[RFC] perf tools: Filter out hidden symbols from labels

Jiri Olsa
2019-01-15T13:54:00Z

hi,
sending this as RFC, because I'm not sure this won't break
something else ;-)

thanks,
jirka

---
When perf is built with annobin plugin (RHEL8 build) extra symbols
are added to its binary:

# nm perf | grep annobin | head -10
0000000000241100 t .annobin_annotate.c
0000000000326490 t .annobin_annotate.c
0000000000249255 t .annobin_annotate.c_end
00000000003283a8 t .annobin_annotate.c_end
00000000001bce18 t .annobin_annotate.c_end.hot
00000000001bce18 t .annobin_annotate.c_end.hot
00000000001bc3e2 t .annobin_annotate.c_end.unlikely
00000000001bc400 t .annobin_annotate.c_end.unlikely
00000000001bce18 t .annobin_annotate.c.hot
00000000001bce18 t .annobin_annotate.c.hot
...

those symbols have no use for report or annotation and should be skipped.
Moreover they interfere with dwarf unwind test on ppc arch, where they
are mixed with checked symbols and test fails:

# perf test dwarf -v
59: Test dwarf unwind :
--- start ---
test child forked, pid 8515
unwind: .annobin_dwarf_unwind.c:ip = 0x10dba40dc (0x2740dc)
...
got: .annobin_dwarf_unwind.c 0x10dba40dc, expecting test__arch_unwind_sample
unwind: failed with 'no error'

The annobin symbols are defined as NOTYPE/LOCAL/HIDDEN:

# readelf -s ./perf | grep annobin | head -1
40: 00000000001bce4f 0 NOTYPE LOCAL HIDDEN 13 .annobin_init.c

They can still pass the check for the label symbol. Adding
check for HIDDEN visibility and filter out such symbols.

Link: http://lkml.kernel.org/n/tip-4yuna6qhhg0df3q147cjdyuu@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/util/symbol-elf.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 66a84d5846c8..39ef2bde6d6d 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -87,6 +87,11 @@ static inline uint8_t elf_sym__type(const GElf_Sym *sym)
return GELF_ST_TYPE(sym->st_info);
}

+static inline uint8_t elf_sym__visibility(const GElf_Sym *sym)
+{
+ return GELF_ST_VISIBILITY(sym->st_other);
+}
+
#ifndef STT_GNU_IFUNC
#define STT_GNU_IFUNC 10
#endif
@@ -111,7 +116,8 @@ static inline int elf_sym__is_label(const GElf_Sym *sym)
return elf_sym__type(sym) == STT_NOTYPE &&
sym->st_name != 0 &&
sym->st_shndx != SHN_UNDEF &&
- sym->st_shndx != SHN_ABS;
+ sym->st_shndx != SHN_ABS &&
+ elf_sym__visibility(sym) != STV_HIDDEN;
}

static bool elf_sym__filter(GElf_Sym *sym)
--
2.17.2