From patchwork Tue Sep 1 11:47:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: thermal-bot for Julien Panis X-Patchwork-Id: 310578 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE3D8C433E2 for ; Tue, 1 Sep 2020 14:48:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB21121D6C for ; Tue, 1 Sep 2020 14:48:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="pHFKC5o6"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="pZw3XDBE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728229AbgIAOsd (ORCPT ); Tue, 1 Sep 2020 10:48:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48296 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727861AbgIALt0 (ORCPT ); Tue, 1 Sep 2020 07:49:26 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF156C06125C; Tue, 1 Sep 2020 04:48:04 -0700 (PDT) Date: Tue, 01 Sep 2020 11:47:59 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1598960880; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SxqMQ1TSEqyEQ+IxBxu5S9u4JXQU8ctP1bgVHjyFv1k=; b=pHFKC5o6R3n4l494bx3212BoYQSmadU6PdLDwU6dAHfLoiUENWYGBNgVKs6bTRymSpJlQb YVTvXcI11Ug/OXYM7RL7rsxTJXGkPwoKVF2mY6RORrinA5cI12+3K0j891DEd7JPe20wAv WNnTf6HjtKg29eG6W+xwUy+Hb1DMJ1M6OugGQ1X0NjBJ50EY/JmzttD3I4+3UBs1IIlFRi EkT1hsqyFtKpGfTbGezlPVKfFIOxotAlrRz8peSsXgnG8ttF3w80LkyfUD7lXFY54yBe3+ 1bFZdtrzfi14+rZY/6+gb+kfzQb2k00An76WGBkbUMBZObKHSnVJYHtA8RihXQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1598960880; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SxqMQ1TSEqyEQ+IxBxu5S9u4JXQU8ctP1bgVHjyFv1k=; b=pZw3XDBEcWLZrfHzVGeT7UR3O9cpTk17enXsS0xz//gHKalFOdP0QPR3lLbFaTaRb1wRcS K3BhpQZQhwnFPlBg== From: "tip-bot2 for Nick Desaulniers" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/build] vmlinux.lds.h: Add PGO and AutoFDO input sections Cc: Jian Cai , maskray@google.com, Nick Desaulniers , Kees Cook , Ingo Molnar , Luis Lozano , Manoj Gupta , linux-arch@vger.kernel.org, stable@vger.kernel.org, x86 , LKML In-Reply-To: <20200821194310.3089815-7-keescook@chromium.org> References: <20200821194310.3089815-7-keescook@chromium.org> MIME-Version: 1.0 Message-ID: <159896087937.20229.4955362311782724603.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The following commit has been merged into the core/build branch of tip: Commit-ID: eff8728fe69880d3f7983bec3fb6cea4c306261f Gitweb: https://git.kernel.org/tip/eff8728fe69880d3f7983bec3fb6cea4c306261f Author: Nick Desaulniers AuthorDate: Fri, 21 Aug 2020 12:42:47 -07:00 Committer: Ingo Molnar CommitterDate: Tue, 01 Sep 2020 09:50:35 +02:00 vmlinux.lds.h: Add PGO and AutoFDO input sections Basically, consider .text.{hot|unlikely|unknown}.* part of .text, too. When compiling with profiling information (collected via PGO instrumentations or AutoFDO sampling), Clang will separate code into .text.hot, .text.unlikely, or .text.unknown sections based on profiling information. After D79600 (clang-11), these sections will have a trailing `.` suffix, ie. .text.hot., .text.unlikely., .text.unknown.. When using -ffunction-sections together with profiling infomation, either explicitly (FGKASLR) or implicitly (LTO), code may be placed in sections following the convention: .text.hot., .text.unlikely., .text.unknown. where , , and are functions. (This produces one section per function; we generally try to merge these all back via linker script so that we don't have 50k sections). For the above cases, we need to teach our linker scripts that such sections might exist and that we'd explicitly like them grouped together, otherwise we can wind up with code outside of the _stext/_etext boundaries that might not be mapped properly for some architectures, resulting in boot failures. If the linker script is not told about possible input sections, then where the section is placed as output is a heuristic-laiden mess that's non-portable between linkers (ie. BFD and LLD), and has resulted in many hard to debug bugs. Kees Cook is working on cleaning this up by adding --orphan-handling=warn linker flag used in ARCH=powerpc to additional architectures. In the case of linker scripts, borrowing from the Zen of Python: explicit is better than implicit. Also, ld.bfd's internal linker script considers .text.hot AND .text.hot.* to be part of .text, as well as .text.unlikely and .text.unlikely.*. I didn't see support for .text.unknown.*, and didn't see Clang producing such code in our kernel builds, but I see code in LLVM that can produce such section names if profiling information is missing. That may point to a larger issue with generating or collecting profiles, but I would much rather be safe and explicit than have to debug yet another issue related to orphan section placement. Reported-by: Jian Cai Suggested-by: Fāng-ruì Sòng Signed-off-by: Nick Desaulniers Signed-off-by: Kees Cook Signed-off-by: Ingo Molnar Tested-by: Luis Lozano Tested-by: Manoj Gupta Acked-by: Kees Cook Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=add44f8d5c5c05e08b11e033127a744d61c26aee Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=1de778ed23ce7492c523d5850c6c6dbb34152655 Link: https://reviews.llvm.org/D79600 Link: https://bugs.chromium.org/p/chromium/issues/detail?id=1084760 Link: https://lore.kernel.org/r/20200821194310.3089815-7-keescook@chromium.org Debugged-by: Luis Lozano --- include/asm-generic/vmlinux.lds.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 98d013d..91dcfb9 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -581,7 +581,10 @@ */ #define TEXT_TEXT \ ALIGN_FUNCTION(); \ - *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ + *(.text.hot .text.hot.*) \ + *(TEXT_MAIN .text.fixup) \ + *(.text.unlikely .text.unlikely.*) \ + *(.text.unknown .text.unknown.*) \ NOINSTR_TEXT \ *(.text..refcount) \ *(.ref.text) \