linux-kernel - Re: [PATCH] Decouple build from userspace headers

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Message-ID: <YO6jdIlu5xy35nix@localhost.localdomain>
Date:   Wed, 14 Jul 2021 11:42:28 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] Decouple build from userspace headers

On Wed, Jul 14, 2021 at 01:54:59PM +0900, Masahiro Yamada wrote:
> On Wed, Jul 14, 2021 at 4:47 AM Alexey Dobriyan <adobriyan@...il.com> wrote:
> >
> > In theory, userspace headers can be under incompatible license.
> >
> > Linux by virtue of being OS kernel is fully independent piece of code
> > and should not require anything from userspace.
> 
> As far as I know,
> <stdarg.h> was the only exception,
> which was borrowed from the compiler.
> 
> 
> I like this as long as:
>   - license is clear (please add SPDX tag to the new header)
>   - it works for both gcc and clang (I guess the answer is yes)

It should. clang version is essentially the same
(with less prehistoric macrology).

> I think removing <stdbool.h> and <stddef.h> are non-controversial.
> Mayby, you can split it into 1/2.
> 
> 
> 
> 
> >
> > For this:
> >
> > * ship minimal <stdarg.h>
> >         2 types, 4 macros
> >
> > * delete "-isystem"
> >         This is what enables leakage.
> >
> > * fixup compilation where necessary.
> >
> > Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> > ---
> >
> >  Makefile                                                               |    2 +-
> >  arch/um/include/shared/irq_user.h                                      |    1 -
> >  arch/um/os-Linux/signal.c                                              |    2 +-
> >  crypto/aegis128-neon-inner.c                                           |    2 --
> >  drivers/net/wwan/iosm/iosm_ipc_imem.h                                  |    1 -
> >  drivers/pinctrl/aspeed/pinmux-aspeed.h                                 |    1 -
> >  drivers/staging/media/atomisp/pci/hive_isp_css_common/host/isp_local.h |    2 --
> >  include/stdarg.h                                                       |    9 +++++++++
> >  sound/aoa/codecs/onyx.h                                                |    1 -
> >  sound/aoa/codecs/tas.c                                                 |    1 -
> >  10 files changed, 11 insertions(+), 11 deletions(-)
> >
> 
> > new file mode 100644
> > --- /dev/null
> > +++ b/include/stdarg.h
> > @@ -0,0 +1,9 @@
> 
> 
> This is a new file, so please add the SPDX tag.
> What project did you copy the code from?
> 
>   If gcc, is it GPL v3 (but not compatible for GPL v2) ?

It is GPL 2, brought to you by Debian! I'll add a link.

	http://archive.debian.org/debian/pool/main/g/gcc-4.2/

>   If clang, is it
>    SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
> 
> Or, can we license this small portion of code
> as GPL v2?
> 
> 
> 
> > +#ifndef _LINUX_STDARG_H
> > +#define _LINUX_STDARG_H
> > +typedef __builtin_va_list __gnuc_va_list;
> 
> Where is __gnuc_va_list needed?
> 
> BTW, once this is accepted, I'd like to
> change all <stdarg.h>  to <linux/stdarg.h>.

Yes. I've just realised <stdarg.h> is the wrong place:

  gcc -Wp,-MMD,scripts/selinux/genheaders/.genheaders.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89     -I/home/ad/linux/linux-1/include/uapi -I/home/ad/linux/linux-1/include -I/home/ad/linux/linux-1/security/selinux/include  -I ./scripts/selinux/genheaders   -o scripts/selinux/genheaders/genheaders /home/ad/linux/linux-1/scripts/selinux/genheaders/genheaders.c
In file included from /home/ad/linux/linux-1/scripts/selinux/genheaders/genheaders.c:6:
/usr/include/stdio.h:52:9: error: unknown type name ‘__gnuc_va_list’
   52 | typedef __gnuc_va_list va_list;

Or maybe <stdarg.h> is the right place by passing all those include
directories to userspace helpers is the wrong thing to do.