From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-1.mta0.migadu.com [91.218.175.1]) (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 D963238228A for ; Sat, 19 Sep 2026 19:33:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.1 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789846384; cv=none; b=kb/0KJKwnfJPjoYmKzMHn/sFd7F926GqCP0AjognqUn727lLP7nNUCFPw0MiumJEjLEmfknFxgCnLnGcD3epcpULmXR8Ou/Xmhw4+nvvMGgGFKeTYjicM6RrypGDXNSIYstNO77nWzvDLRXvmdKdV/F3sXqYVIySChM3+BEf4EE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789846384; c=relaxed/simple; bh=xE6jfuoKYQZYMCxqg6NzQAVyKkFWrTVReaqnbLiNe50=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lVEaXAm3VtuuOHRb1S2f30mUbh8Gm379Gwqoy4+nL/KC15oWFeLJ4CrFbA/KfuAClPvq7srRSn3f0mBQSIr4MWyiu0JsB9LAggTQL76amHvEHPr0a0m4nC8FgyyJK7ft77/tsScpII1SDNpee4E//7UDyKt5S30S+z6Hh26dEzU= 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=PZif4kU0; arc=none smtp.client-ip=91.218.175.1 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="PZif4kU0" X-Envelope-To: bpf@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=xE6jfuoKYQZYMCxqg6NzQAVyKkFWrTVReaqnbLiNe50=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789846379; v=1; x=1790451179; b=PZif4kU00aImbpF0X1VKZhrf97ZVfzeccLTwI06qeDxsH4HnxMQbPvzf4ijTIY+etQERa2FK 0Vqj+PfrCpryMfG6K5gMD9mes0L44H+zppYQBFdSkWGCjjF26wzvnRubH3FwkPKycv2kvhnaDjY EyCMW8fmhidTMn/GZjgvCc7k= X-Envelope-To: bpf@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 96355e51f462fce3; Sat, 19 Sep 2026 19:32:58 +0000 X-Mizu-Trace-ID: 96355e51f462fce3 X-Migadu-Flow: FLOW_OUT Message-ID: <1dfb59b4-9c23-45f7-8fac-ade2cedb3685@linux.dev> Date: Sat, 19 Sep 2026 12:32:53 -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 v2 06/20] bpf: Explore the landing pads no call site reaches Content-Language: en-GB To: bot+bpf-ci@kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, kernel-team@fb.com, martin.lau@kernel.org, mason@kernel.org, ihor.solodrai@linux.dev References: <20260918044228.3287877-1-yonghong.song@linux.dev> From: Yonghong Song In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/17/26 10:44 PM, bot+bpf-ci@kernel.org wrote: >> commit c93117f24a1a9cc39bfeaef79c42dbff02d8c455 >> Author: Yonghong Song >> >> bpf: Explore the landing pads no call site reaches >> >> A cleanup record need not cover a call an exception can unwind out of: a >> frontend is free to emit a region around a helper or an ordinary kfunc, >> both nounwind here. Nothing marks a call site then, and that record's >> landing pad is reached by nothing at all -- leaving bpf_check_cfg() to >> refuse the program over code its own frontend had no way not to emit: >> >> 0: call bpf_preempt_disable >> 1: call bpf_preempt_enable record = { begin = 1, end = 2, pad = 4 } >> 2: r0 = 0 >> 3: exit >> 4: r1 = pads_ran ll landing pad >> 6: r2 = *(u64 *)(r1 + 0) >> 7: r2 |= RAN_NOUNWIND_REC >> 8: *(u64 *)(r1 + 0) = r2 >> 9: call bpf_unwind_resume >> 10: exit >> >> The range [1,2) holds one call, and it is a kfunc, so an exception cannot >> come out of it. cleanup_mark_call_sites() marks nothing, nothing pushes an >> edge to 4, and 4 through 10 are reachable from nothing: "unreachable insn >> 4". The pad is dead, which is correct -- no exception can ever arrive at it >> -- but the program is fine and has to load. >> >> Walk every pad the table names that the edges did not reach, the way the >> walk is already re-seeded at an exception callback. From there the pad is >> code like any other: do_check() never enters it, because no call site >> dispatches to it, so the dead code sweep removes it along with everything >> else that was not reached. >> >> Signed-off-by: Yonghong Song > This looks like a bug fix for the earlier commit that made exception landing > pads reachable in the CFG. Should this include: > > Fixes: a67011bbbca1ba95 ("bpf: Make exception landing pads reachable in the CFG") No need for this Fixes tag. > > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/35308528711