forked from Minki/linux
4a084ecfc8
The 'perf report' tool does not display the addresses of kernel module symbols correctly. For example symbol qeth_send_ipa_cmd in kernel module qeth.ko has this relative address for function qeth_send_ipa_cmd(): [root@s8360047 linux]# nm -g drivers/s390/net/qeth.ko | fgrep send_ipa_cmd 0000000000013088 T qeth_send_ipa_cmd The module is loaded at address: [root@s8360047 linux]# cat /sys/module/qeth/sections/.text 0x000003ff80296d20 [root@s8360047 linux]# This should result in a start address of: 0x13088 + 0x3ff80296d20 = 0x3ff802a9da8 Using crash to verify the address on a live system: [root@s8360046 linux]# crash vmlinux crash 7.1.9++ Copyright (C) 2002-2016 Red Hat, Inc. Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation [...] crash> mod -s qeth drivers/s390/net/qeth.ko MODULE NAME SIZE OBJECT FILE 3ff8028d700 qeth 151552 drivers/s390/net/qeth.ko crash> sym qeth_send_ipa_cmd 3ff802a9da8 (T) qeth_send_ipa_cmd [qeth] /root/linux/drivers/s390/net/qeth_core_main.c: 2944 crash> Now perf report displays the address of symbol qeth_send_ipa_cmd: symbol__new: qeth_send_ipa_cmd 0x130f0-0x132ce There is a difference of 0x68 between the entry in the symbol table (see nm command above) and perf. The difference is from the offset the .text segment of qeth.ko: [root@s8360047 perf]# readelf -a drivers/s390/net/qeth.ko Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align [ 0] NULL 0000000000000000 00000000 0000000000000000 0000000000000000 0 0 0 [ 1] .note.gnu.build-i NOTE 0000000000000000 00000040 0000000000000024 0000000000000000 A 0 0 4 [ 2] .text PROGBITS 0000000000000000 00000068 000000000001c8a0 0000000000000000 AX 0 0 8 As seen the .text segment has an offset of 0x68 with start address 0x0. Therefore 0x68 is added to the address of qeth_send_ipa_cmd and thus 0x13088 + 0x68 = 0x130f0 is displayed. This is wrong, perf report needs to display the start address of symbol qeth_send_ipa_cmd at 0x13088 + qeth.ko.text section start address. The qeth.ko module .text start address is available in the qeth.ko DSO map. Just identify the kernel module symbols and correct the addresses. With the fix I see this correct address for symbol: symbol__new: qeth_send_ipa_cmd 0x3ff802a9da8-0x3ff802a9f86 Signed-off-by: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com> Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com> Cc: Zvonko Kosic <zvonko.kosic@de.ibm.com> LPU-Reference: 20170803134902.47207-1-tmricht@linux.vnet.ibm.com Link: http://lkml.kernel.org/n/tip-q8lktlpoxb5e3dj52u1s1rw4@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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Makefile |