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    SubjectRe: [PATCH 0/2] ftrace: fixes for PPC
    On Mon, Oct 20, 2008 at 12:30:33PM -0400, Steven Rostedt wrote:
    >> Anyway, if you want a tester let me know. It seems 2.6.27.1 should be
    >> fine since FTRACE was disabled, but for .28-rc1 it would be cool if it
    >> worked :).
    >
    >Hi Josh,
    >
    >I've been looking deeper at the code for PPC. I realized that my PPC64 box
    >that I've been testing on did not use modules. While looking at the module
    >code it dawned on me the dynamic ftrace needs a bit of work. This is
    >because the way modules are handled in PPC (and other architectures as
    >well). The jmps used by mcount is a 24 bit jump. Since the modules are
    >loaded farther than 24bits away, a trampoline is needed.

    Ah, indeed.

    >A bit of rework is needed in the ftrace infrastructure to handle the
    >trampoline. Too much work to go into 28. I'll start working on code that
    >can hopefully be ready and tested for 29. It's not that major of a change,
    >but since the merge window for 28 has already been opened, we would like
    >to get a bit more testing in before we hand it over to Linus.

    That seems like a good plan. Should we mark dynamic ftrace as X86 only
    in Kconfig for .28 to prevent people from inadvertently setting it?

    josh


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