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OvmfPkg: Replace BaseAcpiTimerLib with BaseRomAcpiTimerLib in PEI

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The BaseAcpiTimerLib instance contains a static global variable,
'mAcpiTimerIoAddr', that caches the ACPI timer IO base address. As this
library executes during PEI phase prior to the PEIFV measurement into
PCR0, the value of the variable is included into the measurement. This
causes the PEIFV binary footprint to change, preventing a precomputation
of the expected value needed for remote attestation.

Fix this by using the BaseRomAcpiTimerLib in the PEI phase instead of
the BaseAcpiTimerLib. This library dynamically computes the required
address and does not introduce global variables, keeping the PEIFV
binary unchanged.

Co-authored-by: Simon Ott <simon.ott@aisec.fraunhofer.de>
Signed-off-by: Jakov Zauzolkov <jakov.zauzolkov@aisec.fraunhofer.de>
This commit is contained in:
Jakov Zauzolkov 2026-06-30 09:47:21 +02:00 • committed by mergify[bot]
parent 99942e3532
commit 1506c6da7b
3 changed files with 5 additions and 1 deletions
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2
OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf
View file

@ -13,7 +13,7 @@
FILE_GUID = CDD9D74F-213E-4c28-98F7-8B4A167DB936
MODULE_TYPE = BASE
VERSION_STRING = 1.0
LIBRARY_CLASS = TimerLib|SEC
LIBRARY_CLASS = TimerLib|SEC PEI_CORE PEIM
CONSTRUCTOR = AcpiTimerLibConstructor
[Sources]

2
OvmfPkg/OvmfPkgIa32X64.dsc
View file

@ -297,6 +297,7 @@
MemDebugLogLib|OvmfPkg/Library/MemDebugLogLib/MemDebugLogPeiCoreLib.inf
!endif
PeCoffLib|MdePkg/Library/BasePeCoffLib/BasePeCoffLib.inf
TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf
[LibraryClasses.common.PEIM]
HobLib|MdePkg/Library/PeiHobLib/PeiHobLib.inf
@ -325,6 +326,7 @@
MpInitLib|UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
PcdLib|MdePkg/Library/PeiPcdLib/PeiPcdLib.inf
TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf
QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
PlatformInitLib|OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf

2
OvmfPkg/OvmfPkgX64.dsc
View file

@ -329,6 +329,7 @@
!endif
PeCoffLib|MdePkg/Library/BasePeCoffLib/BasePeCoffLib.inf
CcProbeLib|OvmfPkg/Library/CcProbeLib/SecPeiCcProbeLib.inf
TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf
[LibraryClasses.common.PEIM]
HobLib|MdePkg/Library/PeiHobLib/PeiHobLib.inf
@ -357,6 +358,7 @@
MpInitLib|UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
PcdLib|MdePkg/Library/PeiPcdLib/PeiPcdLib.inf
TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf
QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
PlatformInitLib|OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf