From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.126.com (m16.mail.126.com [220.197.31.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 624D137C90F; Wed, 3 Jun 2026 09:12:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.8 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780477972; cv=none; b=h/SjciUIfJ1O4HCkvGyjjNyvSJMUmKRRQ19CuujDMyWoXlPmTzk8VmP5OmDBeFzGkl++PU2vpOoL6E5wfQtXLWXBg7EgVVfecTi641nT8ZbX0VeAlgC2VjWNWfTKQet/pSQb5HaJetr1KFkpIX7ERJcf141m2mfBXO3wU8Be/b0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780477972; c=relaxed/simple; bh=asDLIHKdW5SQkt+AvBPms8hBv1FMDVQtDhA1GC2RjOg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jtVg5CaXVRox4NzBT5vSeOjTKz9FrxrCTtVqKZmhk5jBSa8+2lCOr5kK2aWbpQxjP6ICr3nXQ9KVPG2+EJybjPfxN2dHo3FnWmiBAJGPNQk+pycrI7+0e7OYPwS9UXJ+Xk8TFg1rMpe/KLehOiPsaOObu08y4yE3MhKG2k+VQAc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=126.com; spf=pass smtp.mailfrom=126.com; dkim=pass (1024-bit key) header.d=126.com header.i=@126.com header.b=dk6L+CXa; arc=none smtp.client-ip=220.197.31.8 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=126.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=126.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=126.com header.i=@126.com header.b="dk6L+CXa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=126.com; s=s110527; h=Message-ID:Date:MIME-Version:Subject:To:From: Content-Type; bh=BRtjKeBZ4+8dkfdyf5TNW8mrUZqF45IyG/HSoWHSM1M=; b=dk6L+CXav2r3Vh7oHctwwISdq6vjBKf3KCJqpgNZ86Sfmy4gcJJGYq+Afx+bso ETSNvS1nj440RXH7FAxUKPBXWkO5QipT07DtKeIH4S2Sq+TIMW91oyrQRC6pexlY tK4ZZsAB+y1BjwDpEQQEgmuy+gCigpmzuR4tWtcUdAIvY= Received: from [10.41.105.18] (unknown []) by gzga-smtp-mtada-g1-1 (Coremail) with SMTP id _____wDn_6e97x9q7LHVAg--.13910S2; Wed, 03 Jun 2026 17:11:26 +0800 (CST) Message-ID: <874ee728-51f2-46ac-93a5-7740abcb0a77@126.com> Date: Wed, 3 Jun 2026 17:11:25 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] btf: reject to register duplicated kfunc To: Yonghong Song , martin.lau@linux.dev, ast@kernel.org, alexei.starovoitov@gmail.com, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, kaitao.cheng@linux.dev Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260602110710.19642-1-chensong_2000@126.com> Content-Language: en-US From: Song Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wDn_6e97x9q7LHVAg--.13910S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxAr1fAF43Kw13ur1kGFWruFg_yoWrCw4UpF W5JFZ8uF4xtw17X3W2qF98ury3Gw18Ga1jyF98KFy3Jr1qgrZ7tr1jkF4Y93sayryUCa10 yF4UWrZxu3yjkrDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jaa0PUUUUU= X-CM-SenderInfo: xfkh02prqjsjqqqqqiyswou0bp/xtbBpR+NDWof778pLwAA3Z Hi, 在 2026/6/3 01:13, Yonghong Song 写道: > > > On 6/2/26 4:07 AM, Song Chen wrote: >> I had an ebpf program which calls a kfunc defined and >> implemented in one of my kernel modules, it was working >> fine in 6.16, but was rejected to run by libbpf in 6.19, >> the error message was: >> >> libbpf: extern (func ksym) 'bpf_strstr': func_proto [5] >> incompatible with vmlinux [94389] >> >> The reason is there is a new added kfunc in kernel 6.19 >> which happens to be the same name with my kfunc. However the >> error message is not obvious enough to address problem >> immediately. >> >> Therefore, this patches searches duplicated kfunc in >> both btf_vmlinux and btf_modules list before a kernel module >> attempts to register kfuncs through register_btf_kfunc_id_set, >> it prints clear error message and returns error code if same name >> kfunc has already