From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id dI+KNlqZHVsMEAAAmS7hNA ; Sun, 10 Jun 2018 21:35:19 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 4914560791; Sun, 10 Jun 2018 21:35:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.4 required=2.0 tests=BAYES_00,DATE_IN_PAST_06_12, MAILING_LIST_MULTI autolearn=no autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id 914DE605A5; Sun, 10 Jun 2018 21:35:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 914DE605A5 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=fail (p=none dis=none) header.from=vmware.com Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932366AbeFJVfQ (ORCPT + 21 others); Sun, 10 Jun 2018 17:35:16 -0400 Received: from ex13-edg-ou-001.vmware.com ([208.91.0.189]:16964 "EHLO EX13-EDG-OU-001.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753546AbeFJVeI (ORCPT ); Sun, 10 Jun 2018 17:34:08 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-001.vmware.com (10.113.208.155) with Microsoft SMTP Server id 15.0.1156.6; Sun, 10 Jun 2018 14:33:45 -0700 Received: from sc2-haas01-esx0118.eng.vmware.com (sc2-haas01-esx0118.eng.vmware.com [10.172.44.118]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id 1CD97406F4; Sun, 10 Jun 2018 14:34:06 -0700 (PDT) From: Nadav Amit To: , CC: Nadav Amit , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Josh Poimboeuf Subject: [PATCH v3 5/9] x86: bug: prevent gcc distortions Date: Sun, 10 Jun 2018 07:19:07 -0700 Message-ID: <20180610141911.52948-6-namit@vmware.com> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180610141911.52948-1-namit@vmware.com> References: <20180610141911.52948-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-001.vmware.com: namit@vmware.com does not designate permitted sender hosts) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org GCC considers the number of statements in inlined assembly blocks, according to new-lines and semicolons, as an indication to the cost of the block in time and space. This data is distorted by the kernel code, which puts information in alternative sections. As a result, the compiler may perform incorrect inlining and branch optimizations. The solution is to set an assembly macro and call it from the inlinedv assembly block. As a result GCC considers the inline assembly block as a single instruction. This patch increases the kernel size: text data bss dec hex filename 18146889 10225380 2957312 31329581 1de0d2d ./vmlinux before 18147336 10226688 2957312 31331336 1de1408 ./vmlinux after (+1755) But enables more aggressive inlining (and probably branch decisions). The number of static text symbols in vmlinux is lower. Static text symbols: Before: 40218 After: 40053 (-165) Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: Peter Zijlstra Cc: Josh Poimboeuf Signed-off-by: Nadav Amit --- arch/x86/include/asm/bug.h | 98 ++++++++++++++++++++++---------------- arch/x86/kernel/macros.S | 1 + include/asm-generic/bug.h | 8 ++-- 3 files changed, 61 insertions(+), 46 deletions(-) diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index 6804d6642767..5090035e6d16 100644 --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -4,6 +4,8 @@ #include +#ifndef __ASSEMBLY__ + /* * Despite that some emulators terminate on UD2, we use it for WARN(). * @@ -20,53 +22,15 @@ #define LEN_UD2 2 -#ifdef CONFIG_GENERIC_BUG - -#ifdef CONFIG_X86_32 -# define __BUG_REL(val) ".long " __stringify(val) -#else -# define __BUG_REL(val) ".long " __stringify(val) " - 2b" -#endif - -#ifdef CONFIG_DEBUG_BUGVERBOSE - -#define _BUG_FLAGS(ins, flags) \ -do { \ - asm volatile("1:\t" ins "\n" \ - ".pushsection __bug_table,\"aw\"\n" \ - "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \ - "\t" __BUG_REL(%c0) "\t# bug_entry::file\n" \ - "\t.word %c1" "\t# bug_entry::line\n" \ - "\t.word %c2" "\t# bug_entry::flags\n" \ - "\t.org 2b+%c3\n" \ - ".popsection" \ - : : "i" (__FILE__), "i" (__LINE__), \ - "i" (flags), \ - "i" (sizeof(struct bug_entry))); \ -} while (0) - -#else /* !CONFIG_DEBUG_BUGVERBOSE */ - #define _BUG_FLAGS(ins, flags) \ do { \ - asm volatile("1:\t" ins "\n" \ - ".pushsection __bug_table,\"aw\"\n" \ - "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \ - "\t.word %c0" "\t# bug_entry::flags\n" \ - "\t.org 2b+%c1\n" \ - ".popsection" \ - : : "i" (flags), \ + asm volatile("ASM_BUG ins=\"" ins "\" file=%c0 line=%c1 " \ + "flags=%c2 size=%c3" \ + : : "i" (__FILE__), "i" (__LINE__), \ + "i" (flags), \ "i" (sizeof(struct bug_entry))); \ } while (0) -#endif /* CONFIG_DEBUG_BUGVERBOSE */ - -#else - -#define _BUG_FLAGS(ins, flags) asm volatile(ins) - -#endif /* CONFIG_GENERIC_BUG */ - #define HAVE_ARCH_BUG #define BUG() \ do { \ @@ -82,4 +46,54 @@ do { \ #include +#else /* __ASSEMBLY__ */ + +#ifdef CONFIG_GENERIC_BUG + +#ifdef CONFIG_X86_32 +.macro __BUG_REL val:req + .long \val +.endm +#else +.macro __BUG_REL val:req + .long \val - 2b +.endm +#endif + +#ifdef CONFIG_DEBUG_BUGVERBOSE + +.macro ASM_BUG ins:req file:req line:req flags:req size:req +1: \ins + .pushsection __bug_table,"aw" +2: __BUG_REL val=1b # bug_entry::bug_addr + __BUG_REL val=\file # bug_entry::file + .word \line # bug_entry::line + .word \flags # bug_entry::flags + .org 2b+\size + .popsection +.endm + +#else /* !CONFIG_DEBUG_BUGVERBOSE */ + +.macro ASM_BUG ins:req file:req line:req flags:req size:req +1: \ins + .pushsection __bug_table,"aw" +2: __BUG_REL val=1b # bug_entry::bug_addr + .word \flags # bug_entry::flags + .org 2b+\size + .popsection +.endm + +#endif /* CONFIG_DEBUG_BUGVERBOSE */ + +#else /* CONFIG_GENERIC_BUG */ + +.macro ASM_BUG ins:req file:req line:req flags:req size:req + \ins +.endm + +#endif /* CONFIG_GENERIC_BUG */ + +#endif /* __ASSEMBLY__ */ + #endif /* _ASM_X86_BUG_H */ diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S index 852487a9fc56..66ccb8e823b1 100644 --- a/arch/x86/kernel/macros.S +++ b/arch/x86/kernel/macros.S @@ -9,3 +9,4 @@ #include #include #include +#include diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index a7613e1b0c87..cf7f4ef4749e 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -17,10 +17,8 @@ #ifndef __ASSEMBLY__ #include -#ifdef CONFIG_BUG - -#ifdef CONFIG_GENERIC_BUG struct bug_entry { +#ifdef CONFIG_GENERIC_BUG #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS unsigned long bug_addr; #else @@ -35,8 +33,10 @@ struct bug_entry { unsigned short line; #endif unsigned short flags; -}; #endif /* CONFIG_GENERIC_BUG */ +}; + +#ifdef CONFIG_BUG /* * Don't use BUG() or BUG_ON() unless there's really no way out; one -- 2.17.0