From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) (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 6B8903F4DDA for ; Tue, 2 Jun 2026 17:13:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.185 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780420398; cv=none; b=li+1LCp76Y5C+WxMcWT6aT0zn1pvpW4WES16UtrRNrX5x1o4uk85aIM047EqmSsyuHc68CQM8awTyhalR/Ck6i0r+HEOULGQq04G/G3VFgxFwhMrJDwflOTMAqRZ5IfyvkPkE69HOIf6RjXlC5Axl1/60Vl50Ra39wHvfUfa3N4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780420398; c=relaxed/simple; bh=RPvkBtHirW7YoC7cdCr+rxXe0J+D52+kZlarUlyehaw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DrMkC46IaWpVXA5kxGbcn2vtjiGhj9CBKUV+9HeWihVvyXngSkwdH4+kJX7AWJiT4/MSzj80SQQwuS1e40i8ZbzSpddU0tijV6DY8t40+tjEUuZHjds+02D0oPJrSqPWTmCSricZbM93bZJb8blSuhZAl+a7FilNg8YQA5Lmxt0= 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=UnxVstqe; arc=none smtp.client-ip=91.218.175.185 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="UnxVstqe" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780420394; 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=3RZLBXo0qamZRboc3G6gCp4D+rmYBliqxy5raxOSnRU=; b=UnxVstqexxEp/DyVPxd40OJYbpHFdm+RcTXuo4CwKBUuI52cenfVozpiWeJZLwUXE7bbHh TywMDhpzb9TVe0nz5doG/j/m2G/stf+NxsqrAPQfDKlJSba+j3xNQFKG+VHR40SQSu42JP 0IR1RPGBvbk7Gc5kxKMrD7hNXl7hWls= Date: Tue, 2 Jun 2026 10:13:02 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v4] btf: reject to register duplicated kfunc Content-Language: en-GB To: Song Chen , 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> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20260602110710.19642-1-chensong_2000@126.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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; > +} > + > 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))) ... > return -EINVAL; > > func = btf_type_by_id(btf, func->type);