From: David Daney <ddaney@caviumnetworks.com>
To: Jason Baron <jbaron@akamai.com>,
David Daney <ddaney@caviumnetworks.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sachin Sant <sachinp@linux.vnet.ibm.com>
Cc: linux-mips@linux-mips.org, Chris Metcalf <cmetcalf@mellanox.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Russell King <linux@armlinux.org.uk>,
Ralf Baechle <ralf@linux-mips.org>,
LKML <linux-kernel@vger.kernel.org>, Rabin Vincent <rabin@rab.in>,
Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>,
linux-arm-kernel@lists.infradead.org, Zhigang Lu <zlu@ezchip.com>
Subject: Re: [PATCH] jump_label: align jump_entry table to at least 4-bytes
Date: Tue, 28 Feb 2017 12:15:10 -0800 [thread overview]
Message-ID: <912fa97a-aa1d-c0e4-dc83-fc5c745db1c1@caviumnetworks.com> (raw)
In-Reply-To: <542488db-5c59-afa5-6d1d-a437c87bc613@akamai.com>
[-- Attachment #1: Type: text/plain, Size: 2064 bytes --]
On 02/28/2017 11:34 AM, Jason Baron wrote:
>
>
> On 02/28/2017 02:22 PM, David Daney wrote:
>> On 02/28/2017 11:05 AM, David Daney wrote:
>>> On 02/28/2017 10:39 AM, Jason Baron wrote:
>>>>
>> [...]
>>>>> I suspect that the alignment of the __jump_table section in the .ko
>>>>> files is not correct, and you are seeing some sort of problem due to
>>>>> that.
>>>>>
>>>>>
>>>>
>>>> Hi,
>>>>
>>>> Yes, if you look at the trace that Sachin sent the module being loaded
>>>> that does the WARN_ON() is nfsd.ko.
>>>>
>>>> That module from Sachin's trace has:
>>>>
>>>> [31] __jump_table PROGBITS 0000000000000000 03fd77 0000c0
>>>> 18 WAM 0 0 1
>>>
>>> The problem is then the section alignment (last column) for power.
>>>
>>> On mips with no patches applied, we get:
>>>
>>> [17] __jump_table PROGBITS 0000000000000000 00d2c0 000048
>>> 00 WA 0 0 8
>>>
>>> Look, proper alignment!
>>>
>>> The question I have is why do the power ".llong" and ".long" assembler
>>> directives not force section alignment? Is there an alternative that
>>> could be used that would result in the proper alignment? Would ".word"
>>> work?
>>>
>>> If not, then I would say patch only power with your balign thing. 8-byte
>>> alignment for 64-bit kernel, 4-byte alignment for 32-bit kernel
>>>
>>
>> I think the proper fix is either:
>>
>> A) Modify scripts/module-common.lds to force __jump_table alignment for
>> all architectures.
>>
>> B) Add arch/powerpc/kernel/module.lds to force __jump_table alignment
>> for powerpc only.
>>
>> David.
>>
>>
>
> Ok, I can try adding it to the linger script.
>
> FWIW, here is my before and after with the .balign thing for the nfsd.ko
> module on powperc (using a cross-compiler):
>
> before:
>
> [31] __jump_table PROGBITS 0000000000000000 03ee3e 0000f0
> 00 WA 0 0 1
>
> after:
>
> [31] __jump_table PROGBITS 0000000000000000 03ee40 0000f0
> 00 WA 0 0 4
>
Try the (lightly tested) attached.
If it works and Steven likes it, perhaps someone can merge it.
David.
[-- Attachment #2: 0001-module-set-__jump_table-alignment-to-8.patch --]
[-- Type: text/x-patch, Size: 916 bytes --]
>From 89d4deafbc920351b93afb1ac4b4124995e1f19d Mon Sep 17 00:00:00 2001
From: David Daney <david.daney@cavium.com>
Date: Tue, 28 Feb 2017 12:10:02 -0800
Subject: [PATCH] module: set __jump_table alignment to 8
For powerpc the __jump_table section in modules is not aligned, this
causes an OOPS when loading a module containing a __jump_table.
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>
---
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)) }
}
--
2.9.3
next prev parent reply other threads:[~2017-02-28 20:17 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-27 18:49 [PATCH] jump_label: align jump_entry table to at least 4-bytes Jason Baron
2017-02-27 18:57 ` David Daney
2017-02-27 19:18 ` Jason Baron
2017-02-27 19:59 ` David Daney
2017-02-27 21:06 ` Steven Rostedt
2017-02-27 21:41 ` David Daney
2017-02-27 22:09 ` Steven Rostedt
2017-02-27 22:21 ` David Daney
2017-02-27 22:36 ` Steven Rostedt
2017-02-27 22:45 ` David Daney
2017-02-27 22:50 ` Jason Baron
2017-02-27 23:34 ` David Daney
2017-02-28 4:55 ` Sachin Sant
2017-02-28 16:21 ` Steven Rostedt
2017-02-28 18:16 ` David Daney
2017-02-28 18:39 ` Jason Baron
2017-02-28 19:05 ` David Daney
2017-02-28 19:22 ` David Daney
2017-02-28 19:34 ` Jason Baron
2017-02-28 20:15 ` David Daney [this message]
2017-02-28 22:41 ` Jason Baron
2017-03-01 6:34 ` Michael Ellerman
2017-03-01 16:40 ` David Daney
2017-03-01 20:02 ` Jason Baron
2017-03-01 21:12 ` David Daney
2017-03-01 7:12 ` Sachin Sant
2017-02-27 22:58 ` Steven Rostedt
2017-03-06 2:16 ` [PATCH] MIPS: jump_lable: Give __jump_table elements an entsize kbuild test robot
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