From c18781e37e6bfe153e7c0f2bc8b04df0aecf151d Mon Sep 17 00:00:00 2001
From: Alexey Gavrilov <rebovas@yahoo.com>
Date: Sat, 4 Nov 2023 10:09:44 +0700
Subject: Support for GDT has been written + add makefile debug mode

---
 arch/x86/gdt/Gdt.h | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100755 arch/x86/gdt/Gdt.h

(limited to 'arch/x86/gdt/Gdt.h')

diff --git a/arch/x86/gdt/Gdt.h b/arch/x86/gdt/Gdt.h
new file mode 100755
index 0000000..e3d48a3
--- /dev/null
+++ b/arch/x86/gdt/Gdt.h
@@ -0,0 +1,82 @@
+#ifndef GDT_H
+#define GDT_H
+
+#include "../inc/types.h"
+
+
+// Define access options
+#define PRESENT (1 << 7)        // Present bit
+#define USER (3 << 5)           // Descriptor privelege level
+#define NSYSTEMSEG (1 << 4)     // Descriptor type
+#define EXEC (1 << 3)           // Executable bit
+#define GROWDOWN (1 << 2)       // Direction bit
+#define WRITABLE (1 << 1)       // Readable/Writable bit
+#define ACCESSED 1              // Accessed bit
+
+// Define flags byte
+#define PAGEGRAN (1 << 3)       // Granularity flag
+#define HIGHSIZE (1 << 2)       // Size flag
+#define LONGMODEON (1 << 1)     // Long-mode flag
+
+// Set of segment descriptors assign acesses bits
+#define DATA_RO         0x00        // data seg, grows up, read only, not accessed
+#define DATA_ROA        0x01        // data seg, grows up, read only, accessed
+#define DATA_RW         0x02        // data seg, grows up, read/write, not accessed
+#define DATA_RWA        0x03        // data seg, grows up, read/write, accessed
+#define DATA_ROD        0x04        // data seg, grows down, read only, not accessed
+#define DATA_RODGA      0x05        // data seg, grows down, read only, accessed
+#define DATA_RWD        0x06        // data seg, grows down, read/write, not accessed
+#define DATA_RWDA       0x07        // data seg, grows down, read/write, accessed
+#define CODE_EO         0x08        // code seg, conforming, execute only, not accessed
+#define CODE_EOA        0x09        // code seg, conforming, execute only, accessed
+#define CODE_ER         0x0A        // code seg, conforming, execute/read, not accessed
+#define CODE_ERA        0x0B        // code seg, conforming, execute/read, accessed
+#define CODE_EONC       0x0C        // code seg, not conforming, execute only, not accessed
+#define CODE_EONCA      0x0D        // code seg, not conforming, execute only, accessed
+#define CODE_ERNC       0x0E        // code seg, not conforming, execute/read, not accessed
+#define CODE_ERNCA      0x0F        // code seg, not conforming, execute/read, accessed
+
+class DescSeg32                     // Segment descriptor
+{
+    private:
+        uint16 limitLow;
+        uint16 baseLow;
+        uint8 baseMiddle;
+        uint8 access;
+        uint8 limitMiddle; // one word limit value 19:16
+        uint8 flags;       // one word located 55:52 bits in descriptor
+        uint8 baseHight;
+    public:
+        DescSeg32(uint32 base, uint32 limit, uint8 access, uint8 flags);
+        void setDescriptor(uint32 base, uint32 limit, uint8 access, uint8 flags);
+        uint64 getDescriptor();
+        static uint64 flatCodeKernel();
+        static uint64 flatDataKernel();
+        static uint64 flatCodeUser();
+        static uint64 flatDataUser();
+} __attribute__((packed));
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+extern void GOTOGDTMEMSEG(uint64 pointer);
+#ifdef __cplusplus
+};
+#endif
+
+class MngGdt
+{
+    private:
+       const static uint8 size = 10;
+       static uint64 gdt[size]; 
+       uint8 currIdx;
+       bool isGdtLoaded;
+
+    public:
+       MngGdt();
+       bool addDescriptor(uint64 desc);  // 0 - not set descriptor, 1 - set
+       bool loadGdt();      // 0 - if GDT is not loaded, 1 - loaded
+       bool getIsGdtLoaded();
+};
+
+#endif
-- 
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