This patch somehow breaks the perf-ABI. If I take a program that reads "mmap->cap_usr_rdpmc" and compile it against the new header with this change (say from 3.12-rc1) and then run it on an old kernel (say 3.11) then I get "0" for cap_usr_rdpmc.
If I take the same program and recompile against the old (without this patch) header and run it on 3.11, I get the expected "1" value. So something about this changed the bit pattern in an incompatible fashion. Vince On Tue, 23 Jul 2013, tip-bot for Adrian Hunter wrote: > Commit-ID: 860f085b74e9f0075de8140ed3a1e5b5e3e39aa8 > Gitweb: http://git.kernel.org/tip/860f085b74e9f0075de8140ed3a1e5b5e3e39aa8 > Author: Adrian Hunter <[email protected]> > AuthorDate: Fri, 28 Jun 2013 16:22:17 +0300 > Committer: Ingo Molnar <[email protected]> > CommitDate: Tue, 23 Jul 2013 12:17:10 +0200 > > perf: Fix broken union in 'struct perf_event_mmap_page' > > The capabilities bits must not be "union'ed" together. > Put them in a separate struct. > > Signed-off-by: Adrian Hunter <[email protected]> > Signed-off-by: Peter Zijlstra <[email protected]> > Link: > http://lkml.kernel.org/r/[email protected] > Signed-off-by: Ingo Molnar <[email protected]> > --- > include/uapi/linux/perf_event.h | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index 00d8274..0041aed 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -375,9 +375,11 @@ struct perf_event_mmap_page { > __u64 time_running; /* time event on cpu */ > union { > __u64 capabilities; > - __u64 cap_usr_time : 1, > - cap_usr_rdpmc : 1, > - cap_____res : 62; > + struct { > + __u64 cap_usr_time : 1, > + cap_usr_rdpmc : 1, > + cap_____res : 62; > + }; > }; > > /* > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > k -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
