[PATCH v2 6/6] OvmfPkg IA32: add support for loading X64 images

["Ard Biesheuvel" <ard.biesheuvel@linaro.org>]

This is the UEFI counterpart to my Linux series which generalizes
mixed mode support into a feature that requires very little internal
knowledge about the architecture specifics of booting Linux on the
part of the bootloader or firmware.

Instead, we add a .compat PE/COFF header containing an array of
PE_COMPAT nodes containing <machine type, entrypoint> tuples that
describe alternate entrypoints into the image for different native
machine types, e.g., IA-32 in a 64-bit image so it can be booted
from IA-32 firmware.

This patch implements the PE/COFF emulator protocol to take this new
section into account, so that such images can simply be loaded via
LoadImage/StartImage, e.g., straight from the shell.

This feature is based on the EDK2 specific PE/COFF emulator protocol
that was introduced in commit 57df17fe26cd ("MdeModulePkg/DxeCore:
invoke the emulator protocol for foreign images", 2019-04-14).

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c   | 140 ++++++++++++++++++++
 OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf |  36 +++++
 OvmfPkg/OvmfPkgIa32.dsc                               |   5 +
 OvmfPkg/OvmfPkgIa32.fdf                               |   4 +
 4 files changed, 185 insertions(+)

diff --git a/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c b/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c
new file mode 100644
index 000000000000..d2ae03eabf7f
--- /dev/null
+++ b/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c
@@ -0,0 +1,140 @@
+/** @file
+ *  PE/COFF emulator protocol implementation to start Linux kernel
+ *  images from non-native firmware
+ *
+ *  Copyright (c) 2020, ARM Ltd. All rights reserved.<BR>
+ *
+ *  SPDX-License-Identifier: BSD-2-Clause-Patent
+ *
+ */
+
+#include <PiDxe.h>
+
+#include <Library/BaseMemoryLib.h>
+#include <Library/PeCoffLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/UefiDriverEntryPoint.h>
+
+#include <Protocol/PeCoffImageEmulator.h>
+
+#pragma pack(1)
+typedef struct {
+  UINT8   Type;
+  UINT8   Size;
+  UINT16  MachineType;
+  UINT32  EntryPoint;
+} PE_COMPAT_TYPE1;
+#pragma pack()
+
+STATIC
+BOOLEAN
+EFIAPI
+IsImageSupported (
+  IN  EDKII_PECOFF_IMAGE_EMULATOR_PROTOCOL    *This,
+  IN  UINT16                                  ImageType,
+  IN  EFI_DEVICE_PATH_PROTOCOL                *DevicePath   OPTIONAL
+  )
+{
+  return ImageType == EFI_IMAGE_SUBSYSTEM_EFI_APPLICATION;
+}
+
+STATIC
+EFI_IMAGE_ENTRY_POINT
+EFIAPI
+GetCompatEntryPoint (
+  IN  EFI_PHYSICAL_ADDRESS              ImageBase
+  )
+{
+  EFI_IMAGE_DOS_HEADER                  *DosHdr;
+  UINTN                                 PeCoffHeaderOffset;
+  EFI_IMAGE_NT_HEADERS32                *Pe32;
+  EFI_IMAGE_SECTION_HEADER              *Section;
+  UINTN                                 NumberOfSections;
+  PE_COMPAT_TYPE1                       *PeCompat;
+
+  DosHdr = (EFI_IMAGE_DOS_HEADER *)(UINTN)ImageBase;
+  if (DosHdr->e_magic != EFI_IMAGE_DOS_SIGNATURE) {
+    return NULL;
+  }
+
+  PeCoffHeaderOffset = DosHdr->e_lfanew;
+  Pe32 = (EFI_IMAGE_NT_HEADERS32 *)((UINTN)ImageBase + PeCoffHeaderOffset);
+
+  Section = (EFI_IMAGE_SECTION_HEADER *)((UINTN)&Pe32->OptionalHeader +
+                                         Pe32->FileHeader.SizeOfOptionalHeader);
+  NumberOfSections = (UINTN)Pe32->FileHeader.NumberOfSections;
+
+  while (NumberOfSections--) {
+    if (!CompareMem (Section->Name, ".compat", sizeof (Section->Name))) {
+      //
+      // Dereference the section contents to find the mixed mode entry point
+      //
+      PeCompat = (PE_COMPAT_TYPE1 *)((UINTN)ImageBase + Section->VirtualAddress);
+
+      while (PeCompat->Type != 0) {
