Re: [edk2-devel] [PATCH 2/5] UefiCpuPkg: Contiguous memory allocation and code clean-up.

["Marvin Häuser" <mhaeuser@posteo.de>]

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CC Gerd (sorry the original quote is missing, groups.io <http://groups.io/> is terrible)

I thought he was to be CC'd on all UefiCpuPkg patches?

Best regards,
Marvin

> On 7. Feb 2023, at 17:40, Marvin Häuser <mhaeuser@posteo.de> wrote:
> 
> Hi Yuanhao,
> 
> 1) The code comments and copy code suggest that the stacks are located low and the function is located high (good). However, the SetMemorySpaceAttributes() call un-XP's Address, which is the low address. So, do I misunderstand the changes, or are you un-XP'ing the first stack (and keep the function XP'd)?
> 
> 2) The same SetMemorySpaceAttributes() call, you now pass ApLoopFuncSize over ApSafeBufferSize. The latter was explicitly page-aligned, while the former is not. How is it guaranteed it is indeed aligned? If it is not, I don't think this is supported, at least universally.
> 
> 3) Similar to 2), the stack size is much smaller than the page size, no? How do you guarantee the function is on a page boundary for memory protection?
> 
> 4) A proper W^X flow should be to wait with un-XP till the CopyMem() for the function code has returned. Right before that, the copied code should be marked read-only.
> 
> Best regards,
> Marvin


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