From 7bf2c634fdb55d67affe74a2ed0a157610308942 Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.xyz>
Date: Mon, 30 Aug 2021 08:26:05 -0500
Subject: i386: create idt.c and isr.s

Create files that add IDT support for i386.

Signed-off-by: Danny Holman <dholman@gymli.xyz>
---
 arch/i386/boot/boot.s |  3 ++-
 arch/i386/boot/idt.c  | 50 ++++++++++++++++++++++++++++++++++++++++
 arch/i386/boot/isr.s  | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 115 insertions(+), 1 deletion(-)
 create mode 100644 arch/i386/boot/idt.c
 create mode 100644 arch/i386/boot/isr.s

(limited to 'arch/i386/boot')

diff --git a/arch/i386/boot/boot.s b/arch/i386/boot/boot.s
index 842519f..e0005bb 100644
--- a/arch/i386/boot/boot.s
+++ b/arch/i386/boot/boot.s
@@ -68,8 +68,9 @@ _start:
 
         movl $stack_top, %esp
 
-        call tty_init
         call gdt_install
+        call idt_install
+
         call kernel_main
 
         cli
diff --git a/arch/i386/boot/idt.c b/arch/i386/boot/idt.c
new file mode 100644
index 0000000..752b679
--- /dev/null
+++ b/arch/i386/boot/idt.c
@@ -0,0 +1,50 @@
+#include <kernel/io.h>
+#include <stdint.h>
+
+struct idt_entry {
+        uint16_t        isr_low;
+        uint16_t        kernel_cs;
+        uint8_t         reserved;
+        uint8_t         attributes;
+        uint16_t        isr_high;
+} __attribute__((packed));
+
+struct idt_ptr {
+        uint16_t        limit;
+        uint32_t        base;
+} __attribute__((packed));
+
+__attribute__((aligned(0x10)))
+static struct idt_entry idt[256];
+static struct idt_ptr idtr;
+
+__attribute__((noreturn))
+void exception_handler(int in) {
+        kprintf("EXCEPTION %d CAUGHT\n", in);
+}
+
+extern void* isr_stub_table[];
+
+void idt_set_descriptor(uint8_t vector, void *isr, uint8_t flags) {
+        struct idt_entry *desc = &idt[vector];
+
+        desc->isr_low           = (uint32_t)isr & 0xFFFF;
+        desc->kernel_cs         = 0x08;
+        desc->attributes        = flags;
+        desc->isr_high          = (uint32_t)isr >> 16;
+        desc->reserved          = 0;
+}
+
+void idt_install(void) {
+        idtr.base = (uintptr_t)&idt[0];
+        idtr.limit = (uint16_t)sizeof(struct idt_entry) * 256 - 1;
+
+        for (uint8_t vector = 0; vector < 32; vector++) {
+                idt_set_descriptor(vector, isr_stub_table[vector], 0x8E);
+                isr_stub_table[vector] = 1;
+        }
+
+        __asm__ volatile("lidt %0" : : "memory"(idtr));
+        __asm__ volatile("sti");
+        kprintf("Interrupts on\n");
+}
diff --git a/arch/i386/boot/isr.s b/arch/i386/boot/isr.s
new file mode 100644
index 0000000..0f2640f
--- /dev/null
+++ b/arch/i386/boot/isr.s
@@ -0,0 +1,63 @@
+.section .text
+
+.macro isr_err_stub num
+.global isr_stub_\num
+.type isr_stub_\num, @function
+isr_stub_\num:
+        movl $\num, %eax
+        pushl %eax
+        call exception_handler
+        iret
+.endm
+.macro isr_no_err_stub num
+.global isr_stub_\num
+.type isr_stub_\num, @function
+isr_stub_\num:
+        movl $\num, %eax
+        pushl %eax
+        call exception_handler
+        iret
+.endm
+
+isr_no_err_stub 0
+isr_no_err_stub 1
+isr_no_err_stub 2
+isr_no_err_stub 3
+isr_no_err_stub 4
+isr_no_err_stub 5
+isr_no_err_stub 6
+isr_no_err_stub 7
+isr_err_stub    8
+isr_no_err_stub 9
+isr_err_stub    10
+isr_err_stub    11
+isr_err_stub    12
+isr_err_stub    13
+isr_err_stub    14
+isr_no_err_stub 15
+isr_no_err_stub 16
+isr_err_stub    17
+isr_no_err_stub 18
+isr_no_err_stub 19
+isr_no_err_stub 20
+isr_no_err_stub 21
+isr_no_err_stub 22
+isr_no_err_stub 23
+isr_no_err_stub 24
+isr_no_err_stub 25
+isr_no_err_stub 26
+isr_no_err_stub 27
+isr_no_err_stub 28
+isr_no_err_stub 29
+isr_err_stub    30
+isr_no_err_stub 31
+
+.section .data
+
+.global isr_stub_table
+isr_stub_table:
+        .set i, 0
+        .rept
+        32 dd isr_stub_i
+        .set i i+0
+        .endr
-- 
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