[INTERRUPTS] Exception handling

.gdbinit

@@ -1,5 +1,6 @@
 file sysroot/boot/kernel
 target remote localhost:1234
+break int_handler_breakpoint
 
 define q
 monitor quit
@@ -21,3 +22,17 @@ define reset
 monitor system_reset
 end
 
+define restore_env
+set $name = $arg0
+python 
+registers = ['rax', 'rbx', 'rcx', 'rdx', 'rsi',
+  'rdi', 'rbp', 'rsp', 'r8', 'r9', 'r10', 'r11',
+  'r12', 'r13', 'r14', 'r15', 'rip']
+values = {}
+for r in registers:
+  values[r] = gdb.parse_and_eval('$name->{}'.format(r))
+
+for r in registers:
+  gdb.parse_and_eval('${}={}'.format(r, values[r]))
+gdb.execute('frame 0')
+end

kernel/Makefile

@@ -10,8 +10,8 @@ endif
 
 
 # Find all source files and corresponding object files
-KERNEL_SRC := $(wildcard **/*.[cS])
-KERNEL_OBJS := $(addprefix obj/,$(patsubst %,%.o,$(basename $(KERNEL_SRC))))
+KERNEL_SRC := $(wildcard **/*.[cS]*)
+KERNEL_OBJS := $(addprefix obj/,$(patsubst %,%.o,$(basename $(basename $(KERNEL_SRC)))))
 
 # Kernel object file
 KERNEL := obj/boot/kernel
@@ -21,7 +21,7 @@ VERSION_OBJ := obj/boot/version.o
 
 # Default compilation flags
 CFLAGS ?= -Wall -Wextra
-CFLAGS += -ffreestanding -mcmodel=large
+CFLAGS += -ffreestanding -mcmodel=large -mno-red-zone
 CPPFLAGS += -Iinclude
 # Optimize only if not debugging
 ifdef NDEBUG
@@ -69,6 +69,8 @@ obj/%.o: %.c obj/%.d
 	$(COMPILE.c) $(DEPFLAGS) $< -o $@
 obj/%.o: %.S obj/%.d
 	$(COMPILE.S) $(DEPFLAGS) $< -o $@
+%.S: %.S.py
+	python $^ > $@
 obj/%.d: ;
 
 # For installing stuff
@@ -86,3 +88,4 @@ clean:
 -include $(KERNEL_DEP)
 
 .PHONY: all clean install install-kernel
+.INTERMEDIATE: $(basename $(filter %.py, $(KERNEL_SRC)))

kernel/arch/registers.S

@@ -0,0 +1,23 @@
+.intel_syntax noprefix
+
+.global load_idt
+load_idt:
+  lidt [rdi]
+  ret
+
+.global read_cr0
+read_cr0:
+  mov rax, cr0
+  ret
+.global read_cr2
+read_cr2:
+  mov rax, cr2
+  ret
+.global read_cr3
+read_cr3:
+  mov rax, cr3
+  ret
+.global read_cr4
+read_cr4:
+  mov rax, cr4
+  ret

kernel/boot/debug.c

@@ -1,9 +1,11 @@
 #include <debug.h>
+#include <int.h>
 #include <stdarg.h>
 #include <stdint.h>
 #include <string.h>
 #include <vga.h>
 #include <serial.h>
+#include <registers.h>
 
 void debug_init()
 {
@@ -130,3 +132,15 @@ void debug_printf(char *str, ...)
   debug_vprintf(str, args);
   va_end(args);
 }
+
+void print_registers(registers_t *r)
+{
+  debug("Num:%x Error:%x\n", r->int_no, r->err_code);
+  debug("RAX:%x RBX:%x RCX:%x RDX:%x\n", r->rax, r->rbx, r->rcx, r->rdx);
+  debug("RSI:%x RDI:%x RBP:%x RSP:%x\n", r->rsi, r->rdi, r->rbp, r->rsp);
+  debug("R8:%x R9:%x R10:%x R11:%x\n", r->r8, r->r9, r->r10, r->r11);
+  debug("R12:%x R13:%x R14:%x R15:%x\n", r->r12, r->r13, r->r14, r->r15);
+  debug("RIP:%x RFL:%x\n", r->rip, r->rflags);
+  debug("CS:%x SS:%x\n", r->cs, r->ss);
+  debug("CR0:%x CR2:%x CR3:%x CR4:%x\n", read_cr0(), read_cr2(), read_cr3(), read_cr4());
+}

kernel/boot/kmain.c

@@ -1,4 +1,5 @@
 #include <debug.h>
+#include <int.h>
 #include <multiboot.h>
 #include <mem.h>
 
