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

[Arnaldo Carvalho de Melo]

Em Tue, Jul 17, 2018 at 11:54:30AM +0300, Adrian Hunter escreveu:
> 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?

On the post-vacation pile, will get to it.

- Arnaldo