linux/include
Peter Zijlstra fa73158710 perf: Fix capabilities bitfield compatibility in 'struct perf_event_mmap_page'
Solve the problems around the broken definition of perf_event_mmap_page::
cap_usr_time and cap_usr_rdpmc fields which used to overlap, partially
fixed by:

  860f085b74 ("perf: Fix broken union in 'struct perf_event_mmap_page'")

The problem with the fix (merged in v3.12-rc1 and not yet released
officially), noticed by Vince Weaver is that the new behavior is
not detectable by new user-space, and that due to the reuse of the
field names it's easy to mis-compile a binary if old headers are used
on a new kernel or new headers are used on an old kernel.

To solve all that make this change explicit, detectable and self-contained,
by iterating the ABI the following way:

 - Always clear bit 0, and rename it to usrpage->cap_bit0, to at least not
   confuse old user-space binaries. RDPMC will be marked as unavailable
   to old binaries but that's within the ABI, this is a capability bit.

 - Rename bit 1 to ->cap_bit0_is_deprecated and always set it to 1, so new
   libraries can reliably detect that bit 0 is deprecated and perma-zero
   without having to check the kernel version.

 - Use bits 2, 3, 4 for the newly defined, correct functionality:

	cap_user_rdpmc		: 1, /* The RDPMC instruction can be used to read counts */
	cap_user_time		: 1, /* The time_* fields are used */
	cap_user_time_zero	: 1, /* The time_zero field is used */

 - Rename all the bitfield names in perf_event.h to be different from the
   old names, to make sure it's not possible to mis-compile it
   accidentally with old assumptions.

The 'size' field can then be used in the future to add new fields and it
will act as a natural ABI version indicator as well.

Also adjust tools/perf/ userspace for the new definitions, noticed by
Adrian Hunter.

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Also-Fixed-by: Adrian Hunter <adrian.hunter@intel.com>
Link: http://lkml.kernel.org/n/tip-zr03yxjrpXesOzzupszqglbv@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-09-20 09:45:11 +02:00
..
acpi Merge branch 'acpi-hotplug' 2013-08-30 14:14:25 +02:00
asm-generic Merge branch 'for-v3.12' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping 2013-09-09 10:26:33 -07:00
clocksource ARM: SoC cleanups for 3.12 2013-09-06 13:21:16 -07:00
crypto crypto: scatterwalk - Add support for calculating number of SG elements 2013-08-21 21:27:58 +10:00
drm Merge tag 'drm-intel-fixes-2013-09-06' of git://people.freedesktop.org/~danvet/drm-intel into drm-fixes 2013-09-10 12:36:55 +10:00
dt-bindings Device tree core updates for v3.12 2013-09-10 13:53:52 -07:00
keys
kvm ARM: KVM: vgic: Bump VGIC_NR_IRQS to 256 2013-08-30 16:12:39 +03:00
linux Merge branch 'fixes' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2013-09-17 22:20:30 -04:00
math-emu
media Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-09-05 14:54:29 -07:00
memory
misc
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-09-11 14:33:16 -07:00
pcmcia
ras
rdma Merge branches 'cxgb4', 'flowsteer', 'ipoib', 'iser', 'mlx4', 'ocrdma' and 'qib' into for-next 2013-09-03 09:01:08 -07:00
rxrpc
scsi Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2013-09-12 16:11:45 -07:00
sound sound fixes for 3.12-rc1 2013-09-12 08:52:41 -07:00
target target/iscsi: Bump versions to v4.1.0 2013-09-10 20:23:37 -07:00
trace Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-09-12 15:01:38 -07:00
uapi perf: Fix capabilities bitfield compatibility in 'struct perf_event_mmap_page' 2013-09-20 09:45:11 +02:00
video fbdev changes for 3.12: 2013-09-05 09:49:32 -07:00
xen Features: 2013-09-04 17:45:39 -07:00
Kbuild