From: Linus Torvalds > Sent: 14 February 2022 20:24 > > > > x86-64 has always(*) used TASK_SIZE_MAX for access_ok(), and the > > get_user() assembler implementation does the same. > > Side note: we could just check the sign bit instead, and avoid big > constants that way. The cheap test for most 64bit is (addr | size) >> 62 != 0. I did some tests last week and the compilers correctly optimise out constant size. Doesn't sparc64 still need a wrap test? Or is that assumed because there is always an unmapped page and transfer are 'adequately' done on increasing addresses? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
