perf symbols: Move symbol filtering to event__preprocess_sample()

So that --dsos, --comm, --symbols can bem used in more tools,
like in perf diff:

$ perf record -f find / > /dev/null
$ perf record -f find / > /dev/null
$ perf diff --dsos /lib64/libc-2.10.1.so | head -5
   1        +22392124     /lib64/libc-2.10.1.so   _IO_vfprintf_internal
   2         +6410655     /lib64/libc-2.10.1.so   __GI_memmove
   3    +1   +9192692     /lib64/libc-2.10.1.so   _int_malloc
   4    -1  -15158605     /lib64/libc-2.10.1.so   _int_free
   5           +45669     /lib64/libc-2.10.1.so   _IO_new_file_xsputn
$

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1260914682-29652-3-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 164286a..7707897 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1764,6 +1764,11 @@
 	if (symbol_conf.try_vmlinux_path && vmlinux_path__init() < 0)
 		return -1;
 
+	if (symbol_conf.field_sep && *symbol_conf.field_sep == '.') {
+		pr_err("'.' is the only non valid --field-separator argument\n");
+		return -1;
+	}
+
 	if (setup_list(&symbol_conf.dso_list,
 		       symbol_conf.dso_list_str, "dso") < 0)
 		return -1;