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Re: [PATCH] module: set __jump_table alignment to 8

Started bySteven Rostedt <rostedt@goodmis.org>
First post2017-03-02 19:20 +0100
Last post2017-03-03 00:00 +0100
Articles 3 — 2 participants

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  Re: [PATCH] module: set __jump_table alignment to 8 Steven Rostedt <rostedt@goodmis.org> - 2017-03-02 19:20 +0100
    Re: [PATCH] module: set __jump_table alignment to 8 Jessica Yu <jeyu@redhat.com> - 2017-03-02 19:30 +0100
      Re: [PATCH] module: set __jump_table alignment to 8 Jessica Yu <jeyu@redhat.com> - 2017-03-03 00:00 +0100

#1591382 — Re: [PATCH] module: set __jump_table alignment to 8

FromSteven Rostedt <rostedt@goodmis.org>
Date2017-03-02 19:20 +0100
SubjectRe: [PATCH] module: set __jump_table alignment to 8
Message-ID<tgDuy-67m-17@gated-at.bofh.it>
Can I get an Ack from a module maintainer?

Thanks!

-- Steve


On Wed,  1 Mar 2017 14:04:53 -0800
David Daney <david.daney@cavium.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@cavium.com>
> Tested-by: Sachin Sant <sachinp@linux.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)) }
>  }

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#1591387

FromJessica Yu <jeyu@redhat.com>
Date2017-03-02 19:30 +0100
Message-ID<tgDEe-6cP-21@gated-at.bofh.it>
In reply to#1591382
+++ Steven Rostedt [02/03/17 13:11 -0500]:
>
>Can I get an Ack from a module maintainer?

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

Thanks!

Jessica

>On Wed,  1 Mar 2017 14:04:53 -0800
>David Daney <david.daney@cavium.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@cavium.com>
>> Tested-by: Sachin Sant <sachinp@linux.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)) }
>>  }
>

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#1591530

FromJessica Yu <jeyu@redhat.com>
Date2017-03-03 00:00 +0100
Message-ID<tgHRw-ro-7@gated-at.bofh.it>
In reply to#1591387
+++ David Daney [02/03/17 11:24 -0800]:
>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@redhat.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?

Sure thing. Thanks for the heads up!

Jessica

>>>On Wed,  1 Mar 2017 14:04:53 -0800
>>>David Daney <david.daney@cavium.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@cavium.com>
>>>>Tested-by: Sachin Sant <sachinp@linux.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)) }
>>>> }
>>>
>

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