From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.126.com (m16.mail.126.com [220.197.31.9]) (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 A6B73344D8C; Mon, 1 Jun 2026 09:24:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780305870; cv=none; b=CjKEg6GHi+py/yz5BhMu6CFOwhCFUnP8HIxM4MgSbbS/PAFc0IFJiWMQ1Jp4XyVjNVzxF72thMdlipdRWU/kzam9gQg3erKmuyOFv/XOwkLkVXv0lQATfN/Xxglx8ji41EeKSmoYAECw5g1J/+lQBmv2RW9Sa/IQUJgtUcZdLoM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780305870; c=relaxed/simple; bh=IW5cfo/bC26+LgC0z/aL2YXuQi6OOqMSgcNFJWcxSoM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eGxk78F5C91zhe3TtVQ/qFDMj11vRDZsnpAgQ2wJyzlf1W04vShRKxeFhemEzLCZhGjXo6fOoTHGtiat3Z2INPN4L2KtPNijjRg7cW1LHBiDSZ77zi8eDY1T7dVuh/YyRsGN5BvGzKFPFa/m4cRPMzPALZam0kzXq0+FFz1Nn10= 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=DgJKZXdp; arc=none smtp.client-ip=220.197.31.9 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="DgJKZXdp" 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=e/+rvHoW/ia7sXFiB0Wxz22rzbKfAYctmMx0aF8/tsc=; b=DgJKZXdpqyKuBiRqmd3cR7C+n6UwllJ59ArmSNZHBuO3ZJNBnBPKFuMQ4J5qun 5/5vtZ98Fa9wsbpaQcByjYEZ6TmmtW+SK8zY6t1sokPxgTabb9PtsTIHn2SqUMqK tTJFdZDJO6xrtsmY5+44tOrBXm7NvAsQCThUga3fq4nHE= Received: from [10.41.105.18] (unknown []) by gzga-smtp-mtada-g0-4 (Coremail) with SMTP id _____wBXH5MYTx1qevPZAg--.52898S2; Mon, 01 Jun 2026 17:21:29 +0800 (CST) Message-ID: <9d2609fb-6658-4a47-bdbd-b72538b35ae7@126.com> Date: Mon, 1 Jun 2026 17:21:28 +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 v3] kernel/bpf/btf.c: reject to register duplicated kfunc To: Kaitao Cheng Cc: bpf@vger.kernel.org, martin.lau@linux.dev, ast@kernel.org, alexei.starovoitov@gmail.com, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, linux-kernel@vger.kernel.org References: <20260524082944.10625-1-chensong_2000@126.com> <757e24eb-45d3-4e05-9aa2-f077bec8fea9@linux.dev> Content-Language: en-US From: Song Chen In-Reply-To: <757e24eb-45d3-4e05-9aa2-f077bec8fea9@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wBXH5MYTx1qevPZAg--.52898S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxGry3ZrWDur48Zr1DWw1kGrg_yoWrCrWDpF W5JFZ8uF4Iqw17Xa42qFn8ury3Jw18GF4jyF9xtFW3Gr4qqrsrtr1j9F4Y93sakryUCa4I vF4UWFZF93yjyrDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jaa0PUUUUU= X-CM-SenderInfo: xfkh02prqjsjqqqqqiyswou0bp/xtbBpRq7O2odTxq36gAA3A Hi, 在 2026/5/25 17:18, Kaitao Cheng 写道: > 在 2026/5/24 16:29, Song Chen 写道: >> 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 >> Signed-off-by: Song Chen >> >> --- >> 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. >> >> [1]:https://lore.kernel.org/all/CAADnVQ+jYGMjAC9aNygmhyppUO9foWN4z9cjSpwCEXAFHpRVJQ@mail.gmail.com/ >> --- >> kernel/bpf/btf.c | 44 +++++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 43 insertions(+), 1 deletion(-) >> > > btf: reject to register duplicated kfunc > >> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c >> index 4872d2a6c42d..a14ad3720872 100644 >> --- a/kernel/bpf/btf.c >> +++ b/kernel/bpf/btf.c >> @@ -8618,6 +8618,47 @@ 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; >> + int ret = 0; > > This ret variable may be unnecessary. > >> + >> + if (!btf_is_module(btf)) >> + goto out; >> + >> + id = btf_find_by_name_kind(bpf_get_btf_vmlinux(), >> + func_name, kind); > > It seems unnecessary to split this call across multiple lines. Also, > some of the continuation-line indentation elsewhere does not appear > to follow the kernel coding style. > >> + if (id >= 0) { >> + pr_err("kfunc %s (id: %d) is already present in vmlinux.\n", >> + func_name, id); >> + ret = -EINVAL; >> + goto out; > > 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); > > follow the kernel coding style > >> + ret = -EINVAL; >> + break; > > mutex_unlock(&btf_module_mutex); > return -EINVAL; > >> + } >> + } >> + mutex_unlock(&btf_module_mutex); >> +#endif >> + >> +out: >> + return ret; >> +} >> + >> static int btf_check_kfunc_protos(struct btf *btf, u32 func_id, u32 func_flags) >> { >> const struct btf_type *func; >> @@ -8631,7 +8672,8 @@ 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))) > > follow the kernel coding style > >> return -EINVAL; >> >> func = btf_type_by_id(btf, func->type); > will do, thanks so much. Song