Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 11 Jul 2023 22:20:00 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH] perf probe: read DWARF files from the correct CU |
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On Tue, 11 Jul 2023 09:57:45 -0300 Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> Em Thu, Jun 15, 2023 at 10:01:37PM +0200, Georg Müller escreveu: > > After switching from dwarf_decl_file() to die_get_decl_file(), it is not > > possible to add probes for certain functions of certain binaries: > > > > $ perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed > > A function DIE doesn't have decl_line. Maybe broken DWARF? > > A function DIE doesn't have decl_line. Maybe broken DWARF? > > Probe point 'match_unit_removed' not found. > > Error: Failed to add events. > > > > The problem is that die_get_decl_file() uses the wrong CU to search for > > the file. elfutils commit e1db5cdc9f has some good explanation for this: > > > > dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file > > attribute. This means the attribute might come from a different DIE > > in a different CU. If so, we need to use the CU associated with the > > attribute, not the original DIE, to resolve the file name. > > > > This patch uses the same source of information as elfutils: use attribute > > DW_AT_decl_file and use this CU to search for the file. > > Thanks, applied to the perf-tools branch, that will be submitted for > Linux v6.5.
Thanks Arnaldo and Georg,
It sounds perfect reason why that happened. I didn't expect the case that the attribute comes from another CU...
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > - Arnaldo > > > Fixes: dc9a5d2ccd5c ("perf probe: Fix to get declared file name from clang DWARF5") > > Signed-off-by: Georg Müller <georgmueller@gmx.net> > > Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/ > > --- > > tools/perf/util/dwarf-aux.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c > > index b07414409771..137b3ed9897b 100644 > > --- a/tools/perf/util/dwarf-aux.c > > +++ b/tools/perf/util/dwarf-aux.c > > @@ -478,8 +478,10 @@ static const char *die_get_file_name(Dwarf_Die *dw_die, int idx) > > { > > Dwarf_Die cu_die; > > Dwarf_Files *files; > > + Dwarf_Attribute attr_mem; > > > > - if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) || > > + if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) || > > + !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) || > > dwarf_getsrcfiles(&cu_die, &files, NULL) != 0) > > return NULL; > > > > -- > > 2.41.0 > > > > -- > > - Arnaldo
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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