[edk2-devel] [PATCH 1/2] UefiCpuPkg/PiSmmCpuDxeSmm: Add a new IsShadowStack flag

[duntan]

Add a new IsShadowStack flag to identify whether current memory is
shadow stack. The dirty bit in page table entry for this memory will
be set if IsShadowStack is TRUE, instead of depending on mInternalCr3.

Signed-off-by: Dun Tan <dun.tan at intel.com>
Cc: Eric Dong <eric.dong at intel.com>
Cc: Ray Ni <ray.ni at intel.com>
Cc: Rahul Kumar <rahul1.kumar at intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c b/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c
index 1f7cc15727..b369c0c435 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c
@@ -33,6 +33,7 @@ PAGE_ATTRIBUTE_TABLE  mPageAttributeTable[] = {
 };
 
 UINTN  mInternalCr3;
+UINTN  IsShadowStack = FALSE;
 
 /**
   Set the internal page table base address.
@@ -249,7 +250,7 @@ ConvertPageEntryAttribute (
   if ((Attributes & EFI_MEMORY_RO) != 0) {
     if (IsSet) {
       NewPageEntry &= ~(UINT64)IA32_PG_RW;
-      if (mInternalCr3 != 0) {
+      if (IsShadowStack) {
         // Environment setup
         // ReadOnly page need set Dirty bit for shadow stack
         NewPageEntry |= IA32_PG_D;
@@ -734,10 +735,11 @@ SetShadowStack (
   EFI_STATUS  Status;
 
   SetPageTableBase (Cr3);
-
-  Status = SmmSetMemoryAttributes (BaseAddress, Length, EFI_MEMORY_RO);
+  IsShadowStack = TRUE;
+  Status        = SmmSetMemoryAttributes (BaseAddress, Length, EFI_MEMORY_RO);
 
   SetPageTableBase (0);
+  IsShadowStack = FALSE;
 
   return Status;
 }
-- 
2.31.1.windows.1



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#92268): https://edk2.groups.io/g/devel/message/92268
Mute This Topic: https://groups.io/mt/92928945/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-