From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBAB721B9C2 for ; Fri, 23 May 2025 01:12:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747962760; cv=none; b=Xc0q/b3q1q855Ms1xPS7eUWBtrB0cASDG2DxKLPbjlr+RX05EdSVyJgAEZApjcqmUHNwP3cis693O7uSsaI1PXPTEQtLDdMpyom6ZOD2KUM+aBKtvvGQpuX58WDEnnWiDcrfPSBmYmfNB6xaRp2T7SCWMIVXAiqL7/WkR/6NGwo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747962760; c=relaxed/simple; bh=UShqzNCz201Czk0sQEQ1QBEug+XK2KMiwoF7N3Xe6X8=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=W4uPx/1ZITh4uGTZ5vtTxR0T1EKZk3Piw9frl8KZuhZs9U2gUjfZdBUZNHW7lh3xsgdGTUdvKN6b8ZrOqU7m4q7de0+Ok1JDaf5luIEmKRgHRKLT4dIRizC5XJA4gjUWV3G8p7q/lohQOkMBfmxAtYQjCR9Cvmr1StZYeOVwPg4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=LCGSbkHF; arc=none smtp.client-ip=209.85.214.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LCGSbkHF" Received: by mail-pl1-f176.google.com with SMTP id d9443c01a7336-2321c38a948so63149215ad.2 for ; Thu, 22 May 2025 18:12:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1747962758; x=1748567558; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=YpXANfhf2Ct5qfaU6DfTxP1onXasslWBJgjezcxCNm0=; b=LCGSbkHFNGLBQINLNNN054nF4s7tcKBszj2o0cJSOPscmUhHu3liu5VBPwj/8xP3Qw ZyWjBLg/lkD9gfqWFrxMYg7dPmEQdnVPQawL/eRyv1jvpx/IiiKkRZdIFRtVjydE0E5Y cLk5eTg7mzHMqBtsR+XXcY/2nYgwvrT3E7VE75iD/IcXkUtVGONz3x4ApDGrstMGGUsm DInabBEfkxnXCGH6x1KwEM7tNfjZlm0UIe3YOvwyBlmaNgtiDjvHKqMflVEG3t5K7Wvi 4DeHT3OO9jXM+9ZFndvLkxEfFFHMRz1i8/k+Ss1V6t4cGNTSFBQXZBdoRy032M+A4qij a+5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747962758; x=1748567558; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=YpXANfhf2Ct5qfaU6DfTxP1onXasslWBJgjezcxCNm0=; b=GZW7Q5taTuHkNNqY0CkCZQEKk9hnacGszvrXefg1h496FKFfFf+vsswXyH+5KJUnWR /leT5GIgvdB2JpYcPvpB4jIJFrv86pZHm80wbHKOcnUaAeU3ys82mW9a7x+f25Tn7uTr 3+uyN9auNdc2nFMY4Gy2QM1i+/TKyOO5VveiT8xvIOKQu1J1SpLouL62QzudTGh1tQAL zgiYoJ9iiDtmemymXg4d9IiR8vcaibpGE0wxIro2i5HbL2O+rikpzjNHIf6AjG6e+XIM wwgEWJ1b0PMJJdBpzxls+dG/ris1eBSdfDkDgb8X2kRKokNskYfmK93sCplC07ptseYz BChQ== X-Gm-Message-State: AOJu0YzwRcZxTjNrsXEXAaVjXco4GcrLJUUtGnf45hZyiFuoUEhxKGiQ 2QdLUIEmyaUhjNYQOrfQmCq5MdXzl7xUezv9h4eHXn7AMaFFxrQ+RCp1Q1rC7A== X-Gm-Gg: ASbGncuf4pVcOGOVmF6ERyUtVoINfigsiBcKhBjKeebJq0xwDlBA21F7wTi78Fov62R l1cq/S/MPC8Yatjd9I5kfDA/JQ9yiC+3wuxUAOwXGntykRW9apO4cqiihsGKnm11QUyH+T3u1ik rOtQ4GEE+ltdUkIR8AYadZIt+V9ujtSeXZH9YsAa+9Nrk2WXbf86CzikJdZF/22dfM+jnwaxQFZ KkrhLZV840TRmsGx/zRYTDZeA8DV0/bnGz3AH5C0NAswXQFtuoFzhMejtUFlnYd+SPVl9+hFg2E pswb1M5MSEsz8OEb+fpKm9OKkT7yjihA+pKgDj1GwTqU9XOGG4aSy19DhMK4ukXoJ1LpCIPiuPw 2Fn4XtupUWVJIII+i557TpKcvj0oc X-Google-Smtp-Source: AGHT+IG4lbyy/yitsHbJP14sckD4kOu4XYQSyZkEDub2xpqKUrjnE3mqiForYTJpGD7WQGSWuHdbKg== X-Received: by 2002:a17:902:f78c:b0:21f:85ee:f2df with SMTP id d9443c01a7336-231de35f324mr404838505ad.15.1747962757958; Thu, 22 May 2025 18:12:37 -0700 (PDT) Received: from kodidev-ubuntu (69-172-146-21.cable.teksavvy.com. [69.172.146.21]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-231d4e971cdsm114336375ad.134.2025.05.22.18.12.