+        if (PeCompat->Type == 1 &&
+            PeCompat->Size >= sizeof (PE_COMPAT_TYPE1) &&
+            EFI_IMAGE_MACHINE_TYPE_SUPPORTED (PeCompat->MachineType)) {
+
+          return (EFI_IMAGE_ENTRY_POINT)((UINTN)ImageBase + PeCompat->EntryPoint);
+        }
+        PeCompat = (PE_COMPAT_TYPE1 *)((UINTN)PeCompat + PeCompat->Size);
+      }
+    }
+    Section++;
+  }
+  return NULL;
+}
+
+STATIC
+EFI_STATUS
+EFIAPI
+RegisterImage (
+  IN      EDKII_PECOFF_IMAGE_EMULATOR_PROTOCOL    *This,
+  IN      EFI_PHYSICAL_ADDRESS                    ImageBase,
+  IN      UINT64                                  ImageSize,
+  IN  OUT EFI_IMAGE_ENTRY_POINT                   *EntryPoint
+  )
+{
+  EFI_IMAGE_ENTRY_POINT                           CompatEntryPoint;
+
+  CompatEntryPoint = GetCompatEntryPoint (ImageBase);
+  if (CompatEntryPoint == NULL) {
+    return EFI_UNSUPPORTED;
+  }
+
+  *EntryPoint = CompatEntryPoint;
+  return EFI_SUCCESS;
+}
+
+STATIC
+EFI_STATUS
+EFIAPI
+UnregisterImage (
+  IN  EDKII_PECOFF_IMAGE_EMULATOR_PROTOCOL    *This,
+  IN  EFI_PHYSICAL_ADDRESS                    ImageBase
+  )
+{
+  return EFI_SUCCESS;
+}
+
+STATIC EDKII_PECOFF_IMAGE_EMULATOR_PROTOCOL mCompatLoaderPeCoffEmuProtocol = {
+  IsImageSupported,
+  RegisterImage,
+  UnregisterImage,
+  EDKII_PECOFF_IMAGE_EMULATOR_VERSION,
+  EFI_IMAGE_MACHINE_X64
+};
+
+EFI_STATUS
+EFIAPI
+CompatImageLoaderDxeEntryPoint (
+  IN EFI_HANDLE        ImageHandle,
+  IN EFI_SYSTEM_TABLE  *SystemTable
+  )
+{
+  return gBS->InstallProtocolInterface (&ImageHandle,
+                &gEdkiiPeCoffImageEmulatorProtocolGuid,
+                EFI_NATIVE_INTERFACE,
+                &mCompatLoaderPeCoffEmuProtocol);
+}
diff --git a/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf b/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf
new file mode 100644
index 000000000000..82369384fbe6
--- /dev/null
+++ b/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf
@@ -0,0 +1,36 @@
+## @file
+#  PE/COFF emulator protocol implementation to start Linux kernel
+#  images from non-native firmware
+#
+#  Copyright (c) 2020, ARM Ltd. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.27
+  BASE_NAME                      = CompatImageLoaderDxe
+  FILE_GUID                      = 1019f54a-2560-41b2-87b0-6750b98f3eff
+  MODULE_TYPE                    = DXE_DRIVER
+  VERSION_STRING                 = 1.0
+  ENTRY_POINT                    = CompatImageLoaderDxeEntryPoint
+
+[Sources]
+  CompatImageLoaderDxe.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+
+[LibraryClasses]
+  BaseMemoryLib
+  PeCoffLib
+  UefiBootServicesTableLib
+  UefiDriverEntryPoint
+
+[Protocols]
+  gEdkiiPeCoffImageEmulatorProtocolGuid   ## PRODUCES
+
+[Depex]
+  TRUE
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 870eb7aa7429..a996c0a7a7c9 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -33,6 +33,7 @@ [Defines]
   DEFINE SOURCE_DEBUG_ENABLE     = FALSE
   DEFINE TPM2_ENABLE             = FALSE
   DEFINE TPM2_CONFIG_ENABLE      = FALSE
+  DEFINE LOAD_X64_ON_IA32_ENABLE = FALSE
 
   #
   # Network definition
@@ -932,3 +933,7 @@ [Components]
   SecurityPkg/Tcg/Tcg2Config/Tcg2ConfigDxe.inf
 !endif
 !endif
+
+!if $(LOAD_X64_ON_IA32_ENABLE) == TRUE
+  OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf
+!endif
diff --git a/OvmfPkg/OvmfPkgIa32.fdf b/OvmfPkg/OvmfPkgIa32.fdf
index b6cd5da4f2b3..ff8d80859fb9 100644
--- a/OvmfPkg/OvmfPkgIa32.fdf
+++ b/OvmfPkg/OvmfPkgIa32.fdf
@@ -354,6 +354,10 @@ [FV.DXEFV]
 !endif
 !endif
 
+!if $(LOAD_X64_ON_IA32_ENABLE) == TRUE
+INF  OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf
+!endif
+
 ################################################################################
 
 [FV.FVMAIN_COMPACT]
-- 
2.17.1