| /* |
| * Copyright (c) 2011-2014 Wind River Systems, Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| /** |
| * @file |
| * @brief Global Descriptor Table support |
| * |
| * This module contains routines for updating the global descriptor table (GDT) |
| * for the IA-32 architecture. |
| */ |
| |
| #include <linker-defs.h> |
| #include <toolchain.h> |
| #include <sections.h> |
| |
| #include <kernel_structs.h> |
| #include <arch/cpu.h> |
| #include <arch/x86/segmentation.h> |
| |
| /* |
| * The RAM based global descriptor table. It is aligned on an 8 byte boundary |
| * as the Intel manuals recommend this for best performance, see |
| * Section 3.5.1 of IA architecture SW developer manual, Vol 3. |
| * |
| * TODO: CPU never looks at the 8-byte zero entry at all. Save a few bytes by |
| * stuffing the 6-byte pseudo descriptor there. |
| */ |
| static struct segment_descriptor _gdt_entries[] __aligned(8) = { |
| DT_ZERO_ENTRY, |
| DT_CODE_SEG_ENTRY(0, 0xFFFFF, DT_GRAN_PAGE, 0, DT_READABLE, |
| DT_NONCONFORM), |
| DT_DATA_SEG_ENTRY(0, 0xFFFFF, DT_GRAN_PAGE, 0, DT_WRITABLE, |
| DT_EXPAND_UP) |
| }; |
| |
| struct pseudo_descriptor _gdt = DT_INIT(_gdt_entries); |
| |