[PATCH 1/8] powerpc/uaccess: Add unsafe_copy_from_user

[Christoph Hellwig]

On Thu, Oct 15, 2020 at 10:01:52AM -0500, Christopher M. Riedl wrote:
> Implement raw_copy_from_user_allowed() which assumes that userspace read
> access is open. Use this new function to implement raw_copy_from_user().
> Finally, wrap the new function to follow the usual "unsafe_" convention
> of taking a label argument. The new raw_copy_from_user_allowed() calls
> __copy_tofrom_user() internally, but this is still safe to call in user
> access blocks formed with user_*_access_begin()/user_*_access_end()
> since asm functions are not instrumented for tracing.

Please also add a fallback unsafe_copy_from_user to linux/uaccess.h
so this can be used as a generic API.