/******************************************************************************
COPYRIGHT(C) JONAS 'SORTIE' TERMANSEN 2011.
This file is part of Sortix.
Sortix is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along
with Sortix. If not, see .
descriptor_tables.cpp
Initializes and handles the GDT, TSS and IDT.
******************************************************************************/
#include "platform.h"
#include
#include "descriptor_tables.h"
#include "panic.h"
#include "syscall.h"
using namespace Maxsi;
namespace Sortix
{
namespace GDT
{
extern "C" void gdt_flush(addr_t);
extern "C" void tss_flush();
const size_t GDT_NUM_ENTRIES = 7;
gdt_entry_t gdt_entries[GDT_NUM_ENTRIES];
gdt_ptr_t gdt_ptr;
tss_entry_t tss_entry;
const uint8_t GRAN_64_BIT_MODE = 1<<5;
const uint8_t GRAN_32_BIT_MODE = 1<<6;
const uint8_t GRAN_4KIB_BLOCKS = 1<<7;
void Init()
{
gdt_ptr.limit = (sizeof(gdt_entry_t) * GDT_NUM_ENTRIES) - 1;
gdt_ptr.base = (addr_t) &gdt_entries;
#ifdef PLATFORM_X86
const uint8_t gran = GRAN_4KIB_BLOCKS | GRAN_32_BIT_MODE;
#elif defined(PLATFORM_X64)
const uint8_t gran = GRAN_4KIB_BLOCKS | GRAN_64_BIT_MODE;
#endif
SetGate(0, 0, 0, 0, 0); // Null segment
SetGate(1, 0, 0xFFFFFFFF, 0x9A, gran); // Code segment
SetGate(2, 0, 0xFFFFFFFF, 0x92, gran); // Data segment
SetGate(3, 0, 0xFFFFFFFF, 0xFA, gran); // User mode code segment
SetGate(4, 0, 0xFFFFFFFF, 0xF2, gran); // User mode data segment
WriteTSS(5, 0x10, 0x0);
if ( gdt_ptr.base != (addr_t) &gdt_entries )
{
// If this happens, then either there is a bug in the GDT entry
// writing code - or the struct gdt_entries above is too small.
Panic("Whoops, someone overwrote the GDT pointer while writing "
"to the GDT entries!");
}
gdt_flush((addr_t) &gdt_ptr);
tss_flush();
}
// Set the value of a GDT entry.
void SetGate(int32_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran)
{
gdt_entry_t* entry = (gdt_entry_t*) (&gdt_entries[num]);
entry->base_low = (base & 0xFFFF);
entry->base_middle = (base >> 16) & 0xFF;
entry->base_high = (base >> 24) & 0xFF;
entry->limit_low = (limit & 0xFFFF);
entry->granularity = ((limit >> 16) & 0x0F) | (gran & 0xF0);
entry->access = access;
}
// Set the value of a GDT entry.
void SetGate64(int32_t num, uint64_t base, uint32_t limit, uint8_t access, uint8_t gran)
{
gdt_entry64_t* entry = (gdt_entry64_t*) (&gdt_entries[num]);
entry->base_low = (base & 0xFFFF);
entry->base_middle = (base >> 16) & 0xFF;
entry->base_high = (base >> 24) & 0xFF;
entry->base_highest = (base >> 32);
entry->limit_low = (limit & 0xFFFF);
entry->granularity = ((limit >> 16) & 0x0F) | (gran & 0xF0);
entry->access = access;
entry->zero1 = 0;
}
// Initialise our task state segment structure.
void WriteTSS(int32_t num, uint16_t ss0, addr_t stack0)
{
// First, let's compute the base and limit of our entry in the GDT.
addr_t base = (addr_t) &tss_entry;
uint32_t limit = base + sizeof(tss_entry);
// Now, add our TSS descriptor's address to the GDT.
#ifdef PLATFORM_X86
SetGate(num, base, limit, 0xE9, 0x00);
#elif defined(PLATFORM_X64)
SetGate64(num, base, limit, 0xE9, 0x00);
#endif
// Ensure the descriptor is initially zero.
Memory::Set(&tss_entry, 0, sizeof(tss_entry));
#ifdef PLATFORM_X86
tss_entry.ss0 = ss0; // Set the kernel stack segment.
tss_entry.esp0 = stack0; // Set the kernel stack pointer.
// Here we set the cs, ss, ds, es, fs and gs entries in the TSS.
// These specify what segments should be loaded when the processor
// switches to kernel mode. Therefore they are just our normal
// kernel code/data segments - 0x08 and 0x10 respectively, but with
// the last two bits set, making 0x0b and 0x13. The setting of these
// bits sets the RPL (requested privilege level) to 3, meaning that
// this TSS can be used to switch to kernel mode from ring 3.
tss_entry.cs = 0x08 | 0x3;
tss_entry.ss = tss_entry.ds = tss_entry.es = tss_entry.fs = tss_entry.gs = 0x10 | 0x3;
#elif defined(PLATFORM_X64)
tss_entry.stack0 = stack0;
#endif
}
void SetKernelStack(size_t* stack)
{
#ifdef PLATFORM_X86
tss_entry.esp0 = (uint32_t) stack;
#elif defined(PLATFORM_X64)
tss_entry.stack0 = (uint64_t) stack;
#else
#warning "TSS is not yet supported on this arch!"
while(true);
#endif
}
}
namespace IDT
{
// Lets us access our ASM functions from our C++ code.
extern "C" void idt_flush(uint32_t);
idt_entry_t idt_entries[256];
idt_ptr_t idt_ptr;
void Init()
{
idt_ptr.limit = sizeof(idt_entry_t) * 256 - 1;
idt_ptr.base = (addr_t) &idt_entries;
Memory::Set(&idt_entries, 0, sizeof(idt_entry_t)*256);
// Remap the irq table.
