linux-kernel - Re: [PATCH] module: set __jump

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Message-ID: <20170302131119.6f52203f@gandalf.local.home>
Date:   Thu, 2 Mar 2017 13:11:19 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jessica Yu <jeyu@...hat.com>, Rusty Russell <rusty@...tcorp.com.au>
Cc:     David Daney <david.daney@...ium.com>,
        Jason Baron <jbaron@...mai.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sachin Sant <sachinp@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
        linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Russell King <linux@...linux.org.uk>,
        Rabin Vincent <rabin@....in>,
        Paul Mackerras <paulus@...ba.org>,
        Anton Blanchard <anton@...ba.org>,
        Ingo Molnar <mingo@...nel.org>, Zhigang Lu <zlu@...hip.com>
Subject: Re: [PATCH] module: set __jump_table alignment to 8


Can I get an Ack from a module maintainer?

Thanks!

-- Steve


On Wed,  1 Mar 2017 14:04:53 -0800
David Daney <david.daney@...ium.com> wrote:

> For powerpc the __jump_table section in modules is not aligned, this
> causes a WARN_ON() splat when loading a module containing a __jump_table.
> 
> Strict alignment became necessary with commit 3821fd35b58d
> ("jump_label: Reduce the size of struct static_key"), currently in
> linux-next, which uses the two least significant bits of pointers to
> __jump_table elements.
> 
> Fix by forcing __jump_table to 8, which is the same alignment used for
> this section in the kernel proper.
> 
> Signed-off-by: David Daney <david.daney@...ium.com>
> Tested-by: Sachin Sant <sachinp@...ux.vnet.ibm.com>
> ---
>  scripts/module-common.lds | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/scripts/module-common.lds b/scripts/module-common.lds
> index 73a2c7d..53234e8 100644
> --- a/scripts/module-common.lds
> +++ b/scripts/module-common.lds
> @@ -19,4 +19,6 @@ SECTIONS {
>  
>  	. = ALIGN(8);
>  	.init_array		0 : { *(SORT(.init_array.*)) *(.init_array) }
> +
> +	__jump_table		0 : ALIGN(8) { KEEP(*(__jump_table)) }
>  }