105 lines
3.1 KiB
C
105 lines
3.1 KiB
C
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/*++
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Copyright (c) 1991 Microsoft Corporation
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Module Name:
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gdtsup.c
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Abstract:
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This module implements interfaces that support manipulation of i386 Gdts.
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These entry points only exist on i386 machines.
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Author:
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Dave Hastings (daveh) 28 May 1991
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Environment:
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Kernel mode only.
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--*/
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#include "ki.h"
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#ifdef ALLOC_PRAGMA
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#pragma alloc_text(PAGE,KeI386SetGdtSelector)
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#endif
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VOID Ke386GetGdtEntryThread(IN PKTHREAD Thread, IN ULONG Offset, IN PKGDTENTRY Descriptor)
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/*++
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Routine Description:
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This routine returns the contents of an entry in the Gdt.
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If the entry is thread specific, the entry for the specified thread is created and returned (KGDT_LDT, and KGDT_R3_TEB).
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If the selector is processor dependent, the entry for the current processor is returned (KGDT_R0_PCR).
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Arguments:
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Thread -- Supplies a pointer to the thread to return the entry for.
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Offset -- Supplies the offset in the Gdt. This value must be 0 mod 8.
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Descriptor -- Returns the contents of the Gdt descriptor
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--*/
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{
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PKGDTENTRY Gdt;
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PKPROCESS Process;
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// If the entry is out of range, don't return anything
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if (Offset >= KGDT_NUMBER * sizeof(KGDTENTRY)) {
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return ;
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}
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if (Offset == KGDT_LDT) {
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// Materialize Ldt selector
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Process = Thread->ApcState.Process;
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RtlMoveMemory( Descriptor, &(Process->LdtDescriptor), sizeof(KGDTENTRY));
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} else {
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// Copy Selector from Ldt
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// N.B. We will change the base later, if it is KGDT_R3_TEB
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Gdt = KiPcr()->GDT;
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RtlMoveMemory(Descriptor, (PCHAR)Gdt + Offset, sizeof(KGDTENTRY));
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// if it is the TEB selector, fix the base
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if (Offset == KGDT_R3_TEB) {
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Descriptor->BaseLow = (USHORT)((ULONG)(Thread->Teb) & 0xFFFF);
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Descriptor->HighWord.Bytes.BaseMid = (UCHAR) ( ( (ULONG)(Thread->Teb) & 0xFF0000L) >> 16);
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Descriptor->HighWord.Bytes.BaseHi = (CHAR) ( ( (ULONG)(Thread->Teb) & 0xFF000000L) >> 24);
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}
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}
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}
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NTSTATUS KeI386SetGdtSelector (ULONG Selector, PKGDTENTRY GdtValue)
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/*++
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Routine Description:
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Sets a GDTs returned via KeI386AllocateGdtSelectors to the supplied GdtValue.
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Arguments:
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Selector - Which GDT to set
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GdtValue - GDT value to set into GDT
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Return Value:
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status code
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--*/
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{
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KAFFINITY TargetSet;
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PKPRCB Prcb;
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PKPCR Pcr;
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PKGDTENTRY GdtEntry;
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ULONG GdtIndex, BitNumber;
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PAGED_CODE ();
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// Verify GDT entry passed, and it's above the kernel GDT values
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GdtIndex = Selector >> 3;
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if ((Selector & 0x7) != 0 || GdtIndex < KGDT_NUMBER) {
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return STATUS_UNSUCCESSFUL;
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}
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// Set gdt entry in each processors GDT
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TargetSet = KeActiveProcessors;
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while (TargetSet != 0) {
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BitNumber = KeFindFirstSetRightMember(TargetSet);
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ClearMember(BitNumber, TargetSet);
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Prcb = KiProcessorBlock[BitNumber];
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Pcr = CONTAINING_RECORD (Prcb, KPCR, PrcbData);
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GdtEntry = Pcr->GDT + GdtIndex;
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// set it
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*GdtEntry = *GdtValue;
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}
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return STATUS_SUCCESS;
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}
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