UefiCpuPkg: Simplify the code to set smm page table as RO

Simplify the code to set memory used by smm page table as RO.
Since memory used by smm page table are in PageTablePool list,
we only need to set all PageTablePool as ReadOnly in smm page
table itself. Also, we only need to flush tlb once after
setting all page table pool as Read Only.

Signed-off-by: Dun Tan <dun.tan@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>

UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c

@@ -1753,3 +1753,139 @@ EdkiiSmmGetMemoryAttributes (
 
   return EFI_SUCCESS;
 }
+
+/**
+  Prevent the memory pages used for SMM page table from been overwritten.
+**/
+VOID
+EnablePageTableProtection (
+  VOID
+  )
+{
+  PAGE_TABLE_POOL       *HeadPool;
+  PAGE_TABLE_POOL       *Pool;
+  UINT64                PoolSize;
+  EFI_PHYSICAL_ADDRESS  Address;
+  UINTN                 PageTableBase;
+
+  if (mPageTablePool == NULL) {
+    return;
+  }
+
+  PageTableBase = AsmReadCr3 () & PAGING_4K_ADDRESS_MASK_64;
+
+  //
+  // ConvertMemoryPageAttributes might update mPageTablePool. It's safer to
+  // remember original one in advance.
+  //
+  HeadPool = mPageTablePool;
+  Pool     = HeadPool;
+  do {
+    Address  = (EFI_PHYSICAL_ADDRESS)(UINTN)Pool;
+    PoolSize = Pool->Offset + EFI_PAGES_TO_SIZE (Pool->FreePages);
+    //
+    // Set entire pool including header, used-memory and left free-memory as ReadOnly in SMM page table.
+    //
+    ConvertMemoryPageAttributes (PageTableBase, m5LevelPagingNeeded, Address, PoolSize, EFI_MEMORY_RO, TRUE, NULL, NULL);
+    Pool = Pool->NextPool;
+  } while (Pool != HeadPool);
+}
+
+/**
+  Return whether memory used by SMM page table need to be set as Read Only.
+
+  @retval TRUE  Need to set SMM page table as Read Only.
+  @retval FALSE Do not set SMM page table as Read Only.
+**/
+BOOLEAN
+IfReadOnlyPageTableNeeded (
+  VOID
+  )
+{
+  //
+  // Don't mark page table memory as read-only if
+  //  - no restriction on access to non-SMRAM memory; or
+  //  - SMM heap guard feature enabled; or
+  //      BIT2: SMM page guard enabled
+  //      BIT3: SMM pool guard enabled
+  //  - SMM profile feature enabled
+  //
+  if (!IsRestrictedMemoryAccess () ||
+      ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0) ||
+      FeaturePcdGet (PcdCpuSmmProfileEnable))
+  {
+    if (sizeof (UINTN) == sizeof (UINT64)) {
+      //
+      // Restriction on access to non-SMRAM memory and heap guard could not be enabled at the same time.
+      //
+      ASSERT (
+        !(IsRestrictedMemoryAccess () &&
+          (PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0)
+        );
+
+      //
+      // Restriction on access to non-SMRAM memory and SMM profile could not be enabled at the same time.
+      //
+      ASSERT (!(IsRestrictedMemoryAccess () && FeaturePcdGet (PcdCpuSmmProfileEnable)));
+    }
+
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
+/**
+  This function sets memory attribute for page table.
+**/
+VOID
+SetPageTableAttributes (
+  VOID
+  )
+{
+  BOOLEAN  CetEnabled;
+
+  if (!IfReadOnlyPageTableNeeded ()) {
+    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);
+
+  // Set memory used by page table as Read Only.
+  DEBUG ((DEBUG_INFO, "Start...\n"));
+  EnablePageTableProtection ();
+
+  //
+  // Enable write protection, after page table attribute updated.
+  //
+  AsmWriteCr0 (AsmReadCr0 () | CR0_WP);
+  mIsReadOnlyPageTable = TRUE;
+
+  //
+  // Flush TLB after mark all page table pool as read only.
+  //
+  FlushTlbForAll ();
+
+  if (CetEnabled) {
+    //
+    // re-enable CET.
+    //
+    EnableCet ();
+  }
+
+  return;
+}