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 May 2025 18:12:37 -0700 (PDT) From: Tony Ambardar X-Google-Original-From: Tony Ambardar Date: Thu, 22 May 2025 18:12:35 -0700 To: Alan Maguire Cc: bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Subject: Re: [PATCH bpf-next v1] libbpf: Fix inheritance of BTF pointer size Message-ID: References: <20250522062116.1885601-1-tony.ambardar@gmail.com> <2160a4ad-b09c-4dfb-98c8-5d3b78a6788a@oracle.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=us-ascii Content-Disposition: inline In-Reply-To: <2160a4ad-b09c-4dfb-98c8-5d3b78a6788a@oracle.com> On Thu, May 22, 2025 at 09:48:30AM +0100, Alan Maguire wrote: > On 22/05/2025 07:21, Tony Ambardar wrote: > > Update btf_new_empty() to copy the pointer size from a provided base BTF. > > This ensures split BTF works properly and fixes test failures seen on > > 32-bit targets: > > > > root@qemu-armhf:/usr/libexec/kselftests-bpf# ./test_progs -a btf_split > > __test_btf_split:PASS:empty_main_btf 0 nsec > > __test_btf_split:PASS:main_ptr_sz 0 nsec > > __test_btf_split:PASS:empty_split_btf 0 nsec > > __test_btf_split:FAIL:inherit_ptr_sz unexpected inherit_ptr_sz: actual 4 != expected 8 > > [...] > > #41/1 btf_split/single_split:FAIL > > > > Fixes: ba451366bf44 ("libbpf: Implement basic split BTF support") > > Signed-off-by: Tony Ambardar > > Great catch! Nit: should we use the btf_ptr_sz(base_btf) helper here? > That would cover the edge case where base BTF does not have ptr_sz set, > as in the absence of a base pointer size this will then determine the > pointer size from the BTF itself. The reason I ask is it seems like the > BTF raw parsing codepath may not set the pointer size, and we will use > that raw parsing to parse vmlinux BTF from /sys/kernel/btf/vmlinux (ELF > parsing uses the ELF class to set pointer size so we are good there I think) > > Reviewed-by: Alan Maguire > I tried to keep simple copy semantics consistent with inheritance & heuristics working as expected, so that edge case should have been OK. However, looking more closely after Andrii's prompting, I don't think the original code really works... (see next email). Regarding raw parsing, let me circle back since it's been a while I was deep in that source. Thanks, Tony > > --- > > tools/lib/bpf/btf.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c > > index 8d0d0b645a75..b1977888b35e 100644 > > --- a/tools/lib/bpf/btf.c > > +++ b/tools/lib/bpf/btf.c > > @@ -995,6 +995,7 @@ static struct btf *btf_new_empty(struct btf *base_btf) > > > > if (base_btf) { > > btf->base_btf = base_btf; > > + btf->ptr_sz = base_btf->ptr_sz; > > btf->start_id = btf__type_cnt(base_btf); > > btf->start_str_off = base_btf->hdr->str_len + base_btf->start_str_off; > > btf->swapped_endian = base_btf->swapped_endian; >