Re: [9fans] dhog the corruptor!

[David Gordon Hogan <dhog@plan9.bell-labs.com>]

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Brucee's implementation just patches the call to point to the
correct destination.  You don't have to walk any machine code.
The (modified) linker emits a known call instruction, and relocation
information which says where it is and what symbol to patch
it with.  Symbol lookup is done in a highly controlled way.


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From: George Michaelson <ggm@apnic.net>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] dhog the corruptor!
Date: Wed, 14 Nov 2001 08:59:29 +1000
Message-ID: <24453.1005692369@apnic.net>


One thing I've often wondered about is why dynamic linking methods leave
the indirect call around. I discussed this with a smarter person and he
seemed to think the cost of walking the machinecode to find out the base
call, and write in the binary the direct references was too high.

But surely for inner-loop code, or critical frequent call code, it would
be worth avoiding call(indirect-lookup(real-function-name(args...))) all
the time?

So would a plan9 with dynamic linkage live with stacks of indirection or
does it straight-path to the real code?

cheers
	-George
--
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