[PATCH 34/48] perf dwarf-aux: Add die_collect_vars()

[Namhyung Kim <namhyung@kernel.org>]

The die_collect_vars() is to find all variable information in the scope
including function parameters.  The struct die_var_type is to save the
type of the variable with the location (reg and offset) as well as where
it's defined in the code (addr).

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/dwarf-aux.c | 60 +++++++++++++++++++++++++++++++++++++
 tools/perf/util/dwarf-aux.h | 17 +++++++++++
 2 files changed, 77 insertions(+)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 093d7e82b333..16e63d8caf83 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1545,6 +1545,66 @@ int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset)
 	return -1;
 }
 
+static int __die_collect_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 && tag != DW_TAG_formal_parameter)
+		return DIE_FIND_CB_SIBLING;
+
+	if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	/*
+	 * Only collect the first location as it can reconstruct the
+	 * remaining state by following the instructions.
+	 * start = 0 means it covers the whole range.
+	 */
+	if (dwarf_getlocations(&attr, 0, &base, &start, &end, &ops, &nops) <= 0)
+		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 = start;
+	vt->reg = reg_from_dwarf_op(ops);
+	vt->offset = offset_from_dwarf_op(ops);
+	vt->next = *var_types;
+	*var_types = vt;
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_collect_vars - Save all variables and parameters
+ * @sc_die: a scope DIE
+ * @var_types: a pointer to save the resulting list
+ *
+ * Save all variables and parameters in the @sc_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_vars(Dwarf_Die *sc_die, struct die_var_type **var_types)
+{
+	Dwarf_Die die_mem;
+
+	die_find_child(sc_die, __die_collect_vars_cb, (void *)var_types, &die_mem);
+}
+
 #endif
 
 /*
diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
index dc7e98678216..d0ef41738abd 100644
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -135,6 +135,15 @@ void die_skip_prologue(Dwarf_Die *sp_die, Dwarf_Die *cu_die,
 /* Get the list of including scopes */
 int die_get_scopes(Dwarf_Die *cu_die, Dwarf_Addr pc, Dwarf_Die **scopes);
 
+/* Variable type information */
+struct die_var_type {
+	struct die_var_type *next;
+	u64 die_off;
+	u64 addr;
+	int reg;
+	int offset;
+};
+
 #ifdef HAVE_DWARF_GETLOCATIONS_SUPPORT
 
 /* Get byte offset range of given variable DIE */
@@ -153,6 +162,9 @@ Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr pc,
 /* Get the frame base information from CFA */
 int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset);
 
+/* Save all variables and parameters in this scope */
+void die_collect_vars(Dwarf_Die *sc_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,
@@ -187,6 +199,11 @@ static inline int die_get_cfa(Dwarf *dwarf __maybe_unused, u64 pc __maybe_unused
 	return -1;
 }
 
+static inline void die_collect_vars(Dwarf_Die *sc_die __maybe_unused,
+				    struct die_var_type **var_types __maybe_unused)
+{
+}
+
 #endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
 
 #endif /* _DWARF_AUX_H */
-- 
2.42.0.655.g421f12c284-goog