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/*
* Copyright (c) 2025 Ian Marco Moffett and L5 engineers
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the project nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <machine/gdt.h>
/*
* The GDT should be cache line aligned, since it is accessed every time a
* segment selector is reloaded
*/
struct gdt_entry g_gdt_data[GDT_ENTRY_COUNT] = {
/* Null */
{0},
/* Kernel code (0x08) */
{
.limit = 0x0000,
.base_low = 0x0000,
.base_mid = 0x00,
.attributes = GDT_ATTRIBUTE_64BIT_CODE | GDT_ATTRIBUTE_PRESENT |
GDT_ATTRIBUTE_DPL0 | GDT_ATTRIBUTE_NONSYSTEM |
GDT_ATTRIBUTE_EXECUTABLE | GDT_ATTRIBUTE_READABLE,
.base_hi = 0x00
},
/* Kernel data (0x10) */
{
.limit = 0x0000,
.base_low = 0x0000,
.base_mid = 0x00,
.attributes = GDT_ATTRIBUTE_PRESENT | GDT_ATTRIBUTE_DPL0 |
GDT_ATTRIBUTE_NONSYSTEM | GDT_ATTRIBUTE_WRITABLE,
.base_hi = 0x00
},
/* User code (0x18) */
{
.limit = 0x0000,
.base_low = 0x0000,
.base_mid = 0x00,
.attributes = GDT_ATTRIBUTE_64BIT_CODE | GDT_ATTRIBUTE_PRESENT |
GDT_ATTRIBUTE_DPL3 | GDT_ATTRIBUTE_NONSYSTEM |
GDT_ATTRIBUTE_EXECUTABLE | GDT_ATTRIBUTE_READABLE,
.base_hi = 0x00
},
/* User data (0x20) */
{
.limit = 0x0000,
.base_low = 0x0000,
.base_mid = 0x00,
.attributes = GDT_ATTRIBUTE_PRESENT | GDT_ATTRIBUTE_DPL3 |
GDT_ATTRIBUTE_NONSYSTEM | GDT_ATTRIBUTE_WRITABLE,
.base_hi = 0x00
},
/*
* TSS segment (0x28)
*
* NOTE: 64-bit TSS descriptors are 16 bytes, equivalent to the size of two
* regular descriptor entries.
* See Intel SPG 3/25 Section 9.2.3 - TSS Descriptor in 64-bit mode.
*/
{0}, {0}
};
/* Verify that the GDT is of the correct size */
__static_assert(sizeof(g_gdt_data) == (8 * GDT_ENTRY_COUNT));
const struct gdtr g_gdtr = {
.limit = sizeof(g_gdt_data) - 1,
.offset = (uintptr_t)&g_gdt_data[0]
};
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