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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>
* 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.
*
* 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 HOLDER 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.
*/
#pragma once
#include <AK/Types.h>
#include <Kernel/VirtualAddress.h>
#define GDT_SELECTOR_CODE0 0x08
#define GDT_SELECTOR_DATA0 0x10
#define GDT_SELECTOR_CODE3 0x18
#define GDT_SELECTOR_DATA3 0x20
#define GDT_SELECTOR_TLS 0x28
#define GDT_SELECTOR_PROC 0x30
#define GDT_SELECTOR_TSS 0x38
// SYSENTER makes certain assumptions on how the GDT is structured:
static_assert(GDT_SELECTOR_CODE0 + 8 == GDT_SELECTOR_DATA0); // SS0 = CS0 + 8
// SYSEXIT makes certain assumptions on how the GDT is structured:
static_assert(GDT_SELECTOR_CODE0 + 16 == GDT_SELECTOR_CODE3); // CS3 = CS0 + 16
static_assert(GDT_SELECTOR_CODE0 + 24 == GDT_SELECTOR_DATA3); // SS3 = CS0 + 32
namespace Kernel {
struct [[gnu::packed]] DescriptorTablePointer {
u16 limit;
void* address;
};
union [[gnu::packed]] Descriptor {
struct {
u16 limit_lo;
u16 base_lo;
u8 base_hi;
u8 type : 4;
u8 descriptor_type : 1;
u8 dpl : 2;
u8 segment_present : 1;
u8 limit_hi : 4;
u8 : 1;
u8 operation_size64 : 1;
u8 operation_size32 : 1;
u8 granularity : 1;
u8 base_hi2;
};
struct {
u32 low;
u32 high;
};
enum Type {
Invalid = 0,
AvailableTSS_16bit = 0x1,
LDT = 0x2,
BusyTSS_16bit = 0x3,
CallGate_16bit = 0x4,
TaskGate = 0x5,
InterruptGate_16bit = 0x6,
TrapGate_16bit = 0x7,
AvailableTSS_32bit = 0x9,
BusyTSS_32bit = 0xb,
CallGate_32bit = 0xc,
InterruptGate_32bit = 0xe,
TrapGate_32bit = 0xf,
};
VirtualAddress base() const
{
FlatPtr base = base_lo;
base |= base_hi << 16u;
base |= base_hi2 << 24u;
return VirtualAddress { base };
}
void set_base(VirtualAddress base)
{
base_lo = base.get() & 0xffffu;
base_hi = (base.get() >> 16u) & 0xffu;
base_hi2 = (base.get() >> 24u) & 0xffu;
}
void set_limit(u32 length)
{
limit_lo = length & 0xffff;
limit_hi = (length >> 16) & 0xf;
}
};
}
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