On 23.02.2021 10:37, Masami Hiramatsu wrote:
The kernel modules have .text.* subsections such as .text.unlikely.
Since dso__process_kernel_symbol() only identify the symbols in the ".text"
section as the text symbols and inserts it in the default dso in the map,
the symbols in such subsections can not be found by map__find_symbol().
This adds the symbols in those subsections to the default dso in the map so
that map__find_symbol() can find them. This solves the perf-probe issue on
probing online module.
Without this fix, probing on a symbol in .text.unlikely fails.
----
# perf probe -m nf_conntrack nf_l4proto_log_invalid
Probe point 'nf_l4proto_log_invalid' not found.
Error: Failed to add events.
----
With this fix, it works because map__find_symbol() can find the symbol
correctly.
----
# perf probe -m nf_conntrack nf_l4proto_log_invalid
Added new event:
probe:nf_l4proto_log_invalid (on nf_l4proto_log_invalid in nf_conntrack)
You can now use it in all perf tools, such as:
perf record -e probe:nf_l4proto_log_invalid -aR sleep 1
----
Reported-by: Evgenii Shatokhin <eshatokhin@xxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Thanks for the fix!
It looks like it helps, at least with nf_conntrack in kernel 5.11:
---------------------
# ./perf probe -v -m nf_conntrack nf_ct_resolve_clash
probe-definition(0): nf_ct_resolve_clash
symbol:nf_ct_resolve_clash file:(null) line:0 offset:0 return:0 lazy:(null)
0 arguments
Failed to get build-id from nf_conntrack.
Cache open error: -1
Open Debuginfo file:
/lib/modules/5.11.0-test01/kernel/net/netfilter/nf_conntrack.ko
Try to find probe point from debuginfo.
Matched function: nf_ct_resolve_clash [33616]
Probe point found: nf_ct_resolve_clash+0
Found 1 probe_trace_events.
Opening /sys/kernel/tracing//kprobe_events write=1
Opening /sys/kernel/tracing//README write=0
Writing event: p:probe/nf_ct_resolve_clash
nf_conntrack:nf_ct_resolve_clash+0
Added new event:
probe:nf_ct_resolve_clash (on nf_ct_resolve_clash in nf_conntrack)
You can now use it in all perf tools, such as:
perf record -e probe:nf_ct_resolve_clash -aR sleep 1
---------------------
I guess, the patch is suitable for stable kernel branches as well.
Without the patch, the workaround you suggested earlier (using the full
path to nf_conntrack.ko) works too.
---
tools/perf/util/symbol-elf.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 6dff843fd883..0c1113236913 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -985,7 +985,9 @@ static int dso__process_kernel_symbol(struct dso *dso, struct map *map,
if (strcmp(section_name, (curr_dso->short_name + dso->short_name_len)) == 0)
return 0;
- if (strcmp(section_name, ".text") == 0) {
+ /* .text and .text.* are included in the text dso */
+ if (strncmp(section_name, ".text", 5) == 0 &&
+ (section_name[5] == '\0' || section_name[5] == '.')) {
/*
* The initial kernel mapping is based on
* kallsyms and identity maps. Overwrite it to
.
Regards,
Evgenii
