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