Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field

From: Ingo Molnar
Date: Mon Feb 29 2016 - 03:01:52 EST

* Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:

> > u32?
> It would have to be __u32, but we already use int and unsigned int
> extensively in the siginfo structure (which are both always assumed to
> be 32 bits). So "unsigned int" probably makes most sense.

No. This whole mishap is an object lesson in why it's a bad idea to ever use ABI
types outside of the __[us][8|16|32|64] space: some of them are 'fine', some of
them (like longs) are not.

And we have to start somewhere, so we might as well start with new code that adds
new ABI details: if a patch only uses __[us][8|16|32|64] types then it's easier to
tell whether it's a safe ABI extension.