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

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Message-ID: <20170302182625.GB13268@packer-debian-8-amd64.digitalocean.com>
Date:   Thu, 2 Mar 2017 13:26:25 -0500
From:   Jessica Yu <jeyu@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Rusty Russell <rusty@...tcorp.com.au>,
        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

+++ Steven Rostedt [02/03/17 13:11 -0500]:
>
>Can I get an Ack from a module maintainer?

Acked-by: Jessica Yu <jeyu@...hat.com>

Thanks!

Jessica

>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)) }
>>  }
>