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The freed-memory guard feature will cause a recursive calling of InitializePageTablePool(). This is due to a fact that AllocateAlignedPages() is used to allocate page table pool memory. This function will most likely call gBS->FreePages to free unaligned pages and then cause another round of page attributes change, like below (freed pages will be always marked not-present if freed-memory guard is enabled) FreePages() <===============| => CpuSetMemoryAttributes() | => <if out of page table> | => InitializePageTablePool() | => AllocateAlignedPages() | => FreePages() ================| The solution is add a global variable as a lock in page table pool allocation function and fail any other requests if it has not been done. Since this issue will only happen if free-memory guard is enabled, it won't affect CpuSetMemoryAttributes() in default build of a BIOS. If free-memory guard is enabled, it only affect the pages (failed to mark them as not-present) freed in AllocateAlignedPages(). Since those freed pages haven't been used yet (their addresses not yet exposed to code outside AllocateAlignedPages), it won't compromise the freed-memory guard feature. This change will just fail the CpuSetMemoryAttributes() called from FreePages() but it won't fail the FreePages(). So the error status won't be propagated upper layer of code. Cc: Laszlo Ersek <lersek@redhat.com> Cc: Star Zeng <star.zeng@intel.com> Cc: Michael D Kinney <michael.d.kinney@intel.com> Cc: Jiewen Yao <jiewen.yao@intel.com> Cc: Ruiyu Ni <ruiyu.ni@intel.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Jian J Wang <jian.j.wang@intel.com> Reviewed-by: Eric Dong <eric.dong@intel.com>
EDK II Project
A modern, feature-rich, cross-platform firmware development environment for the UEFI and PI specifications from www.uefi.org.
Contributions to the EDK II open source project are covered by the TianoCore Contribution Agreement 1.1
The majority of the content in the EDK II open source project uses a BSD 2-Clause License. The EDK II open source project contains the following components that are covered by additional licenses:
- AppPkg/Applications/Python/Python-2.7.2/Tools/pybench
- AppPkg/Applications/Python/Python-2.7.2
- AppPkg/Applications/Python/Python-2.7.10
- BaseTools/Source/C/BrotliCompress
- MdeModulePkg/Library/BrotliCustomDecompressLib
- OvmfPkg
- CryptoPkg/Library/OpensslLib/openssl
The EDK II Project is composed of packages. The maintainers for each package are listed in Maintainers.txt.