| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <Z88DfA2ROWNGfpD_@x1>
Date: Mon, 10 Mar 2025 12:21:32 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Stephen Brennan <stephen.s.brennan@...cle.com>
Cc: Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
"Liang, Kan" <kan.liang@...ux.intel.com>,
Mark Rutland <mark.rutland@....com>,
Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
James Clark <james.clark@...aro.org>,
Chaitanya S Prakash <chaitanyas.prakash@....com>,
Ian Rogers <irogers@...gle.com>, linux-perf-users@...r.kernel.org,
Adrian Hunter <adrian.hunter@...el.com>,
Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
On Fri, Mar 07, 2025 at 02:33:01PM -0800, Stephen Brennan wrote:
> Arnaldo Carvalho de Melo <acme@...nel.org> writes:
> > On Fri, Mar 07, 2025 at 05:18:36PM -0300, Arnaldo Carvalho de Melo wrote:
> [...]
> > It has a way to use that section tho:
> > ⬢ [acme@...lbox perf-tools-next]$ man eu-readelf | grep -A2 -- --elf-section
> > [--elf-section [section] ]
> > [-w|
> > --debug-dump[=line,=decodedline,=info,=info+,=abbrev,=pubnames,=aranges,=macro,=frames,=str,=loc,=ranges,=gdb_index,=addr]]
> > --
> > --elf-section [section]
> > Use the named SECTION (default .gnu_debugdata) as (compressed) ELF input data
> > ⬢ [acme@...lbox perf-tools-next]$
> > ⬢ [acme@...lbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | wc -l
> > 339
> > ⬢ [acme@...lbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | head
> > 1: 00000000000056d0 35 FUNC LOCAL DEFAULT 17 entry_hashfunc
> > 2: 0000000000005700 34 FUNC LOCAL DEFAULT 17 entry_comparator
> > 3: 0000000000005920 121 FUNC LOCAL DEFAULT 17 subtree_has_side_effects
> > 4: 00000000000059a0 992 FUNC LOCAL DEFAULT 17 worst_cost.part.0
> > 5: 0000000000005d80 449 FUNC LOCAL DEFAULT 17 traverse_tree
> > 6: 0000000000005f50 73 FUNC LOCAL DEFAULT 17 undangle_file_pointers
> > 7: 0000000000005fa0 72 FUNC LOCAL DEFAULT 17 looks_like_expression
> > 8: 0000000000006030 303 FUNC LOCAL DEFAULT 17 get_fts_info_name
> > 9: 0000000000006190 35 FUNC LOCAL DEFAULT 17 inside_dir.part.0
> > 10: 0000000000006330 451 FUNC LOCAL DEFAULT 17 pred_sanity_check
> > ⬢ [acme@...lbox perf-tools-next]$
> Wow, thank you for teaching me that!
> I had been using:
> gdb /usr/bin/bash --batch -ex 'maint print msymbols'
> Because I knew GDB had support for .gnu_debugdata. But the --elf-section
> argument to eu-readelf is much more useful.
That was a nice assumption and it did the work for you :-)
I thought that the elfutils guys would add something to eu-readelf for
them to dump the compressed data in human readable for, looked at the
man page and voila!
<SNIP>
> > # Overhead Command Shared Object Symbol
> > # ........ ....... ............................... .......................................................
> > #
> > 8.72% find /usr/bin/find 0xb498
> > 7.90% find /usr/lib64/libc.so.6 0xe51e0 B [.] __GI___readdir64
> > 7.44% find /usr/lib64/libc.so.6 0xa77cd B [.] _int_malloc
> > ⬢ [acme@...lbox perf-tools-next]$
> > The only strange thing was not having it resolved in the -v case, which
> > I think its because you added a new type of DSO but didn't update the
> > code that does the 'perf report -v' verbose case?
> > I ran out of time, have to go AFK now, can you please take a look,
> > Stephen?
> Thanks for the catch. I double checked all the places where
> DSO_BINARY_TYPE constants are enumerated, and it turns out I missed
> adding an entry to
> char dso__symtab_origin(const struct dso *dso) ...
>
> I assume that the array defaulted to '\0' which terminated the string
> too early for this line. Oops!
>
> Most of the letters I would associate with ".gnu_debugdata" are
> taken (namely, g/G for GNU, m/M for MiniDebugInfo, d/D for
> debugdata...). So 'n', for the second letter of GNU, is my selection
> unless you feel differently. With that change, the table is fixed for
> "perf report -v". Here it is running against my test data focusing on a
> symbol only found in .gnu_debugdata of bash:
>
> $ ./perf report -v --stdio -i ~/repos/UEK6/perf.data 2>&1 | egrep yy_readline_get\|gnu_debugdata
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/bash
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sed
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/date
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sqlite3
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sleep
> 0.20% 0.00% bash /usr/bin/bash 0x55fdc4509dbe n [.] yy_readline_get
>
> I'll update the patch accordingly.
I just tested it, works as expected:
⬢ [acme@...lbox perf-tools-next]$ perf report -v --stdio |& head -20
build id event received for [vdso]: a2184b81fbbc08eff401d16259eca8ad5f9d8988 [20]
build id event received for /usr/bin/find: 3faf3f04d1b31abc9e5ce8428110e424fd980a37 [20]
build id event received for /usr/lib64/ld-linux-x86-64.so.2: 765f7ab0f3569ffe98de85864a0cedda9b686994 [20]
build id event received for /usr/lib64/libc.so.6: c8c3fa52aaee3f5d73b6fd862e39e9d4c010b6ba [20]
build id event received for [kernel.kallsyms]: c3fbb7df4dfb94762b1648bc65e4363e50f45585 [20]
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/find
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 163 of event 'cpu_core/cycles/Pu'
# Event count (approx.): 68126524
#
# Overhead Command Shared Object Symbol
# ........ ....... ............................... .......................................................
#
8.72% find /usr/bin/find 0xb498 n [.] consider_visiting
7.90% find /usr/lib64/libc.so.6 0xe51e0 B [.] __GI___readdir64
7.44% find /usr/lib64/libc.so.6 0xa77cd B [.] _int_malloc
⬢ [acme@...lbox perf-tools-next]$
I'll reply to the v3 thread with my Tested-by.
Thanks!
- Arnaldo
Powered by blists - more mailing lists