From b7c0de7ea5bfa2b07af5e8a1b51810ab3690b8a5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Wed, 9 Nov 2016 21:16:29 +0100
Subject: [PATCH] [INTERRUPTS] IRQs and the Programmable Interrupt Controller

---
 kernel/boot/kmain.c     |  3 ++
 kernel/include/int.h    | 37 +++++++++++++++++++++++
 kernel/interrupts/pic.c | 65 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 105 insertions(+)
 create mode 100644 kernel/interrupts/pic.c

diff --git a/kernel/boot/kmain.c b/kernel/boot/kmain.c
index 640b996..311334d 100644
--- a/kernel/boot/kmain.c
+++ b/kernel/boot/kmain.c
@@ -29,6 +29,7 @@ int kmain(uint64_t multiboot_magic, void *multiboot_data)
   pmm_init();
   gdt_init();
   scheduler_init();
+  pic_init();
 
   process_t *p1 = process_spawn(0);
   process_t *p2 = process_spawn(p1);
@@ -51,6 +52,8 @@ int kmain(uint64_t multiboot_magic, void *multiboot_data)
   scheduler_insert(t2);
   scheduler_insert(t3);
 
+  IRQ_UNMASK(IRQ_TIMER);
+  asm("sti");
   debug_info("BOOT COMPLETE\n");
   schedule();
   debug_error("PANIC - This line should be unreachable (%s:%d)\n", __FILE__, __LINE__);
diff --git a/kernel/include/int.h b/kernel/include/int.h
index 84f1588..9e173a7 100644
--- a/kernel/include/int.h
+++ b/kernel/include/int.h
@@ -33,6 +33,30 @@
 #define   INT_SX    0x1E // Security exception
 // Unused exception 0x1F
 // User interrupts  0x20 and forward
+#define   INT_IRQ0      0x20
+#define   INT_IRQ1      0x21
+#define   INT_IRQ2      0x22
+#define   INT_IRQ3      0x23
+#define   INT_IRQ4      0x24
+#define   INT_IRQ5      0x25
+#define   INT_IRQ6      0x26
+#define   INT_IRQ7      0x27
+#define   INT_IRQ8      0x28
+#define   INT_IRQ9      0x29
+#define   INT_IRQ10     0x2A
+#define   INT_IRQ11     0x2B
+#define   INT_IRQ12     0x2C
+#define   INT_IRQ13     0x2D
+#define   INT_IRQ14     0x2E
+#define   INT_IRQ15     0x2F
+#define   INT_IRQ16     0x30
+#define   INT_IRQ17     0x31
+#define   INT_IRQ18     0x32
+#define   INT_IRQ19     0x33
+#define   INT_IRQ20     0x34
+#define   INT_IRQ21     0x35
+#define   INT_IRQ22     0x36
+#define   INT_IRQ23     0x37
 
 #ifndef __ASSEMBLER__
 #include <stdint.h>
@@ -54,6 +78,19 @@ struct idtr
   uint64_t addr;
 } __attribute__ ((packed));
 
+void pic_init();
+void pic_ack(uint8_t irq);
+void pic_mask(uint8_t irq);
+void pic_unmask(uint8_t irq);
+#define IRQ_INT(irq) (INT_IRQ0 + irq)
+#define IRQ(irq) (irq)
+#define IRQ_MASK(irq) pic_mask(irq)
+#define IRQ_UNMASK(irq) pic_unmask(irq)
+#define IRQ_ACK(irq) pic_ack(irq)
+
+#define IRQ_TIMER 0
+#define IRQ_KEYBOARD 1
+
 typedef struct registers_st
 {
   uint64_t rax;
diff --git a/kernel/interrupts/pic.c b/kernel/interrupts/pic.c
new file mode 100644
index 0000000..85629f4
--- /dev/null
+++ b/kernel/interrupts/pic.c
@@ -0,0 +1,65 @@
+#include <stdint.h>
+#include <ports.h>
+#include <debug.h>
+#include <int.h>
+
+#define MPIC_CMD  0x0020
+#define MPIC_DATA 0x0021
+#define SPIC_CMD  0x00A0
+#define SPIC_DATA 0x00A1
+
+#define PIC_CMD_INIT 0x10
+#define PIC_CMD_EXTRA 0x01
+#define PIC_CMD_8086 0x01
+#define PIC_CMD_EOI 0x20
+
+
+void pic_init()
+{
+
+  // Send initialize command
+  outb(MPIC_CMD, PIC_CMD_INIT | PIC_CMD_EXTRA);
+  outb(SPIC_CMD, PIC_CMD_INIT | PIC_CMD_EXTRA);
+
+  // Remap offsets
+  outb(MPIC_DATA, INT_IRQ0);
+  outb(SPIC_DATA, INT_IRQ8);
+
+  // Setup slave PIC
+  outb(MPIC_DATA, 0x04);
+  outb(SPIC_DATA, 0x02);
+
+  // Extra environment data
+  outb(MPIC_DATA, PIC_CMD_8086);
+  outb(SPIC_DATA, PIC_CMD_8086);
+
+  // Mask all interrupts
+  outb(MPIC_DATA, 0xFF);
+  outb(SPIC_DATA, 0xFF);
+}
+
+void pic_ack(uint8_t irq)
+{
+  if(irq >= 8)
+    outb(SPIC_CMD, PIC_CMD_EOI);
+  outb(MPIC_CMD, PIC_CMD_EOI);
+}
+
+void pic_mask(uint8_t irq)
+{
+  if(irq >= 8)
+  {
+    outb(SPIC_DATA, inb(SPIC_DATA) | 1 << (irq-8));
+  } else {
+    outb(MPIC_DATA, inb(MPIC_DATA) | 1 << irq);
+  }
+}
+void pic_unmask(uint8_t irq)
+{
+  if(irq >= 8)
+  {
+    outb(SPIC_DATA, inb(SPIC_DATA) & ~(1 << (irq-8)));
+  } else {
+    outb(MPIC_DATA, inb(MPIC_DATA) & ~(1 << irq));
+  }
+}