Re: [PATCH bpf-next 4/7] bpf, arm64: Convert struct_ops arena arguments in the trampoline

On 8/14/2026 3:20 AM, Puranjay Mohan wrote:

[...]

>>> +static void emit_arena_arg_conv(struct jit_ctx *ctx, u8 dst, u8 src, bool nullable, u8 base_lo)
>>> +{
>>> +	if (nullable) {
>>> +		if (dst != src)
>>> +			emit(A64_MOV(1, dst, src), ctx);
>>> +		/* skip the subtraction so that NULL stays NULL */
>>> +		emit(A64_CBZ(1, dst, 2), ctx);
>>> +		src = dst;
>>> +	}
>>> +	emit(A64_SUB(0, dst, src, base_lo), ctx);
>> Maybe I'm missing something, do we need to validate whether the
>> address in the src register is really inside the current bpf
>> prog's arena?
> The JIT can assume that it is a kernel address into the arena as it
> comes from struct ops.

Thanks for the clarification, but I'm still confused. What makes the
assumption hold? How does struct_ops ensure the address passed is
inside the arena used by the current prog?

[...]