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@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@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 69a04dfb23..d7d94c8b6d 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
@@ -1121,6 +1121,9 @@ 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++) {
@@ -1432,14 +1435,20 @@ PerformRemainingTasks (
     SetMemMapAttributes ();
 
     //
-    // For outside SMRAM, we only map SMM communication buffer or MMIO.
+    // Protect memory outside SMRAM when SMM Static Page Table is enabled.
     //
-    SetUefiMemMapAttributes ();
+    if (IsStaticPageTableEnabled ()) {
 
-    //
-    // 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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On 07/27/19 05:28, Ni, Ray wrote:
> 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@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Jian J Wang <jian.j.wang@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 69a04dfb23..d7d94c8b6d 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
> @@ -1121,6 +1121,9 @@ 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++) {
> @@ -1432,14 +1435,20 @@ PerformRemainingTasks (
>      SetMemMapAttributes ();
>  
>      //
> -    // For outside SMRAM, we only map SMM communication buffer or MMIO.
> +    // Protect memory outside SMRAM when SMM Static Page Table is enabled.
>      //
> -    SetUefiMemMapAttributes ();
> +    if (IsStaticPageTableEnabled ()) {
>  
> -    //
> -    // 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.
> 

With the IA32 bug in patch#1 fixed, this patch will also do the right
thing (as part of OVMF anyway):

- on IA32, there will be no change in behavior
(IsStaticPageTableEnabled() will evaluate to constant TRUE)

- on X64, OVMF keeps the DEC-default TRUE value for the underlying PCD
(PcdCpuSmmStaticPageTable), hence IsStaticPageTableEnabled() will return
TRUE, and the behavior won't change.

Because I cannot validate the PcdCpuSmmStaticPageTable==FALSE case, I
won't give R-b. But I can certainly give:

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo

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Reviewed-by: Eric Dong <eric.dong@intel.com>

> -----Original Message-----
> From: Ni, Ray
> Sent: Saturday, July 27, 2019 11:29 AM
> To: devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>;
> Wang, Jian J <jian.j.wang@intel.com>
> Subject: [PATCH 3/3] UefiCpuPkg/PiSmmCpu: Allow SMM access-out when
> static paging is OFF
> 
> 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@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Jian J Wang <jian.j.wang@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 69a04dfb23..d7d94c8b6d 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
> @@ -1121,6 +1121,9 @@ 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++) { @@ -
> 1432,14 +1435,20 @@ PerformRemainingTasks (
>      SetMemMapAttributes ();
> 
>      //
> -    // For outside SMRAM, we only map SMM communication buffer or
> MMIO.
> +    // Protect memory outside SMRAM when SMM Static Page Table is
> enabled.
>      //
> -    SetUefiMemMapAttributes ();
> +    if (IsStaticPageTableEnabled ()) {
> 
> -    //
> -    // 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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