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[2620:137:e000::1:20]) by mx.google.com with ESMTP id w191-20020a6382c8000000b00520603e8e25si16099390pgd.67.2023.05.15.07.31.26; Mon, 15 May 2023 07:31:41 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@alien8.de header.s=dkim header.b=lBxhywZz; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alien8.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238267AbjEOOHt (ORCPT + 99 others); Mon, 15 May 2023 10:07:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240363AbjEOOHj (ORCPT ); Mon, 15 May 2023 10:07:39 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6155D199F for ; Mon, 15 May 2023 07:07:38 -0700 (PDT) Received: from zn.tnic (p5de8e8ea.dip0.t-ipconnect.de [93.232.232.234]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 764FC1EC0646; Mon, 15 May 2023 16:07:36 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1684159656; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type: content-transfer-encoding:content-transfer-encoding:in-reply-to: references; bh=qGlgGqPJ5+LpDeFZFeGUzglsgfTogWZSynQhMOm/vnk=; b=lBxhywZz2bdoLeWWHAQTNpBcAOILfWsxnd+buYhGUheLRKKrjuFs0POLR9GWen66FTbm2Z 5aP0IVFSlLP12RhcPBBiNMF8jHsHJA101M4X/f5tY92RmrVVO6Lqe6lUPGJHNnl1KHXr+d +WPcxsomnxHqURLJAZkfI3mwG0+JkDM= From: Borislav Petkov To: X86 ML Cc: LKML , Andrew Cooper Subject: [PATCH] x86/retbleed: Add __x86_return_thunk alignment checks Date: Mon, 15 May 2023 16:07:26 +0200 Message-Id: <20230515140726.28689-1-bp@alien8.de> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1765970278032883678?= X-GMAIL-MSGID: =?utf-8?q?1765970911264177783?= From: "Borislav Petkov (AMD)" Add a linker assertion and compute the 0xcc padding dynamically so that __x86_return_thunk is always cacheline-aligned. Leave the SYM_START() macro in as the untraining doesn't need ENDBR annotations anyway. Suggested-by: Andrew Cooper Signed-off-by: Borislav Petkov (AMD) --- arch/x86/kernel/vmlinux.lds.S | 4 ++++ arch/x86/lib/retpoline.S | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 25f155205770..03c885d3640f 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -508,4 +508,8 @@ INIT_PER_CPU(irq_stack_backing_store); "fixed_percpu_data is not at start of per-cpu area"); #endif +#ifdef CONFIG_RETHUNK +. = ASSERT((__x86_return_thunk & 0x3f) == 0, "__x86_return_thunk not cacheline-aligned"); +#endif + #endif /* CONFIG_X86_64 */ diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index b3b1e376dce8..3fd066d42ec0 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -143,7 +143,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) * from re-poisioning the BTB prediction. */ .align 64 - .skip 63, 0xcc + .skip 64 - (__x86_return_thunk - zen_untrain_ret), 0xcc SYM_START(zen_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) ANNOTATE_NOENDBR /*