From b6c53800d20eea193b28a5f92fa0445a7ce26761 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johanna=20Am=C3=A9lie=20Schander?= <mimoja@amazon.de>
Date: Mon, 28 Feb 2022 13:15:56 +0100
Subject: [PATCH] BDS: Only call the uefi shell as last resort
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When we are not able to boot one of the Boot Entries the Ovmf Package
defaults to the UEFI shell by adding it to the BootOrder.
Customers, who might have misconfigured their BootOrder in some
way or another (e.g. via a rootdevice replacement or a snapshot restore)
will therefore be dropped into a UEFI shell instead of beeing booted
the removable device path that the current implementation of UEFI
in the EC2 fleet boots.

By removing the UEFI shell entry BDS will now scan for the removable paths
when all BootEntries have failed. If this also fails we manually start the EFI
Shell and reset the instance if that also fails or is exited.

Upstream-status: Not applicable

Signed-off-by: Johanna Amélie Schander <mimoja@amazon.de>
Reviewed-by: Alexander Graf (AWS) <graf@amazon.de>
Reviewed-by: Hendrik Borghorst <hborghor@amazon.de>
CC: Alex Graf <graf@amazon.com>
CC: Hendrik Borghorst <hborghor@amazon.com>

diff --git a/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf b/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf
index 5bac635def..29089dcea1 100644
--- a/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf
+++ b/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf
@@ -37,6 +37,7 @@
 [Packages]
   MdePkg/MdePkg.dec
   MdeModulePkg/MdeModulePkg.dec
+  ShellPkg/ShellPkg.dec
 
 [LibraryClasses]
   DevicePathLib
@@ -74,6 +75,7 @@
   gConnectConInEventGuid                        ## SOMETIMES_CONSUMES ## Event
   gEdkiiStatusCodeDataTypeVariableGuid          ## SOMETIMES_CONSUMES ## GUID
   gEfiEventReadyToBootGuid                      ## CONSUMES           ## Event
+  gUefiShellFileGuid                            ## SOMETIMES_CONSUMES
 
 [Protocols]
   gEfiBdsArchProtocolGuid                       ## PRODUCES
diff --git a/MdeModulePkg/Universal/BdsDxe/BdsEntry.c b/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
index 766dde3aae..33db648c68 100644
--- a/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
+++ b/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
@@ -656,6 +656,49 @@ BdsFormalizeEfiGlobalVariable (
   BdsFormalizeOSIndicationVariable ();
 }
 
+STATIC
+EFI_STATUS
+GetFvLoadOption (
+  EFI_GUID                         *FileGuid,
+  EFI_BOOT_MANAGER_LOAD_OPTION     *NewOption
+  )
+{
+  EFI_STATUS                        Status;
+  MEDIA_FW_VOL_FILEPATH_DEVICE_PATH FileNode;
+  EFI_LOADED_IMAGE_PROTOCOL         *LoadedImage;
+  EFI_DEVICE_PATH_PROTOCOL          *DevicePath;
+
+  Status = gBS->HandleProtocol (
+                  gImageHandle,
+                  &gEfiLoadedImageProtocolGuid,
+                  (VOID **) &LoadedImage
+                  );
+  ASSERT_EFI_ERROR (Status);
+
+  EfiInitializeFwVolDevicepathNode (&FileNode, FileGuid);
+  DevicePath = DevicePathFromHandle (LoadedImage->DeviceHandle);
+  ASSERT (DevicePath != NULL);
+  DevicePath = AppendDevicePathNode (
+                 DevicePath,
+                 (EFI_DEVICE_PATH_PROTOCOL *) &FileNode
+                 );
+  ASSERT (DevicePath != NULL);
+
+  Status = EfiBootManagerInitializeLoadOption (
+             NewOption,
+             LoadOptionNumberUnassigned,
+             LoadOptionTypeBoot,
+             LOAD_OPTION_ACTIVE,
+             L"Internal FV Binary",
+             DevicePath,
+             NULL,
+             0
+             );
+  ASSERT_EFI_ERROR (Status);
+  FreePool (DevicePath);
+  return Status;
+}
+
 /**
 
   Service routine for BdsInstance->Entry(). Devices are connected, the
@@ -691,6 +734,7 @@ BdsEntry (
   EFI_DEVICE_PATH_PROTOCOL        *FilePath;
   EFI_STATUS                      BootManagerMenuStatus;
   EFI_BOOT_MANAGER_LOAD_OPTION    PlatformDefaultBootOption;
+  EFI_BOOT_MANAGER_LOAD_OPTION    BootEfiShell;
 
   HotkeyTriggered = NULL;
   Status          = EFI_SUCCESS;
@@ -1112,6 +1156,27 @@ BdsEntry (
     }
   }
 
+  // Get the Uefi Shell boot entry
+  Status = GetFvLoadOption (
+    &gUefiShellFileGuid,
+    &BootEfiShell
+  );
+
+  if (Status == EFI_SUCCESS) {
+    AsciiPrint (
+      "No bootable option or device was found.\n"
+      "Dropping to the EFI Shell.\n"
+      "Exiting the UEFI shell will restart the system"
+    );
+
+    EfiBootManagerBoot (&BootEfiShell);
+
+    // If we can not drop into the Efi Shell or the shell exited reset
+    gRT->ResetSystem (EfiResetWarm, EFI_SUCCESS, 0, NULL);
+
+    // Unreachable
+  }
+
   EfiBootManagerFreeLoadOption (&PlatformDefaultBootOption);
 
   DEBUG ((DEBUG_ERROR, "[Bds] Unable to boot!\n"));
diff --git a/OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c b/OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c
index ef3abe5b7a..a8a1cf9089 100644
--- a/OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c
+++ b/OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c
@@ -1707,15 +1707,6 @@ PlatformBootManagerAfterConsole (
 
   EfiBootManagerRefreshAllBootOption ();
 
-  //
-  // Register UEFI Shell
-  //
-  PlatformRegisterFvBootOption (
-    &gUefiShellFileGuid,
-    L"EFI Internal Shell",
-    LOAD_OPTION_ACTIVE
-    );
-
   RemoveStaleFvFileOptions ();
   SetBootOrderFromQemu ();