perf inject: Try chroot directory when reading build-id

When reading build-id from a DSO, it should consider if it's from a
chroot task.  In that case, the path is different so it needs to prepend
the root directory to access the file correctly.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220202070828.143303-4-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-inject.c

@@ -25,6 +25,7 @@
 #include "util/synthetic-events.h"
 #include "util/thread.h"
 #include "util/namespaces.h"
+#include "util/util.h"
 
 #include <linux/err.h>
 #include <subcmd/parse-options.h>
@@ -550,6 +551,15 @@ static int dso__read_build_id(struct dso *dso)
 	nsinfo__mountns_enter(dso->nsinfo, &nsc);
 	if (filename__read_build_id(dso->long_name, &dso->bid) > 0)
 		dso->has_build_id = true;
+	else if (dso->nsinfo) {
+		char *new_name;
+
+		new_name = filename_with_chroot(dso->nsinfo->pid,
+						dso->long_name);
+		if (new_name && filename__read_build_id(new_name, &dso->bid) > 0)
+			dso->has_build_id = true;
+		free(new_name);
+	}
 	nsinfo__mountns_exit(&nsc);
 
 	return dso->has_build_id ? 0 : -1;