Re: [PATCH v3 6/6] OvmfPkg IA32: add support for loading X64 images


Ard Biesheuvel
 

On Wed, 26 Feb 2020 at 21:32, Brian J. Johnson <brian.johnson@hpe.com> wrote:

On 2/26/20 1:43 PM, Ard Biesheuvel wrote:
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>
Acked-by: Laszlo Ersek <lersek@redhat.com>
---
OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c | 139 ++++++++++++++++++++
OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.inf | 36 +++++
OvmfPkg/OvmfPkgIa32.dsc | 5 +
OvmfPkg/OvmfPkgIa32.fdf | 4 +
4 files changed, 184 insertions(+)

diff --git a/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c b/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c
new file mode 100644
index 000000000000..6dc07f467752
--- /dev/null
+++ b/OvmfPkg/CompatImageLoaderDxe/CompatImageLoaderDxe.c
@@ -0,0 +1,139 @@
+/** @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 <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);
+ }
Ard,

Cool patch series!
Thanks!

I'm not an official reviewer, but I'd feel better about this patch if
you added a condition to exit the "while (PeCompat->Type != 0)" loop if
PeCompat ever gets pointed outside of the section. Otherwise a
malformed or corrupted .compat section could send you off dereferencing
anything at all.
Good point, I'll look into that.

Similarly, it wouldn't hurt to sanity check the header fields, such as
e_lfanew, OptionalHeader, SizeOfOptionalHeader, and NumberOfSections (or
at least verify that all pointers you calculate from them point within
the overall image. Or has that already been done by the PeCoff loader
by the time this code is called?
At this point, we should be able to rely on the LoadImage() boot
service to have sanity checked the headers, since we also have to rely
on the section having been copied into memory at the correct address.


+ }
+ 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 76e52a3de120..8d91903f8b4e 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]

--

Brian

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"I don't believe personal letters sent bulk rate."
-- me

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