lkml.org 
[lkml]   [2021]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] perf-probe: dso: Add symbols in .text.* subsections to text symbol map in kenrel modules
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?

- 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

--

- Arnaldo

\
 
 \ /
  Last update: 2021-02-23 21:13    [W:0.044 / U:0.348 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site