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
