From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 E1F9F3BBE5 for ; Fri, 14 Mar 2025 18:29:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741976968; cv=none; b=sgyQmp2iBJ9R3I9v4JDPaMluLmiG/tE8YDIskrnxT380ryEQfUr1ow5Gyxbw6M61+mPZYC+7sUPSQtL88xBtQ2mE4QPqeVmF+XdwVDP4mZ2bvpaiYu5Cz2ncI+O9WMMOY9X+1z4aIhuWyeUrRhVvSIdiNZR/oaHjZ3VaYm+5rPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741976968; c=relaxed/simple; bh=vY68TClbdVrf7vczBIBQFMUfXJzLuYL9cKOVsidML4E=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Z6vECK5Xnd78HQ8Y05zRmKl9016F4BVDNlSHamGpb7HmCvUmIl3iYbvAa5bAaTflxxmnHqTKsHTlb28PWGbsVTFJMLQ2AHoFxtEgF3Eb0Ciw7IGiLZPD/13HMgTjQmAp8b8GclM5Cj8YRYzGD97HoSQkymj96PmNdR4VgyBapU8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=MQpa9JhO; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="MQpa9JhO" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=vY68TClbdVrf7vczBIBQFMUfXJzLuYL9cKOVsidML4E=; b=MQpa9JhOLeiLCmwzgsuo5LaYQl 9PqsItBHT0Ndx0KVSyXH1wo2SaFe4TEOnE2wAbmqXZNofeR7WETn2cV9LbbjG7aWY1WnOxG60LpYt +Q9owu0K1w2JTJ6o23BsmkNMVSUVFN9qHYJ1Pwpwz1hq+TqCDGW00CE6o4oN0CUq8bHoWJoM19AU7 kZRHYT15zWAHZDTx0H3R51/4SwpuB9YCQfXbXjb50jvfOkr+wo0BBRCPn5xHPi0onNt9CseJaFyDr JlmWIbb2/DIPLqOtxtveIy2/ac9D5REWcOtgENx71QtAlKM5LY72xEyPImhEGZQYaeoygtjGU1RxL 3w/ROlJA==; Received: from [31.94.74.194] (helo=u09cd745991455d.ant.amazon.com) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tt9mR-00000002vzU-45Zi; Fri, 14 Mar 2025 18:29:12 +0000 Message-ID: Subject: Re: [PATCH v7 8/8] [DO NOT MERGE] x86/kexec: Add CFI type information to relocate_kernel() From: David Woodhouse To: Josh Poimboeuf Cc: kexec@lists.infradead.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , "Kirill A . Shutemov" , Kai Huang , Nikolay Borisov , linux-kernel@vger.kernel.org, Simon Horman , Dave Young , Peter Zijlstra , bsz@amazon.de Date: Fri, 14 Mar 2025 18:29:08 +0000 In-Reply-To: <7tq4tti5pv7fjboiapuglkcsodl4nsk53rj36skg4xb2bkysei@ncoz2ztiddm7> References: <20250312144257.2348250-1-dwmw2@infradead.org> <20250312144257.2348250-9-dwmw2@infradead.org> <7tq4tti5pv7fjboiapuglkcsodl4nsk53rj36skg4xb2bkysei@ncoz2ztiddm7> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-nkM76pZz83D3z85hx+hS" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html --=-nkM76pZz83D3z85hx+hS Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2025-03-14 at 10:52 -0700, Josh Poimboeuf wrote: > On Fri, Mar 14, 2025 at 05:23:15PM +0000, David Woodhouse wrote: > > ISTR this version is OK with Clang and CONFIG_CFI_CLANG but with GCC I > > get this: > >=20 > > vmlinux.o: warning: objtool: relocate_kernel+0x69: unsupported stack re= gister modification > >=20 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* setup a new stack at the = end of the physical control page */ > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 lea=C2=A0=C2=A0=C2=A0=C2=A0 = PAGE_SIZE(%rsi), %rsp > > =C2=A0 79:=C2=A0=C2=A0 48 8d a6 00 10 00 00=C2=A0=C2=A0=C2=A0 lea=C2=A0= =C2=A0=C2=A0 0x1000(%rsi),%rsp > >=20 > >=20 > > Maybe the answer is to put the UNWIND_HINT_FUNC into #ifdef > > CONFIG_CFI_CLANG but that seems wrong. >=20 > The UNWIND_HINT_FUNC definitely looks wrong, why would Clang need it? I think it's when CONFIG_CFI_CLANG makes the SYM_TYPED_FUNC_START() macro actually emit the CFI prologue?=20 > > I'll have another look at putting it in the data section, and see if I > > can remember why I didn't want to do that before (and if that's still > > relevant now). >=20 > IIRC, the reasons were the patched alternative, and also you wanted to > disassemble (but note that's still possible with gdb). >=20 > Here was a patch to make it work: >=20 > =C2=A0 https://lore.kernel.org/20241218212326.44qff3i5n6cxuu5d@jpoimboe Yeah, that does seem reasonable. Sorry, I think I missed that before Christmas. I'll look at rolling it in. This part is kind of orthogonal to the actual debug support so it's fine to keep it separate. 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