From 4a084ecfc8217bca1ab074feb4bc8a2c0f828960 Mon Sep 17 00:00:00 2001 From: Thomas Richter Date: Thu, 3 Aug 2017 15:49:01 +0200 Subject: perf report: Fix module symbol adjustment for s390x 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 Reviewed-by: Arnaldo Carvalho de Melo Cc: Hendrik Brueckner Cc: Thomas-Mich Richter Cc: Zvonko Kosic 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 --- tools/perf/util/symbol.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'tools/perf/util/symbol.h') diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h index b221671070e2..d00a012cfdfb 100644 --- a/tools/perf/util/symbol.h +++ b/tools/perf/util/symbol.h @@ -343,6 +343,9 @@ int setup_intlist(struct intlist **list, const char *list_str, #ifdef HAVE_LIBELF_SUPPORT bool elf__needs_adjust_symbols(GElf_Ehdr ehdr); void arch__sym_update(struct symbol *s, GElf_Sym *sym); +void arch__adjust_sym_map_offset(GElf_Sym *sym, + GElf_Shdr *shdr __maybe_unused, + struct map *map __maybe_unused); #endif #define SYMBOL_A 0 -- cgit v1.2.3