Add support for expanding DW_TAG_subroutine_type and the parameters
in DW_TAG_formal_parameter. Use this to also expand subprograms.

Example output with --dump-dies:

  subprogram (
    formal_parameter pointer_type {
      const_type {
        base_type char byte_size(1) encoding(6)
      }
    }
  )
  -> base_type unsigned long byte_size(8) encoding(7)

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Neal Gompa <neal@gompa.dev>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c         | 84 ++++++++++++++++++++++++++-
 scripts/gendwarfksyms/gendwarfksyms.h |  4 ++
 2 files changed, 85 insertions(+), 3 deletions(-)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 1d67ee18a388..7e6b477d7c12 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -211,6 +211,15 @@ DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(byte_size)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
 
+/* Match functions -- die_match_callback_t */
+#define DEFINE_MATCH(type)                                     \
+	static bool match_##type##_type(Dwarf_Die *die)        \
+	{                                                      \
+		return dwarf_tag(die) == DW_TAG_##type##_type; \
+	}
+
+DEFINE_MATCH(formal_parameter)
+
 bool match_all(Dwarf_Die *die)
 {
 	return true;
@@ -223,19 +232,28 @@ int process_die_container(struct state *state, struct die *cache,
 	Dwarf_Die current;
 	int res;
 
+	/* Track the first item in lists. */
+	if (state)
+		state->first_list_item = true;
+
 	res = checkp(dwarf_child(die, &current));
 	while (!res) {
 		if (match(&current)) {
 			/* <0 = error, 0 = continue, >0 = stop */
 			res = checkp(func(state, cache, &current));
 			if (res)
-				return res;
+				goto out;
 		}
 
 		res = checkp(dwarf_siblingof(&current, &current));
 	}
 
-	return 0;
+	res = 0;
+out:
+	if (state)
+		state->first_list_item = false;
+
+	return res;
 }
 
 static int process_type(struct state *state, struct die *parent,
@@ -255,6 +273,40 @@ static void process_type_attr(struct state *state, struct die *cache,
 	process(cache, "base_type void");
 }
 
+static void process_list_comma(struct state *state, struct die *cache)
+{
+	if (state->first_list_item) {
+		state->first_list_item = false;
+	} else {
+		process(cache, " ,");
+		process_linebreak(cache, 0);
+	}
+}
+
+/* Comma-separated with DW_AT_type */
+static void __process_list_type(struct state *state, struct die *cache,
+				Dwarf_Die *die, const char *type)
+{
+	const char *name = get_name_attr(die);
+
+	process_list_comma(state, cache);
+	process(cache, type);
+	process_type_attr(state, cache, die);
+	if (name) {
+		process(cache, " ");
+		process(cache, name);
+	}
+}
+
+#define DEFINE_PROCESS_LIST_TYPE(type)                                       \
+	static void process_##type##_type(struct state *state,               \
+					  struct die *cache, Dwarf_Die *die) \
+	{                                                                    \
+		__process_list_type(state, cache, die, #type " ");           \
+	}
+
+DEFINE_PROCESS_LIST_TYPE(formal_parameter)
+
 /* Container types with DW_AT_type */
 static void __process_type(struct state *state, struct die *cache,
 			   Dwarf_Die *die, const char *type)
@@ -289,6 +341,29 @@ DEFINE_PROCESS_TYPE(shared)
 DEFINE_PROCESS_TYPE(volatile)
 DEFINE_PROCESS_TYPE(typedef)
 
+static void __process_subroutine_type(struct state *state, struct die *cache,
+				      Dwarf_Die *die, const char *type)
+{
+	process(cache, type);
+	process(cache, " (");
+	process_linebreak(cache, 1);
+	/* Parameters */
+	check(process_die_container(state, cache, die, process_type,
+				    match_formal_parameter_type));
+	process_linebreak(cache, -1);
+	process(cache, ")");
+	process_linebreak(cache, 0);
+	/* Return type */
+	process(cache, "-> ");
+	process_type_attr(state, cache, die);
+}
+
+static void process_subroutine_type(struct state *state, struct die *cache,
+				    Dwarf_Die *die)
+{
+	__process_subroutine_type(state, cache, die, "subroutine_type");
+}
+
 static void process_base_type(struct state *state, struct die *cache,
 			      Dwarf_Die *die)
 {
@@ -359,8 +434,11 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 	PROCESS_TYPE(rvalue_reference)
 	PROCESS_TYPE(shared)
 	PROCESS_TYPE(volatile)
+	/* Subtypes */
+	PROCESS_TYPE(formal_parameter)
 	/* Other types */
 	PROCESS_TYPE(base)
+	PROCESS_TYPE(subroutine)
 	PROCESS_TYPE(typedef)
 	default:
 		debug("unimplemented type: %x", tag);
@@ -390,7 +468,7 @@ static void process_symbol(struct state *state, Dwarf_Die *die,
 static int __process_subprogram(struct state *state, struct die *cache,
 				Dwarf_Die *die)
 {
-	process(cache, "subprogram");
+	__process_subroutine_type(state, cache, die, "subprogram");
 	return 0;
 }
 
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 206ba8e3f1a8..d01fc1488f76 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -63,6 +63,7 @@ extern int dump_dies;
 #define checkp(expr) __check(expr, __res < 0)
 
 /* Consistent aliases (DW_TAG_<type>_type) for DWARF tags */
+#define DW_TAG_formal_parameter_type DW_TAG_formal_parameter
 #define DW_TAG_typedef_type DW_TAG_typedef
 
 /*
@@ -157,6 +158,9 @@ void die_map_free(void);
 struct state {
 	struct symbol *sym;
 	Dwarf_Die die;
+
+	/* List expansion */
+	bool first_list_item;
 };
 
 typedef int (*die_callback_t)(struct state *state, struct die *cache,
-- 
2.47.0.163.g1226f6d8fa-goog