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Date: Mon, 10 Nov 2014 13:11:05 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Paul Mackerras <paulus@samba.org>, Namhyung Kim <namhyung.kim@lge.com>,
        LKML <linux-kernel@vger.kernel.org>, Jiri Olsa <jolsa@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH 1/3] perf tools: Allow vmlinux to fallback to kallsyms on
 NO_LIBELF=1
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On Mon, Nov 10, 2014 at 03:33:11PM +0900, Namhyung Kim wrote:
> Hmm.. I don't think it's specific to the minimal elf parser.  The return
> value of dso__load_sym() is a number of symbols found so when it sees a
> dso with 0 symbols it'll fall back to the next option IMHO (not
> tested).  Did you see a problem with the current code?

So your patch:

+++ b/tools/perf/util/symbol-minimal.c
@@ -335,6 +335,9 @@ int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
        unsigned char *build_id[BUILD_ID_SIZE];
        int ret;

+       if (dso->kernel)
+               return 0;  /* always use kallsyms */
+

changes the symbol-minimal.c file to add this exception. That is very
much specific to the minimal elf parser, or am I just seeing things?

What I was saying, why not have a util/symbol.c change that disregards
all DSOs with 0 symbols in.