Re: Warning for buildok/context_test.stp on utrace kernel

[Mark Wielaard <mjw at redhat dot com>]

On Wed, 2010-02-10 at 17:42 +0800, Wenji Huang wrote:
> Hi,
> 
> There will be warning if we run the following test on
> RHEL5, Fedora kernel or utrace kernel.
> 
> $ stap -p4 testsuite/buildok/context_test.stp
> WARNING: "uprobe_get_pc" 
> [/tmp/staphrGioI/stap_0aef4ead3fec39f2dee30c60b1b684d2_8042.ko] undefined!
> /home/wjhuang/.systemtap/cache/0a/stap_0aef4ead3fec39f2dee30c60b1b684d2_8042.ko
> 
> There reason is from print_ubacktrace() in probe.
> 
> In fact, if we run stap -ve 'probe begin(print_ubacktrace()){}' on
> utrace kernel without loaded uprobes module.  We can see the error
> 
> Error inserting module 
> '/tmp/stap0t5pyH/stap_5bd1a1d6b83ff84cfa8e7c67a402fa40_1153.ko': Unknown 
> symbol in module
> 
> since no symbol uprobe_get_pc can be resolved.

And that is because the uprobes module isn't pulled in?
This seems to come from commit 4c5ce7 which introduced a call to
uprobe_get_pc() in __stp_stack_print().

How can we make sure that if that is used (through ubacktrace) the
uprobes module gets automagically loaded?

> Yes, the test case is a little picky, but maybe we can
> process it in a more graceful way.
> 
> BTW: there is no manual for print_ubacktrace, ubacktrace(), etc.

I got man pages for all of them. Since they are documented in
tapset/ucontext_unwind.stp they should show up in the TapSet Reference
Manual and as individual man pages.

Cheers,

Mark