perf symbols: Add new option --ignore-vmlinux for perf top

Running "perf top" on a machine with possibly invalid or non-matching
vmlinux at the various places results in no symbol resolving despite
/proc/kallsyms being present and valid.

Add a new option --ignore-vmlinux to explicitly indicate that we do not
want to use these kernels and just use what we have (kallsyms).
Signed-off-by: Willy Tarreau <w@1wt.eu>
Cc: Ingo Molnar <mingo@redhat.com>
Link: http://lkml.kernel.org/r/20130914083259.GA3418@1wt.euSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-top.c

@@ -1073,6 +1073,8 @@ int cmd_top(int argc, const char **argv, const char *prefix __maybe_unused)
 		    "list of cpus to monitor"),
 	OPT_STRING('k', "vmlinux", &symbol_conf.vmlinux_name,
 		   "file", "vmlinux pathname"),
+	OPT_BOOLEAN(0, "ignore-vmlinux", &symbol_conf.ignore_vmlinux,
+		    "don't load vmlinux even if found"),
 	OPT_BOOLEAN('K', "hide_kernel_symbols", &top.hide_kernel_symbols,
 		    "hide kernel symbols"),
 	OPT_CALLBACK('m', "mmap-pages", &opts->mmap_pages, "pages",

tools/perf/util/symbol.c

@@ -1215,7 +1215,7 @@ static int dso__load_kernel_sym(struct dso *dso, struct map *map,
 		goto do_kallsyms;
 	}
 
-	if (symbol_conf.vmlinux_name != NULL) {
+	if (!symbol_conf.ignore_vmlinux && symbol_conf.vmlinux_name != NULL) {
 		err = dso__load_vmlinux(dso, map,
 					symbol_conf.vmlinux_name, filter);
 		if (err > 0) {
@@ -1227,7 +1227,7 @@ static int dso__load_kernel_sym(struct dso *dso, struct map *map,
 		return err;
 	}
 
-	if (vmlinux_path != NULL) {
+	if (!symbol_conf.ignore_vmlinux && vmlinux_path != NULL) {
 		err = dso__load_vmlinux_path(dso, map, filter);
 		if (err > 0)
 			return err;

tools/perf/util/symbol.h

@@ -85,6 +85,7 @@ struct symbol_conf {
 	unsigned short	priv_size;
 	unsigned short	nr_events;
 	bool		try_vmlinux_path,
+			ignore_vmlinux,
 			show_kernel_path,
 			use_modules,
 			sort_by_name,