kernel/x86/gdt.cpp

   1 /*
   2 lightOS kernel
   3 Copyright (C) 2007-2009 Jörg Pfähler
   4
   5 This program is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU General Public License
   7 as published by the Free Software Foundation; either version 2
   8 of the License, or (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; if not, write to the Free Software
  17 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  18 */
  19 #include <kernel/x86_shared/gdt.hpp>
  20 #include <kernel/processor.hpp>
  21 using namespace kernel;
  22
  23 void gdt::load()
  24 {
  25         struct
  26         {
  27                 uint16_t size;
  28                 uint32_t gdt;
  29         } __attribute__((packed)) gdtr = {static_cast<uint16_t>(mSize * 8 - 1), reinterpret_cast<uintptr_t>(mGdt)};
  30
  31         asm volatile("lgdt %0" :: "m"(gdtr));
  32 }
  33 #ifdef _LIGHTOS_V86
  34         void gdt::clear_tss_busy_bit(size_t index)
  35         {
  36                 mGdt[index].x86.flags &= ~0x02;
  37         }
  38 #endif
  39 size_t gdt::get_descriptor_count()
  40 {
  41         return  1 +                                             // Zero descriptor
  42                         4 +                                             // Kernel Data & Code, User Data & Code
  43                 #ifdef _LIGHTOS_V86
  44                         2 +                                             // Virtual-8086-mode TSS & Kernel TSS
  45                 #endif
  46                         processor::count();             // Thread TSS
  47 }
  48 size_t gdt::tss_descriptor_size()
  49 {
  50         return 1;
  51 }
  52 void gdt::set_tss_descriptor(   size_t index,
  53                                                                 uintptr_t address)
  54 {
  55         set_segment_descriptor( index,
  56                                                         address,
  57                                                         sizeof(task_state_segment),
  58                                                         0x89,
  59                                                         0x00);
  60 }
  61 void gdt::set_segment_descriptor(       size_t index,
  62                                                                         uintptr_t address,
  63                                                                         size_t limit,
  64                                                                         uint8_t flags,
  65                                                                         uint8_t flags2)
  66 {
  67         mGdt[index].x86.limit = limit & 0xFFFF;
  68         mGdt[index].x86.address0 = address & 0xFFFF;
  69         mGdt[index].x86.address1 = (address >> 16) & 0xFF;
  70         mGdt[index].x86.flags = flags;
  71         mGdt[index].x86.flags_limit = (flags2 << 4) | ((limit >> 16) & 0x0F);
  72         mGdt[index].x86.address2 = (address >> 24) & 0xFF;
  73 }