linux-kernel - Re: [PATCH v1] perf symbol-elf: Avoid a weak cxx_demangle

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAP-5=fWBEGj-bKnfF3bi+qy3nzrV+oWzDj-0M5bRe2kQSsJ2Tw@mail.gmail.com>
Date: Thu, 9 Jan 2025 09:58:34 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	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>, 
	Kan Liang <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf symbol-elf: Avoid a weak cxx_demangle_sym function

On Mon, Nov 18, 2024 at 7:17 PM Ian Rogers <irogers@...gle.com> wrote:
>
> cxx_demangle_sym is weak in case demangle-cxx.c replaces the
> definition in symbol-elf.c. When demangle-cxx.c is built
> HAVE_CXA_DEMANGLE_SUPPORT is defined, as such the define can be used
> to avoid a weak symbol. As weak symbols are outside of the C standard
> their use can lead to strange behaviors, in particular with LTO, as
> well as causing issues to be hidden at link time.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Ping.

Thanks,
Ian

> ---
>  tools/perf/util/symbol-elf.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index e398abfd13a0..66fd1249660a 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -287,8 +287,9 @@ static bool want_demangle(bool is_kernel_sym)
>   * Demangle C++ function signature, typically replaced by demangle-cxx.cpp
>   * version.
>   */
> -__weak char *cxx_demangle_sym(const char *str __maybe_unused, bool params __maybe_unused,
> -                             bool modifiers __maybe_unused)
> +#ifndef HAVE_CXA_DEMANGLE_SUPPORT
> +char *cxx_demangle_sym(const char *str __maybe_unused, bool params __maybe_unused,
> +                      bool modifiers __maybe_unused)
>  {
>  #ifdef HAVE_LIBBFD_SUPPORT
>         int flags = (params ? DMGL_PARAMS : 0) | (modifiers ? DMGL_ANSI : 0);
> @@ -302,6 +303,7 @@ __weak char *cxx_demangle_sym(const char *str __maybe_unused, bool params __mayb
>         return NULL;
>  #endif
>  }
> +#endif /* !HAVE_CXA_DEMANGLE_SUPPORT */
>
>  static char *demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
>  {
> --
> 2.47.0.338.g60cca15819-goog
>