From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lj1-f169.google.com (mail-lj1-f169.google.com [209.85.208.169]) (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 A4DBD29CA for ; Mon, 24 Jan 2022 23:38:53 +0000 (UTC) Received: by mail-lj1-f169.google.com with SMTP id e9so1990340ljq.1 for ; Mon, 24 Jan 2022 15:38:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=FIP6niwFiCcE5eTqnTDWmb/wrXropuAeXBH8bjmRfkM=; b=VrwRqbW7mgBywTPgKBmLBf5J1mchIOr7JqxAATJJaO2MOs9YuCVpjjVNXEzsBml+wp ado8O/B5hhh9+WaOXej80757SD6Mzhj0G7C9BhHFXNvvFWjgiuy15dPxWN9LkKSG3U+6 gpE+me8Rw51avTJbIfG4JbHAU8GoEKfJyjejlkHSYuh6vLn6mpXNjFiANAPJrwEoxGwG 4pZ3FS3eS7llLKrv/WOiSSLxAyUYewvLJ1UbGnehniTPMJrS/per8DLCYHyAVFn10Dcp 0zR68towoUo99m4ogkP8Pl1ssg2Dnq6HhdFZ0vu0iKYz6Qr7WmpUyHrojf5yKD7d03V8 fGqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=FIP6niwFiCcE5eTqnTDWmb/wrXropuAeXBH8bjmRfkM=; b=Aa5zA9WXr9r4y+MAvgFq2raZ+CtMOdQsSwFePMLSlIRF60D9C+AGX0vKYFnG+FJxWN XlQdN34DdmlugPtRq9mHUjQHYMUK/jkGDPX69Ef72U5dY3RTFJ3pJUE8ouQyg7MTjgJx YAnbN2tUjwDqES5agaQo3f37MEQvIOiDxYIn4hGvW7GUIknb9vLPFRhG2uxgKeKHC+R1 llqPrsSd7T56Q55UaqtBU6dyMkznj3r/+dJ8LviVP49EKkioFc67EaB0IY3OVRJ0E7S3 df0qOzmfwz0+V3A+DvtrnxHD1W7G04GpmBl0dJAC8eVHTHA4a/603lt8MiMlq8ygsCtr RWvA== X-Gm-Message-State: AOAM533MoMpaTmWVbUHlAlfEezBtf9s+7cD1uzfFSKc/5xc26OTQzofP gqucogIo48TMlWlwytXM/Z3/Oix56D/jxguY2V/dFg== X-Google-Smtp-Source: ABdhPJxzHN2oG34NI+OLkIh9cUsniM7MENh8SCt8InminhPjzFucnqpWLiy0Rn4gHwCa+ALqvnw7k5IqoQt/rLjLGHg= X-Received: by 2002:a2e:9654:: with SMTP id z20mr12950862ljh.526.1643067531477; Mon, 24 Jan 2022 15:38:51 -0800 (PST) Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20220114010526.1776605-1-ndesaulniers@google.com> <20220118192256.jzk5dnceeusq7x7u@treble> <20220118230120.pivvson7qekfiqic@treble> In-Reply-To: From: Nick Desaulniers Date: Mon, 24 Jan 2022 15:38:38 -0800 Message-ID: Subject: Re: [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__ To: Josh Poimboeuf , Borislav Petkov Cc: Vasily Gorbik , Linus Torvalds , Ingo Molnar , Dave Hansen , Thomas Gleixner , Peter Zijlstra , Luc Van Oostenryck , x86@kernel.org, llvm@lists.linux.dev, linux-sparse@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot , Nathan Chancellor , linux-toolchains@vger.kernel.org Content-Type: text/plain; charset="UTF-8" On Mon, Jan 24, 2022 at 3:26 PM Nick Desaulniers wrote: > > On Tue, Jan 18, 2022 at 3:01 PM Josh Poimboeuf wrote: > > > > Apparently this patch isn't going to work after all :-( > > > > https://lkml.kernel.org/r/202201190632.lhlaiCBk-lkp@intel.com > > I noticed in that report and > https://lore.kernel.org/lkml/202201190702.XNSXrMTK-lkp@intel.com/ > that gcc-9 was used. I wonder if %= has been fixed in gcc-10+? Have > there been other reports with gcc-10+ for my patch? > > Boris' case of xfrm_output_resume is yet a third case; Boris, what > version of gcc did you spot that with? > > If this is fixed in gcc-10, then we can probably add a comment with a > FIXME link to the issue or commit to replace __COUNTER__ with %= one > day. If not, then we can probably come up with a reduced test case > for the GCC devs to take a look at, then add the FIXME comment to > kernel sources. $ wget https://download.01.org/0day-ci/archive/20220119/202201190702.XNSXrMTK-lkp@intel.com/config -O .config $ make -j72 -s olddefconfig drivers/net/wireless/mac80211_hwsim.o drivers/net/wireless/mac80211_hwsim.o: warning: objtool: mac80211_hwsim_tx()+0x9aa: unreachable instruction $ gcc --version gcc (Debian 11.2.0-12) 11.2.0 :( Let me see if I can come up with a reduced test case that I will report upstream to https://gcc.gnu.org/bugzilla/. -- Thanks, ~Nick Desaulniers