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 42F5FC001B0 for ; Wed, 5 Jul 2023 08:52:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232198AbjGEIwk (ORCPT ); Wed, 5 Jul 2023 04:52:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232196AbjGEIwf (ORCPT ); Wed, 5 Jul 2023 04:52:35 -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 E0AAD1716; Wed, 5 Jul 2023 01:52:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4Mcsjo0emh8tYgWsppImcB9AHweArJWJl12Gf8jRhOQ=; b=dJ/Bq9Uh77rfHDu62fLZHMUrCA M3C0hYNpC/NN3is+jkmvZj/by5bpQZlK64GLIxB01SFAPwtVP40eW7Sn35TNOPfblXvXyLFA93bx+ DU8A3V8qvvFG3cZhXxwtdy6Y3MZoV2yZgNjsgXnVtkPqmxrjPgtZfOZ4tUZr5Dxk7NM2kEgzpRpsN 9pk4idSySMBmRkfjCVDCtcFyiRgyQQovn7UFyY/sPke1QXJ44cNlcEUohLs8hQMqJiK/9fXunTsEC OwmxlSaLp1n6Zm47uSizPclqI364QK9CXLtn/jg1qP/pU9Fb5Pi7UBs2y+qct2a8wFmJ+DJyFgX7d 7TycpfPw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qGyFL-00C2sy-1I; Wed, 05 Jul 2023 08:52:25 +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 (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 66CA83001E7; Wed, 5 Jul 2023 10:52:22 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4B3562028F056; Wed, 5 Jul 2023 10:52:22 +0200 (CEST) Date: Wed, 5 Jul 2023 10:52:22 +0200 From: Peter Zijlstra To: Petr Pavlu Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mhiramat@kernel.org, samitolvanen@google.com, x86@kernel.org, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] x86/retpoline,kprobes: Fix position of thunk sections with CONFIG_LTO_CLANG Message-ID: <20230705085222.GF462772@hirez.programming.kicks-ass.net> References: <20230705081547.25130-1-petr.pavlu@suse.com> <20230705081547.25130-2-petr.pavlu@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230705081547.25130-2-petr.pavlu@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 05, 2023 at 10:15:46AM +0200, Petr Pavlu wrote: > Linker script arch/x86/kernel/vmlinux.lds.S matches the thunk sections > ".text.__x86.*" from arch/x86/lib/retpoline.S as follows: > > .text { > [...] > TEXT_TEXT > [...] > __indirect_thunk_start = .; > *(.text.__x86.*) > __indirect_thunk_end = .; > [...] > } > > Macro TEXT_TEXT references TEXT_MAIN which normally expands to only > ".text". However, with CONFIG_LTO_CLANG, TEXT_MAIN becomes > ".text .text.[0-9a-zA-Z_]*" which wrongly matches also the thunk > sections. The range [__indirect_thunk_start, __indirect_thunk_end] is > then empty. > > A visible result is that function insn_is_indirect_jump() misbehaves and > optprobes become allowed in functions where they are not potentially > safe. > > Fix the problem by using ".." as the first separator, for instance, > ".text..__x86.indirect_thunk". This pattern is utilized by other First I hear of this, but yes, indeed. > explicit section names which start with one of the standard prefixes, > such as ".text" or ".data", and that need to be individually selected in > the linker script. > > Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO") > Signed-off-by: Petr Pavlu Acked-by: Peter Zijlstra (Intel) > --- > arch/x86/kernel/vmlinux.lds.S | 2 +- > arch/x86/lib/retpoline.S | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 03c885d3640f..a4cd04c458df 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -134,7 +134,7 @@ SECTIONS > SOFTIRQENTRY_TEXT > #ifdef CONFIG_RETPOLINE > __indirect_thunk_start = .; > - *(.text.__x86.*) > + *(.text..__x86.*) > __indirect_thunk_end = .; > #endif > STATIC_CALL_TEXT > diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S > index 3fd066d42ec0..3bea96341d00 100644 > --- a/arch/x86/lib/retpoline.S > +++ b/arch/x86/lib/retpoline.S > @@ -12,7 +12,7 @@ > #include > #include > > - .section .text.__x86.indirect_thunk > + .section .text..__x86.indirect_thunk > > > .macro POLINE reg > @@ -131,7 +131,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) > */ > #ifdef CONFIG_RETHUNK > > - .section .text.__x86.return_thunk > + .section .text..__x86.return_thunk > > /* > * Safety details here pertain to the AMD Zen{1,2} microarchitecture: > -- > 2.35.3 >