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/** @file
C based implementation of IA32 interrupt handling only
requiring a minimal assembly interrupt entry point.
Copyright (c) 2006 - 2021, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include "CpuDxe.h"
#include "CpuGdt.h"
//
// Global descriptor table (GDT) Template
//
STATIC GDT_ENTRIES mGdtTemplate = {
//
// NULL_SEL
//
{
0x0, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x0, // type
0x0, // limit 19:16, flags
0x0, // base 31:24
},
//
// LINEAR_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x092, // present, ring 0, data, read/write
0x0CF, // page-granular, 32-bit
0x0,
},
//
// LINEAR_CODE_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x09F, // present, ring 0, code, execute/read, conforming, accessed
0x0CF, // page-granular, 32-bit
0x0,
},
//
// SYS_DATA_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x093, // present, ring 0, data, read/write, accessed
0x0CF, // page-granular, 32-bit
0x0,
},
//
// SYS_CODE_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x09A, // present, ring 0, code, execute/read
0x0CF, // page-granular, 32-bit
0x0,
},
//
// SYS_CODE16_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x09A, // present, ring 0, code, execute/read
0x08F, // page-granular, 16-bit
0x0, // base 31:24
},
//
// LINEAR_DATA64_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x092, // present, ring 0, data, read/write
0x0CF, // page-granular, 32-bit
0x0,
},
//
// LINEAR_CODE64_SEL
//
{
0x0FFFF, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x09A, // present, ring 0, code, execute/read
0x0AF, // page-granular, 64-bit code
0x0, // base (high)
},
//
// SPARE5_SEL
//
{
0x0, // limit 15:0
0x0, // base 15:0
0x0, // base 23:16
0x0, // type
0x0, // limit 19:16, flags
0x0, // base 31:24
},
};
/**
Initialize Global Descriptor Table.
**/
VOID
InitGlobalDescriptorTable (
VOID
)
{
EFI_STATUS Status;
GDT_ENTRIES *Gdt;
IA32_DESCRIPTOR Gdtr;
EFI_PHYSICAL_ADDRESS Memory;
//
// Allocate Runtime Data below 4GB for the GDT
// AP uses the same GDT when it's waken up from real mode so
// the GDT needs to be below 4GB.
//
Memory = SIZE_4GB - 1;
Status = gBS->AllocatePages (
AllocateMaxAddress,
EfiRuntimeServicesData,
EFI_SIZE_TO_PAGES (sizeof (mGdtTemplate)),
&Memory
);
ASSERT_EFI_ERROR (Status);
ASSERT ((Memory != 0) && (Memory < SIZE_4GB));
Gdt = (GDT_ENTRIES *)(UINTN)Memory;
//
// Initialize all GDT entries
//
CopyMem (Gdt, &mGdtTemplate, sizeof (mGdtTemplate));
//
// Write GDT register
//
Gdtr.Base = (UINT32)(UINTN)Gdt;
Gdtr.Limit = (UINT16)(sizeof (mGdtTemplate) - 1);
AsmWriteGdtr (&Gdtr);
//
// Update selector (segment) registers base on new GDT
//
SetCodeSelector ((UINT16)CPU_CODE_SEL);
SetDataSelectors ((UINT16)CPU_DATA_SEL);
}
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