On 8/16/26 4:36 PM, Eduard Zingerman wrote:
> On Sun, 2026-08-16 at 16:17 -0700, Eduard Zingerman wrote:
>> On Sun, 2026-08-16 at 10:56 +0000, Yiyang Chen wrote:
>>> Add a verifier test with one atomic RMW instruction reached through
>>> PTR_TO_ARENA and PTR_TO_STACK paths. The verifier must reject the
>>> shared instruction with the existing incompatible-pointer diagnostic.
>>>
>>> Signed-off-by: Yiyang Chen <[email protected]>
>>> ---
>>> [...]
>>> +SEC("socket")
>>> +__description("arena and stack atomic at the same instruction")
>>> +__failure __msg("same insn cannot be used with different pointers")
>>> +__arch_x86_64
>>> +__load_if_JITed()
>>> +__naked void mixed_arena_stack_atomic(void)
>>> +{
>>> + asm volatile (" \
>>> + r1 = %[arena] ll; \
>>> + r6 = r10; \
>>> + r6 += -8; \
>>> + r9 = 0; \
>>> + *(u64 *)(r6 + 0) = r9; \
>>> + r7 = 8192; \
>>> + .8byte %[addr_space_cast]; \
>>
>> I'm going to fix this to:
>>
>> r7 = addr_space_cast(r7, 0, 1); \
>>
>> as in the test case above.
>> Waiting for CI [1].
>>
>> [1] https://github.com/kernel-patches/bpf/pull/13325
>
>
> A...and it requires another exception for GCC-BPF:
> https://github.com/kernel-patches/bpf/blob/bpf-next_base/ci/vmtest/configs/DENYLIST.test_progs-bpf_gcc
>
> Ihor, it's a third time GCC-BPF strikes this weekend.
> What do people think about downgrading it to may-fail until the
> DENYLIST decreases to something reasonable?
I get your frustration, but red CI makes us to look at things
which is good. "May fail" runs and "warnings" are very likely
to be ignored.
I think the tests and the denylist will be in a stable shape soon.
Flakiness on the way there is expected.
>
> Anyway, I'll wrap-up with this patch-set in the evening.
>
>>> + call %[bpf_get_prandom_u32]; \
>>> + if w0 != 0 goto 1f; \
>>> + r8 = r6; \
>>> + goto 2f; \
>>> +1: r8 = r7; \
>>> +2: r9 = 1; \
>>> + lock *(u64 *)(r8 + 0) += r9; \
>>> + r0 = 0; \
>>> + exit; \
>>> +" :
>>> + : __imm_addr(arena),
>>> + __imm_insn(addr_space_cast, addr_space_cast_insn),
>>> + __imm(bpf_get_prandom_u32)
>>> + : __clobber_all);
>>> +}
>>> +
>>> static __noinline
>>> u32 __arena *check_arena_arg_nonglobal(u32 __arena *arg)
>>> {
