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Got GDT working

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This commit is contained in:
Tom-on
2025-03-21 12:30:04 +01:00
parent 5076d1c56b
commit 05c8ee8f67
6 changed files with 71 additions and 104 deletions
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kernel/include/gdt.h
+30 -37
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@@ -3,24 +3,6 @@
#include <kernel.h>
/*
* Entries:
* 0 Null desc.
* 1 Kernel code desc.
* 2 Kernel data desc.
* 3 SYSENTER
* 4 SYSEXIT
* 5 User code desc.
* 6 User data desc.
* 7 Task State Segment
*/
#define GDT_ENTRIES 8
#define GDT_KERNEL_CODE 0x28
#define GDT_KERNEL_DATA 0x30
#define GDT_USER_CODE 0x50
#define GDT_USER_DATA 0x48
#define GDT_TSS 0x50
/*
* Segment selector explanation (why kcode is 0x08?)
*
@@ -47,13 +29,39 @@
#define SEGMENT_SEL(_priv, _tab, _i)\
(uint16_t)(((_i) << 3) | ((_tab) << 2) | (_priv))
/*
* Entries:
* 0 Null desc.
* 1 Kernel code desc.
* 2 Kernel data desc.
* 3 User code desc.
* 4 User data desc.
* 5 Task State Segment
*/
#define GDT_ENTRIES 6
#define GDT_NULL SEGMENT_SEL(0, 0, 0)
#define GDT_KERNEL_CODE SEGMENT_SEL(0, 0, 1)
#define GDT_KERNEL_DATA SEGMENT_SEL(0, 0, 2)
#define GDT_USER_CODE SEGMENT_SEL(3, 0, 3)
#define GDT_USER_DATA SEGMENT_SEL(3, 0, 4)
#define GDT_TSS SEGMENT_SEL(0, 0, 5)
#define GDT_DESC(_lim, _base, _acc, _flag) (struct gdt_entry){\
.limit = (_lim) & 0xffff,\
.baseLow = (uint16_t)(_base),\
.baseMid = (uint8_t)((_base) >> 16),\
.access = (_acc),\
.flags = (_flag << 4) | (((_lim) >> 16) & 0x0f),\
.baseHigh = (uint8_t)((_base) >> 24),\
}
struct gdt_entry {
uint16_t limit;
uint16_t baseLow;
uint8_t baseMid;
uint8_t access;
uint8_t granulatiry;
uint8_t baseHigh;
uint8_t baseMid;
uint8_t access;
uint8_t flags; // low 4 bits are 4 msbs of limit, high 4 bits are flags
uint8_t baseHigh;
} __packed;
struct gdt_pointer {
@@ -61,15 +69,6 @@ struct gdt_pointer {
uint32_t base;
} __packed;
struct tss_entry {
uint16_t length;
uint16_t baseLow;
uint8_t baseMid;
uint8_t flags1;
uint8_t flags2;
uint8_t baseHigh;
} __packed;
struct tss_pointer {
uint16_t link;
uint16_t __reserved0;
@@ -90,7 +89,6 @@ struct tss_pointer {
uint32_t edx;
uint32_t ebx;
uint32_t esp;
uint32_t ebs;
uint32_t ebp;
uint32_t esi;
uint32_t edi;
@@ -112,11 +110,6 @@ struct tss_pointer {
uint32_t ssp;
} __packed;
struct gdt_entries {
struct gdt_entry descriptors[GDT_ENTRIES - 1]; // Subtract one for TSS
struct tss_entry tss;
};
int gdt_init(void);
#endif