[PATCHv2 0/8] hw_breakpoint: Breakpoint modification fixes and new modify ioctl

From: Jiri Olsa <jolsa@kernel.org>
To: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	David Ahern <dsahern@gmail.com>, Andi Kleen <ak@linux.intel.com>,
	Milind Chabbi <chabbi.milind@gmail.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Hari Bathini <hbathini@linux.vnet.ibm.com>,
	Jin Yao <yao.jin@linux.intel.com>,
	Kan Liang <kan.liang@intel.com>,
	Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
	Oleg Nesterov <onestero@redhat.com>,
	Will Deacon <will.deacon@arm.com>
Subject: [PATCHv2 0/8] hw_breakpoint: Breakpoint modification fixes and new modify ioctl
Date: Wed, 29 Nov 2017 09:38:45 +0100	[thread overview]
Message-ID: <20171129083853.28022-1-jolsa@kernel.org> (raw)

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

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       |   2 ++
 kernel/events/core.c                  |  53 +++++++++++++++++++++++++++++--
 kernel/events/hw_breakpoint.c         | 115 ++++++++++++++++++++++++++++++++++++++++++++++++-------------------
 tools/include/uapi/linux/perf_event.h |   2 ++
 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, 344 insertions(+), 36 deletions(-)
 create mode 100644 tools/perf/tests/bp_account.c