X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?p=palacios.git;a=blobdiff_plain;f=geekos%2Fsrc%2Fgeekos%2Fgdt.c;fp=geekos%2Fsrc%2Fgeekos%2Fgdt.c;h=707e34a2a4ea08d46b22ee2497a32151bbccf7f9;hp=0000000000000000000000000000000000000000;hb=ddc16b0737cf58f7aa90a69c6652cdf4090aec51;hpb=626595465a2c6987606a6bc697df65130ad8c2d3

diff --git a/geekos/src/geekos/gdt.c b/geekos/src/geekos/gdt.c
new file mode 100644
index 0000000..707e34a
--- /dev/null
+++ b/geekos/src/geekos/gdt.c
@@ -0,0 +1,179 @@
+/*
+ * Initialize kernel GDT.
+ * 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".
+ */
+
+#include <geekos/kassert.h>
+#include <geekos/segment.h>
+#include <geekos/int.h>
+#include <geekos/tss.h>
+#include <geekos/gdt.h>
+#include <libc/string.h>
+
+#include <geekos/debug.h>
+
+/*
+ * This is defined in lowlevel.asm.
+ */
+extern void Load_GDTR(ushort_t* limitAndBase);
+
+/* ----------------------------------------------------------------------
+ * Data
+ * ---------------------------------------------------------------------- */
+
+/*
+ * Number of entries in the kernel GDT.
+ */
+#define NUM_GDT_ENTRIES 16
+
+/*
+ * This is the kernel's global descriptor table.
+ */
+struct Segment_Descriptor s_GDT[NUM_GDT_ENTRIES];
+/*
+ * Number of allocated GDT entries.
+ */
+static int s_numAllocated = 0;
+
+
+
+
+
+void DumpGDT()
+{
+  int i;
+  PrintBoth("GDT Contents:\n");
+
+  for (i=0;i<NUM_GDT_ENTRIES;i++) { 
+    if (s_GDT[i].present) { 
+      PrintBoth("%d: base=%u, limit=%u, sizeLow=%u,  baseLow=%u, type=%u, system=%u, dpl=%u, preent=%u, sizeHigh=%u, avail=%u, reserved=%u, dbBit=%u, granularity=%u, baseHigh=%u\n", 
+	    i,
+	    (s_GDT[i].baseHigh<<24) + s_GDT[i].baseLow,
+	    (s_GDT[i].sizeHigh<<16) + s_GDT[i].sizeLow,
+	    s_GDT[i].sizeLow,
+	    s_GDT[i].baseLow,
+	    s_GDT[i].type,
+	    s_GDT[i].system,
+    	    s_GDT[i].dpl,
+	    s_GDT[i].present,
+	    s_GDT[i].sizeHigh,
+	    s_GDT[i].avail,
+	    s_GDT[i].reserved,
+	    s_GDT[i].dbBit,
+	    s_GDT[i].granularity,
+	    s_GDT[i].baseHigh  );
+    } else {
+      PrintBoth("%d: Not Present\n",i);
+    }
+  }
+}
+
+
+/* ----------------------------------------------------------------------
+ * Functions
+ * ---------------------------------------------------------------------- */
+
+/*
+ * Allocate an descriptor from the GDT.
+ * Returns null if there are none left.
+ */
+struct Segment_Descriptor* Allocate_Segment_Descriptor(void)
+{
+    struct Segment_Descriptor* result = 0;
+    int i;
+    bool iflag;
+
+    iflag = Begin_Int_Atomic();
+
+    /* Note; entry 0 is unused (thus never allocated) */
+    for (i = 1; i < NUM_GDT_ENTRIES; ++i) {
+	struct Segment_Descriptor *desc = &s_GDT[ i ];
+	if (desc->avail) {
+	    ++s_numAllocated;
+	    desc->avail = 0;
+	    result = desc;
+	    break;
+	}
+    }
+
+    End_Int_Atomic(iflag);
+
+    return result;
+}
+
+/*
+ * Free a segment descriptor.
+ */
+void Free_Segment_Descriptor(struct Segment_Descriptor* desc)
+{
+    bool iflag = Begin_Int_Atomic();
+
+    KASSERT(!desc->avail);
+
+    Init_Null_Segment_Descriptor(desc);
+    desc->avail = 1;
+    --s_numAllocated;
+
+    End_Int_Atomic(iflag);
+}
+
+/*
+ * Get the index (int the GDT) of given segment descriptor.
+ */
+int Get_Descriptor_Index(struct Segment_Descriptor* desc)
+{
+    return (int) (desc - s_GDT);
+}
+
+/*
+ * Initialize the kernel's GDT.
+ */
+void Init_GDT(void)
+{
+    ushort_t limitAndBase[3];
+    ulong_t gdtBaseAddr = (ulong_t) s_GDT;
+    struct Segment_Descriptor* desc;
+    int i;
+
+
+    KASSERT(sizeof(struct Segment_Descriptor) == 8);
+
+    /* Clear out entries. */
+    for (i = 0; i < NUM_GDT_ENTRIES; ++i) {
+	desc = &s_GDT[ i ];
+	Init_Null_Segment_Descriptor(desc);
+	desc->avail = 1;
+    }
+
+    /* Kernel code segment. */
+    desc = Allocate_Segment_Descriptor();
+    Init_Code_Segment_Descriptor(
+	desc,
+	0,		 /* base address */
+	0x100000,	 /* num pages (== 2^20) */
+	0		 /* privilege level (0 == kernel) */
+    );
+    KASSERT(Get_Descriptor_Index(desc) == (KERNEL_CS >> 3));
+
+    /* Kernel data segment. */
+    desc = Allocate_Segment_Descriptor();
+    Init_Data_Segment_Descriptor(
+	desc,
+	0,		 /* base address */
+	0x100000,	 /* num pages (== 2^20) */
+	0		 /* privilege level (0 == kernel) */
+    );
+    KASSERT(Get_Descriptor_Index(desc) == (KERNEL_DS >> 3));
+
+    Print("GDT: Base=0x%.8x, limit=%d\n", (uint_t)gdtBaseAddr,  (uint_t)(sizeof(struct Segment_Descriptor) * NUM_GDT_ENTRIES));
+
+    /* Activate the kernel GDT. */
+    limitAndBase[0] = sizeof(struct Segment_Descriptor) * NUM_GDT_ENTRIES;
+    limitAndBase[1] = gdtBaseAddr & 0xffff;
+    limitAndBase[2] = gdtBaseAddr >> 16;
+    Load_GDTR(limitAndBase);
+}