systemtap java hotspot backtrace support

[Mark Wielaard]

On Fri, 2009-12-11 at 16:32 -0500, jon.vanalten at redhat.com wrote:
> Gave this a go, seems to work as advertised (for better or worse).  I
> tend to agree that the dependency on info extracted in the vm_init
> probe is less than desireable.  From a usefulness perspective, this is
> especially because an attempt to target an already-running java
> process will fail horribly.  Even so, once the x86_64 blocker is
> resolved and the unreleased systemtap fixes you mentioned are
> released, I'd also like to see this in IcedTea with the tapsets
> already there.  It might then be a good idea to note the systemtap
> version dependency in the comments at the top of the script.

Thanks for testing. I do have some ideas how to resolve the init
dependency, but it will need some systemtap extensions to access
program/library globals from function contexts.

The x86_64 blocker has been fixed:
http://sourceware.org/bugzilla/show_bug.cgi?id=11034

Good idea to note the dependency in the script. I added that.

I also added one small addition to work around the fact that on 32bit
systems get_long might return negative longs. So we now mask against a
new global ptr_mask that is set in the init probe depending on
architecture. Just like we do with user_char. Maybe there should be a
systemtap tapset for fetching unsigned user data?

2009-12-13  Mark Wielaard  <mjw at redhat.com>

        * Makefile.am (stamps/icedtea.stamp): Install jstack.stp.
        (stamps/icedtea-debug.stamp): Likewise.
        * configure.ac (AC_CONFIG_FILES): Add tapset/jstack.stp.
        * tapset/jstack.stp.in: New tapset.

Cheers,

Mark