Hi Ilya,
On Fri, Feb 07, 2025 at 12:28:43PM +0100, Ilya Leoshkevich wrote:
> Acked-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Thanks!
> s390x has a strong memory model, and the regular load and store
> instructions are atomic as long as operand addresses are aligned.
I see.
> IIUC the verifier already enforces this unless BPF_F_ANY_ALIGNMENT
> is set, in which case whoever loaded the program is responsible for the
> consequences: memory accesses that happen to be unaligned would
> not trigger an exception, but they would not be atomic either.
The verifier rejects misaligned BPF_ATOMIC instructions since commit
ca36960211eb ("bpf: allow xadd only on aligned memory"), even if
BPF_F_ANY_ALIGNMENT is set - so this patch makes the verifier reject
misaligned load-acquires and store-releases, too, to keep the behaviour
consistent:
Specifically, check_atomic_load() calls check_load_mem() (and
check_atomic_store() calls check_store_reg()) with the
@strict_alignment_once argument equals true. See also selftests
load_acquire_misaligned() and store_release_misaligned() in PATCH 8/9.
> So I can implement the new instructions as normal loads/stores after
> this series is merged.
That would be great!
Thanks,
Peilin Ye
