site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com Sorry for not providing more context. Yes, what I'm looking for is something that has memory semantics (i.e. I don't need to call map/unmap functions ever time I want to access this piece of memory), where the memory is allocated in a user space task, but should be accessible without these map/unmap calls like "global" memory within a KEXT, for all tasks running the KEXT code as part of a synchronous system call, and also for all kernel threads running the KEXT code as some sort of a "bottom-half". I understand that in the context of the userspace task that allocates and owns the memory, the kernel (KEXT) doesn't need any special mapping code to access the tasks userspace memory. I'm also not looking for the bounce buffer element of Linux's kmap. All I would like is a way to, through non-kernel-private APIs, be able to map the userspace memory into the kernel map, so that all tasks can access it in KEXT code. -- Terry _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a... On Mar 7, 2007, at 9:54 AM, Bhavesh Davda wrote: You really want the device to own the memory, and then map it into the user space process(es). If you do it the other way, and the user space process restarts, you are going to have a really hard time replacing the mapping in kernel space (because it might be in use, and you just don't know) with a new one from your process address space for the replacement process. For example, if you were trying to implement a firewall with a user interface component in a network extension, and mapped memory in from a user space control process to communicate rules and status information to the user space process, and potentially to communicate information back to the kernel after popping up a dialog that said something like "Application foo is attempting to access the Internet; Cancel or Allow?". If that user space process ended up dying it'd take all your current rules state and historical status information with it; but you'd still have a reference to the mapping to the vm region map in kernel space; until that reference goes away, your mapping in kernel space would stay around (it's there because you put it there, and it stay around because it still has a non-zero reference count. Now you start up a replacement control process; how do you transfer the existing data into the new process? How do you replace the mapping in kernel space now that the network extension is already loaded, and you have active threads looking in the memory region that came from the original process? You are much better off having the kernel own the memory, and mapping it into the user space process, instead of trying to go the other way around. A minimal recovery strategy would require you to map the vm region into the address space of the new control process, and if you are going to do that anyway, then you might as well do that in the first place, and make things a lot simpler for yourself. This email sent to site_archiver@lists.apple.com