text: /** @file
  Page table manipulation functions for IA-32 processors
  
  Copyright (c) 2009 - 2019, Intel Corporation. All rights reserved.<BR>
  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
  
  This program and the accompanying materials
  are licensed and made available under the terms and conditions of the BSD License
  which accompanies this distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php
  
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  
  **/
  
  #include "PiSmmCpuDxeSmm.h"
  
  /**
    Disable CET.
  **/
  VOID
  EFIAPI
  DisableCet (
    VOID
    );
  
  /**
    Enable CET.
  **/
  VOID
  EFIAPI
  EnableCet (
    VOID
    );
  
  /**
    Create PageTable for SMM use.
  
    @return     PageTable Address
  
  **/
  UINT32
  SmmInitPageTable (
    VOID
    )
  {
    UINTN                             PageFaultHandlerHookAddress;
    IA32_IDT_GATE_DESCRIPTOR          *IdtEntry;
    EFI_STATUS                        Status;
  
    //
    // Initialize spin lock
    //
    InitializeSpinLock (mPFLock);
  
    mPhysicalAddressBits = 32;
  
    if (FeaturePcdGet (PcdCpuSmmProfileEnable) ||
        HEAP_GUARD_NONSTOP_MODE ||
        NULL_DETECTION_NONSTOP_MODE) {
      //
      // Set own Page Fault entry instead of the default one, because SMM Profile
      // feature depends on IRET instruction to do Single Step
      //
      PageFaultHandlerHookAddress = (UINTN)PageFaultIdtHandlerSmmProfile;
      IdtEntry  = (IA32_IDT_GATE_DESCRIPTOR *) gcSmiIdtr.Base;
      IdtEntry += EXCEPT_IA32_PAGE_FAULT;
      IdtEntry->Bits.OffsetLow      = (UINT16)PageFaultHandlerHookAddress;
      IdtEntry->Bits.Reserved_0     = 0;
      IdtEntry->Bits.GateType       = IA32_IDT_GATE_TYPE_INTERRUPT_32;
      IdtEntry->Bits.OffsetHigh     = (UINT16)(PageFaultHandlerHookAddress >> 16);
    } else {
      //
      // Register SMM Page Fault Handler
      //
      Status = SmmRegisterExceptionHandler (&mSmmCpuService, EXCEPT_IA32_PAGE_FAULT, SmiPFHandler);
      ASSERT_EFI_ERROR (Status);
    }
  
    //
    // Additional SMM IDT initialization for SMM stack guard
    //
    if (FeaturePcdGet (PcdCpuSmmStackGuard)) {
      InitializeIDTSmmStackGuard ();
    }
    return Gen4GPageTable (TRUE);
  }
  
  /**
    Page Fault handler for SMM use.
  
  **/
  VOID
  SmiDefaultPFHandler (
    VOID
    )
  {
    CpuDeadLoop ();
  }
  
  /**
    ThePage Fault handler wrapper for SMM use.
  
    @param  InterruptType    Defines the type of interrupt or exception that
                             occurred on the processor.This parameter is processor architecture specific.
    @param  SystemContext    A pointer to the processor context when
                             the interrupt occurred on the processor.
  **/
  VOID
  EFIAPI
  SmiPFHandler (
    IN EFI_EXCEPTION_TYPE   InterruptType,
    IN EFI_SYSTEM_CONTEXT   SystemContext
    )
  {
    UINTN             PFAddress;
    UINTN             GuardPageAddress;
    UINTN             CpuIndex;
  
    ASSERT (InterruptType == EXCEPT_IA32_PAGE_FAULT);
  
    AcquireSpinLock (mPFLock);
  
    PFAddress = AsmReadCr2 ();
  
