From 6f342db5c24a69ffd8160f687d091bb419957789 Mon Sep 17 00:00:00 2001
From: Masato Imai <mii@sfc.wide.ad.jp>
Date: Sun, 27 Apr 2025 09:12:19 +0000
Subject: [PATCH] add EPT

---
 src/lib.rs     |  1 +
 src/main.rs    |  6 +++-
 src/memory.rs  |  4 +++
 src/vmm/ept.rs | 75 ++++++++++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 83 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 20539c4..2725a9a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,7 @@
 #![feature(abi_x86_interrupt)]
 #![feature(alloc_error_handler)]
 #![feature(naked_functions)]
+#![feature(generic_const_exprs)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
diff --git a/src/main.rs b/src/main.rs
index d3ec8f7..aff8d86 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@
 #![feature(custom_test_frameworks)]
 #![feature(new_zeroed_alloc)]
 #![feature(naked_functions)]
+#![feature(generic_const_exprs)]
 #![test_runner(nel_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 #![allow(unreachable_code)]
@@ -10,7 +11,7 @@
 extern crate alloc;
 
 use bootloader::{entry_point, BootInfo};
-use core::panic::PanicInfo;
+use core::{panic::PanicInfo, sync::atomic::Ordering};
 use nel_os::{
     allocator, info,
     memory::{self, BootInfoFrameAllocator},
@@ -43,6 +44,9 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     nel_os::init();
 
     let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+
+    memory::PHYSICAL_MEMORY_OFFSET.store(phys_mem_offset.as_u64(), Ordering::Relaxed);
+
     let mut mapper = unsafe { memory::init(phys_mem_offset) };
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
diff --git a/src/memory.rs b/src/memory.rs
index 64e7549..f23224b 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,9 +1,13 @@
+use core::sync::atomic::AtomicU64;
+
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
     structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB},
     PhysAddr, VirtAddr,
 };
 
+pub static PHYSICAL_MEMORY_OFFSET: AtomicU64 = AtomicU64::new(0);
+
 pub struct BootInfoFrameAllocator {
     memory_map: &'static MemoryMap,
     next: usize,
diff --git a/src/vmm/ept.rs b/src/vmm/ept.rs
index 1827b96..9710570 100644
--- a/src/vmm/ept.rs
+++ b/src/vmm/ept.rs
@@ -1,6 +1,61 @@
+use core::sync::atomic::Ordering;
+
 use bitfield::bitfield;
 use x86_64::PhysAddr;
 
+use crate::memory;
+
+pub enum Assert<const CHECK: bool> {}
+
+pub trait IsTrue {}
+
+impl IsTrue for Assert<true> {}
+
+pub struct TableEntry<const LEVEL: u8> {
+    pub entry: EntryBase,
+}
+
+impl<const LEVEL: u8> TableEntry<LEVEL> {
+    pub fn new_map_table<const L: u8>(table: TableEntry<L>) -> Self
+    where
+        Assert<{ LEVEL > L }>: IsTrue,
+        Assert<{ L > 0 }>: IsTrue,
+        Assert<{ LEVEL < 5 }>: IsTrue,
+    {
+        let mut entry = EntryBase::default();
+        entry.set_map_memory(false);
+        entry.set_typ(0);
+        entry.set_phys(
+            (&table as *const _ as u64 + memory::PHYSICAL_MEMORY_OFFSET.load(Ordering::Relaxed))
+                >> 12,
+        );
+
+        Self { entry }
+    }
+
+    pub fn new_map_page<const L: u8>(phys: u64) -> Self
+    where
+        Assert<{ L < 4 }>: IsTrue,
+        Assert<{ L > 0 }>: IsTrue,
+    {
+        let mut entry = EntryBase::default();
+        entry.set_read(true);
+        entry.set_write(true);
+        entry.set_exec_super(true);
+        entry.set_exec_user(true);
+        entry.set_map_memory(true);
+        entry.set_typ(0);
+        entry.set_phys((phys + memory::PHYSICAL_MEMORY_OFFSET.load(Ordering::Relaxed)) >> 12);
+
+        Self { entry }
+    }
+}
+
+pub type Lv4Entry = TableEntry<4>;
+pub type Lv3Entry = TableEntry<3>;
+pub type Lv2Entry = TableEntry<2>;
+pub type Lv1Entry = TableEntry<1>;
+
 bitfield! {
     pub struct EntryBase(u64);
     impl Debug;
@@ -25,6 +80,22 @@ impl EntryBase {
     pub fn address(&self) -> PhysAddr {
         PhysAddr::new(self.phys() << 12)
     }
-
-    pub fn new_map_table() {}
+}
+
+impl Default for EntryBase {
+    fn default() -> Self {
+        let mut entry = EntryBase(0);
+        entry.set_read(true);
+        entry.set_write(true);
+        entry.set_exec_super(true);
+        entry.set_typ(0);
+        entry.set_ignore_pat(false);
+        entry.set_map_memory(false);
+        entry.set_accessed(false);
+        entry.set_dirty(false);
+        entry.set_exec_user(true);
+        entry.set_phys(0);
+
+        entry
+    }
 }