linux/tools
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
..
cgroup cgroups: fix cgroup_event_listener error handling 2013-01-08 10:00:44 -08:00
firewire tools/firewire: nosy-dump: check for allocation failure 2012-12-02 20:10:18 +01:00
hv Tools: hv: use full nlmsghdr in netlink_send 2013-08-12 15:44:57 -07:00
include/tools tools/include: use stdint types for user-space byteshift headers 2013-07-03 16:02:28 +02:00
lguest tools/lguest: offer VIRTIO_F_ANY_LAYOUT for net device. 2013-07-15 11:18:32 +09:30
lib tools lib lk: Uninclude linux/magic.h in debugfs.c 2013-09-19 15:08:53 -03:00
net filter: add minimal BPF JIT image disassembler 2013-03-21 11:35:41 -04:00
nfsd NFSD: Added fault injection script 2011-11-07 21:10:47 -05:00
perf perf: Fix capabilities bitfield compatibility in 'struct perf_event_mmap_page' 2013-09-20 09:45:11 +02:00
power cpupower: Add Haswell family 0x45 specific idle monitor to show PC8,9,10 states 2013-07-05 01:52:19 +02:00
scripts tools: Get only verbose output with V=1 2013-07-08 17:31:34 -03:00
testing selftests: Add test of PMU instruction counting on powerpc 2013-08-14 14:57:10 +10:00
usb tools: usb: ffs-test: Fix build failure 2013-03-07 12:23:17 +08:00
virtio virtio tools: add .gitignore 2013-07-15 11:18:31 +09:30
vm tools/vm: Switch to liblk library 2013-03-15 13:06:01 -03:00
Makefile Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-05-01 14:08:52 -07:00