Re: [PATCH] [v4] x86, pkeys: fix siginfo ABI breakage from new field

From: Ingo Molnar
Date: Thu Mar 03 2016 - 10:41:15 EST



* Dave Hansen <dave@xxxxxxxx> wrote:

> To fix this, we replace the u64 with an '__u32'. The __u32 is guaranteed to
> union well with the pointers from _addr_bnd. It is also plenty large enough to
> store the 16-bit pkey we have today on x86.

The 'union well' sentence is really a leftover from the earlier changelog (the
problem was never about interaction between union members) - a better explantion
is:

> To fix this, we replace the u64 with an '__u32'. The __u32 does not change the
> minimum alignment requirements of the structure and it is also plenty large
> enough to store the 16-bit pkey we have today on x86.

I fixed this up locally, no need to resend.

Thanks,

Ingo