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 X-Spam-Level: X-Spam-Status: No, score=-11.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60037C352A3 for ; Mon, 10 Feb 2020 11:01:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20FB020733 for ; Mon, 10 Feb 2020 11:01:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ellerman.id.au header.i=@ellerman.id.au header.b="I+3CIT97" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727417AbgBJLBo (ORCPT ); Mon, 10 Feb 2020 06:01:44 -0500 Received: from ozlabs.org ([203.11.71.1]:45029 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726796AbgBJLBo (ORCPT ); Mon, 10 Feb 2020 06:01:44 -0500 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 48GNJP0Cxwz9sP7; Mon, 10 Feb 2020 22:01:40 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ellerman.id.au; s=201909; t=1581332501; bh=PJQpp+82DbTtRtYpFA6iKQwKJ/YFQPhWyqk91A7RpFM=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=I+3CIT97uU9eN2rACI2HGPBGIt5YdJcCu3JmWSUcLrqAke3ZaBnFwzXcF4moZBOtD 3l33M5rqyE+U3GWzC69car4xZrQiExj+M+CbM3XsuykI/jifpdxSSaKNFYnIP7Kj6G FpoZl9RXUaM140vnDOHX+TmUzKL4SvkRLOGY2hueQATjBsm6WhFvr1wEiAVP529+OH O78MF45p885mczAWziqTzyJ7jdy5Q246/dfdf7cQISMO+n20pHgXySs7LDduzbliHf clCngKK97t9Woye+hhuWf4htUQeB5I1nWisLTOKXzhVaffPHjzIDiE9MJ9hz3Ll+xY b2jOw5KNOzDpA== From: Michael Ellerman To: Fangrui Song , Benjamin Herrenschmidt , Paul Mackerras , Christophe Leroy Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Fangrui Song Subject: Re: [PATCH] powerpc/vdso32: mark __kernel_datapage_offset as STV_PROTECTED In-Reply-To: <20200205005054.k72fuikf6rwrgfe4@google.com> References: <20200205005054.k72fuikf6rwrgfe4@google.com> Date: Mon, 10 Feb 2020 22:01:37 +1100 Message-ID: <87pnemzoxa.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fangrui Song writes: > A PC-relative relocation (R_PPC_REL16_LO in this case) referencing a > preemptible symbol in a -shared link is not allowed. GNU ld's powerpc > port is permissive and allows it [1], but lld will report an error after > https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id=ec0895f08f99515194e9fcfe1338becf6f759d38 > > Make the symbol protected so that it is non-preemptible but still > exported. "preemptible" means something different to me, and I assume we're not using it to mean the same thing. Can you explain it using small words that a kernel developer can understand? :) cheers > [1]: https://sourceware.org/bugzilla/show_bug.cgi?id=25500 > > Link: https://github.com/ClangBuiltLinux/linux/issues/851 > Signed-off-by: Fangrui Song > --- > arch/powerpc/kernel/vdso32/datapage.S | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/vdso32/datapage.S b/arch/powerpc/kernel/vdso32/datapage.S > index 217bb630f8f9..2831a8676365 100644 > --- a/arch/powerpc/kernel/vdso32/datapage.S > +++ b/arch/powerpc/kernel/vdso32/datapage.S > @@ -13,7 +13,8 @@ > #include > > .text > - .global __kernel_datapage_offset; > + .global __kernel_datapage_offset > + .protected __kernel_datapage_offset > __kernel_datapage_offset: > .long 0 > > -- > 2.25.0.341.g760bfbb309-goog