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

["Dong, Eric" <eric.dong@intel.com>]

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

> -----Original Message-----
> From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of Ni,
> Ray
> Sent: Thursday, July 18, 2019 2:58 PM
> 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: [edk2-devel] [PATCH] 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 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
> 
> 
>