From 25262960d980d04882b0c79e19b5c276fd49e84e Mon Sep 17 00:00:00 2001
From: Quinten Kock <quinten@quinten.space>
Date: Mon, 14 Dec 2020 23:10:58 +0100
Subject: [PATCH] add basic interrupt support

---
 kernel/src/arch/x86_64/entry-stivale2.c |  4 ++-
 kernel/src/arch/x86_64/idt.c            | 26 +++++++++++++++++
 kernel/src/arch/x86_64/idt.h            | 22 ++++++++++++++
 kernel/src/arch/x86_64/idt.nasm         | 20 +++++++++++++
 kernel/src/arch/x86_64/interrupt.c      | 39 +++++++++++++++++++++++++
 kernel/src/arch/x86_64/interrupt.h      |  1 +
 6 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 kernel/src/arch/x86_64/idt.c
 create mode 100644 kernel/src/arch/x86_64/idt.h
 create mode 100644 kernel/src/arch/x86_64/idt.nasm
 create mode 100644 kernel/src/arch/x86_64/interrupt.c
 create mode 100644 kernel/src/arch/x86_64/interrupt.h

diff --git a/kernel/src/arch/x86_64/entry-stivale2.c b/kernel/src/arch/x86_64/entry-stivale2.c
index 584176c..8f8f1f2 100644
--- a/kernel/src/arch/x86_64/entry-stivale2.c
+++ b/kernel/src/arch/x86_64/entry-stivale2.c
@@ -4,6 +4,7 @@
 
 #include <arch/x86/stivale2-parse.h>
 #include <arch/x86_64/gdt.h>
+#include <arch/x86_64/interrupt.h>
 #include <print/print.h>
 
 #include <main.h>
@@ -46,6 +47,7 @@ void stivale2_main(struct stivale2_struct *info) {
     loadgdt();
     print_gdt();
 
-    asmpanic();
+    setup_ints();
+
     kmain();
 }
diff --git a/kernel/src/arch/x86_64/idt.c b/kernel/src/arch/x86_64/idt.c
new file mode 100644
index 0000000..adef57b
--- /dev/null
+++ b/kernel/src/arch/x86_64/idt.c
@@ -0,0 +1,26 @@
+#include "idt.h"
+
+struct IDTInfo {
+    uint16_t size;
+    uint64_t offset;
+} __attribute__((packed));
+
+struct IDTDescr IDT[256];
+static struct IDTInfo idt_info;
+
+void set_idt_ent(uint8_t index, uint64_t offset, uint8_t ist, uint8_t min_priv_level, enum GateType type) {
+    IDT[index].offset_1 = offset & 0xFFFF;
+    IDT[index].offset_2 = (offset >> 16) & 0xFFFF;
+    IDT[index].offset_3 = (offset >> 32) & 0xFFFFFFFF;
+    IDT[index].ist = ist;
+    IDT[index].selector = 8; // assume for now that it's always in-kernel
+    IDT[index].zero = 0;
+    IDT[index].type_attr = type | (min_priv_level << 5) | 0x80;
+}
+
+void* get_idt_fn(uint8_t index) {
+    struct IDTDescr* i = &IDT[index];
+    return (uintptr_t)( ((uint64_t)i->offset_3 << 32) | ((uint64_t)i->offset_2 << 16) | (uint64_t)i->offset_1);
+}
+
+void clear_idt_ent(uint8_t index);
diff --git a/kernel/src/arch/x86_64/idt.h b/kernel/src/arch/x86_64/idt.h
new file mode 100644
index 0000000..8dae756
--- /dev/null
+++ b/kernel/src/arch/x86_64/idt.h
@@ -0,0 +1,22 @@
+#include <stdint.h>
+
+struct IDTDescr {
+   uint16_t offset_1; // offset bits 0..15
+   uint16_t selector; // a code segment selector in GDT or LDT
+   uint8_t ist;       // bits 0..2 holds Interrupt Stack Table offset, rest of bits zero.
+   uint8_t type_attr; // type and attributes
+   uint16_t offset_2; // offset bits 16..31
+   uint32_t offset_3; // offset bits 32..63
+   uint32_t zero;     // reserved
+};
+
+enum GateType {
+    CALL64 = 0xC,
+    INT64  = 0xE,
+    TRAP64 = 0xF,
+};
+
+void init_idt();
+void set_idt_ent(uint8_t index, uint64_t offset, uint8_t ist, uint8_t min_priv_level, enum GateType type);
+void* get_idt_fn(uint8_t index);
+void clear_idt_ent(uint8_t index);
diff --git a/kernel/src/arch/x86_64/idt.nasm b/kernel/src/arch/x86_64/idt.nasm
new file mode 100644
index 0000000..cbe5f97
--- /dev/null
+++ b/kernel/src/arch/x86_64/idt.nasm
@@ -0,0 +1,20 @@
+extern IDT;
+
+section .rodata
+align 8
+idtpointer:
+    dw (256*16) - 1
+    dq IDT
+
+section .text
+global init_idt
+init_idt:
+    lidt [idtpointer]
+    ret
+
+global isr_wrapper
+extern interrupt_handler
+align 8
+isr_wrapper:
+    call interrupt_handler
+    iretq
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/interrupt.c b/kernel/src/arch/x86_64/interrupt.c
new file mode 100644
index 0000000..faa9c92
--- /dev/null
+++ b/kernel/src/arch/x86_64/interrupt.c
@@ -0,0 +1,39 @@
+#include <stdint.h>
+
+#include "idt.h"
+#include "interrupt.h"
+
+typedef uint64_t uword_t;
+
+extern void isr_wrapper();
+
+struct interrupt_frame
+{
+    uword_t ip;
+    uword_t cs;
+    uword_t flags;
+    uword_t sp;
+    uword_t ss;
+};
+ 
+void interrupt_handler()
+{
+    printf("interrupted\n");
+    // panic("ee");
+}
+
+
+void setup_ints() {
+    set_idt_ent(0x80, (uint64_t)&isr_wrapper, 0, 0, INT64);
+    init_idt();
+
+    typedef void (*MyFunctionType)(void);
+    MyFunctionType handler_0x80 = get_idt_fn(0x80);
+    printf("interrupt handler: %x\n", handler_0x80);
+    // interrupt_handler(0);
+    
+
+    __asm__ volatile("int $0x80");
+
+    printf("interrupt handled!\n");
+}
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/interrupt.h b/kernel/src/arch/x86_64/interrupt.h
new file mode 100644
index 0000000..18972a5
--- /dev/null
+++ b/kernel/src/arch/x86_64/interrupt.h
@@ -0,0 +1 @@
+void setup_ints();
\ No newline at end of file