mirror of https://github.com/acidanthera/audk.git
1034d223f8
The DXE core implementation of PcdDxeNxMemoryProtectionPolicy already contains an assertion that EfiConventionalMemory and EfiBootServicesData are subjected to the same policy when it comes to the use of NX permissions. The reason for this is that we may otherwise end up with unbounded recursion in the page table code, given that allocating a page table would then involve a permission attribute change, and this could result in the need for a block entry to be split, which would trigger the allocation of a page table recursively. For the same reason, a shortcut exists in ApplyMemoryProtectionPolicy() where, instead of setting the memory attributes unconditionally, we compare the NX policies and avoid touching the page tables if they are the same for the old and the new memory types. Without this shortcut, we may end up in a situation where, as the CPU arch protocol DXE driver is ramping up, the same unbounded recursion is triggered, due to the fact that the NX policy for EfiConventionalMemory has not been applied yet. To break this cycle, let's remap all EfiConventionalMemory regions according to the NX policy for EfiBootServicesData before exposing the CPU arch protocol to the DXE core and other drivers. This ensures that creating EfiBootServicesData allocations does not result in memory attribute changes, and therefore no recursion. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com> |
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| Application/ArmCpuInfo | ||
| Drivers | ||
| Filesystem/SemihostFs | ||
| Include | ||
| Library | ||
| Universal/Smbios | ||
| ArmPkg.ci.yaml | ||
| ArmPkg.dec | ||
| ArmPkg.dsc | ||