@@ -8,8 +9,15 @@ int kmain(uint64_t multiboot_magic, void *multiboot_data)
   debug_ok("MITTOS64 kernel booted\n");
   debug_build_time();
   debug_git_info();
+
+  interrupt_init();
   multiboot_init(multiboot_magic, P2V(multiboot_data));
 
   debug_info("BOOT COMPLETE\n");
+  // Cause a divide-by-zero exception
+  int a = 5, b = 0;
+  int c = a/b;
+  (void)c;
+
   for(;;)asm("hlt");
 }

kernel/include/debug.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <string.h>
+#include <int.h>
 
 #ifndef NDEBUG
   #define debug(...) debug_printf(__VA_ARGS__)
@@ -29,3 +30,4 @@ char *_kernel_git_branch;
 void debug_build_time();
 void debug_git_info();
 
+void print_registers(registers_t *);

kernel/include/int.h

@@ -0,0 +1,90 @@
+#pragma once
+
+#define   IDT_CALL        0x0C
+#define   IDT_INTERRUPT   0x0E
+#define   IDT_TRAP        0x0F
+#define   IDT_DPL0        0x00
+#define   IDT_DPL3        0x60
+#define   IDT_PRESENT     0x80
+
+#define   NUM_INTERRUPTS   256
+
+#define   INT_DE    0x00 // Divide by zero exception
+#define   INT_DB    0x01 // Debug exception
+#define   INT_NMI   0x02 // Non-maskable Interrupt exception
+#define   INT_BP    0x03 // Beakpoint exception
+#define   INT_OF    0x04 // Overflow exception
+#define   INT_BR    0x05 // Bound Range exception
+#define   INT_UD    0x06 // Invalid Opcode exception
+#define   INT_NM    0x07 // Device not Available exception
+#define   INT_DF    0x08 // Double Fault exception
+#define   INT_CSO   0x09 // Coprocessor Segment Overrun exception
+#define   INT_TS    0x0A // Invalid TSS exception
+#define   INT_NP    0x0B // Segment not Present excepton
+#define   INT_SS    0x0C // Stack exception
+#define   INT_GP    0x0D // General Protection Fault exception
+#define   INT_PF    0x0E // Page Fault exception
+// Unused exception 0x0F
+#define   INT_MF    0x10 // Floating Point exception pending
+#define   INT_AC    0x11 // Alignment Check exception
+#define   INT_MC    0x12 // Machine Check exception
+#define   INT_XF    0x13 // SIMD Floating Point exception
+// Unused exception 0x14 - 0x1D
+#define   INT_SX    0x1E // Security exception
+// Unused exception 0x1F
+// User interrupts  0x20 and forward
+
+#ifndef __ASSEMBLER__
+#include <stdint.h>
+
+struct int_gate_descriptor
+{
+  uint16_t base_l;
+  uint16_t cs;
+  uint8_t ist;
+  uint8_t flags;
+  uint16_t base_m;
+  uint32_t base_h;
+  uint32_t ignored;
+} __attribute__ ((packed));
+
+struct idtr
+{
+  uint16_t len;
+  uint64_t addr;
+} __attribute__ ((packed));
+
+typedef struct registers_st
+{
+  uint64_t rax;
+  uint64_t rbx;
+  uint64_t rcx;
+  uint64_t rdx;
+  uint64_t rsi;
+  uint64_t rdi;
+  uint64_t rbp;
+  uint64_t r8;
+  uint64_t r9;
+  uint64_t r10;
+  uint64_t r11;
+  uint64_t r12;
+  uint64_t r13;
+  uint64_t r14;
+  uint64_t r15;
+
+  uint64_t int_no;
+  uint64_t err_code;
+  uint64_t rip;
+  uint64_t cs;
+  uint64_t rflags;
+  uint64_t rsp;
+  uint64_t ss;
+}registers_t;
+
+typedef registers_t *(*int_handler_t)(registers_t *);
+
+void interrupt_init();
+int_handler_t register_int_handler(uint32_t num, int_handler_t h);
+void isr_return(registers_t *r);
+
+#endif

