linux-kernel - Re: [PATCH v15 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack

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Date:   Mon, 30 Nov 2020 12:30:38 -0800
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Dave.Martin@....com, arnd@...db.de, bp@...en8.de,
        bsingharora@...il.com, corbet@....net, dave.hansen@...ux.intel.com,
        esyr@...hat.com, fweimer@...hat.com, gorcunov@...il.com,
        hjl.tools@...il.com, hpa@...or.com, jannh@...gle.com,
        keescook@...omium.org, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, luto@...nel.org,
        mike.kravetz@...cle.com, mingo@...hat.com, nadav.amit@...il.com,
        oleg@...hat.com, pavel@....cz, pengfei.xu@...el.com,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        rdunlap@...radead.org, tglx@...utronix.de,
        vedvyas.shanbhogue@...el.com, weijiang.yang@...el.com,
        x86@...nel.org, Sami Tolvanen <samitolvanen@...gle.com>,
        Will Deacon <will@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: Re: [PATCH v15 05/26] x86/cet/shstk: Add Kconfig option for user-mode
 Shadow Stack

On 11/30/2020 11:56 AM, Nick Desaulniers wrote:
> In response to https://lore.kernel.org/lkml/20201110162211.9207-6-yu-cheng.yu@intel.com/.
> 
> Hi Yu-cheng,
> This feature reminds me very much of
> ARCH_SUPPORTS_SHADOW_CALL_STACK/CC_HAVE_SHADOW_CALL_STACK implemented in
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5287569a790d2546a06db07e391bf84b8bd6cf51.
> 
> Do you think it would be worthwhile to share the same config name between x86
> and aarch64?

The CET series has ARCH_HAS_SHADOW_STACK.  In response to Boris' earlier 
comment, I think this maybe eliminated.  In case it is still needed, I 
think it is better to have different names (but I am open to changing it).

> 
> (Though, it seems on x86 there will be a distinction between kernel mode and
> user mode configs, if I understand correctly?)
> 

Yes, on x86, kernel and user-mode can be enabled separately.

Yu-cheng