Messages in this thread | | | Date | Mon, 16 Sep 2013 18:25:22 +0200 | From | Laszlo Ersek <> | Subject | Re: [edk2] Corrupted EFI region |
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On 09/16/13 17:57, Josh Triplett wrote:
>> The edk2 commit that flipped the memory type underneath the image data >> from EfiReservedMemoryType to EfiBootServicesData is: >> >> https://github.com/tianocore/edk2/commit/4c58575e >> >> I think this commit is wrong. It's fine for OSPM to release the image >> data at some point, but not right after ExitBootServices(), because >> referencing pointers in ACPI tables survive strictly longer. >> >> ... Actually, the commit does follow the ACPI spec 5.0: >> >> 5.2.22.4 Image Address >> >> The Image Address contains the location in memory where an >> in-memory copy of the boot image can be found. The image should be >> stored in EfiBootServicesData, allowing the system to reclaim >> the memory when the image is no longer needed. >> >> The ACPI spec 5.0 should recommend EfiACPIReclaimMemory here IMO. (I >> take the current wording ("should be stored") as a recommendation only.) > > I agree that UEFI *should* store the BGRT in EfiACPIReclaimMemory, but > in practice the UEFI firmware I've seen with a BGRT does follow that > recommendation and store it in EfiBootServicesData. So, even if the > recommendation in the spec changed, the kernel would still have to > accomodate both possibilities.
Just for the theoretical debate:
The edk2 commit linked above is 5 days old. All UEFI firmware in the wild (on released hardware) should be using EfiReservedMemoryType (the pre-patch memory type), which is even stricter.
EfiReservedMemoryType can never be released & repurposed, so it should make no difference for crash kernel allocation, shouldn't it?
- call efi_free_boot_services() -- doesn't touch the image data (which is in RAM of EfiReservedMemoryType), - reserve crash kernel, - access BGRT via ACPI.
BGRT had appeared in edk2 with
https://github.com/tianocore/edk2/commit/0284e90c
and EfiReservedMemoryType used to be the allocation type until commit 4c58575e.
Or are you alluding to UEFI firmware that's not based on TianoCore?
Laszlo
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