kernel-hardening - Re: [PATCH v7 00/17] Add support for Clang LTO

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202012010929.3788AF5@keescook>
Date: Tue, 1 Dec 2020 09:31:00 -0800
From: Kees Cook <keescook@...omium.org>
To: Will Deacon <will@...nel.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	clang-built-linux@...glegroups.com,
	kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v7 00/17] Add support for Clang LTO

On Mon, Nov 30, 2020 at 12:01:31PM +0000, Will Deacon wrote:
> Hi Sami,
> 
> On Wed, Nov 18, 2020 at 02:07:14PM -0800, Sami Tolvanen wrote:
> > This patch series adds support for building the kernel with Clang's
> > Link Time Optimization (LTO). In addition to performance, the primary
> > motivation for LTO is to allow Clang's Control-Flow Integrity (CFI) to
> > be used in the kernel. Google has shipped millions of Pixel devices
> > running three major kernel versions with LTO+CFI since 2018.
> > 
> > Most of the patches are build system changes for handling LLVM bitcode,
> > which Clang produces with LTO instead of ELF object files, postponing
> > ELF processing until a later stage, and ensuring initcall ordering.
> > 
> > Note that v7 brings back arm64 support as Will has now staged the
> > prerequisite memory ordering patches [1], and drops x86_64 while we work
> > on fixing the remaining objtool warnings [2].
> 
> Sounds like you're going to post a v8, but that's the plan for merging
> that? The arm64 parts look pretty good to me now.

I haven't seen Masahiro comment on this in a while, so given the review
history and its use (for years now) in Android, I will carry v8 (assuming
all is fine with it) it in -next unless there are objections.

-- 
Kees Cook

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.