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

Palmer Dabbelt
2015-09-15T18:40:17Z

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?