Re: IOUserClient kIOUCStructIStructO

Subject: Re: IOUserClient kIOUCStructIStructO

From: Chris Sarcone <email@hidden>

Date: Mon, 11 Dec 2006 10:18:55 -0800

Delivered-to: email@hidden

Jürgen --

This looks like the parameter from userpace is copied into the kernal space memory allocation inStruct (not mapped) and if I do modifications to that memory they will not be seen in the Userspace. So I have to copy the *outStruct = *inStruct and do modifcations to the outStruct.

It does copy. If you want to map, you have to pass a pointer in the structure and wrap it with an IOMemoryDescriptor (using IOMemoryDescriptor::withAddress, and passing the task_t passed to your initWithTask() method).

But who allocates the outStruct?

The kernel.

How is the mechanism working?

Mach messaging.

-- Chris

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References:

>IOUserClient kIOUCStructIStructO (From: devmaillists <email@hidden>)