[Bug dyninst/15614] New: stapdyn only partially fills registers on ppc

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15614

            Bug ID: 15614
           Summary: stapdyn only partially fills registers on ppc
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dyninst
          Assignee: systemtap at sourceware dot org
          Reporter: jistone at redhat dot com
            Blocks: 14573

In Dyninst's EmitterPOWER::emitCall() on powerpc, they enforce a limit of 8
arguments in synthesized calls.  This limits our current strategy of passing
all DWARF registers as a series of varargs.  We already use one argument for
the probe index, and one for the number of arguments following, which only
leaves us space to pass 6 registers.  That will be the ip and r1-r5.

To do more, we'll either have to extend Dyninst itself (which has a comment
stating that additional ppc arguments could go on the stack), or find a way to
build a full pt_regs and pass that as one pointer argument.  The latter might
be possible to do manually, but even nicer would be native Dyninst support to
expose its spill area, also desired for bug 15386.

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