1 files changed, 55 insertions, 0 deletions
diff --git a/kernel/x86.h b/kernel/x86.h
new file mode 100644
index 0000000..716cb6c
--- /dev/null
+++ b/kernel/x86.h
@@ -0,0 +1,55 @@
+#ifndef _X86_H_
+#define _X86_H_
+
+// Privilege levels
+#define DPL_USER    0x3
+#define DPL_KERNEL  0x0
+
+// Selectors
+#define LDT_SELECTOR    0x4
+
+// Descriptor types for code and data segments
+#define TYPE_DATA_READONLY     1
+#define TYPE_DATA_READWRITE    3
+#define TYPE_CODE_EXECONLY     9
+#define TYPE_CODE_EXECREAD    11
+
+// Descriptor types for system segments and gates
+#define TYPE_LDT               2
+#define TYPE_TASK_GATE         5
+#define TYPE_TSS               9
+#define TYPE_CALL_GATE         12
+#define TYPE_TRAP_GATE         15
+#define TYPE_INTERRUPT_GATE    14
+
+// Descriptor system bit (S)
+// For code or data segments
+#define S_CODE_OR_DATA   1
+// For TSS segment, LDT, call gate, interrupt gate, trap gate, task gate
+#define S_SYSTEM   0
+
+// D/B bit
+#define DB_SEG  1
+#define DB_SYS  0
+
+// kernel code and data selectors in the GDT
+#define GDT_KERNEL_CODE_SELECTOR  0x08
+#define GDT_KERNEL_DATA_SELECTOR  0x10
+
+// Disable hardware interrupts.
+static inline void cli() {
+    asm volatile("cli");
+}
+
+// Enable hardware interrupts.
+static inline void sti() {
+    asm volatile("sti");
+}
+
+// Halt the processor.
+// External interrupts wake up the CPU, hence the cli instruction.
+static inline void halt() {
+	while (1) asm volatile("cli\nhlt");
+}
+
+#endif