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-rw-r--r--src/stem/mem/gdt.c36
1 files changed, 36 insertions, 0 deletions
diff --git a/src/stem/mem/gdt.c b/src/stem/mem/gdt.c
new file mode 100644
index 0000000..5aaad41
--- /dev/null
+++ b/src/stem/mem/gdt.c
@@ -0,0 +1,36 @@
+#include "gdt.h"
+#include <stdlib.h>
+#include <core/monitor.h>
+
+extern void gdt_flush(uint32_t); //ASM (idt_.asm)
+
+#define GDT_ENTRIES 5
+
+static struct gdt_entry gdt_entries[GDT_ENTRIES];
+static struct gdt_ptr gdt_ptr;
+
+static void gdt_setGate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
+ gdt_entries[num].base_low = (base & 0xFFFF);
+ gdt_entries[num].base_middle = (base >> 16) & 0xFF;
+ gdt_entries[num].base_high = (base >> 24) & 0xFF;
+
+ gdt_entries[num].limit_low = (limit & 0xFFFF);
+ gdt_entries[num].granularity = (limit >> 16) & 0x0F;
+ gdt_entries[num].granularity |= gran & 0xF0;
+ gdt_entries[num].access = access;
+}
+
+void gdt_init() {
+ gdt_ptr.limit = (sizeof(struct gdt_entry) * GDT_ENTRIES) - 1;
+ gdt_ptr.base = (uint32_t)&gdt_entries;
+
+ gdt_setGate(0, 0, 0, 0, 0); //Null segment
+ gdt_setGate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); //Kernel code segment
+ gdt_setGate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); //Kernel data segment
+ gdt_setGate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF); //User code segment
+ gdt_setGate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF); //User data segment
+
+ gdt_flush((uint32_t)&gdt_ptr);
+
+ monitor_write("GDT ok\n");
+}