Re: [RFC PATCH bpf 1/6] bpf: Disallow interpreter fallback for user BPF_ADDR_SPACE_CAST insn

[Leon Hwang <leon.hwang@linux.dev>]

On 2026/6/30 22:29, KaFai Wan wrote:
> On Fri, 2026-06-26 at 23:43 +0800, Leon Hwang wrote:
[...]
>>  /* Fix up helper call offsets on JIT fallback path. */
>> -static void bpf_fixup_fallback_helpers(struct bpf_verifier_env *env, struct bpf_prog *fp)
>> +static int bpf_fixup_fallback_helpers(struct bpf_verifier_env *env, struct bpf_prog *fp)
>>  {
>>  	struct bpf_insn *insn = fp->insnsi;
>>  	const struct bpf_func_proto *fn;
>>  	int i;
>>  
>> -	if (!env || !env->ops->get_func_proto)
>> -		return;
>> +	if (!env)
>> +		return 0;
>>  
>>  	for (i = 0; i < fp->len; i++, insn++) {
>> -		if (bpf_helper_call(insn) && bpf_jit_inlines_helper_call(insn->imm)) {
>> +		if (env->ops->get_func_proto && bpf_helper_call(insn) &&
>> +		    bpf_jit_inlines_helper_call(insn->imm)) {
>>  			fn = env->ops->get_func_proto(insn->imm, env->prog);
>>  			if (fn && fn->func)
>>  				insn->imm = fn->func - __bpf_call_base;
> It might be better to use the BPF_CALL_IMM macro. insn->imm = BPF_CALL_IMM(fn->func);


Makes sense.

This might be applied to Tiezhu's patch.

Thanks,
Leon

>>  		}
>> +
>> +		if (bpf_insn_requires_jit(insn))
>> +			return -EOPNOTSUPP;
>>  	}
>> [...]