From patchwork Wed Oct 27 08:52:53 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 12586709 X-Patchwork-Delegate: bpf@iogearbox.net 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6CA9C43219 for ; Wed, 27 Oct 2021 08:58:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C32F961039 for ; Wed, 27 Oct 2021 08:58:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239736AbhJ0JBC (ORCPT ); Wed, 27 Oct 2021 05:01:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239756AbhJ0JA5 (ORCPT ); Wed, 27 Oct 2021 05:00:57 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 422B3C061570 for ; Wed, 27 Oct 2021 01:58:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:To:From:Date:Message-ID:Sender:Reply-To:Cc:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=+sOTmecnIakflIXpIKeS+SSr11ao3M3ORAInvCdoZxM=; b=LscryZGkon8MTkh/6bQ310Xcwt NANFoMx7ywu/6OUOsG4kQagbcYp1laSbKTXfHc+s2g5I4VwH8CXllYG7lvTF2Jcw/yvWnX1bvDs+u cyrDPONc8mepAoXslnoZjD8UJ5ZKLioudgdLcWpBN7HrvgNNT0j35DUs3Cgnl/WeYyFnAo/puRhjI qe0w8wH4LkwY1whKcFU9Llo/F2YER9wF+jZdLYQWVeeRFTxFX19OiyJ+C6lY4XCTqSntM1GCXvlBy 32cg1NV6QXr22vYM7iOyzqjzTZYUZlJCRqTMuhcAEtoGNUr0AAwEQrt2OtoLL85ll7ZPWqGBVsZoO fS+jMU0g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mfelQ-00CWW9-5B for bpf@vger.kernel.org; Wed, 27 Oct 2021 08:58:29 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A075D300C9D for ; Wed, 27 Oct 2021 10:58:20 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 913E5236E43D9; Wed, 27 Oct 2021 10:58:20 +0200 (CEST) Message-ID: <20211027085520.684740055@infradead.org> User-Agent: quilt/0.66 Date: Wed, 27 Oct 2021 10:52:53 +0200 From: Peter Zijlstra To: bpf@vger.kernel.org Subject: [PATCH bpf-next 10/17] x86/retpoline: Create a retpoline thunk array References: <20211027085243.008677168@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Stick all the retpolines in a single symbol and have the individual thunks as inner labels, this should guarantee thunk order and layout. Previously there were 16 (or rather 15 without rsp) separate symbols and a toolchain might reasonably expect it could displace them however it liked, with disregard for their relative position. However, now they're part of a larger symbol. Any change to their relative position would disrupt this larger _array symbol and thus not be sound. This is the same reasoning used for data symbols. On their own there is no guarantee about their relative position wrt to one aonther, but we're still able to do arrays because an array as a whole is a single larger symbol. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/nospec-branch.h | 8 +++++++- arch/x86/lib/retpoline.S | 14 +++++++++----- 2 files changed, 16 insertions(+), 6 deletions(-) --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -12,6 +12,8 @@ #include #include +#define RETPOLINE_THUNK_SIZE 32 + /* * Fill the CPU return stack buffer. * @@ -120,11 +122,15 @@ #ifdef CONFIG_RETPOLINE +typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE]; + #define GEN(reg) \ - extern asmlinkage void __x86_indirect_thunk_ ## reg (void); + extern retpoline_thunk_t __x86_indirect_thunk_ ## reg; #include #undef GEN +extern retpoline_thunk_t __x86_indirect_thunk_array[]; + #ifdef CONFIG_X86_64 /* --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -28,16 +28,14 @@ .macro THUNK reg - .align 32 - -SYM_FUNC_START(__x86_indirect_thunk_\reg) + .align RETPOLINE_THUNK_SIZE +SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL) + UNWIND_HINT_EMPTY ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \ __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD -SYM_FUNC_END(__x86_indirect_thunk_\reg) - .endm /* @@ -55,10 +53,16 @@ SYM_FUNC_END(__x86_indirect_thunk_\reg) #define __EXPORT_THUNK(sym) _ASM_NOKPROBE(sym); EXPORT_SYMBOL(sym) #define EXPORT_THUNK(reg) __EXPORT_THUNK(__x86_indirect_thunk_ ## reg) + .align RETPOLINE_THUNK_SIZE +SYM_CODE_START(__x86_indirect_thunk_array) + #define GEN(reg) THUNK reg #include #undef GEN + .align RETPOLINE_THUNK_SIZE +SYM_CODE_END(__x86_indirect_thunk_array) + #define GEN(reg) EXPORT_THUNK(reg) #include #undef GEN