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Date: Mon, 6 May 2024 17:05:18 -0700
From: Kees Cook <keescook@chromium.org>
To: Fangrui Song <maskray@google.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Shuah Khan <shuah@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Yang Yingliang <yangyingliang@huawei.com>, kernel@collabora.com,
	linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v2] selftests: exec: make binaries position independent
Message-ID: <202405061704.DD3AF674@keescook>
References: <20240416152831.3199999-1-usama.anjum@collabora.com>
 <202404161027.63F4D4FDEB@keescook>
 <CAFP8O3Jjkh0U94CbS=epXELMtCBpYt4fGejX3spH4=GdF7zVSw@mail.gmail.com>
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On Mon, May 06, 2024 at 04:30:27PM -0700, Fangrui Song wrote:
> On Tue, Apr 16, 2024 at 10:28 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Tue, Apr 16, 2024 at 08:28:29PM +0500, Muhammad Usama Anjum wrote:
> > > The -static overrides the -pie and binaries aren't position independent
> > > anymore. Use -static-pie instead which would produce a static and
> > > position independent binary. This has been caught by clang's warnings:
> > >
> > >   clang: warning: argument unused during compilation: '-pie'
> > >   [-Wunused-command-line-argument]
> > >
> > > Tested with both gcc and clang after this change.
> > >
> > > Fixes: 4d1cd3b2c5c1 ("tools/testing/selftests/exec: fix link error")
> > > Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
> >
> > Thanks for this!
> >
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> >
> > --
> > Kees Cook
> 
> GCC versions before 8.1 do not support -static-pie,
> while https://www.kernel.org/doc/html/next/process/changes.html says
> the minimal version is GCC 5.1.
> Is this a problem?
> 
> If not, and CFLAGS is guaranteed to include -fpie/-fpic/-fPIE/-fPIC
> (PIC), using -static-pie looks good to me.

Should we use this alternative, which may be more portable?
https://lore.kernel.org/all/20240504022301.35250-1-jhubbard@nvidia.com/

-Kees

-- 
Kees Cook