Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field

From	Stephen Rothwell <sfr@canb.auug.org.au>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field
Date	2016-02-28 00:30 +0100
Message-ID	<r6Wtc-1Rk-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <r6uGC-6KV-23@gated-at.bofh.it> <r6yTU-1pV-13@gated-at.bofh.it> <r6LxL-2kH-1@gated-at.bofh.it> <r6Szf-7Cl-1@gated-at.bofh.it> <r6SSC-7LP-11@gated-at.bofh.it>
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Hi H.,

On Sat, 27 Feb 2016 11:35:08 -0800 "H. Peter Anvin" <hpa@zytor.com> wrote:
>
> On February 27, 2016 11:16:44 AM PST, Dave Hansen <dave@sr71.net> wrote:
> >On 02/27/2016 03:41 AM, Ingo Molnar wrote:  
> >> * Stephen Rothwell <sfr@canb.auug.org.au> wrote:  
> >>> > On Fri, 26 Feb 2016 09:44:00 -0800 "H. Peter Anvin"  
> ><hpa@zytor.com> wrote:  
> >>>> > > __u64 is okay, "unsigned long" is really messy in the presence  
> >of 32-on-64 bit ABIs...  
> >>> > 
> >>> > Yeah, but unfortunately, any 64 bit scalar type here will change  
> >the  
> >>> > alignment of the enclosing unions on (some) 32 bit platforms and  
> >thus  
> >>> > break the ABI.  
> >> Then a different solution has to be found.  
> >
> >I've acked Stephen's initial patch changing the 'u64' to an 'int'.  x86
> >only needs 4 bits, and in the remote chance that a future
> >implementation
> >needed more space, we could easily add a second 32-bit field "_pkey_hi"
> >or something that wouldn't have the alignment issues of a true 64-bit
> >type.
> >
> >How should we get Stephen's patch in to the tip tree?  
> 
> u32?

It would have to be __u32, but we already use int and unsigned int
extensively in the siginfo structure (which are both always assumed to
be 32 bits).  So "unsigned int" probably makes most sense.

I will submit that patch - with Dave's Ack.
-- 
Cheers,
Stephen Rothwell

Thread

[PATCH] x86, pkeys: fix siginfo ABI breakage from new field Dave Hansen <dave@sr71.net> - 2016-02-26 18:40 +0100
  Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field "H. Peter Anvin" <hpa@zytor.com> - 2016-02-26 18:50 +0100
    Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Stephen Rothwell <sfr@canb.auug.org.au> - 2016-02-26 23:20 +0100
      Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Ingo Molnar <mingo@kernel.org> - 2016-02-27 12:50 +0100
        Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Dave Hansen <dave@sr71.net> - 2016-02-27 20:20 +0100
          Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field "H. Peter Anvin" <hpa@zytor.com> - 2016-02-27 20:40 +0100
            Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Stephen Rothwell <sfr@canb.auug.org.au> - 2016-02-28 00:30 +0100
              [PATCH v2] signals, pkeys: make si_pkey 32 bits Stephen Rothwell <sfr@canb.auug.org.au> - 2016-02-28 00:50 +0100
                Re: [PATCH v2] signals, pkeys: make si_pkey 32 bits Ingo Molnar <mingo@kernel.org> - 2016-02-29 09:00 +0100
              Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Ingo Molnar <mingo@kernel.org> - 2016-02-29 09:10 +0100
                Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Stephen Rothwell <sfr@canb.auug.org.au> - 2016-03-01 00:00 +0100

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