Re: [PATCH v23 00/28] Control-flow Enforcement: Shadow Stack - Yu, Yu-cheng

From: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>,
	Haitao Huang <haitao.huang@intel.com>
Subject: Re: [PATCH v23 00/28] Control-flow Enforcement: Shadow Stack
Date: Tue, 23 Mar 2021 14:03:41 -0700	[thread overview]
Message-ID: <80890046-f91f-f512-6c71-b6c963905636@intel.com> (raw)
In-Reply-To: <20210323204932.GC4746@worktop.programming.kicks-ass.net>

On 3/23/2021 1:49 PM, Peter Zijlstra wrote:
> On Fri, Mar 19, 2021 at 02:43:04PM -0700, Yu, Yu-cheng wrote:
>> On 3/16/2021 2:15 PM, Peter Zijlstra wrote:
>>> On Tue, Mar 16, 2021 at 08:10:26AM -0700, Yu-cheng Yu wrote:
>>>> Control-flow Enforcement (CET) is a new Intel processor feature that blocks
>>>> return/jump-oriented programming attacks.  Details are in "Intel 64 and
>>>> IA-32 Architectures Software Developer's Manual" [1].
>>>>
>>>> CET can protect applications and the kernel.  This series enables only
>>>> application-level protection, and has three parts:
>>>>
>>>>     - Shadow stack [2],
>>>>     - Indirect branch tracking [3], and
>>>>     - Selftests [4].
>>>
>>> CET is marketing; afaict SS and IBT are 100% independent and there's no
>>> reason what so ever to have them share any code, let alone a Kconfig
>>> knob.
>>>> In fact, I think all of this would improve is you remove the CET name
>>> from all of this entirely. Put this series under CONFIG_X86_SHSTK (or
>>> _SS) and use CONFIG_X86_IBT for the other one.
>>>
>>> Similarly with the .c file.
>>>
>>> All this CET business is just pure confusion.
>>>
>>
>> What about this, we bring back CONFIG_X86_SHSTK and CONFIG_X86_IBT.
>> For the CET name itself, can we change it to CFE (Control Flow Enforcement),
>> or just CF?
> 
> Carry Flag :-)
> 
>> In signal handling, ELF header parsing and arch_prctl(), shadow stack and
>> IBT pretty much share the same code.  It is better not to split them into
>> two sets of files.
> 
> Aside from redoing the UAPI we're stuck with that I suppose :/ And since
> I think the CET name is all over the UAPI, you might as well keep it for
> the kernel part of it as well :-(
> 
> But if there's sufficient !UAPI bits it might still make sense to also
> have ibt.c and shstk.c
> 

I will move code around and separate it into shadow stack and ibt. 
Hopefully in the next iteration, things will be more organized.

Thanks,
Yu-cheng