File systemtap-build-source-dir.patch of Package systemtap

From: Tony Jones <tonyj@suse.de>
Subject: adjust build source dir for SuSE packaging
References: bnc#796574

kernel-$flavor:
    /lib/modules/$version-$flavor

kernel-$flavor-devel: requires kernel-source
   /usr/src/linux-$version-obj/$arch/$flavor
   /lib/modules/$version-$flavor/build -> /usr/src/linux-$version-obj/$arch/$flavor
   /lib/modules/$version-$flavor/source -> /usr/src/linux-$version [kernel-source]

kernel-flavor-debugsource:
   /usr/src/debug/kernel-$flavor/
      linux-obj/ {corresponds to /lib/modules/$version-$flavor/build}
      linux-3.0/ {mirrors kernel-source}

DW_AT_comp_dir points to debugsource/linux-obj directory but internal trace
headers are only found in linux-3.0.  Regardless, we don't want to require
debugsource as devel already requires kernel-source which provides the 
necessary headers.

---
 session.cxx |   28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

--- a/session.cxx
+++ b/session.cxx
@@ -100,6 +100,7 @@ systemtap_session::systemtap_session ():
   kernel_release = string (buf.release);
   release = kernel_release;
   kernel_build_tree = "/lib/modules/" + kernel_release + "/build";
+  kernel_source_tree = "/lib/modules/" + kernel_release + "/source";
   architecture = machine = normalize_machine(buf.machine);
 
   for (unsigned i=0; i<5; i++) perpass_verbose[i]=0;
@@ -277,6 +278,7 @@ systemtap_session::systemtap_session (co
 {
   release = kernel_release = kern;
   kernel_build_tree = "/lib/modules/" + kernel_release + "/build";
+  kernel_source_tree = "/lib/modules/" + kernel_release + "/source";
   architecture = machine = normalize_machine(arch);
   setup_kernel_release(kern.c_str());
   native_build = false; // assumed; XXX: could be computed as in check_options()
@@ -1734,21 +1736,39 @@ systemtap_session::setup_kernel_release
       // normal search in tapsets.cxx.  Without CONFIG_DEBUG_INFO, we'd
       // need heuristics such as this one:
 
-      string some_random_source_only_file = kernel_build_tree + "/COPYING";
+      // SUSE: if "build" link specified, attempt to determine "source" link
+      // N.B we won't match using above tapsets.cxx check
+      struct stat buf;
+      string source_tree = kernel_build_tree;
+
+      if (lstat(kernel_build_tree.c_str(), &buf) != -1 && S_ISLNK(buf.st_mode)) {
+	size_t pos = source_tree.find_last_of('/');
+	if (pos < source_tree.length() && source_tree.substr(pos+1, string::npos) == "build")
+	   source_tree.replace(pos+1, string::npos, "source");
+      }
+
+retry:
+      string some_random_source_only_file = source_tree + "/COPYING";
       ifstream epic (some_random_source_only_file.c_str());
       if (! epic.fail())
         {
-          kernel_source_tree = kernel_build_tree;
+          kernel_source_tree = source_tree;
           if (verbose > 2)
             clog << _F("Located kernel source tree (COPYING) at '%s'", kernel_source_tree.c_str()) << endl;
-        }
+        } else if (source_tree != kernel_build_tree) {
+		// one last try using kernel_build_tree (local fs build)
+		source_tree = kernel_build_tree;
+		goto retry;
+	}
     }
   else
     {
       update_release_sysroot = true;
       kernel_release = string (kstr);
-      if (!kernel_release.empty())
+      if (!kernel_release.empty()) {
         kernel_build_tree = "/lib/modules/" + kernel_release + "/build";
+        kernel_source_tree = "/lib/modules/" + kernel_release + "/source";
+      }
 
       // PR10745
       // Let's not look for the kernel_source_tree; it's definitely