Message-ID: <59522F8A.4010709@arm.com>
Date: Tue, 27 Jun 2017 11:12:26 +0100
From: James Morse <james.morse@arm.com>
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To: Yury Norov <ynorov@caviumnetworks.com>, zhouchengming1@huawei.com
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Subject: Re: [PATCH 18/20] arm64: ptrace: handle ptrace_request differently
 for aarch32 and ilp32
References: <20170604120009.342-1-ynorov@caviumnetworks.com> <20170604120009.342-19-ynorov@caviumnetworks.com> <594D49E9.7090900@arm.com> <20170623222852.hao3gi7ppwexu7wq@yury-thinkpad>
In-Reply-To: <20170623222852.hao3gi7ppwexu7wq@yury-thinkpad>
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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