Date: Thu, 08 Jul 2004 22:47:18 +0900 From: Eitarou Kamo <e-kamo@trio.plala.or.jp> To: Julian Elischer <julian@elischer.org>, freebsd-hackers@freebsd.org Subject: Re: Article on Sun's DTrace Message-ID: <40ED5066.4050704@trio.plala.or.jp> In-Reply-To: <Pine.BSF.4.21.0407080218460.66234-100000@InterJet.elischer.org> References: <Pine.BSF.4.21.0407080218460.66234-100000@InterJet.elischer.org>
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Hi Julian,
Julian Elischer wrote:
>On Thu, 8 Jul 2004, Steven Smith wrote:
>
>
>
>>It's also possible to put probes on the return instruction of the
>>function. I'm not sure how they're actually finding that, though.
>>
>>
>
>I think the return probe is done by adding a call probe that changes the
>return address.
>
>
>
The pointer to function seems to be the key word. "return_p" is
the pointer to function. In case of normal mode return _p points the
dummy address or Null pointer. In case of DTrace mode return_p
points the address of probe. This may be magic of the DTrace.
What all the DTrace do are to know the address of probe. If DTrace
get the pointer of probes "return_p"s via structure or else, lang D
would get the return value of the probe from memory.
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