diff --git a/kernel/x86.h b/kernel/x86.h
new file mode 100644
index 0000000..5d88b2d
--- /dev/null
+++ b/kernel/x86.h
@@ -0,0 +1,148 @@
+/*
+Copyright (C) 2015-2019 The University of Notre Dame
+This software is distributed under the GNU General Public License.
+See the file LICENSE for details.
+*/
+
+#ifndef X86_H
+#define X86_H
+
+#include "kernel/types.h"
+
+#define X86_SEGMENT_SELECTOR( seg, rpl )  (((seg)<<3)+(rpl))
+
+#define X86_SEGMENT_KERNEL_CODE  X86_SEGMENT_SELECTOR(1,0)
+#define X86_SEGMENT_KERNEL_DATA  X86_SEGMENT_SELECTOR(2,0)
+#define X86_SEGMENT_USER_CODE    X86_SEGMENT_SELECTOR(3,3)
+#define X86_SEGMENT_USER_DATA    X86_SEGMENT_SELECTOR(4,3)
+#define X86_SEGMENT_TSS          X86_SEGMENT_SELECTOR(5,0)
+
+struct x86_eflags {
+	unsigned carry:1;
+	unsigned reserved0:1;
+	unsigned parity:1;
+	unsigned reserved1:1;
+
+	unsigned auxcarry:1;
+	unsigned reserved2:1;
+	unsigned zero:1;
+	unsigned sign:1;
+
+	unsigned trap:1;
+	unsigned interrupt:1;
+	unsigned direction:1;
+	unsigned overflow:1;
+
+	unsigned iopl:2;
+	unsigned nested:1;
+	unsigned reserved3:1;
+
+	unsigned resume:1;
+	unsigned v86:1;
+	unsigned align:1;
+	unsigned vinterrupt:1;
+
+	unsigned vpending:1;
+	unsigned id:1;
+};
+
+struct x86_regs {
+	int32_t eax;
+	int32_t ebx;
+	int32_t ecx;
+	int32_t edx;
+	int32_t esi;
+	int32_t edi;
+	int32_t ebp;
+};
+
+struct x86_stack {
+	/* Registers saved by process_switch */
+	struct x86_regs regs2;
+	/* Stack frame of process_switch */
+	int32_t old_ebp;
+	int32_t old_eip;
+	/* Pushed by intr_handler in kernelcore */
+	struct x86_regs regs1;
+	int32_t gs;
+	int32_t fs;
+	int32_t es;
+	int32_t ds;
+	/* Pushed by intrXX in kernelcore. */
+	int32_t intr_num;
+	int32_t intr_code;
+	/* Pushed by X86 CPU Hardware. */
+	int32_t eip;
+	int32_t cs;
+	struct x86_eflags eflags;
+	int32_t esp;
+	int32_t ss;
+};
+
+struct x86_segment {
+	uint16_t limit0;
+	uint16_t base0;
+
+	uint8_t base1;
+
+	unsigned type:4;
+	unsigned stype:1;
+	unsigned dpl:2;
+	unsigned present:1;
+
+	unsigned limit1:4;
+	unsigned avail:1;
+	unsigned zero:1;
+	unsigned size:1;
+	unsigned granularity:1;
+
+	uint8_t base2;
+};
+
+struct x86_tss {
+	int16_t prev;
+	int16_t reserved;
+	int32_t esp0;
+	int16_t ss0;
+	int16_t reserved0;
+	int32_t esp1;
+	int16_t ss1;
+	int16_t reserved1;
+	int32_t esp2;
+	int16_t ss2;
+	int16_t reserved2;
+	int32_t cr3;
+	int32_t eip;
+	int32_t eflags;
+	int32_t eax;
+	int32_t ecx;
+	int32_t edx;
+	int32_t ebx;
+	int32_t esp;
+	int32_t ebp;
+	int32_t esi;
+	int32_t edi;
+	int16_t es;
+	int16_t reserved3;
+	int16_t cs;
+	int16_t reserved4;
+	int16_t ss;
+	int16_t reserved5;
+	int16_t ds;
+	int16_t reserved6;
+	int16_t fs;
+	int16_t reserved7;
+	int16_t gs;
+	int16_t reserved8;
+	int16_t ldt;
+	int16_t reserved9;
+	int16_t t;
+	int16_t iomap;
+};
+
+struct x86_gdt_init {
+	int16_t size;
+	struct x86_segment *base;
+};
+
+#endif