From: Andy Lutomirski > Sent: 30 April 2020 19:42 ... > I suppose there could be a consistent naming like this: > > copy_from_user() > copy_to_user() > > copy_from_unchecked_kernel_address() [what probe_kernel_read() is] > copy_to_unchecked_kernel_address() [what probe_kernel_write() is] > > copy_from_fallible() [from a kernel address that can fail to a kernel > address that can't fail] > copy_to_fallible() [the opposite, but hopefully identical to memcpy() on x86] > > copy_from_fallible_to_user() > copy_from_user_to_fallible() You missed out: copy_to/from_io() copy_to_io_from_user() copy_from_io_to_user() All of which want aligned addresses on the 'io' side. It might even be worth saying that the copy_to/from_io() can fail due to bad IO accesses (rather than bad addresses). This is not entirely unexpected since all PCIe accesses can fail unexpectedly (usually without a trap and returning -1). But a system could arrange to generate a synchronous fault. If you are copying directly from io to user you need to differentiate between a user page fault and an io access error. The latter shouldn't generate SIGSEGV. Possibly return -EFAULT on user page fault and 'transfer length remaining' on io access error. Although filling the rest of the buffer with 0xff might be appropriate. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
