}
+
+unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
+	use x86_64::registers::control::Cr3;
+
+	let (level_4_table_frame, _) = Cr3::read();
+
+	let phys = level_4_table_frame.start_address();
+	let virt = physical_memory_offset + phys.as_u64();
+	let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
+
+	// THIS IS UNSAFE
+	&mut *page_table_ptr
+}
+
+fn translate_addr_inner(addr: VirtAddr, physical_memory_offset: VirtAddr) -> Option<PhysAddr> {
+	use x86_64::registers::control::Cr3;
+	use x86_64::structures::paging::page_table::FrameError;
+
+	let (level_4_table_frame, _) = Cr3::read();
+
+	let table_indexes = [
+		addr.p4_index(),
+		addr.p3_index(),
+		addr.p2_index(),
+		addr.p1_index(),
+	];
+	let mut frame = level_4_table_frame;
+
+	for &index in &table_indexes {
+		// convert the frame into a page table reference
+		let virt = physical_memory_offset + frame.start_address().as_u64();
+		let table_ptr: *const PageTable = virt.as_ptr();
+		let table = unsafe { &*table_ptr };
+
+		let entry = &table[index];
+		frame = match entry.frame() {
+			Ok(frame) => frame,
+			Err(FrameError::FrameNotPresent) => return None,
+			Err(FrameError::HugeFrame) => panic!["huge pages not supported"],
+		};
+	}
+
+	Some(frame.start_address() + u64::from(addr.page_offset()))
+}
+
+pub unsafe fn translate_addr(addr: VirtAddr, physical_memory_offset: VirtAddr) -> Option<PhysAddr> {
+	translate_addr_inner(addr, physical_memory_offset)
+}
+
+pub fn create_example_mapping(
+	page: Page,
+	mapper: &mut OffsetPageTable,
+	frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) {
+	use x86_64::structures::paging::PageTableFlags as Flags;
+
+	let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
+	let flags = Flags::PRESENT | Flags::WRITABLE;
+
+	let map_to_result = unsafe { mapper.map_to(page, frame, flags, frame_allocator) };
+	map_to_result.expect("map_to failed").flush();
+}
+
+pub struct EmptyFrameAllocator;
+
+unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
+	fn allocate_frame(&mut self) -> Option<PhysFrame<Size4KiB>> {
+		None
+	}
+}
+
+pub struct BootInfoFrameAllocator {
+	memory_map: &'static MemoryMap,
+	next: usize,
+}
+
+impl BootInfoFrameAllocator {
+	pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
+		Self {
+			memory_map,
+			next: 0,
+		}
+	}
+
+	fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
+		let regions = self.memory_map.iter();
+		let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
+		let addr_range = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
+		let frame_address = addr_range.flat_map(|r| r.step_by(4096));
+		frame_address.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
+	}
+}
+
+unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
+	fn allocate_frame(&mut self) -> Option<PhysFrame<Size4KiB>> {
+		let frame = self.usable_frames().nth(self.next);
+		self.next += 1;
+		frame
+	}
+}

ableos/src/arch/x86_64/mod.rs

@@ -1,13 +1,15 @@
 use x86_64::instructions::hlt;
+use bootloader::BootInfo;
 pub mod drivers;
 pub mod gdt;
 pub mod init;
 pub mod interrupts;
-#[no_mangle]
-pub extern "C" fn _start() -> ! {
-    crate::kmain::kernel_main();
-    sloop();
-}
+pub mod memory;
+// #[no_mangle]
+// pub extern "C" fn _start(boot_info: &'static BootInfo) -> ! {
+//     crate::kmain::kernel_main(boot_info);
+//     // sloop();
+// }
 
 #[allow(unused)]
 pub fn shutdown() -> ! {

ableos/src/kmain.rs

@@ -1,18 +1,29 @@
 #![allow(clippy::empty_loop)]
 use crate::{
-    arch::{drivers::graphics::GraphicsBuffer, init},
+	arch::{
+		drivers::graphics::GraphicsBuffer,
+		init,
+		memory::{self, translate_addr},
+		sloop,
+	},
 	driver_traits::{graphics::Graphics, serial::Serial},
-    experiments::systeminfo::{KERNEL_VERSION, RELEASE_TYPE},
-    keyboard::DecodedKey,
 	relib::math::rand::{linearshift::LinearShiftRegister, prand::PRand, RAND_HANDLE, RNG},
 	serial_print, serial_println,
+
+    experiments::systeminfo::{KERNEL_VERSION, RELEASE_TYPE},
+    keyboard::DecodedKey,
 };
+use bootloader::{entry_point, BootInfo};
 use lazy_static::lazy_static;
 
+
+use x86_64::{VirtAddr, structures::paging::Page};
+
 #[no_mangle]
 #[allow(unconditional_recursion)]
 pub extern "C" fn stack_overflow() -> u8 {
 	stack_overflow();
+	// meme number
 	69 // NOTE: Any specific reason for this number asside from memes?
 }
 
@@ -20,8 +31,10 @@ lazy_static! {
 	pub static ref KEY_BUFFER: [DecodedKey; 256] = [DecodedKey::RawKey(123); 256];
 	pub static ref KEY_BUFFER_POINTER: u8 = 0;
 }
+// Defines the entry point
+entry_point![kernel_main];
 #[no_mangle]
-pub extern "C" fn kernel_main() {
+pub fn kernel_main(boot_info: &'static BootInfo) -> ! {
 	init::init();
 
 	GraphicsBuffer::draw();
@@ -32,8 +45,9 @@ pub extern "C" fn kernel_main() {
 	/* If AES is present then AES init rng as well
 	// Maybe via a cfg
 		AES::init_rng();
+*/
+
        
-        */
 
     println!("{} v{}", RELEASE_TYPE, KERNEL_VERSION);
 
@@ -45,9 +59,22 @@ pub extern "C" fn kernel_main() {
 		// x.dump_flags();
 	}
 
+	let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+
+	let mut mapper = unsafe { memory::init(phys_mem_offset) };
+	let mut frame_allocator = unsafe {
+      memory::BootInfoFrameAllocator::init(&boot_info.memory_map)
+   };
+
+	let page = Page::containing_address(VirtAddr::new(0xdeadbeaf000));
+	memory::create_example_mapping(page, &mut mapper, &mut frame_allocator);
+
+	let page_ptr: *mut u64 = page.start_address().as_mut_ptr();
+	unsafe { page_ptr.offset(400).write_volatile(0xf021_f077_f065_804e) };
+
 	// stack_overflow();
 	// crate::arch::shutdown();
-    loop {}
+	sloop()
 }
 // TODO: reimplement for the random handler
 pub fn seed_rng() -> PRand {

ableos/src/lib.rs

@@ -36,3 +36,4 @@ pub mod panic;
 pub mod relib;
 
 use experiments::server;
+