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 970F2C43334 for ; Tue, 12 Jul 2022 18:53:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234740AbiGLSxN (ORCPT ); Tue, 12 Jul 2022 14:53:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234646AbiGLSwc (ORCPT ); Tue, 12 Jul 2022 14:52:32 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FA51DA0E4; Tue, 12 Jul 2022 11:45:08 -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 ams.source.kernel.org (Postfix) with ESMTPS id 69763B81BBB; Tue, 12 Jul 2022 18:44:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9A49C3411C; Tue, 12 Jul 2022 18:44:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657651495; bh=BFyioED30kwJD9PGGxY9ZF6TW0CFgre5ZqlPuYrWpL8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vllPcmRsJzbogyCvHz6x0VkXzTnRaggOi/NPTI+jWrYZuongHs7g82kMm44pl9d1T iL2X19+KZQrZjugnA/rsNiCFjzVew004SKvqZ0x3TbbDO1dPqJSjVe2GO6YFrJjcLE Xr1MZ+0pjnzIxIOiy2CSgv0s/xxbVlCu+cB7kNCA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Borislav Petkov , Josh Poimboeuf , Thadeu Lima de Souza Cascardo , Ben Hutchings Subject: [PATCH 5.10 093/130] x86: Use return-thunk in asm code Date: Tue, 12 Jul 2022 20:38:59 +0200 Message-Id: <20220712183250.755673482@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220712183246.394947160@linuxfoundation.org> References: <20220712183246.394947160@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 aa3d480315ba6c3025a60958e1981072ea37c3df upstream. Use the return thunk in asm code. If the thunk isn't needed, it will get patched into a RET instruction during boot by apply_returns(). Since alternatives can't handle relocations outside of the first instruction, putting a 'jmp __x86_return_thunk' in one is not valid, therefore carve out the memmove ERMS path into a separate label and jump to it. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov [cascardo: no RANDSTRUCT_CFLAGS] Signed-off-by: Thadeu Lima de Souza Cascardo [bwh: Backported to 5.10: adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/vdso/Makefile | 1 + arch/x86/include/asm/linkage.h | 8 ++++++++ arch/x86/lib/memmove_64.S | 7 ++++++- 3 files changed, 15 insertions(+), 1 deletion(-) --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -91,6 +91,7 @@ endif endif $(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL) +$(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO # # vDSO code runs in userspace and -pg doesn't help with profiling anyway. --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -18,19 +18,27 @@ #define __ALIGN_STR __stringify(__ALIGN) #endif +#if defined(CONFIG_RETPOLINE) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO) +#define RET jmp __x86_return_thunk +#else /* CONFIG_RETPOLINE */ #ifdef CONFIG_SLS #define RET ret; int3 #else #define RET ret #endif +#endif /* CONFIG_RETPOLINE */ #else /* __ASSEMBLY__ */ +#if defined(CONFIG_RETPOLINE) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO) +#define ASM_RET "jmp __x86_return_thunk\n\t" +#else /* CONFIG_RETPOLINE */ #ifdef CONFIG_SLS #define ASM_RET "ret; int3\n\t" #else #define ASM_RET "ret\n\t" #endif +#endif /* CONFIG_RETPOLINE */ #endif /* __ASSEMBLY__ */ --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -40,7 +40,7 @@ SYM_FUNC_START(__memmove) /* FSRM implies ERMS => no length checks, do the copy directly */ .Lmemmove_begin_forward: ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM - ALTERNATIVE "", __stringify(movq %rdx, %rcx; rep movsb; RET), X86_FEATURE_ERMS + ALTERNATIVE "", "jmp .Lmemmove_erms", X86_FEATURE_ERMS /* * movsq instruction have many startup latency @@ -206,6 +206,11 @@ SYM_FUNC_START(__memmove) movb %r11b, (%rdi) 13: RET + +.Lmemmove_erms: + movq %rdx, %rcx + rep movsb + RET SYM_FUNC_END(__memmove) SYM_FUNC_END_ALIAS(memmove) EXPORT_SYMBOL(__memmove)