Messages in this thread | | | Date | Wed, 25 Mar 2009 09:34:07 -0700 | From | Tim Bird <> | Subject | Re: Anyone working on ftrace function graph support on ARM? |
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Russell King - ARM Linux wrote: > As pointed out in my previous mail, identifying where on the stack the > return address is stored is only possible for OABI with frame pointers. > > EABI will probably be possible with the stack unwinding code, but it > probably won't be cheap. The EABI unwinder is scheduled for merging > during the present now-open merge window. >
-finstrument-functions is looking better and better. I know it adds more overhead than the mcount call, and may wreak havoc with the dynamic ftrace mechanisms, but at least the callouts are simple, clear, and you get both entry and exit, at fixed costs. I'll take a look at the EABI unwinder to see what kind of variability it introduces (e.g. if it does a stack scan or something).
Thanks very much for the information! -- Tim
============================= Tim Bird Architecture Group Chair, CE Linux Forum Senior Staff Engineer, Sony Corporation of America =============================
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