On Wednesday, February 22, 2012 8:06:20 pm Ryan Stone wrote: > On Wed, Feb 22, 2012 at 2:15 PM, Ian Lepore > <free...@damnhippie.dyndns.org> wrote: > > I've never done this, but if I needed to, I think the first thing I'd > > try is to use an mmap(2) of /dev/kmem to map the memory you need into > > userspace (of course your userspace app will need to be running with > > root privs to do this). > > > > That leaves the interesting problem of locating what offset within the > > kernel virtual address space you need to map to get at your data. Two > > things come to mind... have your kernel module export the address in a > > sysctl (that feels kind of hack-ish but it should be quick and easy to > > do), or use libkvm's kvm_nlist() function to locate the symbol within > > your module (I think that should be possible; again I've never actually > > done any of this). > > A far easier way to do this is to have the module create its own > device in /dev that exports the memory by implementing the mmap > interface in the cdev.
Yes. Another option you can do if you want to let userland "donate" a buffer to the kernel is to let userland create a buffer using shm_open() (probably with SHM_ANON) and then use shm_map() in the kernel to map that into KVA. -- John Baldwin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
