1 files changed, 111 insertions, 0 deletions
diff --git a/arch/x86_64/gdt.c b/arch/x86_64/gdt.c
new file mode 100644
index 0000000..e8ca912
--- /dev/null
+++ b/arch/x86_64/gdt.c
@@ -0,0 +1,111 @@
+#include "arch/x86_64/tables.h"
+#include "arch/x86_64/processor.h"
+#include "string.h"
+
+static segment_descriptor_t s_gdt[] = {
+    { 0 }, //Kernel NULL
+    {      //Kernel Code
+        .limit_0_15 = 0xFFFF,
+        .base_0_15 = 0x0,
+        .type = CD_SEGMENT_TYPE_CODE | CD_SEGMENT_TYPE_WRITEABLE,
+        .s = 1,
+        .dpl = 0,
+        .p = 1,
+        .limit_16_19 = 0xF,
+        .avl = 0,
+        .l = 1,
+        .d_b = 0,
+        .g = 1,
+        .base_24_31 = 0x0
+    },
+    {      //Kernel Data
+        .limit_0_15 = 0xFFFF,
+        .base_0_15 = 0x0,
+        .type = CD_SEGMENT_TYPE_WRITEABLE,
+        .s = 1,
+        .dpl = 0,
+        .p = 1,
+        .limit_16_19 = 0xF,
+        .avl = 0,
+        .l = 0,
+        .d_b = 1,
+        .g = 1,
+        .base_24_31 = 0x0
+    },
+    { 0 }, //User NULL
+    {      //User Data
+        .limit_0_15 = 0xFFFF,
+        .base_0_15 = 0x0,
+        .type = CD_SEGMENT_TYPE_WRITEABLE,
+        .s = 1,
+        .dpl = 3,
+        .p = 1,
+        .limit_16_19 = 0xF,
+        .avl = 0,
+        .l = 0,
+        .d_b = 1,
+        .g = 1,
+        .base_24_31 = 0x0
+    },
+    {      //User Code
+        .limit_0_15 = 0xFFFF,
+        .base_0_15 = 0x0,
+        .type = CD_SEGMENT_TYPE_CODE | CD_SEGMENT_TYPE_WRITEABLE,
+        .s = 1,
+        .dpl = 3,
+        .p = 1,
+        .limit_16_19 = 0xF,
+        .avl = 0,
+        .l = 1,
+        .d_b = 0,
+        .g = 1,
+        .base_24_31 = 0x0
+    },
+    {       //TSS Low
+        .limit_0_15 = 0,
+        .base_0_15 = 0,
+        .base_16_23 = 0,
+        .type = S_SEGMENT_TYPE_TSS_AVAIL,
+        .avl = 0,
+        .s = 0,
+        .dpl = 0,
+        .p = 1,
+        .limit_16_19 = 0,
+        .l = 0,
+        .d_b = 0,
+        .g = 0,
+        .base_24_31 = 0
+    },
+    { 0 }   //TSS High
+};
+
+void
+gdt_setup(processor_t *processor)
+{
+    memcpy(processor->gdt, s_gdt, sizeof(s_gdt));
+
+    processor->gdtr.base = (uintptr_t)&s_gdt;
+    processor->gdtr.length = sizeof(s_gdt) - 1;
+
+    segment_descriptor_t *tss_lo = &processor->gdt[GDT_ENTRY_TSS_LOW];
+    segment_descriptor_t *tss_hi = &processor->gdt[GDT_ENTRY_TSS_HIGH];
+
+    uintptr_t tssb = (uintptr_t)&processor->tss;
+    tss_lo->base_0_15 = tssb & 0xFFFF;
+    tss_lo->base_16_23 = (tssb >> 16) & 0xFF;
+    tss_lo->base_24_31 = (tssb >> 24) & 0xFF;
+    tss_hi->limit_0_15 = (tssb >> 32) & 0xFFFF;
+    tss_hi->base_0_15 = (tssb >> 48) & 0xFFFF;
+
+    size_t tssl = sizeof(tss_t);
+    tss_lo->limit_0_15 = tssl & 0xFFFF;
+    tss_lo->limit_16_19 = (tssl >> 16) & 0xF;
+
+    processor->tss.iopb = tssl;
+    
+    extern void gdt_load(void*);
+    gdt_load(&processor->gdtr);
+
+    extern void tss_flush(uint16_t);
+    tss_flush(GDT_ENTRY_TSS_LOW * sizeof(segment_descriptor_t));
+}