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From: Fangrui Song <maskray@google.com>
Date: Mon, 6 May 2024 17:14:36 -0700
Message-ID: <CAFP8O3Kx+bVCVQpQJVBrPkjrQO9d5rdcxGGP-Jn6t_Mpc995RA@mail.gmail.com>
Subject: Re: [PATCH v2] selftests: exec: make binaries position independent
To: Kees Cook <keescook@chromium.org>
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
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On Mon, May 6, 2024 at 5:05=E2=80=AFPM Kees Cook <keescook@chromium.org> wr=
ote:
>
> On Mon, May 06, 2024 at 04:30:27PM -0700, Fangrui Song wrote:
> > On Tue, Apr 16, 2024 at 10:28=E2=80=AFAM Kees Cook <keescook@chromium.o=
rg> 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 indepen=
dent
> > > > anymore. Use -static-pie instead which would produce a static and
> > > > position independent binary. This has been caught by clang's warnin=
gs:
> > > >
> > > >   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

s/-fPIE -static/-static/ then it looks good to me:)

-static creates a position-dependent executable.
It doesn't matter whether the compiler uses -fno-pic/-fpie/-fpic
codegen, so -fPIE can be removed.


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