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

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Message-ID: <CAFP8O3Jjkh0U94CbS=epXELMtCBpYt4fGejX3spH4=GdF7zVSw@mail.gmail.com>
Date: Mon, 6 May 2024 16:30:27 -0700
From: Fangrui Song <maskray@...gle.com>
To: Kees Cook <keescook@...omium.org>, Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: 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 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.


-- 
宋方睿