system76-edk2/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c

/** @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>

SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "PiSmmCpuDxeSmm.h"

/**
  Disable CET.
**/
VOID
EFIAPI
DisableCet (
  VOID
  );

/**
  Enable CET.
**/
VOID
EFIAPI
EnableCet (
  VOID
  );

/**
  Get page table base address and the depth of the page table.

  @param[out] Base        Page table base address.
  @param[out] FiveLevels  TRUE means 5 level paging. FALSE means 4 level paging.
**/
VOID
GetPageTable (
  OUT UINTN   *Base,
  OUT BOOLEAN *FiveLevels OPTIONAL
  )
{
  *Base = ((mInternalCr3 == 0) ?
            (AsmReadCr3 () & PAGING_4K_ADDRESS_MASK_64) :
            mInternalCr3);
  if (FiveLevels != NULL) {
    *FiveLevels = FALSE;
  }
}

/**
  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;
  UINTN                 PageTableBase;
  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;

    GetPageTable (&PageTableBase, NULL);
    L3PageTable = (UINT64 *)PageTableBase;

    SmmSetMemoryAttributesEx ((EFI_PHYSICAL_ADDRESS)PageTableBase, 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 ;
}

/**
  Return whether access to non-SMRAM is restricted.

  @retval TRUE  Access to non-SMRAM is restricted.
  @retval FALSE Access to non-SMRAM is not restricted.
**/
BOOLEAN
IsRestrictedMemoryAccess (
  VOID
  )
{
  return TRUE;
}