linux-kernel - Re: [PATCH v2 1/3] perf tools: Introduce dso__decompress_kmodule

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Date:   Tue, 6 Jun 2017 10:36:12 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        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>
Subject: Re: [PATCH v2 1/3] perf tools: Introduce dso__decompress_kmodule_{fd,path}

Hi Jiri,

On Mon, Jun 5, 2017 at 6:58 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Sat, Jun 03, 2017 at 11:00:31AM +0900, Namhyung Kim wrote:
>> Move decompress_kmodule() to util/dso.c and split it to two functions
>> returning fd and (decompressed) file path.  Existing user only wants the
>> fd version but the path version will be used soon.
>>
>> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>> ---
>>  tools/perf/util/dso.c        | 51 ++++++++++++++++++++++++++++++++++++++++++++
>>  tools/perf/util/dso.h        |  3 +++
>>  tools/perf/util/symbol-elf.c | 36 +------------------------------
>>  3 files changed, 55 insertions(+), 35 deletions(-)
>>
>> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
>> index b27d127cdf68..fc4747a8c283 100644
>> --- a/tools/perf/util/dso.c
>> +++ b/tools/perf/util/dso.c
>> @@ -248,6 +248,57 @@ bool dso__needs_decompress(struct dso *dso)
>>               dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE_COMP;
>>  }
>>
>> +static int decompress_kmodule(struct dso *dso, const char *name, char *tmpbuf)
>> +{
>> +     int fd = -1;
>> +     struct kmod_path m;
>> +
>> +     if (!dso__needs_decompress(dso))
>> +             return -1;
>
> the original code had also DSO_BINARY_TYPE__BUILD_ID_CACHE check,
> not sure why though.. ;-)

It's because decompressed modules which were found in the build-id
cache didn't set dso->symtab_type properly.  It was fixed by my
previous patch so checking symtab_type will cover the (compressed)
build-id cache case too now.

Thanks,
Namhyung