Data Structures
union	Base

struct	Entry

union	Limit

Functions
void	init ()

Variables
struct Entry	gdt [ARCH_GDT_MAX_ENTRIES]

struct Registers::GDTR	gdtr

Function Documentation

◆ init()

void GDT::init ( )

Setup and install the GDT onto the system.

Definition at line 22 of file gdt.cpp.

 {
     uint8_t gdtIndex = 0;
     const union Base nullSegmentBase = { .value = 0 };
     const union Limit nullSegmentLimit = { .value = 0 };
     gdt[gdtIndex++] = {
         .limit_low = nullSegmentLimit.section.low,
         .base_low = nullSegmentBase.section.low,
         .accessed = 0,
         .rw = 0,
         .dc = 0,
         .executable = 0,
         .system = 0,
         .privilege = 0,
         .present = 0,
         .limit_high = nullSegmentLimit.section.high,
         .reserved = 0,
         .longMode = 0,
         .size = 0,
         .granulatity = 0,
         .base_high = nullSegmentBase.section.high,
     };
  
     const union Base kernelCodeBase = { .value = 0 };
     const union Limit kernelCodeLimit = { .value = 0x000FFFFF };
     gdt[gdtIndex++] = {
         .limit_low = kernelCodeLimit.section.low,
         .base_low = kernelCodeBase.section.low,
         .accessed = 0,
         .rw = 1,
         .dc = 0,
         .executable = 1,
         .system = 1,
         .privilege = 0,
         .present = 1,
         .limit_high = kernelCodeLimit.section.high,
         .reserved = 0,
         .longMode = 0,
         .size = 1,
         .granulatity = 1,
         .base_high = kernelCodeBase.section.high,
     };
  
     const union Base kernelDataBase = { .value = 0 };
     const union Limit kernelDataLimit = { .value = 0x000FFFFF };
     gdt[gdtIndex++] = {
         .limit_low = kernelDataLimit.section.low,
         .base_low = kernelDataBase.section.low,
         .accessed = 0,
         .rw = 1,
         .dc = 0,
         .executable = 0,
         .system = 1,
         .privilege = 0,
         .present = 1,
         .limit_high = kernelDataLimit.section.high,
         .reserved = 0,
         .longMode = 0,
         .size = 1,
         .granulatity = 1,
         .base_high = kernelDataBase.section.high,
     };
  
     const union Base userCodeBase = { .value = 0 };
     const union Limit userCodeLimit = { .value = 0x000FFFFF };
     gdt[gdtIndex++] = {
         .limit_low = userCodeLimit.section.low,
         .base_low = userCodeBase.section.low,
         .accessed = 0,
         .rw = 1,
         .dc = 0,
         .executable = 1,
         .system = 1,
         .privilege = 3,
         .present = 1,
         .limit_high = userCodeLimit.section.high,
         .reserved = 0,
         .longMode = 0,
         .size = 1,
         .granulatity = 1,
         .base_high = userCodeBase.section.high,
     };
  
     const union Base userDataBase = { .value = 0 };
     const union Limit userDataLimit = { .value = 0x000FFFFF };
     gdt[gdtIndex++] = {
         .limit_low = userDataLimit.section.low,
         .base_low = userDataBase.section.low,
         .accessed = 0,
         .rw = 1,
         .dc = 0,
         .executable = 0,
         .system = 1,
         .privilege = 3,
         .present = 1,
         .limit_high = userDataLimit.section.high,
         .reserved = 0,
         .longMode = 0,
         .size = 1,
         .granulatity = 1,
         .base_high = userDataBase.section.high,
     };
  
     // Update GDT register and flush
     gdtr.size = sizeof(gdt) - 1;
     gdtr.base = (uint32_t)&gdt;
  
     gdt_flush((uint32_t)&gdtr);
 }