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

[Peter Zijlstra]

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,

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>