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;
Date:   Fri, 26 Jun 2020 13:37:00 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        linux-efi <linux-efi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] kbuild: remove cc-option test of -fno-stack-protector
Message-ID: <202006261331.3A94DB7@keescook>
References: <20200626185913.92890-1-masahiroy@kernel.org>
 <CAKwvOd=V_M43CP7G87K3TqSsxua2NcXPz6BnDt-z6167O2WAzQ@mail.gmail.com>
 <202006261319.F130204@keescook>
 <CAKwvOdmFpgSGow3X4AhEC1B-xWNORTgAFBXgYPQHLGyhgefddw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAKwvOdmFpgSGow3X4AhEC1B-xWNORTgAFBXgYPQHLGyhgefddw@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Jun 26, 2020 at 01:25:27PM -0700, Nick Desaulniers wrote:
> Ah, right. Thanks for pointing that out.  I'm still curious if the
> CFLAGS_<file>.o rules get appended or overwrite all flags for that
> translation unit?

CFLAGS_file.o gets appended to the CFLAGS. For example, after my updated
patch[1], the command line for syscall_64.o looks like this:

gcc -Wp,-MMD,arch/x86/entry/.syscall_64.o.d  -nostdinc -isystem \
...
-Wframe-larger-than=2048 -fstack-protector-strong \
...
-fno-stack-protector -Wno-override-init \
-DKBUILD_MODFILE='"arch/x86/entry/syscall_64"' \
-DKBUILD_BASENAME='"syscall_64"' \
-DKBUILD_MODNAME='"syscall_64"' \
-c -o arch/x86/entry/syscall_64.o \
arch/x86/entry/syscall_64.c

-Kees

[1] https://lore.kernel.org/lkml/202006261333.585319CA6B@keescook/

-- 
Kees Cook