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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
#include <Kernel/VirtualAddress.h>
#if ARCH(I386)
# 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
#else
# define GDT_SELECTOR_CODE0 0x08
# define GDT_SELECTOR_CODE3 0x10
# define GDT_SELECTOR_DATA3 0x18
# define GDT_SELECTOR_TSS 0x20
# define GDT_SELECTOR_TSS_PART2 0x28
#endif
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;
VERIFY(base.get() <= 0xffffffff);
}
void set_limit(u32 length)
{
limit_lo = length & 0xffff;
limit_hi = (length >> 16) & 0xf;
}
};
static_assert(AssertSize<Descriptor, 8>());
enum class IDTEntryType {
TaskGate32 = 0b0101,
InterruptGate16 = 0b110,
TrapGate16 = 0b111,
InterruptGate32 = 0b1110,
TrapGate32 = 0b1111,
};
// Clang doesn't format this right due to the compiler magic
// clang-format off
struct [[gnu::packed]] IDTEntry
{
u16 offset_1; // offset bits 0..15
u16 selector; // a code segment selector in GDT or LDT
#if ARCH(I386)
u8 zero; // unused, set to 0
#else
struct {
u8 interrupt_stack_table : 3;
u8 zero : 5; // unused, set to 0
};
#endif
struct {
u8 gate_type : 4;
u8 storage_segment : 1;
u8 descriptor_privilege_level : 2;
u8 present : 1;
} type_attr; // type and attributes
u16 offset_2; // offset bits 16..31
#if !ARCH(I386)
u32 offset_3;
u32 zeros;
#endif
IDTEntry() = default;
IDTEntry(FlatPtr callback, u16 selector_, IDTEntryType type, u8 storage_segment, u8 privilege_level)
: offset_1 { (u16)((FlatPtr)callback & 0xFFFF) }
, selector { selector_ }
#if !ARCH(I386)
, interrupt_stack_table { 0 }
#endif
, zero { 0 }
, type_attr {
.gate_type = (u8)type,
.storage_segment = storage_segment,
.descriptor_privilege_level = (u8)(privilege_level & 0b11),
.present = 1,
}
, offset_2 { (u16)((FlatPtr)callback >> 16) }
#if !ARCH(I386)
, offset_3 { (u32)(((FlatPtr)callback) >> 32) }
, zeros { 0 }
#endif
{
}
FlatPtr off()
{
#if ARCH(I386)
return (u32)offset_2 << 16 & (u32)offset_1;
#else
return (u64)offset_3 << 32 & (u64)offset_2 << 16 & (u64)offset_1;
#endif
}
IDTEntryType type()
{
return IDTEntryType(type_attr.gate_type);
}
};
// clang-format on
static_assert(AssertSize<IDTEntry, 2 * sizeof(void*)>());
}
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