linux-kernel - [PATCH 0/2] perf: support specify vdso path in cmdline

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Date: Thu, 13 Jun 2024 14:35:08 +0800
From: Changbin Du <changbin.du@...wei.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim
	<namhyung@...nel.org>, Nathan Chancellor <nathan@...nel.org>
CC: Mark Rutland <mark.rutland@....com>, Alexander Shishkin
	<alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Ian
 Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, "Liang,
 Kan" <kan.liang@...ux.intel.com>, Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
	<linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<llvm@...ts.linux.dev>, Changbin Du <changbin.du@...wei.com>
Subject: [PATCH 0/2] perf: support specify vdso path in cmdline

The vdso dumped from process memory (in buildid-cache) lacks debugging
info. To annotate vdso symbols with source lines we need specify a
debugging version.

For x86, we can find them from your local build as
arch/x86/entry/vdso/vdso{32,64}.so.dbg. Or they may resides in
/lib/modules/<version>/vdso/vdso{32,64}.so on Ubuntu. But notice that the
builid has to match.

$ sudo perf record -a
$ sudo perf report --objdump=llvm-objdump \
      --vdso arch/x86/entry/vdso/vdso64.so.dbg,arch/x86/entry/vdso/vdso32.so.dbg

Samples: 17K of event 'cycles:P', 4000 Hz, Event count (approx.): 1760
__vdso_clock_gettime  /work/linux-host/arch/x86/entry/vdso/vdso64.so.d
Percent│       movq    -48(%rbp),%rsi                                ▒
       │       testq   %rax,%rax                                     ▒
       │     ;               return vread_hvclock();                 ▒
       │       movq    %rax,%rdx                                     ▒
       │     ;               if (unlikely(!vdso_cycles_ok(cycles)))  ▒
       │     ↑ js      eb                                            ▒
       │     ↑ jmp     74                                            ▒
       │     ;               ts->tv_sec = vdso_ts->sec;              ▒
  0.02 │147:   leaq    2(%rbx),%rax                                  ▒
       │       shlq    $4, %rax                                      ▒
       │       addq    %r10,%rax                                     ▒
       │     ;               while ((seq = READ_ONCE(vd->seq)) & 1) {▒
  9.38 │152:   movl    (%r10),%ecx                                   ▒


When doing cross platform analysis, we also need specify the vdso path if
we are interested in its symbols.

Changbin Du (2):
  perf: support specify vdso path in cmdline
  perf: disasm: prefer symsrc_filename for filename

 tools/perf/builtin-annotate.c |  2 +
 tools/perf/builtin-c2c.c      |  2 +
 tools/perf/builtin-inject.c   |  2 +
 tools/perf/builtin-report.c   |  2 +
 tools/perf/builtin-script.c   |  2 +
 tools/perf/builtin-top.c      |  2 +
 tools/perf/util/disasm.c      |  5 +++
 tools/perf/util/symbol.c      | 82 ++++++++++++++++++++++++++++++++++-
 tools/perf/util/symbol_conf.h |  5 +++
 9 files changed, 102 insertions(+), 2 deletions(-)

-- 
2.34.1