From nobody Sun Jun 28 05:34:51 2026 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 57CBEC433EF for ; Mon, 14 Feb 2022 06:27:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240836AbiBNG1N (ORCPT ); Mon, 14 Feb 2022 01:27:13 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:40390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240827AbiBNG1M (ORCPT ); Mon, 14 Feb 2022 01:27:12 -0500 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0D9855499 for ; Sun, 13 Feb 2022 22:27:03 -0800 (PST) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4JxvQF72nXz9sSV; Mon, 14 Feb 2022 07:27:01 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CcvDBiVlpTGQ; Mon, 14 Feb 2022 07:27:01 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4JxvQF62XPz9sST; Mon, 14 Feb 2022 07:27:01 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id B68248B768; Mon, 14 Feb 2022 07:27:01 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 54KbfFUlKOnC; Mon, 14 Feb 2022 07:27:01 +0100 (CET) Received: from PO20335.IDSI0.si.c-s.fr (unknown [172.25.230.108]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8E5458B763; Mon, 14 Feb 2022 07:27:01 +0100 (CET) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.16.1) with ESMTPS id 21E6Qsku2064992 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 14 Feb 2022 07:26:54 +0100 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 21E6QsM32064991; Mon, 14 Feb 2022 07:26:54 +0100 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Andrew Morton Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v6] mm: Uninline copy_overflow() Date: Mon, 14 Feb 2022 07:26:53 +0100 Message-Id: X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1644820013; l=2946; s=20211009; h=from:subject:message-id; bh=BkbZOFoVwjCYtAh4mbluDExLZ2VZuVGDEbW30wjsWT0=; b=nJf7OmDU/LItjDZsdMCkTDCY6BJLEHk5n+TMa4y0kIwcDqL6wBkmw4SkQ5gSQBadM2ojbCL0glJg 4kFYYtLoDqCVLk0PcfML/vvi8fthC271kGlKjWlS+hUvGQU/oyH5 X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" While building a small config with CONFIG_CC_OPTIMISE_FOR_SIZE, I ended up with more than 50 times the following function in vmlinux because GCC doesn't honor the 'inline' keyword: c00243bc : c00243bc: 94 21 ff f0 stwu r1,-16(r1) c00243c0: 7c 85 23 78 mr r5,r4 c00243c4: 7c 64 1b 78 mr r4,r3 c00243c8: 3c 60 c0 62 lis r3,-16286 c00243cc: 7c 08 02 a6 mflr r0 c00243d0: 38 63 5e e5 addi r3,r3,24293 c00243d4: 90 01 00 14 stw r0,20(r1) c00243d8: 4b ff 82 45 bl c001c61c <__warn_printk> c00243dc: 0f e0 00 00 twui r0,0 c00243e0: 80 01 00 14 lwz r0,20(r1) c00243e4: 38 21 00 10 addi r1,r1,16 c00243e8: 7c 08 03 a6 mtlr r0 c00243ec: 4e 80 00 20 blr With -Winline, GCC tells: /include/linux/thread_info.h:212:20: warning: inlining failed in call to '= copy_overflow': call is unlikely and code size would grow [-Winline] copy_overflow() is a non conditional warning called by check_copy_size() on an error path. check_copy_size() have to remain inlined in order to benefit from constant folding, but copy_overflow() is not worth inlining. Uninline the warning when CONFIG_BUG is selected. When CONFIG_BUG is not selected, WARN() does nothing so skip it. This reduces the size of vmlinux by almost 4kbytes. Signed-off-by: Christophe Leroy --- v6: I should have gone sleeping yesterday night instead of sending v5 out. = Sorry for the noise. Fix EXPORT_SYMBOL() v5: Change to EXPORT_SYMBOL() instead of EXPORT_SYMBOL_GPL() v4: Make copy_overflow() a no-op when CONFIG_BUG is not selected v3: Added missing ; after EXPORT_SYMBOL() v2: Added missing EXPORT_SYMBOL() and enhanced commit message --- include/linux/thread_info.h | 5 ++++- mm/maccess.c | 6 ++++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index 73a6f34b3847..9f392ec76f2b 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -209,9 +209,12 @@ __bad_copy_from(void); extern void __compiletime_error("copy destination size is too small") __bad_copy_to(void); =20 +void __copy_overflow(int size, unsigned long count); + static inline void copy_overflow(int size, unsigned long count) { - WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); + if (IS_ENABLED(CONFIG_BUG)) + __copy_overflow(size, count); } =20 static __always_inline __must_check bool diff --git a/mm/maccess.c b/mm/maccess.c index d3f1a1f0b1c1..3fed2b876539 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -335,3 +335,9 @@ long strnlen_user_nofault(const void __user *unsafe_add= r, long count) =20 return ret; } + +void __copy_overflow(int size, unsigned long count) +{ + WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); +} +EXPORT_SYMBOL(__copy_overflow); --=20 2.34.1