From b84c5822df6bf79b0fc9d146a93e58d9cba6cde1 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Sat, 28 May 2016 15:22:18 +0200
Subject: [PATCH] Create interrupt module with IDT submodule

---
 Cargo.toml            |   5 +-
 src/interrupts/idt.rs | 103 ++++++++++++++++++++++++++++++++++++++++++
 src/interrupts/mod.rs |   1 +
 src/lib.rs            |   3 ++
 4 files changed, 110 insertions(+), 2 deletions(-)
 create mode 100644 src/interrupts/idt.rs
 create mode 100644 src/interrupts/mod.rs

diff --git a/Cargo.toml b/Cargo.toml
index d0cb6f3c..a5503538 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,10 +4,11 @@ name = "blog_os"
 version = "0.1.0"
 
 [dependencies]
+bit_field = "0.1.0"
+bitflags = "0.7.0"
 once = "0.2.1"
 rlibc = "0.1.4"
 spin = "0.3.4"
-bitflags = "0.7.0"
 
 [dependencies.hole_list_allocator]
 path = "libs/hole_list_allocator"
@@ -17,7 +18,7 @@ git = "https://github.com/phil-opp/multiboot2-elf64"
 
 [dependencies.x86]
 default-features = false
-version = "0.6.0"
+version = "0.7.0"
 
 [lib]
 crate-type = ["staticlib"]
diff --git a/src/interrupts/idt.rs b/src/interrupts/idt.rs
new file mode 100644
index 00000000..ea7c41cd
--- /dev/null
+++ b/src/interrupts/idt.rs
@@ -0,0 +1,103 @@
+use x86::segmentation::{self, SegmentSelector};
+
+pub struct Idt([Entry; 16]);
+
+impl Idt {
+    pub fn new() -> Idt {
+        Idt([Entry::missing(); 16])
+    }
+
+    pub fn set_handler(&mut self, entry: u8, handler: HandlerFunc) -> &mut EntryOptions {
+        self.0[entry as usize] = Entry::new(segmentation::cs(), handler);
+        &mut self.0[entry as usize].options
+    }
+
+    pub fn load(&'static self) {
+        use x86::dtables::{DescriptorTablePointer, lidt};
+        use core::mem::size_of;
+
+        let ptr = DescriptorTablePointer {
+            base: self as *const _ as u64,
+            limit: (size_of::<Self>() - 1) as u16,
+        };
+
+        unsafe { lidt(&ptr) };
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+#[repr(C, packed)]
+pub struct Entry {
+    pointer_low: u16,
+    gdt_selector: SegmentSelector,
+    options: EntryOptions,
+    pointer_middle: u16,
+    pointer_high: u32,
+    reserved: u32,
+}
+
+type HandlerFunc = extern "C" fn() -> !;
+
+impl Entry {
+    fn new(gdt_selector: SegmentSelector, handler: HandlerFunc) -> Self {
+        let pointer = handler as u64;
+        Entry {
+            gdt_selector: gdt_selector,
+            pointer_low: pointer as u16,
+            pointer_middle: (pointer >> 16) as u16,
+            pointer_high: (pointer >> 32) as u32,
+            options: EntryOptions::new(),
+            reserved: 0,
+        }
+    }
+
+    fn missing() -> Self {
+        Entry {
+            gdt_selector: SegmentSelector::new(0),
+            pointer_low: 0,
+            pointer_middle: 0,
+            pointer_high: 0,
+            options: EntryOptions::minimal(),
+            reserved: 0,
+        }
+    }
+}
+
+use bit_field::BitField;
+
+#[derive(Debug, Clone, Copy)]
+pub struct EntryOptions(BitField<u16>);
+
+impl EntryOptions {
+    fn minimal() -> Self {
+        let mut options = BitField::new(0);
+        options.set_range(9..12, 0b111); // 'must-be-one' bits
+        EntryOptions(options)
+    }
+
+    fn new() -> Self {
+        let mut options = Self::minimal();
+        options.set_present(true).disable_interrupts(true);
+        options
+    }
+
+    fn set_present(&mut self, present: bool) -> &mut Self {
+        self.0.set_bit(15, present);
+        self
+    }
+
+    fn disable_interrupts(&mut self, disable: bool) -> &mut Self {
+        self.0.set_bit(8, !disable);
+        self
+    }
+
+    fn set_privilege_level(&mut self, dpl: u16) -> &mut Self {
+        self.0.set_range(13..15, dpl);
+        self
+    }
+
+    fn set_stack_index(&mut self, index: u16) -> &mut Self {
+        self.0.set_range(0..3, index);
+        self
+    }
+}
diff --git a/src/interrupts/mod.rs b/src/interrupts/mod.rs
new file mode 100644
index 00000000..e640a3f1
--- /dev/null
+++ b/src/interrupts/mod.rs
@@ -0,0 +1 @@
+mod idt;
diff --git a/src/lib.rs b/src/lib.rs
index 9b131ead..d0512afd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -20,6 +20,7 @@ extern crate bitflags;
 extern crate x86;
 #[macro_use]
 extern crate once;
+extern crate bit_field;
 
 extern crate hole_list_allocator;
 extern crate alloc;
@@ -30,6 +31,8 @@ extern crate collections;
 mod vga_buffer;
 mod memory;
 
+mod interrupts;
+
 #[no_mangle]
 pub extern "C" fn rust_main(multiboot_information_address: usize) {
     // ATTENTION: we have a very small stack and no guard page