From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DC087FED3FA for ; Fri, 24 Apr 2026 18:54:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vwajK7fE/xSxkYUMIjDnVxjmAHQBthF3xbKoitB/mqA=; b=xhfuTaFIuGGV/q1I5lw3IghtY/ Zk6W7bfTbyjtjrB1T1Dcw0EPqEgDFth9RsoIZpyPJCOrcjhRVcpxR2mV1OWXFV6qclrKK/AwixXCP FJiMo5BTc6Y6cytEo7NnzaXFdjb2icHwch3QiuhuJTgKl43O3UKwb02a1S/aX5rS/TnbF291jFsB6 K/+2nIH8J3FmDYL3rmdBV7kbZrMONOL5zawIc09XoESvY1CnqkelSovQ1R3L7J/TekFKhu6jEaDEQ ZJlEwxoTXHuOnvGr2c51LWYExeU1134deeg/0SeVTRnAHXZoOVvFnpCNDWUCeCpl36MOvUisEdEQg ip/ibgcA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wGLfR-0000000DfSE-2P4G; Fri, 24 Apr 2026 18:54:21 +0000 Received: from fanzine2.igalia.com ([213.97.179.56]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wGLfN-0000000DfRs-08Wy for linux-arm-kernel@lists.infradead.org; Fri, 24 Apr 2026 18:54:18 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=vwajK7fE/xSxkYUMIjDnVxjmAHQBthF3xbKoitB/mqA=; b=jxiKcELyUOnwZdMhYogsS3eKzz 8ULx/9UH9pQeTcaFWe+TMv98to+FLm13JmjIQB2RCOf6nsYEkuhLclz11KvEilXxsH9+1syjDdv12 kLrur/lUVwx7sZO5j+jPP0k2sMKu4rodgSyyGKl29akb4VCc2O0yz2pEAfgWpkAaF1brQmons02Fp LWuSF79Qp0dyFJ01vc0pqUONDdjBKKFZPRmuLyomrCNV/aNr9DvMuEBQ0MA/OazT2gkUUnsbyOi0l Bm3YEMMXExEnnY9+S5rbdSiEdS0SuCTRUO2J23llRmM+AHazn0FxGufOMZp0S7sIAOyHkE5ayxCQf X2sVCdAQ==; Received: from [187.57.76.96] (helo=[192.168.15.100]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1wGLef-001iyP-V0; Fri, 24 Apr 2026 20:53:33 +0200 Message-ID: <7c240ce3-dc27-42a1-a21d-d677d9822638@igalia.com> Date: Fri, 24 Apr 2026 15:53:21 -0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 1/2] arm64: vdso: Prepare for robust futex unlock support To: =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= Cc: Catalin Marinas , Will Deacon , Thomas Gleixner , Mark Rutland , Mathieu Desnoyers , Sebastian Andrzej Siewior , Carlos O'Donell , Peter Zijlstra , Florian Weimer , Rich Felker , Torvald Riegel , Darren Hart , Ingo Molnar , Davidlohr Bueso , Arnd Bergmann , "Liam R . Howlett" , Uros Bizjak , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kernel-dev@igalia.com References: <20260417-tonyk-robust_arm-v1-0-03aa64e2ff1a@igalia.com> <20260417-tonyk-robust_arm-v1-1-03aa64e2ff1a@igalia.com> <1a06fee7-65ff-4828-85f1-e3ee1e82610f@t-8ch.de> Content-Language: en-US From: =?UTF-8?Q?Andr=C3=A9_Almeida?= In-Reply-To: <1a06fee7-65ff-4828-85f1-e3ee1e82610f@t-8ch.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260424_115417_410165_165D1767 X-CRM114-Status: GOOD ( 13.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Em 22/04/2026 10:17, Thomas Weißschuh escreveu: > On 2026-04-22 15:02:45+0200, Thomas Weißschuh wrote: >> On 2026-04-17 11:56:10-0300, André Almeida wrote: >>> There will be a VDSO function to unlock non-contended robust futexes in >>> user space. The unlock sequence is racy vs. clearing the list_pending_op >>> pointer in the task's robust list head. To plug this race the kernel needs >>> to know the critical section window so it can clear the pointer when the >>> task is interrupted within that race window. The window is determined by >>> labels in the inline assembly. >>> >>> Signed-off-by: André Almeida >>> --- >>> RFC: Those symbols can't be found by the linker after patch 2/2, it fails with: >>> >>> ld: arch/arm64/kernel/vdso.o: in function `vdso_futex_robust_unlock_update_ips': >>> arch/arm64/kernel/vdso.c:72:(.text+0x200): undefined reference to `__futex_list64_try_unlock_cs_success' >>> ld: arch/arm64/kernel/vdso.o: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `__futex_list64_try_unlock_cs_success' which may bind externally can not be used when making a shared object; recompile with -fPIC >>> arch/arm64/kernel/vdso.c:72:(.text+0x200): dangerous relocation: unsupported relocation >> >> arch/arm64/kernel/vdso.o is a kernel object. >> __futex_list64_try_unlock_cs_success is a vDSO symbol. >> They live in wholly different objects, which are never linked together. >> Look at VDSO_SYMBOL() to get the offset of the vDSO symbol in kernel code. >> >> (...) > > The diff below shows the idea. Compat code is not fixed, and I didn't > even try to run it. Also please use CONFIG_COMPAT_VDSO over plain > CONFIG_COMPAT. > VDSO_SYMBOL() did the tricky, I fixed this for the v2, thanks Thomas! André