perf symbols: Constify some DSO methods parameters

Those methods are not supposed to change the data structures they
manipulate, so make that clearer by using the const qualifier in the
function signature and in some variables.

Suggested-by: Ingo Molnar <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/build-id.c

···
 	return raw - build_id;
 }
 
-char *dso__build_id_filename(struct dso *dso, char *bf, size_t size)
+char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size)
 {
 	char build_id_hex[BUILD_ID_SIZE * 2 + 1];
 

tools/perf/util/build-id.h

···
 struct dso;
 
 int build_id__sprintf(const u8 *build_id, int len, char *bf);
-char *dso__build_id_filename(struct dso *dso, char *bf, size_t size);
+char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size);
 
 int build_id__mark_dso_hit(struct perf_tool *tool, union perf_event *event,
 			   struct perf_sample *sample, struct perf_evsel *evsel,

tools/perf/util/dso.c

···
 	return origin[dso->symtab_type];
 }
 
-int dso__binary_type_file(struct dso *dso, enum dso_binary_type type,
+int dso__binary_type_file(const struct dso *dso, enum dso_binary_type type,
 			  char *root_dir, char *file, size_t size)
 {
 	char build_id_hex[BUILD_ID_SIZE * 2 + 1];
···
 	}
 }
 
-static struct dso_cache*
-dso_cache__find(struct rb_root *root, u64 offset)
+static struct dso_cache *dso_cache__find(const struct rb_root *root, u64 offset)
 {
-	struct rb_node **p = &root->rb_node;
-	struct rb_node *parent = NULL;
+	struct rb_node * const *p = &root->rb_node;
+	const struct rb_node *parent = NULL;
 	struct dso_cache *cache;
 
 	while (*p != NULL) {
···
 	list_add_tail(&dso->node, head);
 }
 
-struct dso *dsos__find(struct list_head *head, const char *name, bool cmp_short)
+struct dso *dsos__find(const struct list_head *head, const char *name, bool cmp_short)
 {
 	struct dso *pos;
 

tools/perf/util/dso.h

···
 int dso__kernel_module_get_build_id(struct dso *dso, const char *root_dir);
 
 char dso__symtab_origin(const struct dso *dso);
-int dso__binary_type_file(struct dso *dso, enum dso_binary_type type,
+int dso__binary_type_file(const struct dso *dso, enum dso_binary_type type,
 			  char *root_dir, char *file, size_t size);
 
 int dso__data_fd(struct dso *dso, struct machine *machine);
···
 				const char *short_name, int dso_type);
 
 void dsos__add(struct list_head *head, struct dso *dso);
-struct dso *dsos__find(struct list_head *head, const char *name,
+struct dso *dsos__find(const struct list_head *head, const char *name,
 		       bool cmp_short);
 struct dso *__dsos__findnew(struct list_head *head, const char *name);
 bool __dsos__read_build_ids(struct list_head *head, bool with_hits);