Re: [PATCH 00/18] uaccess: fix sparse warning on get_user for bitwise types

From: Michael Ellerman
Date: Sun Dec 14 2014 - 19:41:26 EST

On Sun, 2014-12-14 at 18:51 +0200, Michael S. Tsirkin wrote:
> At the moment, if p and x are both tagged as bitwise types,
> get_user(x, p) produces a sparse warning on many architectures.
> This is because *p on these architectures is loaded into long
> (typically using asm), then cast back to typeof(*p).
> When typeof(*p) is a bitwise type (which is uncommon), such a cast needs
> __force, otherwise sparse produces a warning.

What does __force actually mean? Force the cast even though it's a bitfield? Or
does it mean more than that?

ie. are we loosing the ability to detect any actual errors by adding force?


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