hazel/include/kernel/kernel.h

#ifndef HAZEL_KERNEL_H_
#define HAZEL_KERNEL_H_

#include <kernel/multiboot.h>
#include <kernel/log.h>
#include <kernel/task.h>

#define cpu_relax asm volatile ("pause" ::)
#define CHECK_FLAG(x, n) (x & (1<<n))

#define KERNEL_VMA 0xC0000000

typedef struct {
   multi_mmap_t *multi_mmap;
   uint32_t multi_mmap_size;
   uint32_t *mmap;
   uint32_t mmap_size;
   log_method_t log_method;
   uint64_t ticks;
   task_t *current_task;
} kernel_ctx_t;

#define GDT_NULL 0
#define GDT_KERNEL_CODE 1
#define GDT_KERNEL_DATA 2
#define GDT_USER_CODE 3
#define GDT_USER_DATA 4

#define RING0 0
#define RING3 3

#define GDT_SEGMENT_SELECTOR(i, p) ((i << 3) | p)

struct gdt_entry {
    uint16_t limit_low;
    uint16_t base_low;
    uint8_t base_middle;
    uint8_t access;
    uint8_t granularity;
    uint8_t base_high;
} __attribute__((packed));
typedef struct gdt_entry gdt_t;

#define PAGE_PRESENT (1<<0)
#define PAGE_RW (1<<1)
#define PAGE_USER (1<<2)

#define PAGE_DIR_INDEX(x) (((x) >> 22) & 0x3FF)
#define PAGE_TAB_INDEX(x) (((x) >> 12) & 0x3FF)
#define PAGE_OFFSET(x) ((x) & 0xFFF)

struct tss_entry {
    uint32_t prev_tss;    // The previous TSS - with hardware task switching this is used
    uint32_t esp0;        // The stack pointer to load when we change to kernel mode
    uint32_t ss0;         // The stack segment to load when we change to kernel mode
    uint32_t esp1;        // Unused...
    uint32_t ss1;
    uint32_t esp2;
    uint32_t ss2;
    uint32_t cr3;
    uint32_t eip;
    uint32_t eflags;
    uint32_t eax;
    uint32_t ecx;
    uint32_t edx;
    uint32_t ebx;
    uint32_t esp;
    uint32_t ebp;
    uint32_t esi;
    uint32_t edi;
    uint32_t es;          // The value to load into ES when we change to kernel mode
    uint32_t cs;          // The value to load into CS when we change to kernel mode
    uint32_t ss;          // The value to load into SS when we change to kernel mode
    uint32_t ds;          // The value to load into DS when we change to kernel mode
    uint32_t fs;          // The value to load into FS when we change to kernel mode
    uint32_t gs;          // The value to load into GS when we change to kernel mode
    uint32_t ldt;         // Unused...
    uint16_t trap;
    uint16_t iomap_base;
} __attribute__((packed));
typedef struct tss_entry tss_t;

#endif