linux-kernel - Re: [PATCH 05/20] arm64: rename COMPAT to AARCH32

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Date:   Wed, 21 Jun 2017 02:10:03 +0300
From:   Yury Norov <ynorov@...iumnetworks.com>
To:     James Morse <james.morse@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Andrew Pinski <pinskia@...il.com>,
        Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
        Adam Borowski <kilobyte@...band.pl>,
        Chris Metcalf <cmetcalf@...hip.com>,
        Steve Ellcey <sellcey@...iumnetworks.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@...aro.org>,
        Ramana Radhakrishnan <ramana.gcc@...glemail.com>,
        Florian Weimer <fweimer@...hat.com>,
        Bamvor Zhangjian <bamvor.zhangjian@...wei.com>,
        Andreas Schwab <schwab@...e.de>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        schwidefsky@...ibm.com, broonie@...nel.org,
        Joseph Myers <joseph@...esourcery.com>,
        christoph.muellner@...obroma-systems.com, szabolcs.nagy@....com,
        klimov.linux@...il.com, Nathan_Lynch@...tor.com, agraf@...e.de,
        Prasun.Kapoor@...iumnetworks.com, geert@...ux-m68k.org,
        philipp.tomsich@...obroma-systems.com, manuel.montezelo@...il.com,
        linyongting@...wei.com, davem@...emloft.net,
        zhouchengming1@...wei.com, Andrew Pinski <apinski@...ium.com>,
        Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>
Subject: Re: [PATCH 05/20] arm64: rename COMPAT to AARCH32_EL0 in Kconfig

On Mon, Jun 19, 2017 at 04:58:16PM +0100, James Morse wrote:
> Hi Yury,
> 
> On 04/06/17 12:59, Yury Norov wrote:
> > From: Andrew Pinski <apinski@...ium.com>
> > 
> > In this patchset  ILP32 ABI support is added. Additionally to AARCH32,
> > which is binary-compatible with ARM, ILP32 is (mostly) ABI-compatible.
> > 
> > From now, AARCH32_EL0 (former COMPAT) config option means the support of
> > AARCH32 userspace, ARM64_ILP32 - support of ILP32 ABI (see next patches),
> > and COMPAT indicates that one of them, or both, is enabled.
> > 
> > Where needed, CONFIG_COMPAT is changed over to use CONFIG_AARCH32_EL0 instead
> 
> Nit: You have 'COMPAT' around compat_hwcap_str's definition, but its only user
> is wrapped in 'AARCH32_EL0'.
> 
> 
> After this patch
> arch/arm64/kernel/perf_callchain.c::perf_callchain_user() still has:
> >	if (!compat_user_mode(regs)) {
> >		/* AARCH64 mode */
> ...
> >	} else {
> > #ifdef CONFIG_COMPAT
> > 		/* AARCH32 compat mode */
> ...
> > #endif
> >	}
> 
> I think this one should become CONFIG_AARCH32_EL0. compat to this code means the
> fp is 'compat_fp' in x11, and it should read a 32bit call chain from user-space.
 
Thanks, will fix it. 

> This is confusing as 'is_compat_task()' matches one of aarch32 or ilp32, but
> compat_user_mode(regs) only matches aarch32 as it checks the saved spsr. I can't
> see any problem caused by this today, but its going to bite someone in the
> future. Can this be renamed aarch32_user_mode()? (turns out 'a32' is the name of
> just one of aarch32's instruction sets[0].)

compat_thumb_mode may be also renamed, and compat_setup_frame and
compat_setup_rt_frame, and some others. If you think that it may
confuse, I'll do rename.

Yury