PR9959: hide tracepoint arguments of unknown type

We always have to know the type name of tracepoint arguments, so we can
declare the right function callback, but we can suppress access to those
types which we don't (yet) know how to read.

1 files changed, 22 insertions, 18 deletions

diff --git a/tapsets.cxx b/tapsets.cxx
index a4da7811..42be4556 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -9231,9 +9231,9 @@ mark_builder::build(systemtap_session & sess,
 struct tracepoint_arg
 {
   string name, c_type;
-  bool used, isptr;
+  bool usable, used, isptr;
   Dwarf_Die type_die;
-  tracepoint_arg(): used(false), isptr(false) {}
+  tracepoint_arg(): usable(false), used(false), isptr(false) {}
 };
 
 struct tracepoint_derived_probe: public derived_probe
@@ -9285,7 +9285,7 @@ tracepoint_var_expanding_visitor::visit_target_symbol_arg (target_symbol* e)
   // search for a tracepoint parameter matching this name
   tracepoint_arg *arg = NULL;
   for (unsigned i = 0; i < args.size(); ++i)
-    if (args[i].name == argname)
+    if (args[i].usable && args[i].name == argname)
       {
         arg = &args[i];
         arg->used = true;
@@ -9504,6 +9504,8 @@ tracepoint_var_expanding_visitor::visit_target_symbol_context (target_symbol* e)
 
       for (unsigned i = 0; i < args.size(); ++i)
         {
+          if (!args[i].usable)
+            continue;
           if (i > 0)
             pf->raw_components += " ";
           pf->raw_components += args[i].name;
@@ -9649,28 +9651,29 @@ dwarf_type_name(Dwarf_Die& type_die, string& c_type)
 
 
 static bool
-resolve_tracepoint_arg_type(Dwarf_Die& type_die, bool& isptr)
+resolve_tracepoint_arg_type(tracepoint_arg& arg)
 {
   Dwarf_Attribute type_attr;
-  switch (dwarf_tag(&type_die))
+  switch (dwarf_tag(&arg.type_die))
     {
     case DW_TAG_typedef:
     case DW_TAG_const_type:
     case DW_TAG_volatile_type:
       // iterate on the referent type
-      return (dwarf_attr_integrate(&type_die, DW_AT_type, &type_attr)
-              && dwarf_formref_die(&type_attr, &type_die)
-              && resolve_tracepoint_arg_type(type_die, isptr));
+      return (dwarf_attr_integrate(&arg.type_die, DW_AT_type, &type_attr)
+              && dwarf_formref_die(&type_attr, &arg.type_die)
+              && resolve_tracepoint_arg_type(arg));
     case DW_TAG_base_type:
       // base types will simply be treated as script longs
-      isptr = false;
+      arg.isptr = false;
       return true;
     case DW_TAG_pointer_type:
-      // pointers can be either script longs,
-      // or dereferenced with their referent type
-      isptr = true;
-      return (dwarf_attr_integrate(&type_die, DW_AT_type, &type_attr)
-              && dwarf_formref_die(&type_attr, &type_die));
+      // pointers can be treated as script longs,
+      // and if we know their type, they can also be dereferenced
+      if (dwarf_attr_integrate(&arg.type_die, DW_AT_type, &type_attr)
+          && dwarf_formref_die(&type_attr, &arg.type_die))
+        arg.isptr = true;
+      return true;
     default:
       // should we consider other types too?
       return false;
@@ -9694,12 +9697,12 @@ tracepoint_derived_probe::build_args(dwflpp& dw, Dwarf_Die& func_die)
           Dwarf_Attribute type_attr;
           if (!dwarf_attr_integrate (&arg, DW_AT_type, &type_attr)
               || !dwarf_formref_die (&type_attr, &tparg.type_die)
-              || !dwarf_type_name(tparg.type_die, tparg.c_type)
-              || !resolve_tracepoint_arg_type(tparg.type_die, tparg.isptr))
+              || !dwarf_type_name(tparg.type_die, tparg.c_type))
             throw semantic_error ("cannot get type of tracepoint '"
                                   + tracepoint_name + "' parameter '"
                                   + tparg.name + "'");
 
+          tparg.usable = resolve_tracepoint_arg_type(tparg);
           args.push_back(tparg);
           if (sess.verbose > 4)
             clog << "found parameter for tracepoint '" << tracepoint_name
@@ -9712,8 +9715,9 @@ tracepoint_derived_probe::build_args(dwflpp& dw, Dwarf_Die& func_die)
 void
 tracepoint_derived_probe::printargs(std::ostream &o) const
 {
-      for (unsigned i = 0; i < args.size(); ++i)
-       o << " $" << args[i].name << ":" << args[i].c_type;
+  for (unsigned i = 0; i < args.size(); ++i)
+    if (args[i].usable)
+      o << " $" << args[i].name << ":" << args[i].c_type;
 }
 
 void