BZ 5892: Add stap -B to sic systemtap at an alternate kernel build tree

7 files changed, 91 insertions, 22 deletions

diff --git a/ChangeLog b/ChangeLog
index 80cb6b3c..bde86e62 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2008-12-01  Rajan Arora  <rarora@redhat.com>
+
+	PR 5892: Add -B and parameterize all occurences of /lib/modules/...
+	* buildrun.cxx (compile_pass, kernel_built_uprobes): Audit
+	mentions of /lib/modules/... with path to kernel_build_tree
+	provided by -B.
+	* tapsets.cxx (setup_kernel, setup_user, mark_builder::build):
+	Likewise.
+	* translate.cxx (emit_symbol_data): Likewise.
+	* session.h (struct systemtap_session): New member kernel_build_tree.
+	* main.cxx (main): Add case for 'B' and attempt to fetch Version for
+	the kernel build tree using include/config/kernel.release in build
+	path, remove -r REV implies -p4 logic altogether.
+	
+
 2008-11-29  Frank Ch. Eigler  <fche@elastic.org>
 
 	Warnings cleanup.
diff --git a/NEWS b/NEWS
index eecee974..374bcec3 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,8 @@
 * What's new
 
+- A new stap -B option is now available which enables user to sic systemtap
+  at a kernel build tree in any oddball directory.
+
 - A serious problem associated with user-space probing in shared libraries
   was corrected, making it now possible to experiment with probe shared
   libraries.  Assuming dwarf debugging information is installed, use this
diff --git a/buildrun.cxx b/buildrun.cxx
index f9588906..86da95d3 100644
--- a/buildrun.cxx
+++ b/buildrun.cxx
@@ -150,8 +150,12 @@ compile_pass (systemtap_session& s)
   o.close ();
 
   // Generate module directory pathname and make sure it exists.
-  string module_dir = string("/lib/modules/")
-    + s.kernel_release + "/build";
+  string module_dir;
+  if (! s.kernel_build_tree.size ())
+    module_dir = string("/lib/modules/")
+      + s.kernel_release + "/build";
+  else
+    module_dir = s.kernel_build_tree;
   struct stat st;
   rc = stat(module_dir.c_str(), &st);
   if (rc != 0)
@@ -176,14 +180,20 @@ static const string uprobes_home = string(PKGDATADIR "/runtime/uprobes");
 
 /*
  * If uprobes was built as part of the kernel build (either built-in
- * or as a module), the uprobes exports should show up in
- * /lib/modules/`uname -r`/build/Module.symvers.  Return true if so.
+ * or as a module), the uprobes exports should show up in either
+ * /lib/modules/`uname -r`/build/Module.symvers or in the oddball
+ * directory where the user's kernel is built.  Return true if so.
  */
 static bool
 kernel_built_uprobes (systemtap_session& s)
 {
-  string grep_cmd = string ("/bin/grep -q unregister_uprobe /lib/modules/")
-    + s.kernel_release + string ("/build/Module.symvers");
+  string grep_cmd;
+  if (! s.kernel_build_tree.size ())
+    grep_cmd = string ("/bin/grep -q unregister_uprobe /lib/modules/")
+      + s.kernel_release + string ("/build/Module.symvers");
+  else
+    grep_cmd = string ("/bin/grep -q unregister_uprobe ") + 
+      s.kernel_build_tree + string ("/Module.symvers");
   int rc = system (grep_cmd.c_str());
   return (rc == 0);
 }
diff --git a/main.cxx b/main.cxx
index 9d322fe4..7907080d 100644
--- a/main.cxx
+++ b/main.cxx
@@ -328,7 +328,6 @@ main (int argc, char * const argv [])
   string cmdline_script; // -e PROGRAM
   string script_file; // FILE
   bool have_script = false;
-  bool release_changed = false;
   bool save_module = false;
 
   // Initialize defaults
@@ -435,7 +434,7 @@ main (int argc, char * const argv [])
         { "vp", 1, &long_opt, LONG_OPT_VERBOSE_PASS },
         { NULL, 0, NULL, 0 }
       };
-      int grc = getopt_long (argc, argv, "hVMvtp:I:e:o:R:r:m:kgPc:x:D:bs:uqwl:d:L:F",
+      int grc = getopt_long (argc, argv, "hVMvtp:I:e:o:R:r:B:m:kgPc:x:D:bs:uqwl:d:L:F",
                                                           long_options, NULL);
       if (grc < 0)
         break;
@@ -551,9 +550,36 @@ main (int argc, char * const argv [])
 
         case 'r':
           s.kernel_release = string (optarg);
-	  release_changed = true;
           break;
 
