Re: [PATCH 18/20] arm64: ptrace: handle ptrace_request differently for aarch32 and ilp32

From: James Morse <james.morse@arm.com>
To: Yury Norov <ynorov@caviumnetworks.com>, zhouchengming1@huawei.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>,
	Adam Borowski <kilobyte@angband.pl>,
	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,
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	Prasun.Kapoor@caviumnetworks.com, geert@linux-m68k.org,
	philipp.tomsich@theobroma-systems.com,
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	davem@davemloft.net,
	Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Subject: Re: [PATCH 18/20] arm64: ptrace: handle ptrace_request differently for aarch32 and ilp32
Date: Tue, 27 Jun 2017 11:12:26 +0100	[thread overview]
Message-ID: <59522F8A.4010709@arm.com> (raw)
In-Reply-To: <20170623222852.hao3gi7ppwexu7wq@yury-thinkpad>

Hi Yury, Zhou,

On 23/06/17 23:28, Yury Norov wrote:
> 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?

I've reproduced this on big endian compat-aarch32: yes its broken. I will respin
Zhou's patch as a fix.

Thanks,

James