From: Evgenii Shatokhin <eshatokhin@virtuozzo.com> To: Masami Hiramatsu <mhiramat@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Kristen Carlson Accardi <kristen@linux.intel.com>, live-patching@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org, Konstantin Khorenko <khorenko@virtuozzo.com> Subject: Re: [PATCH] perf-probe: dso: Add symbols in .text.* subsections to text symbol map in kenrel modules Date: Tue, 23 Feb 2021 18:02:58 +0300 [thread overview] Message-ID: <00abcbd4-e2c2-a699-8eb5-f8804035b46e@virtuozzo.com> (raw) In-Reply-To: <161406587251.969784.5469149622544499077.stgit@devnote2> 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: --------------------- # ./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
next prev parent reply other threads:[~2021-02-23 15:05 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-02-18 17:09 'perf probe' and symbols from .text.<something> Evgenii Shatokhin 2021-02-18 19:35 ` Josh Poimboeuf 2021-02-22 15:05 ` Masami Hiramatsu 2021-02-22 15:12 ` Masami Hiramatsu 2021-02-22 17:51 ` Josh Poimboeuf 2021-02-23 1:23 ` Masami Hiramatsu 2021-02-23 7:36 ` Masami Hiramatsu 2021-02-23 19:45 ` Josh Poimboeuf 2021-02-24 8:00 ` Masami Hiramatsu 2021-02-23 1:48 ` [PATCH] perf-probe: Failback to symbol-base probe for probes on module Masami Hiramatsu 2021-02-23 7:36 ` Masami Hiramatsu 2021-02-23 7:09 ` 'perf probe' and symbols from .text.<something> Masami Hiramatsu 2021-02-23 7:37 ` [PATCH] perf-probe: dso: Add symbols in .text.* subsections to text symbol map in kenrel modules Masami Hiramatsu 2021-02-23 15:02 ` Evgenii Shatokhin [this message] 2021-02-23 20:11 ` Arnaldo Carvalho de Melo 2021-02-24 7:47 ` Evgenii Shatokhin
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