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#include <gdt.h>
#include <tss.h>
gdt_seg_entry gdt[7];
gdt_p gdt_pointer;
void add_gdt_entry(uint32_t num, uint32_t offset, uint32_t limit, uint8_t access, uint8_t flags)
{
gdt[num].offset1 = offset & 0xffff;
gdt[num].offset2 = (offset >> 16) & 0xff;
gdt[num].offset3 = (uint8_t)(offset >> 24) & 0xff;
gdt[num].limit = limit & 0xffff;
gdt[num].limitflags = (limit >> 16) & 0xf;
gdt[num].access = access;
gdt[num].limitflags = (uint8_t)(flags << 4);
}
void add_gdt_tss(uint32_t num, uint64_t offset, uint32_t limit, uint8_t access, uint8_t flags)
{
uint32_t offset_low = (offset & 0xffffffff);
uint32_t offset_high = (uint32_t)(offset >> 32);
add_gdt_entry(num, offset_low, limit, access, flags);
gdt[num+1].limit = (offset_high & 0xffff);
gdt[num+1].offset1 = (uint16_t)(offset_high >> 16);
}
void reload_gdt()
{
__asm__ volatile (
// reload segment registers
"mov $0x10, %ax;"
"mov %ax, %ds;"
"mov %ax, %es;"
"mov %ax, %ss;"
"mov %ax, %fs;"
"mov %ax, %gs;"
);
}
void load_gdt(gdt_p* pointer)
{
__asm__ volatile ("lgdt (%0);" : : "r"(pointer) : );
reload_gdt();
}
void init_gdt()
{
gdt_pointer.offset = (uint64_t)&gdt;
gdt_pointer.size = sizeof(gdt) - 1;
add_gdt_entry(0, 0, 0, 0, 0);
add_gdt_entry(1, 0, 0xfffff, 0x9a, 0xa); // code ring0
add_gdt_entry(2, 0, 0xfffff, 0x92, 0xc); // data ring0
add_gdt_entry(3, 0, 0xfffff, 0xf2, 0xc); // data ring3
add_gdt_entry(4, 0, 0xfffff, 0xfa, 0xa); // code ring3
add_gdt_tss(5, (uint64_t)&tss, sizeof(tss_type), 0x89, 0);
load_gdt(&gdt_pointer);
}
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