Adding gdt

1 files changed, 49 insertions, 0 deletions

diff --git a/src/gdt.c b/src/gdt.c
new file mode 100644
index 0000000..9f87032
--- /dev/null
+++ b/src/gdt.c
@@ -0,0 +1,49 @@
+#include<stdbool.h>
+#include<stddef.h>
+#include<stdint.h>
+
+struct gdt_entry
+{
+    uint16_t limit;
+    uint16_t base1;
+    uint8_t base2;
+    uint8_t access;
+    uint8_t limit_flags;
+    uint8_t base3;
+} __attribute__((packed));
+
+struct gdt_pointer
+{
+    uint16_t size;
+    uint32_t offset;
+} __attribute__((packed));
+
+// asm function
+extern void load_gdt(struct gdt_pointer *gdtp);
+
+struct gdt_entry gdt[3];
+struct gdt_pointer gdtp;
+
+void init_gdt_entry(size_t num, uint32_t limit, uint32_t base1, uint32_t base2, uint8_t access, uint8_t limit_flags, uint8_t base3)
+{
+    gdt[num].limit=limit;
+    gdt[num].base1=base1;
+    gdt[num].access=access;
+    gdt[num].limit_flags=limit_flags;
+    gdt[num].base3=base3;
+}
+
+void init_gdt_table()
+{
+    gdtp.size=sizeof(gdt)-1;
+    gdtp.offset=(uint32_t)&gdt;
+
+    //null
+    init_gdt_entry(0,0,0,0,0,0,0);
+    //code
+    init_gdt_entry(1,0xffff,0x0000,0x00,0b10011010,0b11001111,0x00);
+    //data
+    init_gdt_entry(2,0xffff,0x0000,0x00,0b10010010,0b11001111,0x00);
+
+    load_gdt(&gdtp);
+}