From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 004701097E; Tue, 15 Aug 2023 14:35:57 +0000 (UTC) Received: from mail-ed1-x52f.google.com (mail-ed1-x52f.google.com [IPv6:2a00:1450:4864:20::52f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3D3719A6; Tue, 15 Aug 2023 07:35:54 -0700 (PDT) Received: by mail-ed1-x52f.google.com with SMTP id 4fb4d7f45d1cf-5234b80e9b6so7461639a12.2; Tue, 15 Aug 2023 07:35:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1692110153; x=1692714953; h=mime-version:user-agent:content-transfer-encoding:references :in-reply-to:date:cc:to:from:subject:message-id:from:to:cc:subject :date:message-id:reply-to; bh=5ExkU1aXgwbVZAT4/86NsHH+oPTHRo8kokP8esTR6pM=; b=T8JfBGRKfRbUqDuTJiwMDTGkrsRIKO5jTVuAqeDt45jhDd+MoPa0r9rX6d+JXB2SLH +PdVegksVN7bVdmYt0loLcqvellOQIle4Gh8C4S0uUSTNbGFG/T1RJl2QvLFUj6BVGsi fpLg6c77iRfXi/coDfTa7VaY7bVSsXhSeZmxhUS0UEWcVpiUmO2MkQoZFY6YHpkt9Ltv XzWstHS/9nWlHwYLdZhEtS2nCeZx3HXivTZv7prynNSMvoL5EfqyMFQJFwL4WjM0xpZm N/tnxa2KLrWGXfxKLLIqTwz+bs1lST0+VmoajwsrbVuLtgVk/XpaFyfJZXlHNXb58Qyw Cizw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692110153; x=1692714953; h=mime-version:user-agent:content-transfer-encoding:references :in-reply-to:date:cc:to:from:subject:message-id:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=5ExkU1aXgwbVZAT4/86NsHH+oPTHRo8kokP8esTR6pM=; b=iLrb6NVavHradzfYV9cbPUdV03q0U14iyiR5YoXPjcZGWczPo7NcDHjg7tE8T3UeHv k7kNNzcwt0HzKC2gJCoLbpPaVwX2+Rcu/zRU/gMOwmF/3rVh5K1ZZf60NG0Mwl4ysk8D Vveoxik8QYJiGyLv6DgQkF4LhKXxnm4d7rdneeulkxUS2r3Nm0NUBldMR+KRf4KeQmem xLJS+Flsc5eRp3qb/5MdRKHBlL6spE1mEZeKiZeSaORiGTmBWMW9yCsXtvwpksAaMJoM IpcdDvuzDy1fA+RL/AL90f/s1xHoqiUff4Q/MrYzzMUj1AmqiKVmGvZF06w6XB1cc+EC lgGg== X-Gm-Message-State: AOJu0Yw/Qy1GpeZvuMV+OLBGQB7ouGOF9SraQlfNiJkXhnGe5eyNw+QF LdgR6nChaItJ9/Ke9GXNOdvbxIDsIl/csA== X-Google-Smtp-Source: AGHT+IFsmByXjHI0wnLzrSXkFNHsDb7aGcOCiExsey2xd2N/qfCGkxS21qOBHQU7rf4CmMMPM/mEAg== X-Received: by 2002:aa7:c612:0:b0:522:20a0:7eb8 with SMTP id h18-20020aa7c612000000b0052220a07eb8mr9909900edq.33.1692110152723; Tue, 15 Aug 2023 07:35:52 -0700 (PDT) Received: from [192.168.1.95] (host-176-36-0-241.b024.la.net.ua. [176.36.0.241]) by smtp.gmail.com with ESMTPSA id n19-20020aa7c453000000b0052328d4268asm6831254edr.81.2023.08.15.07.35.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Aug 2023 07:35:52 -0700 (PDT) Message-ID: <841306f0691a7d56be72be0bb3c7472eadcc3367.camel@gmail.com> Subject: Re: [RFC PATCH bpf-next 1/2] bpf, x64: Fix tailcall infinite loop bug From: Eduard Zingerman To: Leon Hwang , bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mykolal@fb.com, shuah@kernel.org, davem@davemloft.net, dsahern@kernel.org, tangyeechou@gmail.com, kernel-patches-bot@fb.com, maciej.fijalkowski@intel.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Date: Tue, 15 Aug 2023 17:35:50 +0300 In-Reply-To: <43201fd2-dca7-9294-1dea-8460a9e99296@gmail.com> References: <20230814134147.70289-1-hffilwlqm@gmail.com> <20230814134147.70289-2-hffilwlqm@gmail.com> <43201fd2-dca7-9294-1dea-8460a9e99296@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.4-0ubuntu1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-1.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Tue, 2023-08-15 at 11:01 +0800, Leon Hwang wrote: [...] > a) Initial value of RAX is in emit_prologue(). > if (!ebpf_from_cbpf) { > if (tail_call_reachable && !is_subprog) > /* When it's the entry of the whole > * tailcall context, zeroing the RAX > * means init tail_call_cnt. > */ > EMIT2(0x31, 0xC0); /* xor eax, eax */ > else > // Keep the same asm layout. > EMIT2(0x66, 0x90); /* nop2 */ > } > I'd like to add this comment to emit_prologue(). Got it, thank you. [...]