Re: cache clearing from keeping code and data in the same segment
Re: cache clearing from keeping code and data in the same segment
- Subject: Re: cache clearing from keeping code and data in the same segment
- From: Eli Bach <email@hidden>
- Date: Mon, 19 Jan 2009 03:48:41 -0800
On Jan 19, 2009, at 3:14 AM, Joel Reymont wrote:
Eli,
On Jan 19, 2009, at 11:11 AM, Eli Bach wrote:
Maybe so your app doesn't get hacked by means of writing to the
data segment, and then getting that data executed somehow.
Where's this protection mechanism explained, though?
Thanks, Joel
Are you looking for why your custom-written executable is running slow
(just from looking at your previous posts to darwin-dev)?
I would guess that information like this isn't explicitly listed/
documented somewhere, other than perhaps by reading the code in
Apple's developer tools (gcc/linker/etc), maybe in changelogs when
Apple pushes their changes upstream.
This is the kind of thing that would explain why Apple's engineers
steered you towards at least using their linker. Maybe it would be
easier to port it to your build platform instead of trying to reverse-
engineer it's functionality into your code. And it's not just what's
in there today, it's what Apple updates tomorrow as well, as that will
wind up biting you.
But don't take my word for any of this, as I have no actual knowledge
of the reasoning Apple used to decide to implement this 'feature'.
This is just something I came up with that seems plausible. The only
'hacking' of applications that I have done involved patching traps on
MacOS 9.
Eli
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