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Re: IOUserClient size limit?


On Nov 10, 2008, at 5:35 PM, Duane Murphy wrote: 
Thanks Chris! I would have completely missed the prepare() and
complete() methods.

On a follow up question. My user client APIs map to kernel functions
that expect to get a buffer that they can write into.
IOMemoryDescriptors are setup to use readBytes() and writeBytes() rather
than direct memory access (e.g. a pointer).

I really hope your doing something different than what it sounds like your describing. Your UserClient should be exporting an API specific to your needs, not a generic copy of kernel API's. Generic API's make it easier to subvert your UserClient and force it do things contrary to it's intended purpose. If your API is generic, much of your security comes from secretiveness- Security through obscurity at it's worse.

Is there a way of getting "buffer" access? Some way of writing directly
to the underlying memory by address? Is that what map() and IOMemoryMap
is for?

Map gives you pointer level access to the memory described by the descriptor.
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References: 
 >IOUserClient size limit? (From: "Duane Murphy" <email@hidden>)
 >Re: IOUserClient size limit? (From: Chris Sarcone <email@hidden>)
 >Re: IOUserClient size limit? (From: "Duane Murphy" <email@hidden>)



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