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

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Message-ID: <f38431ab-ad33-ac14-03b5-7cb4a172be64@caviumnetworks.com>
Date:   Thu, 2 Mar 2017 11:24:23 -0800
From:   David Daney <ddaney@...iumnetworks.com>
To:     Jessica Yu <jeyu@...hat.com>, 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

On 03/02/2017 10:26 AM, Jessica Yu wrote:
> +++ 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

Thanks Jessica,

Can you also add scripts/module-common.lds to MAINTAINERS so that 
get_maintainers.pl will indicate that Jessica Yu and Rusty Russell be 
CCed on things like this in the future?


>
>> 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)) }
>>>  }
>>