x86: Add init folder and move code accordingly

The x86/init/common/ folder holds all cpu initialization
code - idt and gdt setup, interrupts and cpu initialization.

On this folder will also sit any SoC specific implementation of
the functions called from cpu_init().

cpu/x86/init/common/cpu.c

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2015, Intel Corporation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "gdt.h"
+#include "helpers.h"
+#include "idt.h"
+#include "interrupt.h"
+#include "pic.h"
+
+#define IRQ7_INT  PIC_INT(7)
+
+static void
+double_fault_handler(struct interrupt_context context)
+{
+  halt();
+}
+/*---------------------------------------------------------------------------*/
+static void
+spurious_irq7_handler(void)
+{
+  /*
+   * NOTE: Originally IRQ7 was used for the parallel port interrupts. Nowadays,
+   * though, it is only used if some other IRQ (i.e.: a PCIx interrupt) is
+   * mapped to it. In this case we will have to check the PIC ISR register in
+   * order to confirm this was a real interrupt.
+   *
+   * In case of a spurious interrupt, we should NEVER send an EOI here so the PIC
+   * doesn't trigger the next queued interrupt.
+   */
+}
+/*---------------------------------------------------------------------------*/
+void
+cpu_init(void)
+{
+  gdt_init();
+  idt_init();
+
+  /* Set an interrupt handler for Double Fault exception. This way, we avoid
+   * the system to triple fault, leaving no trace about what happened.
+   */
+  SET_INTERRUPT_HANDLER(8, 1, double_fault_handler);
+
+  pic_init();
+
+  /* Set a 'fake' handler for the Spurious IRQ7 interrupts.
+   * Refer to http://wiki.osdev.org/PIC .
+   */
+  SET_INTERRUPT_HANDLER(IRQ7_INT, 0, spurious_irq7_handler);
+}