On Mon, Nov 14, 2016 at 11:24 AM, Helge Deller <deller@xxxxxx> wrote: > What I want to archieve is to modify the return pointer, in order > to be able to track when the function returns to his caller. > The kernel ftracer uses this then to generate call stacks and to > time the function. > Looking at the above code, it should then be possible for me > to modify -10(r3), but is there a guarantee that it's always at > -10(r3) and that r3 is used? > That's the reason I asked if we could modify mcount to > give the address (in the stack) of the return pointer, but maybe > it's just overkill for this use case ? Why do you need to modify the value? AFAICT ftrace uses these values heuristically e.g. HAVE_FUNCTION_GRAPH_FP_TEST, HAVE_FUNCTION_GRAPH_RET_ADDR_PTR? For example the only uses I see are in ftrace_pop_return_trace() and they are purely heuristic. Cheers, Carlos. -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
