hw_breakpoint: Breakpoint modification fixes and new modify ioctl

hi,
Milind Chabbi introduced new ioctl interface to change live breakpoint [1]. It allows to change its bp_addr, bp_len and bp_type throught new ioctl for perf breakpoint event.

We already have a kernel interface for this via modify_user_hw_breakpoint function. This function however does not update the breakpoint slot counts.

So when the same functionality was exposed to user space (Milind's change), with simple test program I could put wrong slots count on arm server [2] and ended up with no breakpoints available on the system. Note it's not an issue on x86, because it shares slot single counter for both data and inst types (CONFIG_HAVE_MIXED_BREAKPOINTS_REGS).

This patchset contains my fixes for keeping breakpoint slots count updated. On top of it there's Milind's change for new _IOC_MODIFY_ATTRIBUTES ioctl interface to change a breakpoint.

As I mentioned above there're kernel users of modify_user_hw_breakpoint function, all ptrace related AFAICS, which could got broken.. so cc-ing Oleg ;-)

I ran gdb and strace tests suites and got same amount of skip/fail tests as when I run them on unpatched machine, so I assume nothing new got broken.

It's also available in here:
https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
perf/bp

v3 changes:
- rebased on Arnaldo's perf/core
- minor format changes in PERF_EVENT_IOC_* hunks

v2 changes:
- added check for the rest of the perf_event_attr fields to be the same as for kernel event

thanks,
jirka

[1] https://marc.info/?l=linux-kernel&m=151012255331565&w=2
[2] https://marc.info/?l=linux-man&m=151172469807302&w=2
---
Jiri Olsa (7):
hw_breakpoint: Pass bp_type directly as find_slot_idx argument
hw_breakpoint: Pass bp_type argument to __reserve_bp_slot|__release_bp_slot
hw_breakpoint: Add modify_bp_slot function
hw_breakpoint: Factor out __modify_user_hw_breakpoint function
hw_breakpoint: Add perf_event_attr fields check in __modify_user_hw_breakpoint perf/core: Move perf_event_attr::sample_max_stack into perf_copy_attr perf tests: Add breakpoint accounting/modify test

Milind Chabbi (1):
perf/core: fast breakpoint modification via _IOC_MODIFY_ATTRIBUTES.

 include/linux/hw_breakpoint.h         |   7 +++++
 include/uapi/linux/perf_event.h       |  23 ++++++++-------
 kernel/events/core.c                  |  54 ++++++++++++++++++++++++++++++++--
 kernel/events/hw_breakpoint.c         | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++---------------------
 tools/include/uapi/linux/perf_event.h |  23 ++++++++-------
 tools/perf/tests/Build                |   1 +
 tools/perf/tests/bp_account.c         | 195 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/tests/builtin-test.c       |   4 +++
 tools/perf/tests/tests.h              |   1 +
 9 files changed, 365 insertions(+), 58 deletions(-)
 create mode 100644 tools/perf/tests/bp_account.c