From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (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 168103AA1B5 for ; Mon, 25 May 2026 09:20:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779700824; cv=none; b=TQL0mrhF82Q2VS05e1T2gLL+Ew4pP198hF2MMWsfl4/PhyzBFRXAHU/k1zlvlAFj+Zq4Czdxk7VUcEFm56zxP8VzNag8YsnIDRLmRhx/ZV8AVnVZdRE7Ae/ae1hBsoMLTVr+pPC4xI6hm0Ofnz6tHEYUIGhgRvx8wgoi7EudzVc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779700824; c=relaxed/simple; bh=eoIjGVys9Sm423vlMOv8UCXJnx7/3ydXByfeim9xswM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=REJbcgSGv00U5Hm49diYriW61h0gN8SAMeBtc/HEqr5UewqrayNZoto4sW5OHWOgTAKORKU2DO/1in6ePWsRSFuh9j+DLdt5faxEwn2FlfqBgT6vT3rbwZwkS+RerU0oI9NFm0h9I46cXtoiRvQHDv+X+DiavVkDVmOZf7Ve5UM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=OH59pHa6; arc=none smtp.client-ip=91.218.175.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="OH59pHa6" Message-ID: <757e24eb-45d3-4e05-9aa2-f077bec8fea9@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779700821; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=I+eeKht/TCorkLGr3qhDvSA2GY+v+dhddDd9N0vNzJE=; b=OH59pHa62MLKpHXZDcV2HRLnP05+4v/mrvRglfb9zsZzOs1bKreXTAkRoNQHcu0IqeX676 XTiCCd/6bbr+UF9Vf82QkM0m5F3TDLkg7IQ/pewetU4wAtr2j1XfO7JMmeP4uHivpiUUPk t6EcMPSXbRAcyWoZuhDYh5LeQ6Bnwbw= Date: Mon, 25 May 2026 17:18:53 +0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3] kernel/bpf/btf.c: reject to register duplicated kfunc To: Song Chen 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> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Kaitao Cheng In-Reply-To: <20260524082944.10625-1-chensong_2000@126.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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); -- Thanks Kaitao Cheng