linux-kernel - Re: [PATCH v3 4/6] perf test: Decompress kernel module before objdump

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Date:   Thu, 8 Jun 2017 09:37:37 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        David Ahern <dsahern@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH v3 4/6] perf test: Decompress kernel module before objdump

On Wed, Jun 07, 2017 at 07:25:20PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jun 08, 2017 at 12:39:01AM +0900, Namhyung Kim escreveu:
> > If a kernel modules is compressed, it should be decompressed before
> > running objdump to parse binary data correctly.  This fixes a failure of
> > object code reading test for me.
> > 
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/tests/code-reading.c | 20 +++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
> > index 1f14e7612cbb..94b7c7b02bde 100644
> > --- a/tools/perf/tests/code-reading.c
> > +++ b/tools/perf/tests/code-reading.c
> > @@ -229,6 +229,8 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
> >  	unsigned char buf2[BUFSZ];
> >  	size_t ret_len;
> >  	u64 objdump_addr;
> > +	const char *objdump_name;
> > +	char decomp_name[KMOD_DECOMP_LEN];
> >  	int ret;
> >  
> >  	pr_debug("Reading object code for memory address: %#"PRIx64"\n", addr);
> > @@ -289,9 +291,25 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
> >  		state->done[state->done_cnt++] = al.map->start;
> >  	}
> >  
> > +	objdump_name = al.map->dso->long_name;
> > +	if (dso__needs_decompress(al.map->dso)) {
> > +		if (dso__decompress_kmodule_path(al.map->dso, objdump_name,
> > +						 decomp_name,
> > +						 sizeof(decomp_name)) < 0) {
> > +			pr_debug("decompression failed\n");
> 
> This is a too vague message, to help with debugging I suggest printing
> more detauls such as the file being decompressed and perhaps the
> decomp_name as well.

Looking at the code, it already printed the filename so current
message seems ok.

  $ sudo perf test -v 'code reading'
  22: Object code reading                        :
  --- start ---
  ...
  Reading object code for memory address: 0xffffffffa0305c56
  File is: /lib/modules/4.11.3-1-ARCH/kernel/fs/btrfs/btrfs.ko.gz
  On file address is: 0x61cc6
  decompression failed
  test child finished with -1
  ---- end ----
  Object code reading: FAILED!

Thanks,
Namhyung