bcc/tools: Introduce bpf_probe_read_user to the tools.

This is essential for architecture which do have overlapping address space.
- bpf_probe_read_kernel() shall be used for reading data from kernel space
to the bpf vm.
- bpf_probe_read_user() shall be used for reading data from user space
  to the bpf vm.

Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
diff --git a/tools/lib/uflow.py b/tools/lib/uflow.py
index 4779ba2..de3d7e2 100755
--- a/tools/lib/uflow.py
+++ b/tools/lib/uflow.py
@@ -81,8 +81,8 @@
 
     READ_CLASS
     READ_METHOD
-    bpf_probe_read(&data.clazz, sizeof(data.clazz), (void *)clazz);
-    bpf_probe_read(&data.method, sizeof(data.method), (void *)method);
+    bpf_probe_read_user(&data.clazz, sizeof(data.clazz), (void *)clazz);
+    bpf_probe_read_user(&data.method, sizeof(data.method), (void *)method);
 
     FILTER_CLASS
     FILTER_METHOD