Hi, Johnson:

Thanks for your reply!

 

I tried and found it seemed causing some other problems.

 

It hang in eary pei stage.

 

It seems below code could also cause an exception if using expand-down mode in CAR phase’s stack established.

mov eax, ss:[ebx]  

 mov eax, [ebp]

  mov eax, [esp]

 

Thanks

发件人: Brian J. Johnson <brian.johnson@hpe.com>
发送时间: 2022年9月20日 7:10
收件人: devel@edk2.groups.io; ray.ni@intel.com; Tiger Liu(BJ-RD) <TigerLiu@zhaoxin.com>
抄送: Fan, Jeff <fanjianfeng@byosoft.com.cn>
主题: Re: [edk2-devel] How to guard CAR's stack overflow

 

You could also try modifying the Ia32 segment descriptors to mark the stack segment as an "expand down" type with a limit set just below the low end of the stack area.  That should generate a stack-fault exception if the stack overflows, and wouldn't require building page tables.  See sections 5.1 - 5.3 of the Intel SDM, volume 3.

 

Brian J. Johnson

 

From: Ni, Ray [mailto:ray.ni@intel.com]

Sent: Wednesday, September 14, 2022, 10:25 PM

To: devel@edk2.groups.io <devel@edk2.groups.io>, tigerliu@zhaoxin.com <tigerliu@zhaoxin.com>

Cc: Fan, Jeff <fanjianfeng@byosoft.com.cn>

Subject: [edk2-devel] How to guard CAR's stack overflow

 

It’s doable.

You need to enable paging and mark the very low 4K area of the stack as not-present.

You could use the UefiCpuPkg/Library/CpuPageTableLib to help you create the 1:1 page table with the specific
4K area as not-present (if you are using x86 processors).

 

Thanks,

Ray

 

From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Tiger Liu(BJ-RD)
Sent: Thursday, September 15, 2022 8:50 AM
To: devel@edk2.groups.io
Subject: [edk2-devel] How to guard CAR's stack overflow

 

Hi, Experts:

Usually, we use Cache As Ram to setup stack and heap for C language running environment before permanent memory has been initialized.

 

So, is there a method to guard this phase’s stack overflow?

 

Note:

I find udk has introduced a method to guard stack overflow after memory has been initialized and discovered.

 

Thanks

 

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