[edk2-devel] [PATCH 1/2] OvmfPkg: Introduce NULL class library to inhibit driver load
Ard Biesheuvel
ardb at kernel.org
Mon Aug 15 09:40:29 UTC 2022
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 IPv6 and IPv6 network protocol
driver to be controlled from the QEMU command line.
Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.c | 30 ++++++++++++++++++++
OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.inf | 28 ++++++++++++++++++
OvmfPkg/OvmfPkg.dec | 4 +++
3 files changed, 62 insertions(+)
diff --git a/OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.c b/OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.c
new file mode 100644
index 000000000000..dc8544bc38be
--- /dev/null
+++ b/OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.c
@@ -0,0 +1,30 @@
+// @file
+// Copyright (c) 2022, Google LLC. All rights reserved.<BR>
+// SPDX-License-Identifier: BSD-2-Clause-Patent
+//
+
+#include <PiDxe.h>
+
+#include <Library/QemuFwCfgSimpleParserLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+
+STATIC CHAR16 mExitData[] = L"Driver dispatch inhibited by QEMU fw_cfg variable.";
+
+EFI_STATUS
+EFIAPI
+DriverLoadInhibitorLibConstructor (
+ IN EFI_HANDLE Handle,
+ IN EFI_SYSTEM_TABLE *SystemTable
+ )
+{
+ RETURN_STATUS Status;
+ BOOLEAN Enabled;
+
+ Status = QemuFwCfgParseBool (FixedPcdGetPtr (PcdDriverInhibitorFwCfgVarName),
+ &Enabled);
+ if (!RETURN_ERROR (Status) && !Enabled) {
+ return gBS->Exit (Handle, EFI_REQUEST_UNLOAD_IMAGE, sizeof mExitData,
+ mExitData);
+ }
+ return EFI_SUCCESS;
+}
diff --git a/OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.inf b/OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.inf
new file mode 100644
index 000000000000..ed521d12d335
--- /dev/null
+++ b/OvmfPkg/Library/DriverLoadInhibitorLib/DriverLoadInhibitorLib.inf
@@ -0,0 +1,28 @@
+## @file
+# Copyright (c) 2022, Google LLC. All rights reserved.<BR>
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+ INF_VERSION = 1.29
+ BASE_NAME = DriverLoadInhibitorLib
+ FILE_GUID = af4c2c0b-f7ed-4d61-ad97-5953982c3531
+ MODULE_TYPE = DXE_DRIVER
+ VERSION_STRING = 1.0
+ LIBRARY_CLASS = NULL
+ CONSTRUCTOR = DriverLoadInhibitorLibConstructor
+
+[Sources]
+ DriverLoadInhibitorLib.c
+
+[LibraryClasses]
+ QemuFwCfgSimpleParserLib
+ UefiBootServicesTableLib
+
+[Packages]
+ MdePkg/MdePkg.dec
+ OvmfPkg/OvmfPkg.dec
+
+[FixedPcd]
+ gUefiOvmfPkgTokenSpaceGuid.PcdDriverInhibitorFwCfgVarName
diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 5af76a540529..e9a22cab088c 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -399,6 +399,10 @@ [PcdsFixedAtBuild]
## The Tdx accept page size. 0x1000(4k),0x200000(2M)
gUefiOvmfPkgTokenSpaceGuid.PcdTdxAcceptPageSize|0x200000|UINT32|0x65
+ ## The QEMU fw_cfg variable that DriverLoadInhibitorLib will check to
+ # decide whether to abort dispatch of the driver it is linked into.
+ gUefiOvmfPkgTokenSpaceGuid.PcdDriverInhibitorFwCfgVarName|""|VOID*|0x68
+
[PcdsDynamic, PcdsDynamicEx]
gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
--
2.35.1
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