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Subject[tip:perf/core] perf report: Fix module symbol adjustment for s390x
Commit-ID:  4a084ecfc8217bca1ab074feb4bc8a2c0f828960
Gitweb: http://git.kernel.org/tip/4a084ecfc8217bca1ab074feb4bc8a2c0f828960
Author: Thomas Richter <tmricht@linux.vnet.ibm.com>
AuthorDate: Thu, 3 Aug 2017 15:49:01 +0200
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 11 Aug 2017 16:06:32 -0300

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 <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>
---
tools/perf/arch/s390/util/sym-handling.c | 7 +++++++
tools/perf/util/symbol-elf.c | 8 +++++++-
tools/perf/util/symbol.h | 3 +++
3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/perf/arch/s390/util/sym-handling.c b/tools/perf/arch/s390/util/sym-handling.c
index b6cd056..e103f6e 100644
--- a/tools/perf/arch/s390/util/sym-handling.c
+++ b/tools/perf/arch/s390/util/sym-handling.c
@@ -19,4 +19,11 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
return ehdr.e_type == ET_REL || ehdr.e_type == ET_DYN;
}

+void arch__adjust_sym_map_offset(GElf_Sym *sym,
+ GElf_Shdr *shdr __maybe_unused,
+ struct map *map)
+{
+ if (map->type == MAP__FUNCTION)
+ sym->st_value += map->start;
+}
#endif
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 98deabb..a704790 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -793,6 +793,12 @@ static u64 ref_reloc(struct kmap *kmap)
void __weak arch__sym_update(struct symbol *s __maybe_unused,
GElf_Sym *sym __maybe_unused) { }

+void __weak arch__adjust_sym_map_offset(GElf_Sym *sym, GElf_Shdr *shdr,
+ struct map *map __maybe_unused)
+{
+ sym->st_value -= shdr->sh_addr - shdr->sh_offset;
+}
+
int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,
struct symsrc *runtime_ss, int kmodule)
{
@@ -973,7 +979,7 @@ int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,

/* Adjust symbol to map to file offset */
if (adjust_kernel_syms)
- sym.st_value -= shdr.sh_addr - shdr.sh_offset;
+ arch__adjust_sym_map_offset(&sym, &shdr, map);

if (strcmp(section_name,
(curr_dso->short_name +
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index b221671..d00a012 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
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