[PATCH 2/4] perf dwarf-aux: Support DW_OP_addrx locations for global variables

[James Clark <james.clark@linaro.org>]

die_find_variable_by_addr() and die_collect_global_vars() only accept
global variables with a DW_OP_addr location. DWARF 5 producers like
clang use DW_OP_addrx instead, which is an index into .debug_addr, so
global variables are never found when Perf is built with LLVM=1.

Add a helper that also resolves DW_OP_addrx and DW_OP_GNU_addr_index
through dwarf_getlocation_attr() and dwarf_formaddr(), and use it in
both places. This fixes the "perf data type profiling tests" test:

  $ perf test -vvv "perf data type profiling tests"
  ...
  Basic C perf annotate test
  Basic annotate [Failed: missing target data type]
  ...
  Pipe C perf annotate test
  Pipe annotate [Failed: missing target data type]
  ...
  Basic FS perf annotate test
  Basic annotate [Failed: missing target data type]
  ...
  Pipe FS perf annotate test
  Pipe annotate [Failed: missing target data type]
  ---- end(-1) ----
   88: perf data type profiling tests : FAILED!

Fixes: d60469d7c0e5 ("perf dwarf-aux: Add die_find_variable_by_addr()")
Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/perf/util/dwarf-aux.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 742fccba5376..2f0c4b229659 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1658,6 +1658,27 @@ Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg,
 	return result;
 }
 
+/*
+ * Get the absolute address of a location op. DWARF 5 producers like clang use
+ * DW_OP_addrx, which is an index into .debug_addr, instead of DW_OP_addr.
+ */
+static bool die_get_op_addr(Dwarf_Attribute *attr, Dwarf_Op *op, Dwarf_Addr *addr)
+{
+	Dwarf_Attribute addr_attr;
+
+	switch (op->atom) {
+	case DW_OP_addr:
+		*addr = op->number;
+		return true;
+	case DW_OP_addrx:
+	case DW_OP_GNU_addr_index:
+		return dwarf_getlocation_attr(attr, op, &addr_attr) == 0 &&
+		       dwarf_formaddr(&addr_attr, addr) == 0;
+	default:
+		return false;
+	}
+}
+
 /* Only checks direct child DIEs in the given scope */
 static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg)
 {
@@ -1665,7 +1686,7 @@ static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg)
 	int tag = dwarf_tag(die_mem);
 	ptrdiff_t off = 0;
 	Dwarf_Attribute attr;
-	Dwarf_Addr base, start, end;
+	Dwarf_Addr base, start, end, addr;
 	Dwarf_Op *ops;
 	size_t nops;
 
@@ -1676,11 +1697,11 @@ static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg)
 		return DIE_FIND_CB_SIBLING;
 
 	while ((off = dwarf_getlocations(&attr, off, &base, &start, &end, &ops, &nops)) > 0) {
-		if (ops->atom != DW_OP_addr)
+		if (!die_get_op_addr(&attr, ops, &addr))
 			continue;
 
 		if (check_allowed_ops(ops, nops) &&
-		    match_var_offset(die_mem, data, data->addr, ops->number,
+		    match_var_offset(die_mem, data, data->addr, addr,
 				     /*is_pointer=*/false))
 			return DIE_FIND_CB_END;
 	}
@@ -1806,7 +1827,7 @@ static int __die_collect_global_vars_cb(Dwarf_Die *die_mem, void *arg)
 	Dwarf_Die type_die;
 	int tag = dwarf_tag(die_mem);
 	Dwarf_Attribute attr;
-	Dwarf_Addr base, start, end;
+	Dwarf_Addr base, start, end, addr;
 	Dwarf_Op *ops;
 	size_t nops;
 	struct die_var_type *vt;
@@ -1821,7 +1842,7 @@ static int __die_collect_global_vars_cb(Dwarf_Die *die_mem, void *arg)
 	if (dwarf_getlocations(&attr, 0, &base, &start, &end, &ops, &nops) <= 0)
 		return DIE_FIND_CB_SIBLING;
 
-	if (ops->atom != DW_OP_addr)
+	if (!die_get_op_addr(&attr, ops, &addr))
 		return DIE_FIND_CB_SIBLING;
 
 	if (!check_allowed_ops(ops, nops))
@@ -1837,7 +1858,7 @@ static int __die_collect_global_vars_cb(Dwarf_Die *die_mem, void *arg)
 	vt->die_off = dwarf_dieoffset(&type_die);
 	vt->die_tag = dwarf_tag(&type_die);
 	vt->from_alt = !die_same_file(die_mem, &type_die);
-	vt->addr = ops->number;
+	vt->addr = addr;
 	vt->end = 0;
 	vt->has_range = false;
 	vt->reg = -1;

-- 
2.43.0