Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201201213707.541432-1-samitolvanen@google.com>
 <20201203112622.GA31188@willie-the-truck> <CABCJKueby8pUoN7f5=6RoyLSt4PgWNx8idUej0sNwAi0F3Xqzw@mail.gmail.com>
 <20201203182252.GA32011@willie-the-truck> <CAKwvOdnvq=L=gQMv9MHaStmKMOuD5jvffzMedhp3gytYB6R7TQ@mail.gmail.com>
In-Reply-To: <CAKwvOdnvq=L=gQMv9MHaStmKMOuD5jvffzMedhp3gytYB6R7TQ@mail.gmail.com>
From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Fri, 4 Dec 2020 14:52:41 -0800
Message-ID: <CABCJKufgkq+k0DeYaXrzjXniy=T_N4sN1bxoK9=cUxTZN5xSVQ@mail.gmail.com>
Subject: Re: [PATCH v8 00/16] Add support for Clang LTO
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Kees Cook <keescook@chromium.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-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-kbuild <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        PCI <linux-pci@vger.kernel.org>, Jian Cai <jiancai@google.com>,
        Kristof Beyls <Kristof.Beyls@arm.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, Dec 3, 2020 at 2:32 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> So I'd recommend to Sami to simply make the Kconfig also depend on
> clang's integrated assembler (not just llvm-nm and llvm-ar).

Sure, sounds good to me. What's the preferred way to test for this in Kconfig?

It looks like actually trying to test if we have an LLVM assembler
(e.g. using $(as-instr,.section
".linker-options","e",@llvm_linker_options)) doesn't work as Kconfig
doesn't pass -no-integrated-as to clang here. I could do something
simple like $(success,echo $(LLVM) $(LLVM_IAS) | grep -q "1 1").

Thoughts?

Sami