[Bug runtime/17696] Systemtap fails to find kernel tracepoints when kernel is built in a separate directory from source tree

["zhuo at bitoasis dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17696

--- Comment #2 from Zhuo QL <zhuo at bitoasis dot com> ---
(In reply to Josh Stone from comment #1)
> Please let me know if this commit fixed it for you:
> 
> commit b19a43768009076de3aea638922dfaebb687e3e9
> Author: Josh Stone <jistone@redhat.com>
> Date:   Thu Jan 8 14:47:20 2015 -0800
> 
>     Use the kernel source symlink for tracepoints
>     
>     When the source symlink is different than the build symlink, as for
>     out-of-tree kernel builds and Debian linux-headers, then we should use
>     that path as a prefix for finding tracepoint headers.

Thanks for your work, it works well with the debian system provided kernel!

But, it still does not work with my self-built kernel(built with a seperate
KBUILD_OUTPUT).

I read the lines around your commit and some logs, then found line 11132 of
tapsets.cxx: 

const char* name = dwarf_formstring (dwarf_attr (cudie, DW_AT_comp_dir,
&attr));

Here we still get the dir to /lib/modules/${uname -r}/build  under this
situation.

----------8<-------------
diff --git a/tapsets.cxx b/tapsets.cxx
index 85fd76b..1b82f55 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -11153,7 +11153,8 @@ tracepoint_builder::init_dw(systemtap_session& s)
     }

   // find kernel_source_tree from a source link, when different from build
-  if (s.kernel_source_tree == "" && endswith(s.kernel_build_tree, "/build"))
+  if ((s.kernel_source_tree == "" || endswith(s.kernel_source_tree, "/build"))
+      && endswith(s.kernel_build_tree, "/build"))
     {
       string source_tree = s.kernel_build_tree;
       source_tree.replace(source_tree.length() - 5, 5, "source");
---------->8--------------

This patch fixes it, could you consider applying it? 

Thanks again.

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