linux-kernel - Re: [RFC 0/6] perf probe: Attempt to improve C++ probing

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Message-Id: <20180514220844.9ba3da2ab9a675f634f22349@kernel.org>
Date:   Mon, 14 May 2018 22:08:44 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Holger Freyther <automatic+kernel@...yther.de>
Cc:     linux-kernel@...r.kernel.org,
        Holger Hans Peter Freyther <holgar+kernel@...gle.com>
Subject: Re: [RFC 0/6] perf probe: Attempt to improve C++ probing

Hi Holger,

Thank you for your great work!

On Mon, 14 May 2018 12:19:34 +0800
Holger Freyther <automatic+kernel@...yther.de> wrote:

> From: Holger Hans Peter Freyther <holgar+kernel@...gle.com>
> 
> Currently perf probe -x app --funcs will list and demangle C++ functions
> but the other probe actions can't work with them. When asking probe to not
> demangle it will not list any of the application symbols creating the
> impression that there are no symbols at all.
> 
> Make --funcs --no-demangle list all C++ functions and modify the handling
> for listing code, variables and adding the uprobe work with the demangled
> C++ function name.
> 
> I tried to keep this as minimal as possible but having to keep the dso in
> the debuginfo and passing it everywhere to be able to demangle the linkage
> name isn't pretty (and for C++ demangling the struct dso is not of much
> use. Maybe having a static "empty" dso could avoid a lot of the changes).
> 
> Maybe the easiest first patch is to default to --no-demangle and change
> the DEFAULT_FUNC_FILTER to not include mangled C++ symbols. The remaining
> tooling would work then.
> 
> This has seen very little testing outside the following commands.
> 
> My test set includes:
> 
>  ./perf probe -x . -L "std::vector<int, std::allocator<int> >::at"
>  ./perf probe -x . -L "std::vector<int, std::allocator<int> >::at:2-3"
> 
>  ./perf probe -x . -V "std::vector<int, std::allocator<int> >::at"
>  ./perf probe -x . -V "std::vector<int, std::allocator<int> >::at:2"
>  ./perf probe -x . -V "std::vector<int, std::allocator<int> >::size%return"

OK, let me review it.

> 
> 
> Holger Hans Peter Freyther (6):
>   perf probe: Do not exclude mangled C++ funcs
>   perf probe: Parse linerange for C++ functions
>   perf probe: Make listing of C++ functions work
>   perf probe: Show variables for C++ functions
>   perf probe: Make listing of variables work for C++ functions
>   perf probe: Make it possible to add a C++ uprobe
> 
>  tools/perf/builtin-probe.c     |   2 +-
>  tools/perf/util/probe-event.c  |  77 ++++++++++++++++++++-
>  tools/perf/util/probe-finder.c | 152 ++++++++++++++++++++++++++++++-----------
>  tools/perf/util/probe-finder.h |   3 +
>  tools/perf/util/string.c       |  57 ++++++++++++++++
>  tools/perf/util/string2.h      |   1 +
>  6 files changed, 247 insertions(+), 45 deletions(-)
> 
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>