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

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

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:

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


[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 
      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 
      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

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