From: Frank Ch. Eigler <fche@redhat.com>
Date: Thu, 28 May 2020 16:45:06 +0000 (-0400)
Subject: PR14013: don't reject DW_OP_GNU_push_tls_address DWARF location operator
X-Git-Tag: release-4.3~32
X-Git-Url: https://sourceware.org/git/?a=commitdiff_plain;h=f29f23213cc9668fb6c54a34c815257b7cbeaf5c;p=systemtap.git

PR14013: don't reject DW_OP_GNU_push_tls_address DWARF location operator

Subject DWARF OP is used for accessing TLS variables in GCC-compiled C
code.  In all but the simplest cases, we must emulate libthread_db
logic for resolving TLS addresses.  Step 1 is to map this operator to
a tapset function call __push_tls_address, which will implement the
architecture-specific lookup functionality.

We also tweak systemtap_session::print_error to ensure even isolated
little error messages seen only once do get printed.

See also: https://infinitynotes.org/wiki/Glibc
---

diff --git a/elaborate.cxx b/elaborate.cxx
index e90f97e8b..6cbc85038 100644
--- a/elaborate.cxx
+++ b/elaborate.cxx
@@ -2941,7 +2941,8 @@ symresolution_info::visit_functioncall (functioncall* e)
   else
     {
       string sugs = levenshtein_suggest(e->function, collect_functions(), 5); // print 5 funcs
-      throw SEMANTIC_ERROR(_F("unresolved function%s",
+      throw SEMANTIC_ERROR(_F("unresolved function %s%s",
+                              string(e->function).c_str(),
                               sugs.empty() ? "" : (_(" (similar: ") + sugs + ")").c_str()),
                            e->tok);
     }
diff --git a/loc2stap.cxx b/loc2stap.cxx
index d4fd05182..6e6069dcf 100644
--- a/loc2stap.cxx
+++ b/loc2stap.cxx
@@ -690,6 +690,18 @@ location_context::translate (const Dwarf_Op *expr, const size_t len,
 	    }
 	    break;
 
+          case DW_OP_GNU_push_tls_address:
+            {
+              POP(addr);
+              functioncall *fc = new functioncall;
+              fc->tok = e->tok;
+              fc->function = std::string("__push_tls_address");
+              fc->synthetic = true;
+              fc->args.push_back(addr);
+	      PUSH(fc);
+            }
+            break;
+            
 	  default:
 	    DIE ("unhandled DW_OP operation");
 	    break;
diff --git a/session.cxx b/session.cxx
index 1304570cd..d0959f018 100644
--- a/session.cxx
+++ b/session.cxx
@@ -2382,6 +2382,7 @@ systemtap_session::print_error (const semantic_error& se)
   if (verbose > 0 || seen_errors[se.errsrc_chain()] < 1)
     {
       seen_errors[se.errsrc_chain()]++;
+      cerr << build_error_msg(se);
       for (const semantic_error *e = &se; e != NULL; e = e->get_chain())
         if (verbose > 1 || seen_errors[e->errsrc] < 1) // dupe-eliminate chained errors too
           {