perf dwarf-aux: Add die_collect_global_vars()

This function is to search all global variables in the CU.  We want to
have the list of global variables at once and match them later.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240502060011.1838090-2-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/dwarf-aux.c

@@ -1630,6 +1630,68 @@ void die_collect_vars(Dwarf_Die *sc_die, struct die_var_type **var_types)
 
 	die_find_child(sc_die, __die_collect_vars_cb, (void *)var_types, &die_mem);
 }
+
+static int __die_collect_global_vars_cb(Dwarf_Die *die_mem, void *arg)
+{
+	struct die_var_type **var_types = arg;
+	Dwarf_Die type_die;
+	int tag = dwarf_tag(die_mem);
+	Dwarf_Attribute attr;
+	Dwarf_Addr base, start, end;
+	Dwarf_Op *ops;
+	size_t nops;
+	struct die_var_type *vt;
+
+	if (tag != DW_TAG_variable)
+		return DIE_FIND_CB_SIBLING;
+
+	if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	/* Only collect the location with an absolute address. */
+	if (dwarf_getlocations(&attr, 0, &base, &start, &end, &ops, &nops) <= 0)
+		return DIE_FIND_CB_SIBLING;
+
+	if (ops->atom != DW_OP_addr)
+		return DIE_FIND_CB_SIBLING;
+
+	if (!check_allowed_ops(ops, nops))
+		return DIE_FIND_CB_SIBLING;
+
+	if (die_get_real_type(die_mem, &type_die) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	vt = malloc(sizeof(*vt));
+	if (vt == NULL)
+		return DIE_FIND_CB_END;
+
+	vt->die_off = dwarf_dieoffset(&type_die);
+	vt->addr = ops->number;
+	vt->reg = -1;
+	vt->offset = 0;
+	vt->next = *var_types;
+	*var_types = vt;
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_collect_global_vars - Save all global variables
+ * @cu_die: a CU DIE
+ * @var_types: a pointer to save the resulting list
+ *
+ * Save all global variables in the @cu_die and save them to @var_types.
+ * The @var_types is a singly-linked list containing type and location info.
+ * Actual type can be retrieved using dwarf_offdie() with 'die_off' later.
+ *
+ * Callers should free @var_types.
+ */
+void die_collect_global_vars(Dwarf_Die *cu_die, struct die_var_type **var_types)
+{
+	Dwarf_Die die_mem;
+
+	die_find_child(cu_die, __die_collect_global_vars_cb, (void *)var_types, &die_mem);
+}
 #endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
 
 #ifdef HAVE_DWARF_CFI_SUPPORT

tools/perf/util/dwarf-aux.h

@@ -171,6 +171,9 @@ Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr addr,
 /* Save all variables and parameters in this scope */
 void die_collect_vars(Dwarf_Die *sc_die, struct die_var_type **var_types);
 
+/* Save all global variables in this CU */
+void die_collect_global_vars(Dwarf_Die *cu_die, struct die_var_type **var_types);
+
 #else /*  HAVE_DWARF_GETLOCATIONS_SUPPORT */
 
 static inline int die_get_var_range(Dwarf_Die *sp_die __maybe_unused,
@@ -203,6 +206,11 @@ static inline void die_collect_vars(Dwarf_Die *sc_die __maybe_unused,
 {
 }
 
+static inline void die_collect_global_vars(Dwarf_Die *cu_die __maybe_unused,
+					   struct die_var_type **var_types __maybe_unused)
+{
+}
+
 #endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
 
 #ifdef HAVE_DWARF_CFI_SUPPORT