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

[Yury Norov]

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