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OvmfPkg: Introduce alternate UefiDriverEntrypoint to inhibit driver load 

Add a new library that can be incorporated into any driver built from
source, and which permits loading of the driver to be inhibited based on
the value of a QEMU fw_cfg boolean variable. This will be used in a
subsequent patch to allow dispatch of the IPv4 and IPv6 network protocol
driver to be controlled from the QEMU command line.

This approach is based on the notion that all UEFI and DXE drivers share
a single UefiDriverEntryPoint implementation, which we can easily swap
out at build time with one that will abort execution based on the value
of some QEMU fw_cfg variable.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Ard Biesheuvel 2022-08-15 10:47:51 +02:00 committed by mergify[bot]
parent 34969dd260
commit 477b5b7d55
3 changed files with 209 additions and 0 deletions
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148
OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.c Normal file
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@ -0,0 +1,148 @@
/** @file
Entry point to a EFI/DXE driver. This version is specific to QEMU, and ties
dispatch of the driver in question on the value of a QEMU fw_cfg boolean
variable which is referenced by name via a fixed pointer PCD.
Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2022, Google LLC. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Uefi.h>
#include <Protocol/LoadedImage.h>
#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgSimpleParserLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiDriverEntryPoint.h>
/**
Unloads an image from memory.
This function is a callback that a driver registers to do cleanup
when the UnloadImage boot service function is called.
@param ImageHandle The handle to the image to unload.
@return Status returned by all unload().
**/
STATIC
EFI_STATUS
EFIAPI
_DriverUnloadHandler (
EFI_HANDLE ImageHandle
)
{
EFI_STATUS Status;
//
// If an UnloadImage() handler is specified, then call it
//
Status = ProcessModuleUnloadList (ImageHandle);
//
// If the driver specific unload handler does not return an error, then call
// all of the library destructors. If the unload handler returned an error,
// then the driver can not be unloaded, and the library destructors should
// not be called
//
if (!EFI_ERROR (Status)) {
ProcessLibraryDestructorList (ImageHandle, gST);
}
//
// Return the status from the driver specific unload handler
//
return Status;
}
/**
The entry point of PE/COFF Image for a DXE Driver, DXE Runtime Driver, or
UEFI Driver.
@param ImageHandle The image handle of the DXE Driver, DXE
Runtime Driver, or UEFI Driver.
@param SystemTable A pointer to the EFI System Table.
@retval EFI_SUCCESS The DXE Driver, DXE Runtime Driver, or
UEFI Driver exited normally.
@retval EFI_INCOMPATIBLE_VERSION _gUefiDriverRevision is greater than
SystemTable->Hdr.Revision.
@retval Other Return value from
ProcessModuleEntryPointList().
**/
EFI_STATUS
EFIAPI
_ModuleEntryPoint (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
)
{
EFI_STATUS Status;
EFI_LOADED_IMAGE_PROTOCOL *LoadedImage;
RETURN_STATUS RetStatus;
BOOLEAN Enabled;
if (_gUefiDriverRevision != 0) {
//
// Make sure that the EFI/UEFI spec revision of the platform is >= EFI/UEFI
// spec revision of the driver
//
if (SystemTable->Hdr.Revision < _gUefiDriverRevision) {
return EFI_INCOMPATIBLE_VERSION;
}
}
//
// Call constructor for all libraries
//
ProcessLibraryConstructorList (ImageHandle, SystemTable);
//
// Install unload handler...
//
if (_gDriverUnloadImageCount != 0) {
Status = gBS->HandleProtocol (
ImageHandle,
&gEfiLoadedImageProtocolGuid,
(VOID **)&LoadedImage
);
ASSERT_EFI_ERROR (Status);
LoadedImage->Unload = _DriverUnloadHandler;
}
RetStatus = QemuFwCfgParseBool (
FixedPcdGetPtr (PcdEntryPointOverrideFwCfgVarName),
&Enabled
);
if (!RETURN_ERROR (RetStatus) && !Enabled) {
//
// The QEMU fw_cfg variable tells us not to load this image. So abort.
//
Status = EFI_ABORTED;
} else {
//
// Call the driver entry point
//
Status = ProcessModuleEntryPointList (ImageHandle, SystemTable);
}
//
// If all of the drivers returned errors, or we if are aborting, then invoke
// all of the library destructors
//
if (EFI_ERROR (Status)) {
ProcessLibraryDestructorList (ImageHandle, SystemTable);
}
//
// Return the cumulative return status code from all of the driver entry
// points
//
return Status;
}

57
OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.inf Normal file
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@ -0,0 +1,57 @@
## @file
# Entry point to a EFI/DXE driver. This version is specific to QEMU, and ties
# dispatch of the driver in question on the value of a QEMU fw_cfg boolean
# variable which is referenced by name via a fixed pointer PCD.
#
# Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
# Copyright (c) 2022, Google LLC. All rights reserved.<BR>
#
# SPDX-License-Identifier: BSD-2-Clause-Patent
#
#
##
[Defines]
INF_VERSION = 1.29
BASE_NAME = UefiDriverEntryPointFwCfgOverrideLib
FILE_GUID = 73349b79-f148-43b8-b24e-9098a6f3e1db
MODULE_TYPE = UEFI_DRIVER
VERSION_STRING = 1.0
LIBRARY_CLASS = UefiDriverEntryPoint|DXE_DRIVER DXE_RUNTIME_DRIVER UEFI_DRIVER
[Sources]
UefiDriverEntryPointFwCfgOverrideLib.c
[Packages]
MdePkg/MdePkg.dec
OvmfPkg/OvmfPkg.dec
[LibraryClasses]
BaseLib
DebugLib
QemuFwCfgSimpleParserLib
UefiBootServicesTableLib
[Protocols]
gEfiLoadedImageProtocolGuid ## SOMETIMES_CONSUMES
[FixedPcd]
gUefiOvmfPkgTokenSpaceGuid.PcdEntryPointOverrideFwCfgVarName
#
# For UEFI drivers, these architectural protocols defined in PI 1.0 spec need
# to be appended and merged to the final dependency section.
#
[Depex.common.UEFI_DRIVER]
gEfiBdsArchProtocolGuid AND
gEfiCpuArchProtocolGuid AND
gEfiMetronomeArchProtocolGuid AND
gEfiMonotonicCounterArchProtocolGuid AND
gEfiRealTimeClockArchProtocolGuid AND
gEfiResetArchProtocolGuid AND
gEfiRuntimeArchProtocolGuid AND
gEfiSecurityArchProtocolGuid AND
gEfiTimerArchProtocolGuid AND
gEfiVariableWriteArchProtocolGuid AND
gEfiVariableArchProtocolGuid AND
gEfiWatchdogTimerArchProtocolGuid

4
OvmfPkg/OvmfPkg.dec
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@ -400,6 +400,10 @@
## The Tdx accept page size. 0x1000(4k),0x200000(2M)
gUefiOvmfPkgTokenSpaceGuid.PcdTdxAcceptPageSize|0x200000|UINT32|0x65
## The QEMU fw_cfg variable that UefiDriverEntryPointFwCfgOverrideLib will
# check to decide whether to abort dispatch of the driver it is linked into.
gUefiOvmfPkgTokenSpaceGuid.PcdEntryPointOverrideFwCfgVarName|""|VOID*|0x68
[PcdsDynamic, PcdsDynamicEx]
gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10