Messages in this thread |  | | Date | Sun, 26 Nov 2000 15:11:20 +0000 | From | Philipp Rumpf <> | Subject | Re: How to transfer memory from PCI memory directly to user space safely and portable? |
| |
On Sun, Nov 26, 2000 at 02:21:31PM +0100, Anders Torger wrote: > memcpy_toio(iobase, user_space_src, count);
I hope count isn't provided by userspace here ?
> 1. What happens if the user space memory is swapped to disk? Will > verify_area() make sure that the memory is in physical RAM when it returns, > or will it return -EFAULT, or will something even worse happen?
On i386, you'll sleep implicitly waiting for the page fault to be handled; in the generic case, anything could happen.
> 2. Is this code really portable? I currently have an I386 architecture, and I > could use copy_to/from_user on that instead, but that is not portable. Now, > by using memcpy_to/fromio instead, is this code fully portable?
No. It would be portable if you were using memcpy_fromuser_toio and it existed.
> 3. Will the current process always be the correct one? The copy functions is > directly initiated by the user, and not through an interrupt, so I think the > user space mapping will always be to the correct process. Is that correct?
current should be fine if you're not in a bh/interrupt/kernel thread. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
|  |