linux-kernel - Re: [PATCH v2] selftests: exec: make binaries position independent

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Date: Mon, 6 May 2024 17:05:18 -0700
From: Kees Cook <keescook@...omium.org>
To: Fangrui Song <maskray@...gle.com>
Cc: Muhammad Usama Anjum <usama.anjum@...labora.com>,
	John Hubbard <jhubbard@...dia.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Shuah Khan <shuah@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Yang Yingliang <yangyingliang@...wei.com>, kernel@...labora.com,
	linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v2] selftests: exec: make binaries position independent

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@...omium.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@...labora.com>
> >
> > Thanks for this!
> >
> > Reviewed-by: Kees Cook <keescook@...omium.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