linux-kernel - Re: [PATCH 0/3] tools/perf: Fix perf probe crash by broken DWARF file

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Message-Id: <20221101222959.0815521a31e45c1ddabad756@kernel.org>
Date:   Tue, 1 Nov 2022 22:29:59 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 0/3] tools/perf: Fix perf probe crash by broken DWARF
 file

On Tue,  1 Nov 2022 22:14:01 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> Hi,
> 
> Here is a series of patches for perf probe which improves the robustness
> against broken DWARF file.
> 
> Since the Clang generates the out of standard DWARF5 file, the perf probe
> crashes or failed to analyze it. There are actually fragile code against
> it, so I fixed it ([1/3]) to avoid crash by SEGV. And make it accepts
> Clang's DWARF5 file ([2/3],[3/3]).
> 
> Without this series, the perf probe crashes with the DWARF5 file
> which generated by clang as below;
>  
>   $ ./perf probe -k $BIN_PATH/vmlinux -s $SRC_PATH -L vfs_read:10
>   Segmentation fault
> 
> This series fixes it to handle such file correctly;
> 
>   $ ./perf probe -k $BIN_PATH/vmlinux -s $SRC_PATH -L vfs_read:10
>   <vfs_read@...C_PATH/fs/read_write.c:10>
>  
>        11         ret = rw_verify_area(READ, file, pos, count);
>        12         if (ret)
>                            return ret;
> 
> This issue is reported on LLVM ML;
> https://www.mail-archive.com/dwarf-discuss@lists.dwarfstd.org/msg00884.html

Hmm, according to the discussion in this thread, this spec is under discussion
(still?). As far as I can see the "DWARF Debugging Information Format Version 5"
2.14, it says "The value 0 indicates that no source line has been specified."
But the description will be updated(?)
http://wiki.dwarfstd.org/index.php?title=DWARF5_Line_Table_File_Numbers

Let me update the series so that carefully remove the "broken". Maybe "clang"
DWARF5?

Thank you,

> 
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (Google) (3):
>       tools/perf: Fix to avoid crashing with a broken DWARF file
>       tools/perf: Fix to use dwarf_attr_integrate for generic attr accessor
>       tools/perf: Fix to get declared file name from broken DWARF5
> 
> 
>  tools/perf/util/dwarf-aux.c    |   58 ++++++++++++++++++++++++++++------------
>  tools/perf/util/dwarf-aux.h    |    3 ++
>  tools/perf/util/probe-finder.c |   37 +++++++++++++++++---------
>  3 files changed, 68 insertions(+), 30 deletions(-)
> 
> --
> Masami Hiramatsu (Google) <mhiramat@...nel.org>


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>