Re: [PATCH 7/7] selftests/x86: Add tests for signal frame FPU portability

[Borislav Petkov]

On Thu, Sep 24, 2026 at 04:16:03AM +0000, Andrei Vagin wrote:
> Add a new selftest tools/testing/selftests/x86/sigframe_fpu_portability.c
> to verify signal frame portability and consistency when the xstate size
> is shrunk:
> 
> - test_valid_shrunk_xstate_size: Verifies that the kernel correctly
>   restores the xstate context from a signal frame where xstate_size has
>   been manually shrunk to only cover active features, as long as the
>   FP_XSTATE_MAGIC2 marker is correctly placed. This simulates migrating
>   a process created on a host with fewer xstate features to a host with
>   more features.
> 
> - test_invalid_shrunk_xstate_size: Verifies that the kernel rejects
>   (via SIGSEGV) a signal frame where xstate_size is smaller than required
>   by the enabled features in the xfeatures mask.
> 
> Reviewed-by: Alexander Mikhalitsyn <alexander@xxxxxxxxxxxxx>
> Reviewed-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
> ---
>  tools/testing/selftests/x86/Makefile          |   5 +-
>  .../selftests/x86/sigframe_fpu_portability.c  | 246 ++++++++++++++++++
>  tools/testing/selftests/x86/xstate.c          |  12 -
>  tools/testing/selftests/x86/xstate.h          |  20 ++
>  4 files changed, 270 insertions(+), 13 deletions(-)
>  create mode 100644 tools/testing/selftests/x86/sigframe_fpu_portability.c

Sashiko has a comment which sounds valid to me but I haven't looked at the
surrounding code:

https://sashiko.dev/#/patchset/20260924041604.3209659-1-avagin%40google.com

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette