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/gethostlatency.py b/tools/gethostlatency.py
index f7506a8..a6b8080 100755
--- a/tools/gethostlatency.py
+++ b/tools/gethostlatency.py
@@ -64,7 +64,7 @@
     u32 pid = bpf_get_current_pid_tgid();
 
     if (bpf_get_current_comm(&val.comm, sizeof(val.comm)) == 0) {
-        bpf_probe_read(&val.host, sizeof(val.host),
+        bpf_probe_read_user(&val.host, sizeof(val.host),
                        (void *)PT_REGS_PARM1(ctx));
         val.pid = bpf_get_current_pid_tgid();
         val.ts = bpf_ktime_get_ns();