CPU::OutPortB(0x20, 0x11);
CPU::OutPortB(0xA0, 0x11);
CPU::OutPortB(0x21, 0x20);
CPU::OutPortB(0xA1, 0x28);
CPU::OutPortB(0x21, 0x04);
CPU::OutPortB(0xA1, 0x02);
CPU::OutPortB(0x21, 0x01);
CPU::OutPortB(0xA1, 0x01);
CPU::OutPortB(0x21, 0x0);
CPU::OutPortB(0xA1, 0x0);
SetGate( 0, (addr_t) isr0 , 0x08, 0x8E);
SetGate( 1, (addr_t) isr1 , 0x08, 0x8E);
SetGate( 2, (addr_t) isr2 , 0x08, 0x8E);
SetGate( 3, (addr_t) isr3 , 0x08, 0x8E);
SetGate( 4, (addr_t) isr4 , 0x08, 0x8E);
SetGate( 5, (addr_t) isr5 , 0x08, 0x8E);
SetGate( 6, (addr_t) isr6 , 0x08, 0x8E);
SetGate( 7, (addr_t) isr7 , 0x08, 0x8E);
SetGate( 8, (addr_t) isr8 , 0x08, 0x8E);
SetGate( 9, (addr_t) isr9 , 0x08, 0x8E);
SetGate(10, (addr_t) isr10, 0x08, 0x8E);
SetGate(11, (addr_t) isr11, 0x08, 0x8E);
SetGate(12, (addr_t) isr12, 0x08, 0x8E);
SetGate(13, (addr_t) isr13, 0x08, 0x8E);
SetGate(14, (addr_t) isr14, 0x08, 0x8E);
SetGate(15, (addr_t) isr15, 0x08, 0x8E);
SetGate(16, (addr_t) isr16, 0x08, 0x8E);
SetGate(17, (addr_t) isr17, 0x08, 0x8E);
SetGate(18, (addr_t) isr18, 0x08, 0x8E);
SetGate(19, (addr_t) isr19, 0x08, 0x8E);
SetGate(20, (addr_t) isr20, 0x08, 0x8E);
SetGate(21, (addr_t) isr21, 0x08, 0x8E);
SetGate(22, (addr_t) isr22, 0x08, 0x8E);
SetGate(23, (addr_t) isr23, 0x08, 0x8E);
SetGate(24, (addr_t) isr24, 0x08, 0x8E);
SetGate(25, (addr_t) isr25, 0x08, 0x8E);
SetGate(26, (addr_t) isr26, 0x08, 0x8E);
SetGate(27, (addr_t) isr27, 0x08, 0x8E);
SetGate(28, (addr_t) isr28, 0x08, 0x8E);
SetGate(29, (addr_t) isr29, 0x08, 0x8E);
SetGate(30, (addr_t) isr30, 0x08, 0x8E);
SetGate(31, (addr_t) isr31, 0x08, 0x8E);
SetGate(32, (addr_t) irq0, 0x08, 0x8E);
SetGate(33, (addr_t) irq1, 0x08, 0x8E);
SetGate(34, (addr_t) irq2, 0x08, 0x8E);
SetGate(35, (addr_t) irq3, 0x08, 0x8E);
SetGate(36, (addr_t) irq4, 0x08, 0x8E);
SetGate(37, (addr_t) irq5, 0x08, 0x8E);
SetGate(38, (addr_t) irq6, 0x08, 0x8E);
SetGate(39, (addr_t) irq7, 0x08, 0x8E);
SetGate(40, (addr_t) irq8, 0x08, 0x8E);
SetGate(41, (addr_t) irq9, 0x08, 0x8E);
SetGate(42, (addr_t) irq10, 0x08, 0x8E);
SetGate(43, (addr_t) irq11, 0x08, 0x8E);
SetGate(44, (addr_t) irq12, 0x08, 0x8E);
SetGate(45, (addr_t) irq13, 0x08, 0x8E);
SetGate(46, (addr_t) irq14, 0x08, 0x8E);
SetGate(47, (addr_t) irq15, 0x08, 0x8E);
SetGate(128, (addr_t) syscall_handler, 0x08, 0x8E | 0x60); // System Calls
idt_flush((addr_t) &idt_ptr);
}
void SetGate(uint8_t num, addr_t base, uint16_t sel, uint8_t flags)
{
idt_entries[num].base_low = base & 0xFFFF;
idt_entries[num].base_high = (base >> 16) & 0xFFFF;
#ifdef PLATFORM_X64
idt_entries[num].base_highest = (base >> 32 ) & 0xFFFFFFFFU;
idt_entries[num].zero1 = 0;
#endif
idt_entries[num].sel = sel;
idt_entries[num].always0 = 0;
idt_entries[num].flags = flags;
}
}
}