linux-kernel - Re: [PATCH] jump_label: align jump

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Message-ID: <20170227175826.2ddceec2@gandalf.local.home>
Date:   Mon, 27 Feb 2017 17:58:26 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     David Daney <ddaney@...iumnetworks.com>
Cc:     linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>,
        Jason Baron <jbaron@...mai.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, Ingo Molnar <mingo@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anton Blanchard <anton@...ba.org>,
        Rabin Vincent <rabin@....in>,
        Russell King <linux@...linux.org.uk>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Zhigang Lu <zlu@...hip.com>
Subject: Re: [PATCH] jump_label: align jump_entry table to at least 4-bytes

On Mon, 27 Feb 2017 14:45:37 -0800
David Daney <ddaney@...iumnetworks.com> wrote:

> On 02/27/2017 02:36 PM, Steven Rostedt wrote:
> > On Mon, 27 Feb 2017 14:21:21 -0800
> > David Daney <ddaney@...iumnetworks.com> wrote:
> >  
> >> See attached for mips.  It seems to do the right thing.
> >>
> >> I leave it as an exercise to the reader to fix the other architectures.
> >>
> >> Consult your own  binutils experts to verify that what I say is true.  
> >
> > It may still just be safer to do the pointers instead. That way we
> > don't need to worry about some strange arch or off by one binutils
> > messing it up.  
> 
> Obviously it is your choice, but this is bog standard ELF linking.  In 
> theory even the arrays of power-of-2 sized objects should also supply an 
> entity size.  Think __ex_table and its ilk.
> 
> 
> The benefit of supplying an entsize is that you don't have to change the 
> structure of the existing code and risk breaking something in the process.

I agree that this may be the better answer. The issue tracepoints had
is that they were defined in C with a "section" attribute. I'm not sure
you can pass various section attributes via a gcc section attribute.

-- Steve