Messages in this thread | | | Subject | Re: [PATCH] perf-probe: dso: Add symbols in .text.* subsections to text symbol map in kenrel modules | From | Evgenii Shatokhin <> | Date | Wed, 24 Feb 2021 10:47:23 +0300 |
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On 23.02.2021 23:11, Arnaldo Carvalho de Melo wrote: > Em Tue, Feb 23, 2021 at 06:02:58PM +0300, Evgenii Shatokhin escreveu: >> 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@virtuozzo.com> >>> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> >> >> Thanks for the fix! >> >> It looks like it helps, at least with nf_conntrack in kernel 5.11: > > So I'm taking this as you providing a: > > Tested-by: Evgenii Shatokhin <eshatokhin@virtuozzo.com> > > ok?
Sure, thanks!
> > - Arnaldo > >> --------------------- >> # ./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 >
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