    //
    // If a page fault occurs in SMRAM range, it might be in a SMM stack guard page,
    // or SMM page protection violation.
    //
    if ((PFAddress >= mCpuHotPlugData.SmrrBase) &&
        (PFAddress < (mCpuHotPlugData.SmrrBase + mCpuHotPlugData.SmrrSize))) {
      DumpCpuContext (InterruptType, SystemContext);
      CpuIndex = GetCpuIndex ();
      GuardPageAddress = (mSmmStackArrayBase + EFI_PAGE_SIZE + CpuIndex * mSmmStackSize);
      if ((FeaturePcdGet (PcdCpuSmmStackGuard)) &&
          (PFAddress >= GuardPageAddress) &&
          (PFAddress < (GuardPageAddress + EFI_PAGE_SIZE))) {
        DEBUG ((DEBUG_ERROR, "SMM stack overflow!\n"));
      } else {
        if ((SystemContext.SystemContextIa32->ExceptionData & IA32_PF_EC_ID) != 0) {
          DEBUG ((DEBUG_ERROR, "SMM exception at execution (0x%x)\n", PFAddress));
          DEBUG_CODE (
            DumpModuleInfoByIp (*(UINTN *)(UINTN)SystemContext.SystemContextIa32->Esp);
          );
        } else {
          DEBUG ((DEBUG_ERROR, "SMM exception at access (0x%x)\n", PFAddress));
          DEBUG_CODE (
            DumpModuleInfoByIp ((UINTN)SystemContext.SystemContextIa32->Eip);
          );
        }
  
        if (HEAP_GUARD_NONSTOP_MODE) {
          GuardPagePFHandler (SystemContext.SystemContextIa32->ExceptionData);
          goto Exit;
        }
      }
      CpuDeadLoop ();
      goto Exit;
    }
  
    //
    // If a page fault occurs in non-SMRAM range.
    //
    if ((PFAddress < mCpuHotPlugData.SmrrBase) ||
        (PFAddress >= mCpuHotPlugData.SmrrBase + mCpuHotPlugData.SmrrSize)) {
      if ((SystemContext.SystemContextIa32->ExceptionData & IA32_PF_EC_ID) != 0) {
        DumpCpuContext (InterruptType, SystemContext);
        DEBUG ((DEBUG_ERROR, "Code executed on IP(0x%x) out of SMM range after SMM is locked!\n", PFAddress));
        DEBUG_CODE (
          DumpModuleInfoByIp (*(UINTN *)(UINTN)SystemContext.SystemContextIa32->Esp);
        );
        CpuDeadLoop ();
        goto Exit;
      }
  
      //
      // If NULL pointer was just accessed
      //
      if ((PcdGet8 (PcdNullPointerDetectionPropertyMask) & BIT1) != 0 &&
          (PFAddress < EFI_PAGE_SIZE)) {
        DumpCpuContext (InterruptType, SystemContext);
        DEBUG ((DEBUG_ERROR, "!!! NULL pointer access !!!\n"));
        DEBUG_CODE (
          DumpModuleInfoByIp ((UINTN)SystemContext.SystemContextIa32->Eip);
        );
  
        if (NULL_DETECTION_NONSTOP_MODE) {
          GuardPagePFHandler (SystemContext.SystemContextIa32->ExceptionData);
          goto Exit;
        }
  
        CpuDeadLoop ();
        goto Exit;
      }
  
      if (IsSmmCommBufferForbiddenAddress (PFAddress)) {
        DumpCpuContext (InterruptType, SystemContext);
        DEBUG ((DEBUG_ERROR, "Access SMM communication forbidden address (0x%x)!\n", PFAddress));
        DEBUG_CODE (
          DumpModuleInfoByIp ((UINTN)SystemContext.SystemContextIa32->Eip);
        );
        CpuDeadLoop ();
        goto Exit;
      }
    }
  
    if (FeaturePcdGet (PcdCpuSmmProfileEnable)) {
      SmmProfilePFHandler (
        SystemContext.SystemContextIa32->Eip,
        SystemContext.SystemContextIa32->ExceptionData
        );
    } else {
      DumpCpuContext (InterruptType, SystemContext);
      SmiDefaultPFHandler ();
    }
  
