Re: [PATCH V4 3/3] x86: Add entry trampolines to kcore

[Adrian Hunter]

On 06/06/18 16:19, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jun 06, 2018 at 03:16:31PM +0200, Peter Zijlstra escreveu:
>> On Wed, Jun 06, 2018 at 03:54:11PM +0300, Adrian Hunter wrote:
>>> Without program headers for PTI entry trampoline pages, the trampoline
>>> virtual addresses do not map to anything.
>>>
>>
>>>
>>> In addition, entry trampolines all map to the same page.  Represent that by
>>> giving the corresponding program headers in kcore the same offset.
>>>
>>> This has the benefit that, when perf tools uses /proc/kcore as a source for
>>> kernel object code, samples from different CPU trampolines are aggregated
>>> together.  Note, such aggregation is normal for profiling i.e. people want
>>> to profile the object code, not every different virtual address the object
>>> code might be mapped to (across different processes for example).
>>>
>>> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>>> Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>>> ---
>>>  arch/x86/mm/cpu_entry_area.c | 10 ++++++++++
>>>  fs/proc/kcore.c              |  7 +++++--
>>>  include/linux/kcore.h        | 13 +++++++++++++
>>>  3 files changed, 28 insertions(+), 2 deletions(-)
>>
>> This also adds the KCORE_REMAP functionality, but isn't mentioned at all
>> in the Changelog.
>>
>> Still, looks OK I suppose,
> 
> I can add a note about that,
>  
>> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> 
> Thanks, giving it some more hours and will apply and try to test it.

Any update on this?