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Date:   Fri, 20 Nov 2020 13:29:35 -0700
From:   Nathan Chancellor <natechancellor@gmail.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     Sami Tolvanen <samitolvanen@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Will Deacon <will@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-pci@vger.kernel.org
Subject: Re: [PATCH v7 02/17] kbuild: add support for Clang LTO
Message-ID: <20201120202935.GA1220359@ubuntu-m3-large-x86>
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On Fri, Nov 20, 2020 at 11:47:21AM -0800, Kees Cook wrote:
> On Fri, Nov 20, 2020 at 08:23:11AM -0800, Sami Tolvanen wrote:
> > Changing the ThinLTO config to a choice and moving it after the main
> > LTO config sounds like a good idea to me. I'll see if I can change
> > this in v8. Thanks!
> 
> Originally, I thought this might be a bit ugly once GCC LTO is added,
> but this could be just a choice like we're done for the stack
> initialization. Something like an "LTO" choice of NONE, CLANG_FULL,
> CLANG_THIN, and in the future GCC, etc.

Having two separate choices might be a little bit cleaner though? One
for the compiler (LTO_CLANG versus LTO_GCC) and one for the type
(THINLTO versus FULLLTO). The type one could just have a "depends on
CC_IS_CLANG" to ensure it only showed up when needed.

Cheers,
Nathan