  Exit:
    ReleaseSpinLock (mPFLock);
  }
  
  /**
    This function sets memory attribute for page table.
  **/
  VOID
  SetPageTableAttributes (
    VOID
    )
  {
    UINTN                 Index2;
    UINTN                 Index3;
    UINT64                *L1PageTable;
    UINT64                *L2PageTable;
    UINT64                *L3PageTable;
    BOOLEAN               IsSplitted;
    BOOLEAN               PageTableSplitted;
    BOOLEAN               CetEnabled;
  
    //
    // Don't mark page table to read-only if heap guard is enabled.
    //
    //      BIT2: SMM page guard enabled
    //      BIT3: SMM pool guard enabled
    //
    if ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0) {
      DEBUG ((DEBUG_INFO, "Don't mark page table to read-only as heap guard is enabled\n"));
      return ;
    }
  
    //
    // Don't mark page table to read-only if SMM profile is enabled.
    //
    if (FeaturePcdGet (PcdCpuSmmProfileEnable)) {
      DEBUG ((DEBUG_INFO, "Don't mark page table to read-only as SMM profile is enabled\n"));
      return ;
    }
  
    DEBUG ((DEBUG_INFO, "SetPageTableAttributes\n"));
  
    //
    // Disable write protection, because we need mark page table to be write protected.
    // We need *write* page table memory, to mark itself to be *read only*.
    //
    CetEnabled = ((AsmReadCr4() & CR4_CET_ENABLE) != 0) ? TRUE : FALSE;
    if (CetEnabled) {
      //
      // CET must be disabled if WP is disabled.
      //
      DisableCet();
    }
    AsmWriteCr0 (AsmReadCr0() & ~CR0_WP);
  
    do {
      DEBUG ((DEBUG_INFO, "Start...\n"));
      PageTableSplitted = FALSE;
  
      L3PageTable = (UINT64 *)GetPageTableBase ();
  
      SmmSetMemoryAttributesEx ((EFI_PHYSICAL_ADDRESS)(UINTN)L3PageTable, SIZE_4KB, EFI_MEMORY_RO, &IsSplitted);
      PageTableSplitted = (PageTableSplitted || IsSplitted);
  
      for (Index3 = 0; Index3 < 4; Index3++) {
        L2PageTable = (UINT64 *)(UINTN)(L3PageTable[Index3] & ~mAddressEncMask & PAGING_4K_ADDRESS_MASK_64);
        if (L2PageTable == NULL) {
          continue;
        }
  
        SmmSetMemoryAttributesEx ((EFI_PHYSICAL_ADDRESS)(UINTN)L2PageTable, SIZE_4KB, EFI_MEMORY_RO, &IsSplitted);
        PageTableSplitted = (PageTableSplitted || IsSplitted);
  
        for (Index2 = 0; Index2 < SIZE_4KB/sizeof(UINT64); Index2++) {
          if ((L2PageTable[Index2] & IA32_PG_PS) != 0) {
            // 2M
            continue;
          }
          L1PageTable = (UINT64 *)(UINTN)(L2PageTable[Index2] & ~mAddressEncMask & PAGING_4K_ADDRESS_MASK_64);
          if (L1PageTable == NULL) {
            continue;
          }
          SmmSetMemoryAttributesEx ((EFI_PHYSICAL_ADDRESS)(UINTN)L1PageTable, SIZE_4KB, EFI_MEMORY_RO, &IsSplitted);
          PageTableSplitted = (PageTableSplitted || IsSplitted);
        }
      }
    } while (PageTableSplitted);
  
    //
    // Enable write protection, after page table updated.
    //
    AsmWriteCr0 (AsmReadCr0() | CR0_WP);
    if (CetEnabled) {
      //
      // re-enable CET.
      //
      EnableCet();
    }
  
    return ;
  }
  
  /**
    This function returns with no action for 32 bit.
  
    @param[out]  *Cr2  Pointer to variable to hold CR2 register value.
  **/
  VOID
  SaveCr2 (
    OUT UINTN  *Cr2
    )
  {
    return ;
  }
  
  /**
    This function returns with no action for 32 bit.
  
    @param[in]  Cr2  Value to write into CR2 register.
  **/
  VOID
  RestoreCr2 (
    IN UINTN  Cr2
    )
  {
    return ;
  }
  