linux-kernel - Re: [PATCH 03/11] signal/openrisc: Fix do_unaligned

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Date:   Fri, 12 Jan 2018 11:37:40 -0600
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Stafford Horne <shorne@...il.com>
Cc:     linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Oleg Nesterov <oleg@...hat.com>, linux-arch@...r.kernel.org,
        stable@...r.kernel.org, Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Arnd Bergmann <arnd@...db.de>, openrisc@...ts.librecores.org
Subject: Re: [PATCH 03/11] signal/openrisc: Fix do_unaligned_access to send the proper signal

Stafford Horne <shorne@...il.com> writes:

> On Thu, Jan 11, 2018 at 06:59:32PM -0600, Eric W. Biederman wrote:
>> While reviewing the signal sending on openrisc the do_unaligned_access
>> function stood out because it is obviously wrong.  A comment about an
>> si_code set above when actually si_code is never set.  Leading to a
>> random si_code being sent to userspace in the event of an unaligned
>> access.
>> 
>> Looking further SIGBUS BUS_ADRALN is the proper pair of signal and
>> si_code to send for an unaligned access. That is what other
>> architectures do and what is required by posix.
>> 
>> Given that do_unaligned_access is broken in a way that no one can be
>> relying on it on openrisc fix the code to just do the right thing.
>
> Thanks, this looks good to me.
>
> Acked-by: Stafford Horne <shorne@...il.com>
>
> I see you have a series of related issues, so I guess you want to get them
> merged together.  Let me know if I should put this patch onto my queue
> seperately.

Yes,  I have a follow on patch that restructures the code that fills out
siginfo, and makes the it a little less error prone.  I am hoping to
merge all of it in the next merge window.  *Fingers crossed*

And having it all in one tree will facilitate that.

> Trivia: this looks to have been copied from the mm page fault handling code,
> hence the strange comment.
>
>   $ grep -r "info.si_code has been set above" arch/
>   arch/cris/mm/fault.c:           /* info.si_code has been set above */
>   arch/m32r/mm/fault.c:           /* info.si_code has been set above */
>   arch/mn10300/mm/fault.c:                /* info.si_code has been set above */
>   arch/openrisc/mm/fault.c:               /* info.si_code has been set above */
>   arch/openrisc/kernel/traps.c:           /* info.si_code has been set above */
>   arch/arc/mm/fault.c:            /* info.si_code has been set above */
>   arch/xtensa/mm/fault.c:         /* info.si_code has been set above */
>   arch/mips/mm/fault.c:           /* info.si_code has been set above */
>   arch/score/mm/fault.c:          /* info.si_code has been set above */
>   arch/frv/mm/fault.c:            /* info.si_code has been set above */
>

It looks like it.    When I look at those I can actually find the
si_code being set higher up in the code.  It looks like the si_code
value was missed when this work was done.

Eric