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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D4A4C43334 for ; Tue, 12 Jul 2022 19:01:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235192AbiGLTBP (ORCPT ); Tue, 12 Jul 2022 15:01:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42262 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235369AbiGLS7h (ORCPT ); Tue, 12 Jul 2022 14:59:37 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AABB2F4239; Tue, 12 Jul 2022 11:48:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6970260A5A; Tue, 12 Jul 2022 18:48:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 581A4C3411C; Tue, 12 Jul 2022 18:48:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657651699; bh=Lb9QWk96WPTUHtVIDQUUvFBZ7ad51b1dDmFNTdktXKQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tm9+oXXdw20XKg5UIC5GyI1+mXJq9HKr7f1sIUkWqGmyOrJ4YxWQM6TBQaRjE+3iM S8IRbXTa0BZu/fhkuITjznLDhAP339iiF7TLw49qR6n5ZfAfXSjllBCC6vmDelLBEw HCGg1bmC0vXITFHmYpaW+qmjpDf3iZ42N+yqjFR0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Borislav Petkov , Nick Desaulniers , Josh Poimboeuf , Thadeu Lima de Souza Cascardo Subject: [PATCH 5.15 28/78] x86/retpoline: Use -mfunction-return Date: Tue, 12 Jul 2022 20:38:58 +0200 Message-Id: <20220712183239.940184256@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220712183238.844813653@linuxfoundation.org> References: <20220712183238.844813653@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra commit 0b53c374b9eff2255a386f1f1cfb9a928e52a5ae upstream. Utilize -mfunction-return=thunk-extern when available to have the compiler replace RET instructions with direct JMPs to the symbol __x86_return_thunk. This does not affect assembler (.S) sources, only C sources. -mfunction-return=thunk-extern has been available since gcc 7.3 and clang 15. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Nick Desaulniers Reviewed-by: Josh Poimboeuf Tested-by: Nick Desaulniers Signed-off-by: Borislav Petkov [cascardo: RETPOLINE_CFLAGS is at Makefile] [cascardo: remove ANNOTATE_NOENDBR from __x86_return_thunk] Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- Makefile | 2 ++ arch/x86/include/asm/nospec-branch.h | 2 ++ arch/x86/lib/retpoline.S | 12 ++++++++++++ 3 files changed, 16 insertions(+) --- a/Makefile +++ b/Makefile @@ -687,11 +687,13 @@ endif ifdef CONFIG_CC_IS_GCC RETPOLINE_CFLAGS := $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register) +RETPOLINE_CFLAGS += $(call cc-option,-mfunction-return=thunk-extern) RETPOLINE_VDSO_CFLAGS := $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register) endif ifdef CONFIG_CC_IS_CLANG RETPOLINE_CFLAGS := -mretpoline-external-thunk RETPOLINE_VDSO_CFLAGS := -mretpoline +RETPOLINE_CFLAGS += $(call cc-option,-mfunction-return=thunk-extern) endif export RETPOLINE_CFLAGS export RETPOLINE_VDSO_CFLAGS --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -120,6 +120,8 @@ _ASM_PTR " 999b\n\t" \ ".popsection\n\t" +extern void __x86_return_thunk(void); + #ifdef CONFIG_RETPOLINE typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE]; --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -66,3 +66,15 @@ SYM_CODE_END(__x86_indirect_thunk_array) #define GEN(reg) EXPORT_THUNK(reg) #include #undef GEN + +/* + * This function name is magical and is used by -mfunction-return=thunk-extern + * for the compiler to generate JMPs to it. + */ +SYM_CODE_START(__x86_return_thunk) + UNWIND_HINT_EMPTY + ret + int3 +SYM_CODE_END(__x86_return_thunk) + +__EXPORT_THUNK(__x86_return_thunk)