linux-kernel - Re: [PATCH] uapi: fix asm/signal.h userspace compilation errors

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Date:   Thu, 2 Mar 2017 18:48:45 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Carlos O'Donell <carlos@...temhalted.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Haavard Skinnemoen <hskinnemoen@...il.com>,
        Hans-Christian Egtvedt <egtvedt@...fundet.no>,
        Mikael Starvik <starvik@...s.com>,
        Jesper Nilsson <jesper.nilsson@...s.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        David Howells <dhowells@...hat.com>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
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        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] uapi: fix asm/signal.h userspace compilation errors

On Thu, Mar 02, 2017 at 10:22:18AM -0500, Carlos O'Donell wrote:
> On Wed, Mar 1, 2017 at 11:20 AM, Arnd Bergmann <arnd@...db.de> wrote:
> > On Sun, Feb 26, 2017 at 2:01 AM, Dmitry V. Levin <ldv@...linux.org> wrote:
> >> Include <stddef.h> (guarded by #ifndef __KERNEL__) to fix asm/signal.h
> >> userspace compilation errors like this:
> >>
> >> /usr/include/asm/signal.h:126:2: error: unknown type name 'size_t'
> >>   size_t ss_size;
> >>
> >> As no uapi header provides a definition of size_t, inclusion
> >> of <stddef.h> seems to be the most conservative fix available.
[...]
> > I'm not sure if this is the best fix. We generally should not include one
> > standard header from another standard header. Would it be possible
> > to use __kernel_size_t instead of size_t?
> 
> In glibc we handle this with special use of __need_size_t with GCC's
> provided stddef.h.
> 
> For example glibc's signal.h does this:
> 
> # define __need_size_t
> # include <stddef.h>

Just to make it clear, do you suggest this approach for asm/signal.h as well?

[...]
> Changing the fundamental type causes the issues you see in patch v2
> where sizeof(size_t) < sizeof(__kernel_size_t).
> 
> It will only lead to problem substituting the wrong type.

I don't see any appetite for creating more ABIs like x32 with
sizeof(size_t) < sizeof(__kernel_size_t), so v2 approach
is not going to be any different from v1 in maintenance.


-- 
ldv

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