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

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Message-ID: <818f8945-f990-a770-476e-f82bdc77dbda@intel.com>
Date:   Fri, 16 Mar 2018 12:24:44 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org
Cc:     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

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?

View attachment "revert-b68a68d3dcc15ebbf23cbe91af1abf57591bd96b.patch" of type "text/x-patch" (2643 bytes)