[PATCH v2 2/5] UefiCpuPkg/CpuDxe: fix an infinite loop issue

[Jian J Wang <jian.j.wang@intel.com>]

> v2 changes:
> a. Change the type of mPageTablePoolLock to be BOOLEAN. Related code
>    logic is also updated and refined.
> b. Add non-stop mode for freed-memory guard feature

The freed-memory guard feature will cause an infinite calling
of InitializePageTablePool(). This is due to a fact that
AllocateAlignedPages() is used to allocate page table pool memory.
This function will most likely call gBS->FreePages to free unaligned
pages and then cause another round of page attributes change, like
below

   FreePages() <===============|
=> SetMemoryAttributes()       |
=> <if out of page table>      |
=> InitializePageTablePool()   |
=> AllocateAlignedPages()      |
=> FreePages() ================|

The solution is add a global variable as a lock in page table pool
allocation function and fail any other requests if it has not been
done.

This patch also add non-stop mode for freed-memory guard.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
---
 UefiCpuPkg/CpuDxe/CpuDxe.h       |  2 +-
 UefiCpuPkg/CpuDxe/CpuPageTable.c | 19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/CpuDxe/CpuDxe.h b/UefiCpuPkg/CpuDxe/CpuDxe.h
index 064ea05bba..3183a3f7f4 100644
--- a/UefiCpuPkg/CpuDxe/CpuDxe.h
+++ b/UefiCpuPkg/CpuDxe/CpuDxe.h
@@ -58,7 +58,7 @@
                                        )
 
 #define HEAP_GUARD_NONSTOP_MODE       \
-        ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT6|BIT1|BIT0)) > BIT6)
+        ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT6|BIT4|BIT1|BIT0)) > BIT6)
 
 #define NULL_DETECTION_NONSTOP_MODE   \
         ((PcdGet8 (PcdNullPointerDetectionPropertyMask) & (BIT6|BIT0)) > BIT6)
diff --git a/UefiCpuPkg/CpuDxe/CpuPageTable.c b/UefiCpuPkg/CpuDxe/CpuPageTable.c
index 33e8ee2d2c..b7beaf935b 100644
--- a/UefiCpuPkg/CpuDxe/CpuPageTable.c
+++ b/UefiCpuPkg/CpuDxe/CpuPageTable.c
@@ -100,6 +100,7 @@ PAGE_ATTRIBUTE_TABLE mPageAttributeTable[] = {
 };
 
 PAGE_TABLE_POOL                   *mPageTablePool = NULL;
+BOOLEAN                           mPageTablePoolLock = FALSE;
 PAGE_TABLE_LIB_PAGING_CONTEXT     mPagingContext;
 EFI_SMM_BASE2_PROTOCOL            *mSmmBase2 = NULL;
 
@@ -1046,6 +1047,16 @@ InitializePageTablePool (
   VOID                      *Buffer;
   BOOLEAN                   IsModified;
 
+  //
+  // Do not allow re-entrance.
+  //
+  if (mPageTablePoolLock) {
+    return FALSE;
+  }
+
+  mPageTablePoolLock = TRUE;
+  IsModified = FALSE;
+
   //
   // Always reserve at least PAGE_TABLE_POOL_UNIT_PAGES, including one page for
   // header.
@@ -1056,7 +1067,9 @@ InitializePageTablePool (
   Buffer = AllocateAlignedPages (PoolPages, PAGE_TABLE_POOL_ALIGNMENT);
   if (Buffer == NULL) {
     DEBUG ((DEBUG_ERROR, "ERROR: Out of aligned pages\r\n"));
-    return FALSE;
+    goto Done;
+  } else {
+    DEBUG ((DEBUG_INFO, "Paging: added %ld pages to page table pool\r\n", (UINT64)PoolPages));
   }
 
   //
@@ -1092,7 +1105,9 @@ InitializePageTablePool (
     );
   ASSERT (IsModified == TRUE);
 
-  return TRUE;
+Done:
+  mPageTablePoolLock = FALSE;
+  return IsModified;
 }
 
 /**
-- 
2.16.2.windows.1