PR909: store kernel exported symbols in session object

* session.h (kernel_exports): New field.
* main.cxx (parse_kernel_exports): Fill it.
* tapset-perfmon.cxx (perf_builder::build): Check it for our pal
  perf_event_create_kernel_counter.

3 files changed, 40 insertions, 4 deletions

diff --git a/main.cxx b/main.cxx
index 6c5b9e8c..dd2694ae 100644
--- a/main.cxx
+++ b/main.cxx
@@ -471,6 +471,38 @@ int parse_kernel_config (systemtap_session &s)
   return 0;
 }
 
+
+int parse_kernel_exports (systemtap_session &s)
+{
+  string kernel_exports_file = s.kernel_build_tree + "/Module.symvers";
+  struct stat st;
+  int rc = stat(kernel_exports_file.c_str(), &st);
+  if (rc != 0)
+    {
+	clog << "Checking \"" << kernel_exports_file << "\" failed: " << strerror(errno) << endl
+	     << "Ensure kernel development headers & makefiles are installed." << endl;
+	return rc;
+    }
+
+  ifstream kef (kernel_exports_file.c_str());
+  string line;
+  while (getline (kef, line))
+    {
+      vector<string> tokens;
+      tokenize (line, tokens, "\t");
+      if (tokens.size() == 4 &&
+          tokens[2] == "vmlinux" &&
+          tokens[3].substr(0,13) == string("EXPORT_SYMBOL"))
+        s.kernel_exports.insert (tokens[1]);
+    }
+  if (s.verbose > 2)
+    clog << "Parsed kernel \"" << kernel_exports_file << "\", number of vmlinux exports: " << s.kernel_exports.size() << endl;
+  
+  kef.close();
+  return 0;
+}
+
+
 /*
  * Returns a string describing memory resource usage.
  * Since it seems getrusage() doesn't maintain the mem related fields,
@@ -1129,9 +1161,10 @@ main (int argc, char * const argv [])
 
   // Now that no further changes to s.kernel_build_tree can occur, let's use it.
   if (parse_kernel_config (s) != 0)
-    {
-	  exit (1);
-    }
+    exit (1);
+
+  if (parse_kernel_exports (s) != 0)
+    exit (1);
 
 
   // Create the name of the C source file within the temporary
diff --git a/session.h b/session.h
index 1a1a2c9c..f53de57c 100644
--- a/session.h
+++ b/session.h
@@ -1,5 +1,5 @@
 // -*- C++ -*-
-// Copyright (C) 2005-2009 Red Hat Inc.
+// Copyright (C) 2005-2010 Red Hat Inc.
 //
 // This file is part of systemtap, and is free software.  You can
 // redistribute it and/or modify it under the terms of the GNU General
@@ -90,6 +90,7 @@ struct systemtap_session
   std::string kernel_base_release;
   std::string kernel_build_tree;
   std::map<std::string,std::string> kernel_config;
+  std::set<std::string> kernel_exports;
   std::string architecture;
   std::string runtime_path;
   std::string data_path;
diff --git a/tapset-perfmon.cxx b/tapset-perfmon.cxx
index 81d6c2d7..9078dfd9 100644
--- a/tapset-perfmon.cxx
+++ b/tapset-perfmon.cxx
@@ -198,6 +198,8 @@ perf_builder::build(systemtap_session & sess,
 {
   // XXX need additional version checks too?
   // --- perhaps look for export of perf_event_create_kernel_counter
+  if (sess.kernel_exports.find("perf_event_create_kernel_counter") == sess.kernel_exports.end())
+    throw semantic_error ("perf probes not available without exported perf_event_create_kernel_counter");
   if (sess.kernel_config["CONFIG_PERF_EVENTS"] != "y")
     throw semantic_error ("perf probes not available without CONFIG_PERF_EVENTS");