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Minimizing instrumentation impacts

Minimizing instrumentation impacts

Posted Dec 13, 2009 15:39 UTC (Sun) by oak (guest, #2786)
Parent article: Minimizing instrumentation impacts

"The instructions that are located at the address to be probed still need
to be executed once they are replaced by a jump, of course, so a 'detour'
buffer is created. The detour buffer emulates an exception that contains
the instructions copied from the probed location, followed by a jump back
to the original execution path."

Doesn't kernel already use[1] some kind of a "detour" buffer to execute
the instructions (at least I remember reading about something similar)?
And isn't this kind of code architecture specific[2], which archs this
patch supports?

[1] Disabling breakpoint, running the instructions and re-enabling the
breakpoint cannot be used because then there's a race-condition with the
other threads, so the instructions are executed from a buffer set aside
for this purpose.

[2] there are some instructions which need "emulation" when run from a
different location due to using data at relative offsets.


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