[edk2-devel] [PATCH] UefiCpuPkg/PiSmmCpu: Allow SMM access-out when static paging is OFF

[Ni, Ray]

Commit c60d36b4d1ee1f69b7cca897d3621dfa951895c2
* UefiCpuPkg/SmmCpu: Block access-out only when static paging is used

updated page fault handler to treat SMM access-out as allowed
address when static paging is not used.

But that commit is not complete because the page table is still
updated in SetUefiMemMapAttributes() for non-SMRAM memory. When SMM
code accesses non-SMRAM memory, page fault is still generated.

This patch skips to update page table for non-SMRAM memory and
page table itself.

Signed-off-by: Ray Ni <ray.ni at intel.com>
Cc: Eric Dong <eric.dong at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Jian J Wang <jian.j.wang at intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
index 2f7d777ee7..f75e75f55c 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
@@ -1103,6 +1103,9 @@ FindSmramInfo (
   *SmrrBase = (UINT32)CurrentSmramRange->CpuStart;
   *SmrrSize = (UINT32)CurrentSmramRange->PhysicalSize;
 
+  //
+  // Extend *SmrrBase/*SmrrSize to include adjacent SMRAM ranges
+  //
   do {
     Found = FALSE;
     for (Index = 0; Index < mSmmCpuSmramRangeCount; Index++) {
@@ -1414,14 +1417,20 @@ PerformRemainingTasks (
     SetMemMapAttributes ();
 
     //
-    // For outside SMRAM, we only map SMM communication buffer or MMIO.
+    // Do not protect memory outside SMRAM when SMM static page table is not enabled.
     //
-    SetUefiMemMapAttributes ();
+    if (mCpuSmmStaticPageTable) {
 
-    //
-    // Set page table itself to be read-only
-    //
-    SetPageTableAttributes ();
+      //
+      // For outside SMRAM, we only map SMM communication buffer or MMIO.
+      //
+      SetUefiMemMapAttributes ();
+
+      //
+      // Set page table itself to be read-only
+      //
+      SetPageTableAttributes ();
+    }
 
     //
     // Configure SMM Code Access Check feature if available.
-- 
2.21.0.windows.1


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