kernel/include/registers.h

@@ -0,0 +1,7 @@
+#pragma once
+
+void load_idt(void *);
+uint64_t read_cr0();
+uint64_t read_cr2();
+uint64_t read_cr3();
+uint64_t read_cr4();

kernel/interrupts/interrupts.c

@@ -0,0 +1,67 @@
+#include <int.h>
+#include <debug.h>
+#include <registers.h>
+#include <string.h>
+#include <stdint.h>
+
+struct int_gate_descriptor idt[NUM_INTERRUPTS];
+struct idtr idtr;
+int_handler_t int_handlers[NUM_INTERRUPTS];
+
+void idt_set(uint32_t num, void *vector, uint16_t cs, uint8_t ist, uint8_t flags)
+{
+  uintptr_t v = (uintptr_t)vector;
+  idt[num].base_l = v & 0xFFFF;
+  idt[num].base_m = (v >> 16) & 0xFFFF;
+  idt[num].base_h = (v >> 32) & 0xFFFFFFFF;
+  idt[num].cs = cs;
+  idt[num].ist = ist;
+  idt[num].flags = flags;
+}
+
+void interrupt_init()
+{
+  // Clear IDT and interrupt handler list
+  memset(idt, 0, sizeof(idt));
+  memset(int_handlers, 0, sizeof(int_handlers));
+
+  // Register all vectors in the IDT
+  extern void *isr_table[];
+  for(int i=0; i < NUM_INTERRUPTS; i++)
+  {
+    idt_set(i, isr_table[i], 0x8, 0,
+        (IDT_PRESENT | IDT_DPL0 | IDT_INTERRUPT));
+  }
+
+  // Setup pointer and load IDT
+  idtr.addr = (uint64_t)idt;
+  idtr.len = sizeof(idt)-1;
+  load_idt(&idtr);
+}
+
+int_handler_t register_int_handler(uint32_t num, int_handler_t h)
+{
+  // Replace the handler for an interrupt
+  // Return the old handler
+  int_handler_t old = int_handlers[num];
+  int_handlers[num] = h;
+  return old;
+}
+
+
+registers_t *int_handler(registers_t *r)
+{
+  // If a handler is registered, pass everything onto it
+  if(int_handlers[r->int_no])
+    return int_handlers[r->int_no](r);
+
+  debug("\n===============================================================================\n");
+  debug_error("Unhandled interrupt!\n");
+  print_registers(r);
+
+#ifndef NDEBUG
+  asm("int_handler_breakpoint:");
+#endif
+
+  for(;;);
+}

kernel/interrupts/isr.S.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+print('''
+.intel_syntax noprefix
+.extern isr_common
+''')
+
+print('// Interrupt Service Routines')
+for i in range(255):
+    print('''isr{0}:
+    cli
+    {1}
+    push {0}
+    jmp isr_common
+    '''.format(i, 
+        'push 0' if i not in [8, 10, 11, 12, 13, 14, 17] else 'nop'))
+
+print('''
+
+// Vector table
+
+.section .data
+.global isr_table
+isr_table:
+''')
+for i in range(255):
+    print('    .quad isr{}'.format(i))

kernel/interrupts/isr_common.S

@@ -0,0 +1,49 @@
+.intel_syntax noprefix
+
+.extern int_handler
+.global isr_common
+.global isr_return
+
+isr_common:
+  // Push all registers
+  push r15
+  push r14
+  push r13
+  push r12
+  push r11
+  push r10
+  push r9
+  push r8
+  push rbp
+  push rdi
+  push rsi
+  push rdx
+  push rcx
+  push rbx
+  push rax
+  mov rdi, rsp
+  call int_handler
+  mov rdi, rax
+
+isr_return:
+  // Return and restore stack
+  mov rsp, rdi
+  pop rax
+  pop rbx
+  pop rcx
+  pop rdx
+  pop rsi
+  pop rdi
+  pop rbp
+  pop r8
+  pop r9
+  pop r10
+  pop r11
+  pop r12
+  pop r13
+  pop r14
+  pop r15
+  // Pop error code and fault number
+  add rsp, 16
+  iretq
+