Date: Sat, 24 Jun 2017 01:28:52 +0300
From: Yury Norov <ynorov@caviumnetworks.com>
To: James Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        Andrew Pinski <pinskia@gmail.com>,
        Andrew Pinski <Andrew.Pinski@caviumnetworks.com>,
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        Chris Metcalf <cmetcalf@ezchip.com>,
        Steve Ellcey <sellcey@caviumnetworks.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>,
        Ramana Radhakrishnan <ramana.gcc@googlemail.com>,
        Florian Weimer <fweimer@redhat.com>,
        Bamvor Zhangjian <bamvor.zhangjian@huawei.com>,
        Andreas Schwab <schwab@suse.de>, Chris Metcalf <cmetcalf@mellanox.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>, schwidefsky@de.ibm.com,
        broonie@kernel.org, Joseph Myers <joseph@codesourcery.com>,
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        Prasun.Kapoor@caviumnetworks.com, geert@linux-m68k.org,
        philipp.tomsich@theobroma-systems.com, manuel.montezelo@gmail.com,
        linyongting@huawei.com, davem@davemloft.net, zhouchengming1@huawei.com,
        Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Subject: Re: [PATCH 18/20] arm64: ptrace: handle ptrace_request differently
 for aarch32 and ilp32
Message-ID: <20170623222852.hao3gi7ppwexu7wq@yury-thinkpad>
References: <20170604120009.342-1-ynorov@caviumnetworks.com>
 <20170604120009.342-19-ynorov@caviumnetworks.com>
 <594D49E9.7090900@arm.com>
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On Fri, Jun 23, 2017 at 06:03:37PM +0100, James Morse wrote:
> Hi Yury,
> 
> On 04/06/17 13:00, Yury Norov wrote:
> > ILP32 has context-related structures different from both aarch32 and
> > aarch64/lp64. In this patch compat_arch_ptrace() renamed to
> > compat_a32_ptrace(), and compat_arch_ptrace() only makes choice between
> > compat_a32_ptrace() and new compat_ilp32_ptrace() handler.
> > 
> > compat_ilp32_ptrace() calls generic compat_ptrace_request() for all
> > requests except PTRACE_GETSIGMASK and PTRACE_SETSIGMASK, which need
> > special handling.
> 
> Can you elaborate on this special handling?
> 
> How come we don't need to wrap PTRACE_{G,S}ETSIGMASK for aarch32 compat?
> >From kernel/signal32.c that uses compat_sigset_t too.
> 
> It looks like aarch64, ilp32 and aarch32 all use the same size sigset_t,
> so doesn't compat_ptrace_request() already do everything we need?
> 
> ...
> 
> Is this fixing an endian problem? If so, can we document it as such. Do we
> already have the same bug for aarch32 compat?

Originally, the problem was found by Zhou Chengming: https://lkml.org/lkml/2016/6/27/18
But I think you right, this is the fix for endian.

It lookd like aarch32 is buggy, but IIUC to confirm it, the BE arm64
machine is needed. I use qemu and AFAIR it has no BE support.

Zhou, can you test it on your machine and if the bug will be reproduced,
send the patch for aarch32?

Yury