--- /dev/null
+/*
+ * x86 TSS data structure and routines
+ * Copyright (c) 2001,2004 David H. Hovemeyer <daveho@cs.umd.edu>
+ * $Revision: 1.4 $
+ *
+ * This is free software. You are permitted to use,
+ * redistribute, and modify it as specified in the file "COPYING".
+ */
+
+/*
+ * Source: _Protected Mode Software Architecture_ by Tom Shanley,
+ * ISBN 020155447X.
+ */
+
+#include <geekos/kassert.h>
+#include <geekos/defs.h>
+#include <geekos/gdt.h>
+#include <geekos/segment.h>
+#include <geekos/string.h>
+#include <geekos/tss.h>
+
+#include <geekos/serial.h>
+#include <geekos/debug.h>
+
+
+/*
+ * We use one TSS in GeekOS.
+ */
+static struct TSS s_theTSS;
+static struct Segment_Descriptor *s_tssDesc;
+static ushort_t s_tssSelector;
+
+static void __inline__ Load_Task_Register(void)
+{
+
+ /* Critical: TSS must be marked as not busy */
+ s_tssDesc->type = 0x09;
+
+ /* Load the task register */
+ __asm__ __volatile__ (
+ "ltr %0"
+ :
+ : "a" (s_tssSelector)
+ );
+}
+
+/*
+ * Initialize the kernel TSS. This must be done after the memory and
+ * GDT initialization, but before the scheduler is started.
+ */
+void Init_TSS(void)
+{
+ PrintBoth("Initializing TSS\n");
+
+ s_tssDesc = Allocate_Segment_Descriptor();
+ KASSERT(s_tssDesc != 0);
+
+ memset(&s_theTSS, '\0', sizeof(struct TSS));
+ Init_TSS_Descriptor(s_tssDesc, &s_theTSS);
+
+ s_tssSelector = Selector(0, true, Get_Descriptor_Index(s_tssDesc));
+
+ Load_Task_Register();
+}
+
+/*
+ * Set kernel stack pointer.
+ * This should be called before switching to a new
+ * user process, so that interrupts occurring while executing
+ * in user mode will be delivered on the correct stack.
+ */
+void Set_Kernel_Stack_Pointer(ulong_t esp0)
+{
+ s_theTSS.ss0 = KERNEL_DS;
+ s_theTSS.esp0 = esp0;
+
+ /*
+ * NOTE: I read on alt.os.development that it is necessary to
+ * reload the task register after modifying a TSS.
+ * I haven't verified this in the IA32 documentation,
+ * but there is certainly no harm in being paranoid.
+ */
+ Load_Task_Register();
+}
+
+
+/* JRL THIS FUCKING SUCKS */
+
+uint_t GetTR_Base() {
+ return (uint_t)(&s_theTSS);
+}
+uint_t GetTR_Limit() {
+ return sizeof(struct TSS);
+}
+
+ushort_t GetTR_Selector() {
+ return s_tssSelector;
+}
+
+
+
+/* ** */
