linux-kernel - Re: Wrong module .text address in 4.16.0

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Date:   Mon, 16 Apr 2018 08:23:27 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Thomas-Mich Richter <tmricht@...ux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jessica Yu <jeyu@...nel.org>
Subject: Re: Wrong module .text address in 4.16.0

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@...lp76 ~]# lsmod
> Module                  Size  Used by
> qeth_l2                94208  1
> ...
> 
> [root@...lp76 ~]# cat /proc/modules | egrep '^qeth_l2'
> qeth_l2 94208 1 - Live 0x000003ff80401000   <---- This is the correct address in memory
> [root@...lp76 ~]# cat /sys/module/qeth_l2/sections/.text 
> 0x0000000018ea8363      <---- This is the wrong address
> [root@...lp76 ~]# 
> 
> 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@...lp76 linux]# sysctl -a | fgrep kernel.kptr_restrict
> kernel.kptr_restrict = 0
> [root@...lp76 linux]#
> 
> I wonder if somebody else has seen this issue?
> Ideas how to fix this?
> 
> Thanks
>