From 9947a9fbc20f5c0ec0acd002209693081fe8d5ff Mon Sep 17 00:00:00 2001
From: Mattiwatti <mattiwatti@gmail.com>
Date: Sat, 25 Apr 2020 06:33:56 +0200
Subject: Loader: support legacy BIOS boot entries in the fallback path

Fixes #9
---
 Application/Loader/Loader.c       | 43 +++++++++++++++++++++++++++++++++++----
 Application/Loader/Loader.inf     |  2 ++
 Application/Loader/Loader.vcxproj |  2 +-
 3 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/Application/Loader/Loader.c b/Application/Loader/Loader.c
index ae4ded5..eba4f56 100644
--- a/Application/Loader/Loader.c
+++ b/Application/Loader/Loader.c
@@ -4,6 +4,7 @@
 #include <Protocol/EfiGuard.h>
 #include <Protocol/SimpleFileSystem.h>
 #include <Protocol/LoadedImage.h>
+#include <Protocol/LegacyBios.h>
 #include <Library/UefiLib.h>
 #include <Library/DebugLib.h>
 #include <Library/MemoryAllocationLib.h>
@@ -412,6 +413,14 @@ TryBootOptionsInOrder(
 		if ((BootOptions[Index].Attributes & LOAD_OPTION_CATEGORY) != LOAD_OPTION_CATEGORY_BOOT)
 			continue;
 
+		//
+		// Ignore legacy (BBS) entries, unless non-Windows entries are allowed (second boot attempt)
+		//
+		const BOOLEAN IsLegacy = DevicePathType(BootOptions[Index].FilePath) == BBS_DEVICE_PATH &&
+			DevicePathSubType(BootOptions[Index].FilePath) == BBS_BBS_DP;
+		if (OnlyBootWindows && IsLegacy)
+			continue;
+
 		//
 		// Filter out non-Windows boot entries.
 		// Apply some heuristics based on the device path, which must end in "bootmgfw.efi" or "bootx64.efi".
@@ -442,18 +451,24 @@ TryBootOptionsInOrder(
 			MaybeWindows = TRUE;
 		}
 
-		if (ConvertedPath != NULL)
-			FreePool(ConvertedPath);
-
 		if (OnlyBootWindows && !MaybeWindows)
 		{
 			if (FullPath != BootOptions[Index].FilePath)
 				FreePool(FullPath);
-
+			if (ConvertedPath != NULL)
+				FreePool(ConvertedPath);
+			
 			// Not Windows; skip this entry
 			continue;
 		}
 
+		// Print what we're booting
+		if (ConvertedPath != NULL)
+		{
+			Print(L"Booting %Sdevice path %S...\r\n", IsLegacy ? L"legacy " : L"", ConvertedPath);
+			FreePool(ConvertedPath);
+		}
+
 		//
 		// Boot this image.
 		//
@@ -474,6 +489,26 @@ TryBootOptionsInOrder(
 		// Signal the EVT_SIGNAL_READY_TO_BOOT event
 		EfiSignalEventReadyToBoot();
 
+		// Handle BBS entries
+		if (IsLegacy)
+		{
+			Print(L"\r\nNOTE: EfiGuard does not support legacy (non-UEFI) Windows installations.\r\n"
+				L"The legacy OS will be booted, but EfiGuard will not work.\r\nPress any key to acknowledge...\r\n");
+			WaitForKey();
+
+			EFI_LEGACY_BIOS_PROTOCOL *LegacyBios;
+			Status = gBS->LocateProtocol(&gEfiLegacyBiosProtocolGuid,
+										NULL,
+										(VOID**)&LegacyBios);
+			ASSERT_EFI_ERROR(Status);
+
+			BootOptions[Index].Status = LegacyBios->LegacyBoot(LegacyBios,
+															(BBS_BBS_DEVICE_PATH*)BootOptions[Index].FilePath,
+															BootOptions[Index].OptionalDataSize,
+															BootOptions[Index].OptionalData);
+			return !EFI_ERROR(BootOptions[Index].Status);
+		}
+
 		// So again, DO NOT call this abortion:
 		//BmSetMemoryTypeInformationVariable((BOOLEAN)((BootOptions[Index].Attributes & LOAD_OPTION_CATEGORY) == LOAD_OPTION_CATEGORY_BOOT));
 
diff --git a/Application/Loader/Loader.inf b/Application/Loader/Loader.inf
index 1e8e902..e817bd5 100644
--- a/Application/Loader/Loader.inf
+++ b/Application/Loader/Loader.inf
@@ -14,6 +14,7 @@
   MdePkg/MdePkg.dec
   EfiGuardPkg/EfiGuardPkg.dec
   MdeModulePkg/MdeModulePkg.dec
+  OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
   UefiApplicationEntryPoint
@@ -52,6 +53,7 @@
   gEfiFirmwareVolume2ProtocolGuid                  ## CONSUMES
   gEfiSimpleTextInProtocolGuid                     ## CONSUMES
   gEfiSimpleTextOutProtocolGuid                    ## CONSUMES
+  gEfiLegacyBiosProtocolGuid                       ## CONSUMES
 
 [BuildOptions.Common]
   *:DEBUG_*_*_PP_FLAGS = -D EFI_DEBUG
diff --git a/Application/Loader/Loader.vcxproj b/Application/Loader/Loader.vcxproj
index c6aaa95..512b624 100644
--- a/Application/Loader/Loader.vcxproj
+++ b/Application/Loader/Loader.vcxproj
@@ -26,7 +26,7 @@
   <ItemDefinitionGroup>
     <ClCompile>
       <PreprocessorDefinitions Condition="'$(Configuration)|$(Platform)'=='Release|x64'">CONFIGURE_DRIVER=1;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-      <AdditionalIncludeDirectories Condition="'$(Configuration)|$(Platform)'=='Release|x64'">$(SolutionDir)Include</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories Condition="'$(Configuration)|$(Platform)'=='Release|x64'">$(SolutionDir)Include;$(EDK_PATH)\OvmfPkg\Csm\Include</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <AdditionalDependencies>UefiApplicationEntryPoint.lib;BaseMemoryLib.lib;%(AdditionalDependencies)</AdditionalDependencies>
-- 
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