basic interrupt support

6 files changed, 92 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 57100d4..da06cb5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,7 @@
 AS      = i686-elf-as
 CC      = i686-elf-gcc
 CFLAGS  = -std=gnu99 -ffreestanding -O2 -Wall -Wextra
+CFLAGS += -mgeneral-regs-only
 CFLAGS += -I.
 LFLAGS  = -ffreestanding -O2 -nostdlib -lgcc
 QFLAGS  = -no-reboot -d guest_errors,int,pcall,cpu_reset
diff --git a/kernel/idt.c b/kernel/idt.c
new file mode 100644
index 0000000..e1d45b9
--- /dev/null
+++ b/kernel/idt.c
@@ -0,0 +1,71 @@
+#include <kernel/gdt.h>
+#include <kernel/idt.h>
+#include <kernel/isr.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+struct idt_entry {
+	uint16_t offset_low   ;
+	uint16_t code_seg     ;
+	uint8_t  zero         ; // unused, has to be 0
+	uint8_t  type      : 4; // 16/32 bit, task/interrupt/task gate
+	uint8_t  storage   : 1; // 0 for interrupt/trap gates
+	uint8_t  ring      : 2;
+	uint8_t  present   : 1;
+	uint16_t offset_high  ;
+} __attribute__((packed));
+
+// is exactly the same as lgdt_arg, i should combine them into a single struct
+// later
+struct lidt_arg {
+	uint16_t limit;
+	uint32_t base;
+} __attribute__((packed));
+
+
+static struct idt_entry IDT[256];
+static struct lidt_arg lidt_arg;
+
+static inline void idt_add(uint8_t num, bool user, void (*isr));
+static void idt_prepare();
+static void idt_load();
+static void idt_test();
+
+
+static inline void idt_add(uint8_t num, bool user, void (*isr)) {
+	uintptr_t offset = (uintptr_t) isr;
+
+	IDT[num] = (struct idt_entry) {
+		.offset_low  = offset,
+		.offset_high = offset >> 16,
+		.code_seg    = SEG_r0code << 3,
+		.zero        = 0,
+		.present     = 1,
+		.ring        = user ? 3 : 0,
+		.storage     = 0,
+		.type        = 0xE, // 32-bit interrupt gate
+	};
+}
+
+static void idt_prepare() {
+	for (int i = 0; i < 256; i++)
+		IDT[i].present = 0;
+
+	idt_add(0x8, false, isr_double_fault);
+}
+
+static void idt_load() {
+	lidt_arg.limit = sizeof(IDT) - 1;
+	lidt_arg.base = (uintptr_t) &IDT;
+	asm("lidt (%0)" : : "r" (&lidt_arg) : "memory");
+}
+
+static void idt_test() {
+	asm("int $0x34" : : : "memory");
+}
+
+void idt_init() {
+	idt_prepare();
+	idt_load();
+	idt_test();
+}
diff --git a/kernel/idt.h b/kernel/idt.h
new file mode 100644
index 0000000..5627657
--- /dev/null
+++ b/kernel/idt.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void idt_init();
diff --git a/kernel/isr.c b/kernel/isr.c
new file mode 100644
index 0000000..69c688b
--- /dev/null
+++ b/kernel/isr.c
@@ -0,0 +1,9 @@
+#include <kernel/isr.h>
+#include <kernel/tty.h>
+#include <stdint.h>
+
+__attribute__((interrupt))
+void isr_double_fault(struct interrupt_frame *frame) {
+	tty_const("#DF");
+	for(;;);
+}
diff --git a/kernel/isr.h b/kernel/isr.h
new file mode 100644
index 0000000..7230986
--- /dev/null
+++ b/kernel/isr.h
@@ -0,0 +1,6 @@
+#pragma once
+
+struct interrupt_frame;
+
+__attribute__((interrupt))
+void isr_double_fault(struct interrupt_frame *frame);
diff --git a/kernel/main.c b/kernel/main.c
index 5c2c5e8..bc1e0d3 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -1,4 +1,5 @@
 #include <kernel/gdt.h>
+#include <kernel/idt.h>
 #include <kernel/mem.h>
 #include <kernel/proc.h>
 #include <kernel/tty.h>
@@ -10,6 +11,7 @@ void kmain()
 {
 	tty_clear();
 	gdt_init();
+	idt_init();
 	sysenter_setup();
 	mem_init();