From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (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 20EB41C4A10; Thu, 21 Aug 2025 02:55:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755744949; cv=none; b=H/VY/E5zen8jQL2GGikQk8B8Qrr7yj/Ps7Yf895V9z+nuEtUYJMthyZ7y/be6cD1sM8ENbPUV262cWmpLwzPslg9lIy917c4ZY6JV/DXae42MFlpOqVIAQpPX2gfqvUfS9cBy8lcnaviTTo+Doto73y8Sfrs1+inzrDFC9m8c1k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755744949; c=relaxed/simple; bh=QvMUeM4pDlP632rKfYRBprYpHIkWELPeq80btpP7l6o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RfQH9L6qa/uCcD6yZT/lRumfmiPwL/X4++d5HBXNGVc3cDSLIhj4onkY4SEH6eBMsT736EOTaMJwWo9K3LiNlsYtu44stiHmvFOiOBG6YFa72qIX9W9zxYeN72ksPcfVEgU9RZLTBvzoyfqhggEVcbIY2rOqCI6zet7v/jZt+tw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 4fcfd56a7e3a11f0b29709d653e92f7d-20250821 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.45,REQID:31331416-7b38-4d16-a261-b0cb1ce5c005,IP:0,U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:0 X-CID-META: VersionHash:6493067,CLOUDID:33274ee4927d2cea1b83a9d1f9bfd892,BulkI D:nil,BulkQuantity:0,Recheck:0,SF:80|81|82|83|102,TC:nil,Content:0|50,EDM: -3,IP:nil,URL:0,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0, AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 0,NGT X-CID-BAS: 0,NGT,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-UUID: 4fcfd56a7e3a11f0b29709d653e92f7d-20250821 X-User: duanchenghao@kylinos.cn Received: from localhost [(10.44.16.150)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 519076177; Thu, 21 Aug 2025 10:55:36 +0800 Date: Thu, 21 Aug 2025 10:55:32 +0800 From: Chenghao Duan To: Pu Lehui Cc: ast@kernel.org, bjorn@kernel.org, puranjay@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, 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, alex@ghiti.fr, bpf@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: bpf: Fix uninitialized symbol 'retval_off' Message-ID: <20250821025532.GA287128@chenghao-pc> References: <20250820062520.846720-1-duanchenghao@kylinos.cn> <8b836b6e-103a-41c2-b111-0417d8db4dce@huawei.com> <20250820092628.GA1289807@chenghao-pc> <239193b7-7dab-45b0-ab13-06bfe3f96f22@huawei.com> <20250820103530.GA1475460@chenghao-pc> <9cbdefd6-a757-44b3-a1db-69ca8117aacb@huawei.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <9cbdefd6-a757-44b3-a1db-69ca8117aacb@huawei.com> On Thu, Aug 21, 2025 at 09:58:20AM +0800, Pu Lehui wrote: > > > On 2025/8/20 18:35, Chenghao Duan wrote: > > On Wed, Aug 20, 2025 at 06:10:07PM +0800, Pu Lehui wrote: > > > > > > > > > On 2025/8/20 17:26, Chenghao Duan wrote: > > > > On Wed, Aug 20, 2025 at 02:52:01PM +0800, Pu Lehui wrote: > > > > > > > > > > > > > > > On 2025/8/20 14:25, Chenghao Duan wrote: > > > > > > In __arch_prepare_bpf_trampoline(), retval_off is only meaningful when > > > > > > save_ret is true, so the current logic is correct. However, in the > > OK, I think we should make commit msg more explicit. Such like the follow. > wdyt? > > `However, in the fmod_ret logic, the compiler is not aware that the flags of > the fmod_ret prog have set BPF_TRAMP_F_CALL_ORIG, resulting in an > uninitialized symbol compilation warning.` > Good idea > > > > > > > > > > lgtm, and same for `ip_off`, pls patch it together. > > > > > > > > I also checked at the time that ip_off is only initialized and assigned > > > > when flags & BPF_TRAMP_F_IP_ARG is true. However, I noticed that the use > > > > of ip_off also requires this condition, so the compiler did not issue a > > > > warning. > > > > > > > > Chenghao > > > > > > > > > > > > > > > original logic, retval_off is only initialized under certain > > > > > > Can you show how to replay this warning? I guess the warning path is as > > > follow. Compiler didn't know fmod_ret prog need BPF_TRAMP_F_CALL_ORIG. > > > > > > ``` > > > if (fmod_ret->nr_links) { > > > ... > > > emit_sd(RV_REG_FP, -retval_off, RV_REG_ZERO, ctx); > > > } > > > ``` > > > > > > > Exactly, the compiler sees the unconditional use of retval_off. > > > > Chenghao > > > > > > > > conditions, which may cause a build warning. > > > > > > > > > > > > So initialize retval_off unconditionally to fix it. > > > > > > > > > > > > Signed-off-by: Chenghao Duan > > > > > > --- > > > > > > arch/riscv/net/bpf_jit_comp64.c | 5 ++--- > > > > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > > > > > > > diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c > > > > > > index 10e01ff06312..49bbda8372b0 100644 > > > > > > --- a/arch/riscv/net/bpf_jit_comp64.c > > > > > > +++ b/arch/riscv/net/bpf_jit_comp64.c > > > > > > @@ -1079,10 +1079,9 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > > > > > > stack_size += 16; > > > > > > save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); > > > > > > - if (save_ret) { > > > > > > + if (save_ret) > > > > > > stack_size += 16; /* Save both A5 (BPF R0) and A0 */ > > > > > > - retval_off = stack_size; > > > > > > - } > > > > > > + retval_off = stack_size; > > > > > > stack_size += nr_arg_slots * 8; > > > > > > args_off = stack_size;