+	case 'B':
+	  s.kernel_build_tree = string (optarg);
+	  {
+	    string version_file_name = s.kernel_build_tree
+	      + "/include/config/kernel.release";
+	    // The file include/config/kernel.release within the
+	    // build tree is used to pull out the version information
+	    // : Failing which -B is ignored
+	      
+	    ifstream version_file (version_file_name.c_str());
+	    if (version_file.fail ())
+	      {
+		cerr << "error: No file: " << version_file_name 
+		     << " found" << endl;
+		cerr << "Please check path to -B again" << endl;
+		s.kernel_build_tree = "";
+	      }
+	    else 
+	      {
+		char c;
+		string kernel_build_version;
+		while (version_file.get(c) && c != '\n')
+		  kernel_build_version.push_back(c);
+		s.kernel_release = kernel_build_version;
+	      }
+	  }
+	  break;
+
         case 'k':
           s.keep_tmpdir = true;
           s.use_cache = false; /* User wants to keep a usable build tree. */
@@ -712,12 +738,16 @@ main (int argc, char * const argv [])
         s.kernel_symtab_path = string("/boot/System.map-") + s.kernel_release;
     }
 
-  if (s.last_pass > 4 && release_changed)
-    {
-      if (s.verbose)
-        cerr << "Warning: changing last pass to 4 since cross-compiling" << endl;
-      s.last_pass = 4;
-    }
+  //  Since the introduction of -B, the logic of -r REV implies -p4 is dropped.
+  //  If the version of kernel build tree specified by -B is not the same as 
+  //  `uname -r`, stap will give a failure message in pass5 anyways.
+  //
+  //  if (s.last_pass > 4 && release_changed)
+  //  {
+  //    if (s.verbose)
+  //      cerr << "Warning: changing last pass to 4 since cross-compiling" << endl;
+  //    s.last_pass = 4;
+  //  }
 
   for (int i = optind; i < argc; i++)
     {
diff --git a/session.h b/session.h
index 0a1e6fc4..e6b409cf 100644
--- a/session.h
+++ b/session.h
@@ -81,6 +81,7 @@ struct systemtap_session
   std::vector<std::string> args;
   std::string kernel_release;
   std::string kernel_base_release;
+  std::string kernel_build_tree;
   std::string architecture;
   std::string runtime_path;
   std::string data_path;
diff --git a/tapsets.cxx b/tapsets.cxx
index 4e4d471d..88c6ea41 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -898,9 +898,11 @@ struct dwflpp
     static char *debuginfo_env_arr = getenv("SYSTEMTAP_DEBUGINFO_PATH");
 
     static char *debuginfo_path = (debuginfo_env_arr ?
-                                   debuginfo_env_arr : debuginfo_path_arr);
+				   debuginfo_env_arr : sess.kernel_build_tree.size () ?
+				   (char *) sess.kernel_build_tree.c_str() : debuginfo_path_arr);
     static const char *debug_path = (debuginfo_env_arr ?
-                                   debuginfo_env_arr : sess.kernel_release.c_str());
+				     debuginfo_env_arr : sess.kernel_build_tree.size () ?
+				     sess.kernel_build_tree.c_str() : sess.kernel_release.c_str());
 
     static const Dwfl_Callbacks kernel_callbacks =
       {
@@ -951,7 +953,8 @@ struct dwflpp
     // XXX: this is where the session -R parameter could come in
     static char debuginfo_path_arr[] = "-:.debug:/usr/lib/debug:build";
     static char *debuginfo_env_arr = getenv("SYSTEMTAP_DEBUGINFO_PATH");
-    static char *debuginfo_path = (debuginfo_env_arr ?: debuginfo_path_arr);
+    static char *debuginfo_path = (debuginfo_env_arr ?: sess.kernel_build_tree.size () ?
+				   (char *) sess.kernel_build_tree.c_str() : debuginfo_path_arr);
 
     static const Dwfl_Callbacks user_callbacks =
       {
@@ -8712,8 +8715,13 @@ mark_builder::build(systemtap_session & sess,
   if (! cache_initialized)
     {
       cache_initialized = true;
-      string module_markers_path = "/lib/modules/" + sess.kernel_release
+      string module_markers_path;
+      if (! sess.kernel_build_tree.size ())
+	module_markers_path = "/lib/modules/" + sess.kernel_release
 	  + "/build/Module.markers";
+      else
+	module_markers_path = sess.kernel_build_tree + "/Module.markers";
+	
 
       ifstream module_markers;
       module_markers.open(module_markers_path.c_str(), ifstream::in);
diff --git a/translate.cxx b/translate.cxx
index b90bb5ab..dc9f12bc 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -4710,9 +4710,11 @@ emit_symbol_data (systemtap_session& s)
   static char *debuginfo_env_arr = getenv("SYSTEMTAP_DEBUGINFO_PATH");
 
   static char *debuginfo_path = (debuginfo_env_arr ?
-                                 debuginfo_env_arr : debuginfo_path_arr);
-  static const  char *debug_path = (debuginfo_env_arr ?
-                                    debuginfo_env_arr : s.kernel_release.c_str());
+                                 debuginfo_env_arr : s.kernel_build_tree.size () ?
+				 (char *) s.kernel_build_tree.c_str() : debuginfo_path_arr);
+  static const char *debug_path = (debuginfo_env_arr ?
+				   debuginfo_env_arr : s.kernel_build_tree.size () ?
+				   s.kernel_build_tree.c_str() : s.kernel_release.c_str());
 
   // ---- step 1: process any kernel modules listed
   static const Dwfl_Callbacks kernel_callbacks =