implemented and registered, then developer >> knows at the first place. >> >> Suggested-by: Alexei Starovoitov >> Suggested-by: Kaitao Cheng >> Reviewed-by: Yonghong Song >> Signed-off-by: Song Chen > > The subject can be [PATCH bpf v4] bpf: Reject to register duplicated kfunc > >> >> --- >> changelog: >> v1 --- v2: >> libbpf has already specified which module this kfunc belongs to as >> ebpf code onwer's expectation, then verifier uses >> find_kallsyms_symbol_value to search kfunc's addr. >> >> v2 --- v3: >> After v2, I tried a new idea of introducing a namespace in libbpf >> to specify kfunc owner in an ebpf program suggested by Kaitao Cheng, >> please see [1]. Alex suggested to go back to report an error during >> kmod load on conflicting kfunc name for now. What's more, v2 only >> searched bpf_vmlinux, v3 also traverses btf_modules list. >> >> v3 --- v4 >> Fixed some coding style problems suggested from Kaitao Cheng. >> --- >>   kernel/bpf/btf.c | 38 +++++++++++++++++++++++++++++++++++++- >>   1 file changed, 37 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c >> index 4872d2a6c42d..fe1612677a4a 100644 >> --- a/kernel/bpf/btf.c >> +++ b/kernel/bpf/btf.c >> @@ -8618,6 +8618,41 @@ static int btf_check_iter_kfuncs(struct btf >> *btf, const char *func_name, >>       return 0; >>   } >> +static int btf_check_kfunc_name(struct btf *btf, const char >> *func_name, u32 kind) >> +{ >> +#ifdef CONFIG_DEBUG_INFO_BTF_MODULES >> +    struct btf_module *btf_mod, *tmp; >> +#endif >> +    s32 id; > >     s32 err = 0, id; > >> + >> +    if (!btf_is_module(btf)) >> +        return 0; >> + >> +    id = btf_find_by_name_kind(bpf_get_btf_vmlinux(), func_name, kind); >> +    if (id >= 0) { >> +        pr_err("kfunc %s (id: %d) is already present in vmlinux.\n", >> +                func_name, id); >> +        return -EINVAL; >> +    } >> + >> +#ifdef CONFIG_DEBUG_INFO_BTF_MODULES >> +    mutex_lock(&btf_module_mutex); >> +    list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) { >> +        if (btf_mod->btf == btf) >> +            continue; >> +        id = btf_find_by_name_kind(btf_mod->btf, func_name, kind); >> +        if (id >= 0) { >> +            pr_err("kfunc %s (id: %d) is already present in module >> %s.\n", >> +                    func_name, id, btf_mod->module->name); >> +            mutex_unlock(&btf_module_mutex); >> +            return -EINVAL; > > Let us avoid the above mutex_unlock and 'return -EINVAL', just do >     err = -EINVAL; >     break; > >> +        } >> +    } >> +    mutex_unlock(&btf_module_mutex); >> +#endif >> +    return 0; > >     return err; > I will go with guard(mutex), please review my next submit and let me know if you're ok with it or not. Thanks. >> +} >> + >>   static int btf_check_kfunc_protos(struct btf *btf, u32 func_id, u32 >> func_flags) >>   { >>       const struct btf_type *func; >> @@ -8631,7 +8666,8 @@ static int btf_check_kfunc_protos(struct btf >> *btf, u32 func_id, u32 func_flags) >>       /* sanity check kfunc name */ >>       func_name = btf_name_by_offset(btf, func->name_off); >> -    if (!func_name || !func_name[0]) >> +    if (!func_name || !func_name[0] || >> +        btf_check_kfunc_name(btf, func_name, BTF_INFO_KIND(func->info))) > > format issue: >     if (!func_name || !func_name[0] || >         btf_check_kfunc_name(btf, func_name, BTF_INFO_KIND(func->info))) >     ... > I will fix it with indentation plus space. >>           return -EINVAL; >>       func = btf_type_by_id(btf, func->type); > many thanks. Song