(sort of a combo of ubuntu, systemtap and kernel question, hoping
it's not too far off-topic.)

  for the purpose of an upcoming tutorial, i decided to install
systemtap on my fully-updated 64-bit ubuntu 11.10 laptop, then build a
new kernel and show how simple it is to use systemtap.  it didn't turn
out well.

  since i would be using a self-built kernel, i started here:

  http://sourceware.org/systemtap/wiki/SystemTapWithSelfBuiltKernel

but i'm not convinced that page is entirely correct.

  while i made sure all of the listed kernel options were selected, my
first concern is that i'm not sure why i should have to do "make
headers_install".  all that does is populate the in-tree usr/include/
directory with the exported header files.  i'm not sure why that's
necessary.  is it really required?  does systemtap actually go looking
there for header files?

  also, the rest of that page seems to explain how to make sure
systemtap can find your kernel build tree.  but if you build and
install, then /lib/modules/<release>/build is a symlink to the build
tree, so i'm not sure anything else has to be done.  the rest of that
page also seems unnecessary.  thoughts?

  in any event, i configured, built and installed my new kernel (based
on latest "git pull" from development kernel source), and rebooted to
get:

$ uname -r
3.4.0-rc2+
$

which is correct so, theoretically, i should be read to try a simple
systemtap example.  reading here:

  http://www.domaigne.com/blog/random/running-systemtap-on-ubuntu/

i tried:

$ stap -e 'probe kernel.function("sys_open") {log("hello world") exit()}'

and got:

===== start =====

In file included from /usr/share/systemtap/runtime/transport/transport.c:53:0,
                 from /usr/share/systemtap/runtime/print.c:18,
                 from /usr/share/systemtap/runtime/runtime.h:128,
                 from /tmp/stapadEYdA/stap_59bddd394f89d5f186da7e250db36434_876.c:55:
/usr/share/systemtap/runtime/transport/relay_v2.c:242:2: error: initialization from incompatible pointer type [-Werror]
/usr/share/systemtap/runtime/transport/relay_v2.c:242:2: error: (near initialization for ?__stp_relay_callbacks.create_buf_file?) [-Werror]
In file included from /usr/share/systemtap/runtime/print.c:18:0,
                 from /usr/share/systemtap/runtime/runtime.h:128,
                 from /tmp/stapadEYdA/stap_59bddd394f89d5f186da7e250db36434_876.c:55:
/usr/share/systemtap/runtime/transport/transport.c: In function ?_stp_get_root_dir?:
/usr/share/systemtap/runtime/transport/transport.c:380:8: error: ?struct hlist_head? has no member named ?next?
In file included from /tmp/stapadEYdA/stap_59bddd394f89d5f186da7e250db36434_876.c:57:0:
/usr/share/systemtap/runtime/stat.c: In function ?_stp_stat_get?:
/usr/share/systemtap/runtime/stat.c:213:2: error: ?cpu_possible_map? undeclared (first use in this function)
/usr/share/systemtap/runtime/stat.c:213:2: note: each undeclared identifier is reported only once for each function it appears in
/usr/share/systemtap/runtime/stat.c: In function ?_stp_stat_clear?:
/usr/share/systemtap/runtime/stat.c:248:2: error: ?cpu_possible_map? undeclared (first use in this function)
cc1: all warnings being treated as errors

make[1]: *** [/tmp/stapadEYdA/stap_59bddd394f89d5f186da7e250db36434_876.o] Error 1
make: *** [_module_/tmp/stapadEYdA] Error 2
Pass 4: compilation failed.  Try again with another '--vp 0001' option.

===== end =====

  that doesn't look good.  in particular, this error just looks
strange:

/usr/share/systemtap/runtime/transport/transport.c:380:8: error: ?struct hlist_head? has no member named ?next?

  to make a long story short, that diagnostic is entirely correct --
"struct hlist_head" as it's defined in <types.h> is:

struct hlist_head {
        struct hlist_node *first;
};

but that systemtap source file is trying to refer to a member called
"next", which clearly does not exist.

  am i doing something silly?  can someone else with an ubuntu system
try this and let me know what happens?  thanks.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================