Add IDT

8 files changed, 155 insertions, 2 deletions

diff --git a/.gitignore b/.gitignore
index 94e1555..bd048b4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,5 @@ glitch.elf
 glitch.iso
 build/
 isodir/
+
+*.tar*
diff --git a/drivers/ports.h b/drivers/ports.h
index 8671f19..98cac72 100644
--- a/drivers/ports.h
+++ b/drivers/ports.h
@@ -53,3 +53,7 @@ typedef Port<0x3f8, uint8_t> com1_port_t;
 typedef Port<0x2f8, uint8_t> com2_port_t;
 typedef Port<0x3e8, uint8_t> com3_port_t;
 typedef Port<0x2e8, uint8_t> com4_port_t;
+
+/* 8259 PIC */
+typedef Port<0x20, uint8_t> pic1_t;
+typedef Port<0xA0, uint8_t> pic2_t;
diff --git a/libk/types.h b/libk/types.h
index 599f852..08d42b9 100644
--- a/libk/types.h
+++ b/libk/types.h
@@ -13,6 +13,15 @@ typedef short int16_t;
 typedef int int32_t;
 typedef long long int int64_t;
 
+/* in x86:
+ * byte:  1 byte,   8 bits
+ * word:  2 bytes, 16 bits
+ * dword: 4 bytes, 32 bits
+ * qword: 8 bytes, 64 bits
+ * */
+typedef uint16_t uword_t;
+typedef int16_t word_t;
+
 // Type Traits
 
