-------------------------------------------- On Wed, 7/29/15, John-Mark Gurney <j...@funkthat.com> wrote:
Subject: Re: Locking Memory Question To: "Laurie Jennings" <laurie_jennings_1...@yahoo.com> Cc: "John Baldwin" <j...@freebsd.org>, freebsd-net@freebsd.org Date: Wednesday, July 29, 2015, 7:25 PM Laurie Jennings via freebsd-net wrote this message on Wed, Jul 29, 2015 at 15:26 -0700: > > I have a problem and I can't quite figure out where to look. This is what Im doing: > > I have an IOCTL to read a block of data, but the data is too large to return via ioctl. So to get the data, > I allocate a block in a kernel module: > > foo = malloc(1024000,M_DEVBUF,M_WAITOK); > > I pass up a pointer and in user space map it using /dev/kmem: An easier solution would be for your ioctl to pass in a userland pointer and then use copyout(9) to push the data to userland... This means the userland process doesn't have to have /dev/kmem access... Is there a reason you need to use kmem? The only reason you list above is that it's too large via ioctl, but a copyout is fine, and would handle all page faults for you.. __________________________________ I'm using kmem because the only options I could think of was to 1) use shared memory 2) use kmem 3) use a huge ioctl structure. Im not clear how I'd do that. the data being passed up from the kernel is a variable size. To use copyout I'd have to pass a pointer with a static buffer, right? Is there a way to malloc user space memory from within an ioctl call? Or would I just have to pass down a pointer to a huge buffer large enough for the largest possible answer? thanks Laurie _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
