Re: [PATCH 09/13] Move bp_type_idx to kernel/event/hw_breakpoint.c

Peter Zijlstra
2015-09-15T19:39:40Z

On Tue, Sep 15, 2015 at 11:40:11AM -0700, Palmer Dabbelt wrote:
> On Tue, 15 Sep 2015 01:06:07 PDT (-0700), peterz@infradead.org wrote:
> > On Mon, Sep 14, 2015 at 03:50:43PM -0700, Palmer Dabbelt wrote:
> >> This has a "#ifdef CONFIG_*" that used to be exposed to userspace.
> >>
> >> The names in here are so generic that I don't think it's a good idea
> >> to expose them to userspace (or even the rest of the kernel). Since
> >> there's only one kernel user, it's been moved to that file.
> >>
> >> Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
> >> Reviewed-by: Andrew Waterman <waterman@eecs.berkeley.edu>
> >> Reviewed-by: Albert Ou <aou@eecs.berkeley.edu>
> >> ---
> >> include/uapi/linux/hw_breakpoint.h | 10 ----------
> >> kernel/events/hw_breakpoint.c | 10 ++++++++++
> >> 2 files changed, 10 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/include/uapi/linux/hw_breakpoint.h b/include/uapi/linux/hw_breakpoint.h
> >> index b04000a2296a..7a6a5a7f9511 100644
> >> --- a/include/uapi/linux/hw_breakpoint.h
> >> +++ b/include/uapi/linux/hw_breakpoint.h
> >> @@ -17,14 +17,4 @@ enum {
> >> HW_BREAKPOINT_INVALID = HW_BREAKPOINT_RW | HW_BREAKPOINT_X,
> >> };
> >>
> >> -enum bp_type_idx {
> >> - TYPE_INST = 0,
> >> -#ifdef CONFIG_HAVE_MIXED_BREAKPOINTS_REGS
> >> - TYPE_DATA = 0,
> >> -#else
> >> - TYPE_DATA = 1,
> >> -#endif
> >> - TYPE_MAX
> >> -};
> >
> > This is rather unfortunate; you are correct that the naming is too
> > generic (and I tend to agree), but I think these values are required by
> > userspace to fill out:
> >
> > perf_event_attr::bp_type
> >
> > So removing them will break things.
> >
> > Frederic?
>
> perf_event_open(2) says
>
> bp_type (since Linux 2.6.33)
> This chooses the breakpoint type. It is one of:
>
> HW_BREAKPOINT_EMPTY
> No breakpoint.
>
> HW_BREAKPOINT_R
> Count when we read the memory location.
>
> HW_BREAKPOINT_W
> Count when we write the memory location.
>
> HW_BREAKPOINT_RW
> Count when we read or write the memory location.
>
> HW_BREAKPOINT_X
> Count when we execute code at the memory location.
>
> The values can be combined via a bitwise or, but the combination
> of HW_BREAKPOINT_R or HW_BREAKPOINT_W with HW_BREAKPOINT_X is
> not allowed.
>
> so I think removing this enum from userspace is OK. Did I miss
> something?

Nah, could've just been me not being awake. Unless Frederic says
otherwise I'll chalk it up to not having drank enough morning juice.