[RFC PATCH 13/19] OvmfPkg/SecMain: Validate the data/code pages used for the PEI phase

["Brijesh Singh" <brijesh.singh@amd.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

The VMM launch sequence should have validated all the data pages used
in the SEC phase. Before decompressing the firmware volume, validate
the data/code pages used during the decompression steps, and any other
pages used during the PEI phase entry.

Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/Sec/SecMain.c   | 26 ++++++++++++++++++++
 OvmfPkg/Sec/SecMain.inf |  2 ++
 2 files changed, 28 insertions(+)

diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index df6722b546..b491810376 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -351,6 +351,32 @@ DecompressMemFvs (
     return Status;
   }
 
+  if (MemEncryptSevSnpIsEnabled ()) {
+    EFI_PHYSICAL_ADDRESS    LaunchValidatedBase, LaunchValidatedEnd;
+    UINTN                   Size;
+
+    //
+    // The VMM launch sequence should have validated the memory range from
+    // MEMFD_BASE_ADDRESS to PcdOvmfPeiMemFvBase. The PCD values are also
+    // accessible through PcdOvmfSnpLaunchValidatedStart, and PcdOvmfSnpLaunchValidatedEnd.
+    // The pre-validation was sufficent to access the data pages used in the SEC
+    // phase.
+    //
+    // Now that we are getting ready to decompress firmware volumes, and enter
+    // to PEI phase. Lets validate the code/data pages used for entering to the
+    // PEI phase.
+    //
+    // See FvmainCompactScratchEnd.fdf.inc for more detail.
+    //
+    LaunchValidatedBase =
+        (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSnpLaunchValidatedStart);
+    LaunchValidatedEnd = LaunchValidatedBase +
+        (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSnpLaunchValidatedEnd);
+    Size = PcdGet32 (PcdOvmfDecompressionScratchEnd) - LaunchValidatedEnd;
+
+    MemEncryptSevSnpValidateSystemRam (LaunchValidatedEnd, EFI_SIZE_TO_PAGES (Size));
+  }
+
   Status = ExtractGuidedSectionGetInfo (
              Section,
              &OutputBufferSize,
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 7f78dcee27..207accb53c 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -70,6 +70,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gEfiMdeModulePkgTokenSpaceGuid.PcdInitValueInTempStack
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpLaunchValidatedStart
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpLaunchValidatedEnd
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
-- 
2.17.1