README: clarify the suggestion to run the testsuite as root

... and add a bpf smoketest sample while in the vicinity

diff --git a/README b/README
index 511435cdefd53de8d5658981f2ac1df9c379ad95..636012338599c301a4952daa178e83247fcfbe40 100644 (file)
--- a/README
+++ b/README
@@ -98,13 +98,19 @@ Build steps:
   To run a simple test.
   # stap -v -e 'probe vfs.read {printf("read performed\n"); exit()}'
 
-  To run the full test suite from the build tree, install dejagnu, then:
+  To run the full test suite from the build tree, install dejagnu,
+  then run with root privileges:
   # make installcheck
 
   For the prototype dyninst pure-userspace backend, run "stap" as any user.
   % stap --runtime=dyninst -e 'probe process.function("*") { 
                                println(pn(), ":", $$parms) }' -c 'ls'
 
+  For the prototype bpf backend, run "stap" as "root"
+  # stap --runtime=bpf -e 'probe kernel.function("do_exit") {
+                                 printf("bye %d\n", pid()) }'
+
+
 
 Tips: