lkml.org 
[lkml]   [2018]   [Apr]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Wrong module .text address in 4.16.0
From
Date
On 04/16/2018 08:23 AM, Christian Borntraeger wrote:
> FWIW, this breaks at least perf capability to resolve module symbols.
> Adding some more CCs for perf and module.
>
>
> On 04/16/2018 07:51 AM, Thomas-Mich Richter wrote:
>> I just installed 4.16.0 and discovered the module .text address is
>> wrong. It happens on s390 and x86 platforms. I have not tested others.
>>
>> Here is the issue, I have used module qeth_l2 on s390 which is the
>> ethernet device driver:
>>
>> root@s35lp76 ~]# lsmod
>> Module Size Used by
>> qeth_l2 94208 1
>> ...
>>
>> [root@s35lp76 ~]# cat /proc/modules | egrep '^qeth_l2'
>> qeth_l2 94208 1 - Live 0x000003ff80401000 <---- This is the correct address in memory
>> [root@s35lp76 ~]# cat /sys/module/qeth_l2/sections/.text
>> 0x0000000018ea8363 <---- This is the wrong address
>> [root@s35lp76 ~]#
>>
>> File /sys/module/qeth_l2/sections/.text displays a very strange
>> address which is definitely wrong. It should be something like
>> 0x000003ff80401xxx.
>>
>> Same on x86.
>>
>> I have checked file kernel/module.c function add_sect_attrs()
>> and it calls module_sect_show() when the sysfs file is read.
>> And module_sect_show() uses
>>
>> sprintf(buf, "0x%pK\n", (void *)sattr->address);
>>
>> and my sysctl setting should be correct:
>> [root@s35lp76 linux]# sysctl -a | fgrep kernel.kptr_restrict
>> kernel.kptr_restrict = 0
>> [root@s35lp76 linux]#
>>
>> I wonder if somebody else has seen this issue?
>> Ideas how to fix this?
>>
>> Thanks
>>

This new behavior actually break perf report/record/top on s390 for
module address resolution. On s390 each module .text segment actually
start at some offset after the module load addess shown with
/proc/modules. That is the reason why we need
/sys/module/<module-name>/sections/.text to get the actual
.text segment start address.

--
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

\
 
 \ /
  Last update: 2018-04-16 13:41    [W:0.045 / U:6.252 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site