 template <class T, T v>
diff --git a/src/idt.cc b/src/idt.cc
new file mode 100644
index 0000000..fe4c159
--- /dev/null
+++ b/src/idt.cc
@@ -0,0 +1,51 @@
+#include "idt.h"
+#include <stdlib.h>
+#include "ports.h"
+
+static_assert(sizeof(IDT::Pointer) == 6);
+// size of IDT::Entry in protected mode is 64 bits
+// and in long mode is 128 bits
+static_assert(sizeof(IDT::Entry) == 8);
+
+/* reinitialize the PIC controllers, giving them specified vector offsets
+   rather than 8h and 70h, as configured by default */
+
+#define ICW1_ICW4 0x01      /* ICW4 (not) needed */
+#define ICW1_SINGLE 0x02    /* Single (cascade) mode */
+#define ICW1_INTERVAL4 0x04 /* Call address interval 4 (8) */
+#define ICW1_LEVEL 0x08     /* Level triggered (edge) mode */
+#define ICW1_INIT 0x10      /* Initialization - required! */
+
+#define ICW4_8086 0x01       /* 8086/88 (MCS-80/85) mode */
+#define ICW4_AUTO 0x02       /* Auto (normal) EOI */
+#define ICW4_BUF_SLAVE 0x08  /* Buffered mode/slave */
+#define ICW4_BUF_MASTER 0x0C /* Buffered mode/master */
+#define ICW4_SFNM 0x10       /* Special fully nested (not) */
+
+IDT::IDT() {
+  pic1_t pic1;
+  pic2_t pic2;
+
+  const auto mask1 = pic1.read(0x1);
+  const auto mask2 = pic2.read(0x1);
+
+  pic1.write(ICW1_INIT | ICW1_ICW4);
+  pic2.write(ICW1_INIT | ICW1_ICW4);
+  pic1.write(0x20, 0x1);  // offset 0x20
+  pic2.write(0x28, 0x1);  // offset 0x28
+  pic1.write(4, 0x1);     // tell master pic there is a slave pic
+  pic2.write(2, 0x1);     // tell slave pic its cascade identity
+  pic1.write(ICW4_8086, 0x1);
+  pic2.write(ICW4_8086, 0x1);
+
+  pic1.write(mask1);
+  pic2.write(mask2);
+
+  table[32] = Entry((unsigned long)kirq<0x0>, 0x08, InterruptGate);
+  table[33] = Entry((unsigned long)kirq<0x1>, 0x08, InterruptGate);
+
+  Pointer ptr{.limit = sizeof(table), .base = (uint32_t)table};
+  asm volatile("lidt %0" : : "m"(ptr));
+
+  printk("IDT installed at ", (uint32_t)table, '\n');
+}
diff --git a/src/idt.h b/src/idt.h
new file mode 100644
index 0000000..3aa5a1e
--- /dev/null
+++ b/src/idt.h
@@ -0,0 +1,61 @@
+#pragma once
+
+#include <types.h>
+
+class IDT {
+public:
+  struct Pointer {
+    uint16_t limit;
+    uint32_t base;
+  } __attribute__((packed));
+
+  enum InterruptType : uint8_t {
+    Null = 0,
+    InterruptGate = 0b110,  // hardware interrupts are disabled while the handler runs
+    TrapGate = 0b111,       // hardware interrupts remain active while the handler runs
+    TaskGate = 0b101,       // selector points to TSS rather than a code segment
+  };
+
+  class Entry {
+  public:
+    Entry(uint32_t offset = 0, uint16_t select = 0, InterruptType t = Null) {
+      offset_0_15 = offset & 0xffff;
+      offset_16_31 = (offset & 0xffff0000) >> 16;
+      selector = select;
+      type = t;
+    }
+
+  private:
+    uint16_t offset_0_15;                //  0-15 offset in the segment
+    uint16_t selector;                   // 16-31 selector of the code segment
+    [[maybe_unused]] uint8_t null = 0;   // 32-39 unused in protected mode
+    InterruptType type : 3;              // 40-42 type
+    [[maybe_unused]] bool d : 1 = true;  //    43 true: 32-bit, false: 16-bit segment
+    [[maybe_unused]] uint8_t u : 1 = 0;  //    44 unused
+    uint8_t dpl : 2 = 0;                 // 45-46 descriptor privilege level
+    [[maybe_unused]] bool e : 1 = true;  //    47 enable
+    uint16_t offset_16_31;               // 48-63 offset high
+  } __attribute__((packed));
+
+  IDT();
+
+private:
+  Entry table[256];
+};
+
+struct interrupt_frame {
+  uword_t ip;
+  uword_t cs;
+  uword_t flags;
+  uword_t sp;
+  uword_t ss;
+};
+
+/* https://wiki.osdev.org/Interrupt_Service_Routines */
+template <uint8_t irq>
+__attribute__((interrupt)) void kirq(interrupt_frame* frame);
+
+template <>
+void kirq<0x0>(interrupt_frame* frame);
+template <>
+void kirq<0x1>(interrupt_frame* frame);
diff --git a/src/irq/kirq.cc b/src/irq/kirq.cc
new file mode 100644
index 0000000..acd57d4
--- /dev/null
+++ b/src/irq/kirq.cc
@@ -0,0 +1,21 @@
+#include <stdlib.h>
+#include "../idt.h"
+#include "ports.h"
+
+template <>
+void kirq<0x0>(interrupt_frame*) {
+  printk("Interrupt 0x0\n");
+
+  // send end of interrupt
+  pic1_t pic1;
+  pic1.write(0x20);
+}
+
+template <>
+void kirq<0x1>(interrupt_frame*) {
+  printk("Interrupt 0x0\n");
+
+  // send end of interrupt
+  pic1_t pic1;
+  pic1.write(0x20);
+}
diff --git a/src/kernel.cc b/src/kernel.cc
index 1139e3b..7aaaa37 100644
--- a/src/kernel.cc
+++ b/src/kernel.cc
@@ -12,6 +12,7 @@
 #include <types.h>
 #include "cga.h"
 #include "gdt.h"
+#include "idt.h"
 #include "serial.h"
 
 extern "C" {
@@ -38,6 +39,8 @@ void kernel_main([[maybe_unused]] uint32_t mb_magic, [[maybe_unused]] uint32_t m
   GDT gdt;
   dump_gdt();
 
-  abort();
+  IDT idt;
+
+  // abort();
 }
 }  // extern "C"
diff --git a/src/makefile b/src/makefile
index 8214d03..ab08ee2 100644
--- a/src/makefile
+++ b/src/makefile
@@ -5,4 +5,6 @@ CXX_OBJ += src/kernel.o \
 	   src/kernel/dump_multiboot.o \
 	   src/memory.o \
 	   src/gdt.o \
-	   src/gdt/segmentdescriptor.o
+	   src/gdt/segmentdescriptor.o \
+	   src/idt.o \
+	   src/irq/kirq.o