linux-kernel - Re: [PATCH 13/22] signal: Move addr_lsb into the

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Date:   Fri, 16 Mar 2018 15:06:55 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Oleg Nesterov <oleg@...hat.com>, linux-arch@...r.kernel.org,
        Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH 13/22] signal: Move addr_lsb into the _sigfault union for clarity

Dave Hansen <dave.hansen@...el.com> writes:

> On 03/16/2018 12:00 PM, Dave Hansen wrote:
>> On 01/15/2018 04:40 PM, Eric W. Biederman wrote:
>>> The addr_lsb fields is only valid and available when the
>>> signal is SIGBUS and the si_code is BUS_MCEERR_AR or BUS_MCEERR_AO.
>>> Document this with a comment and place the field in the _sigfault union
>>> to make this clear.
>>>
>>> All of the fields stay in the same physical location so both the old
>>> and new definitions of struct siginfo will continue to work.
>> 
>> This breaks the ABI and breaks protection keys.  The physical locations
>> *DO* change.
>> 
>> Before this patch:
>> 
>> #define si_pkey         _sifields._sigfault._pkey
>> (gdb) print &((siginfo_t *)0)->_sifields._sigfault._pkey
>> $1 = (__u32 *) 0x20 <irq_stack_union+32>
>> 
>> and after:
>> 
>> +#define si_pkey                _sifields._sigfault._addr_pkey._pkey
>> (gdb) print &((siginfo_t *)0)->_sifields._sigfault._addr_pkey._pkey
>> $1 = (__u32 *) 0x1c
>> 
>> Can we revert this, please?
>
> It does not revert cleanly so I reverted it manually.  Patch doing that
> is attached.  Should we do this, or is there a better option?

Please see:
859d880cf544 ("signal: Correct the offset of si_pkey in struct siginfo")

Eric