From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-11.mta1.migadu.com [95.215.58.11]) (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 4D2ED41F5D7 for ; Wed, 23 Sep 2026 18:09:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790186971; cv=none; b=ckhZ4OApuzSRTGsiEeGvLWsZ3ZOiEfFfsUOKarIcpxiCBytgjtwGYepF7Gts/1/Jydk7sf0D+nk/OzNPc5EtOPGvsskO0CZPuZL7g1CGT+9o72JxpADuKH+nyslLRtG3QkxnoIKj/C8ivmYjEKFoASavOCjyLjk385+2JQaGNJ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790186971; c=relaxed/simple; bh=2OSwAATVuMCSkiCTvVkrFXgtQXDm39p0VcxTLm/GZ+4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZznT9dmb7O9O6z0AthhpXAUpbwWx2Zb84U4UMsG9+zza59QtfzU8IVBW3Z2/TQrmyzyl1WT9cNqxmfvv0QKPCUubIyyvQn2PQRkKVuw4n3lkCP0a7AZ+O1x5ozI6zaUcwIzO6EIqZ6p8aIbu7piqEuNsTuL5QYX3Ldbt9JDRnRk= 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=gUONVBC8; arc=none smtp.client-ip=95.215.58.11 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="gUONVBC8" X-Envelope-To: bpf@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=2OSwAATVuMCSkiCTvVkrFXgtQXDm39p0VcxTLm/GZ+4=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790186968; v=1; x=1790791768; b=gUONVBC8ahJOvHbWxJKHIyIVhLaNhT2f7po7sn03rIyTQyDhq+ke4NyCqh9oK3leyK2+V8l6 Q20gFLPOwHY1CTScnUcyx1i5FimZ6YfyzeFtT3ooikE3QZg+lFXCHWJEYkfHTCf+YLg3sS2Qx/j SMEB7xFcXccwfowiAJvn3NOQ= X-Envelope-To: bpf@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id c87db9c4947cdb24; Wed, 23 Sep 2026 18:09:28 +0000 X-Mizu-Trace-ID: c87db9c4947cdb24 X-Migadu-Flow: FLOW_OUT Message-ID: <981c9440-2fb8-4236-9d6e-759f9f2bbbaa@linux.dev> Date: Wed, 23 Sep 2026 11:09:24 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v5 07/21] bpf: Explore the landing pads no call site reaches Content-Language: en-GB To: Eduard Zingerman , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com References: <20260923045846.2414643-1-yonghong.song@linux.dev> <20260923045922.2417689-1-yonghong.song@linux.dev> <3469ede8-6c37-49c9-b261-d2c8506eada5@linux.dev> <0c312ad4f725193e714a50c5fcfc31ad2b273f7d.camel@gmail.com> From: Yonghong Song In-Reply-To: <0c312ad4f725193e714a50c5fcfc31ad2b273f7d.camel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/23/26 11:06 AM, Eduard Zingerman wrote: > On Wed, 2026-09-23 at 10:27 -0700, Yonghong Song wrote: > > ... > >> This patch is to avoid a verification failure. Let us say, we remove this >> patch and run the following >> ./test_progs -t exceptions_cleanup >> and we will get the following failure: > ... > >> This patch intends to explore *unreachable* insns to avoid verification failure. >> >> I think due to "record = { begin = 1, end = 2, pad = 4 }", it is considered that the code at 'pad = 4' >> is not dead, but actually it does dead later so we have the above failure. >> >> So I add this patch to avoid failure. But maybe we should just remove this patch, >> and mark this test as failure as indeed landing pad is not reachable. >> >> WDYT? > But that's a self-fulfilling thing, the test you are pointing at looks > as follows: > > /* > * 15. A region around a call the kernel knows cannot unwind: no call site is > * marked, nothing reaches the pad, and the sweep removes it. The program is > * otherwise ordinary and has to load. > */ > static __used __naked __noinline __u64 nounwind_rec_frame(void) > { > ... > } > > So, the test is added to test this cfg pass, the cfg pass is added to > make this test pass, meanwhile compiler does not generate such code. > I don't see a point, tbh. Confirmed. Will remove this patch.