On: Error handling in Rust

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I actually prefer NT exceptions to __copy_from_user for obtaining values from userspace. With SEH exceptions, the kernel can just access user pointers directly and handle possible errors in a natural way. This pattern is especially nice because NT allows ring-0 code to call system call functions directly, and in that case, an input pointer might be a kernel pointer, meaning that the SEH block does no harm and everything Just Works.

__copy_from_user feels very awkward by comparison.