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References: <20240416152831.3199999-1-usama.anjum@collabora.com> <202404161027.63F4D4FDEB@keescook>
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From: Fangrui Song <maskray@google.com>
Date: Mon, 6 May 2024 16:30:27 -0700
Message-ID: <CAFP8O3Jjkh0U94CbS=epXELMtCBpYt4fGejX3spH4=GdF7zVSw@mail.gmail.com>
Subject: Re: [PATCH v2] selftests: exec: make binaries position independent
To: Kees Cook <keescook@chromium.org>, Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: 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 Tue, Apr 16, 2024 at 10:28=E2=80=AFAM 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.


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