compat_loff_t
compat_loff_t __user *, offset, compat_size_t, count)
compat_loff_t l_start;
compat_loff_t l_len;
compat_loff_t __user *offset, compat_size_t count);
compat_loff_t offset;
BUILD_BUG_ON(sizeof(loff_t) != sizeof(compat_loff_t));