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 X-Spam-Level: X-Spam-Status: No, score=0.4 required=3.0 tests=DATE_IN_PAST_06_12, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 2B126C5CFF1 for ; Tue, 12 Jun 2018 19:09:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF23920660 for ; Tue, 12 Jun 2018 19:09:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF23920660 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=vmware.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754395AbeFLTFf (ORCPT ); Tue, 12 Jun 2018 15:05:35 -0400 Received: from ex13-edg-ou-002.vmware.com ([208.91.0.190]:18332 "EHLO EX13-EDG-OU-002.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754060AbeFLTFd (ORCPT ); Tue, 12 Jun 2018 15:05:33 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-002.vmware.com (10.113.208.156) with Microsoft SMTP Server id 15.0.1156.6; Tue, 12 Jun 2018 12:05:30 -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 192C0406AE; Tue, 12 Jun 2018 12:05:33 -0700 (PDT) From: Nadav Amit To: , CC: Nadav Amit , Christopher Li , Subject: [PATCH v4 2/9] x86: objtool: use asm macro for better compiler decisions Date: Tue, 12 Jun 2018 04:50:43 -0700 Message-ID: <20180612115050.185112-3-namit@vmware.com> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180612115050.185112-1-namit@vmware.com> References: <20180612115050.185112-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-002.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. In the case of objtool, this distortion is extreme, since anyhow the annotations of objtool are discarded during linkage. The solution is to set an assembly macro and call it from the inline assembly block. As a result GCC considers the inline assembly block as a single instruction. This patch slightly increases the kernel size. text data bss dec hex filename 18140829 10224724 2957312 31322865 1ddf2f1 ./vmlinux before 18140970 10225412 2957312 31323694 1ddf62e ./vmlinux after (+829) Static text symbols: Before: 40321 After: 40302 (-19) Cc: Christopher Li Cc: linux-sparse@vger.kernel.org Reviewed-by: Josh Poimboeuf Signed-off-by: Nadav Amit --- arch/x86/kernel/macros.S | 2 ++ include/linux/compiler.h | 56 ++++++++++++++++++++++++++++++---------- 2 files changed, 45 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S index cfc1c7d1a6eb..cee28c3246dc 100644 --- a/arch/x86/kernel/macros.S +++ b/arch/x86/kernel/macros.S @@ -5,3 +5,5 @@ * commonly used. The macros are precompiled into assmebly file which is later * assembled together with each compiled file. */ + +#include diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ab4711c63601..3efd85334774 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -99,22 +99,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, * unique, to convince GCC not to merge duplicate inline asm statements. */ #define annotate_reachable() ({ \ - asm volatile("%c0:\n\t" \ - ".pushsection .discard.reachable\n\t" \ - ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__COUNTER__)); \ + asm volatile("ANNOTATE_REACHABLE counter=%c0" \ + : : "i" (__COUNTER__)); \ }) #define annotate_unreachable() ({ \ - asm volatile("%c0:\n\t" \ - ".pushsection .discard.unreachable\n\t" \ - ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__COUNTER__)); \ + asm volatile("ANNOTATE_UNREACHABLE counter=%c0" \ + : : "i" (__COUNTER__)); \ }) -#define ASM_UNREACHABLE \ - "999:\n\t" \ - ".pushsection .discard.unreachable\n\t" \ - ".long 999b - .\n\t" \ - ".popsection\n\t" #else #define annotate_reachable() #define annotate_unreachable() @@ -280,6 +271,45 @@ unsigned long read_word_at_a_time(const void *addr) #endif /* __KERNEL__ */ +#else /* __ASSEMBLY__ */ + +#ifdef __KERNEL__ +#ifndef LINKER_SCRIPT + +#ifdef CONFIG_STACK_VALIDATION +.macro ANNOTATE_UNREACHABLE counter:req +\counter: + .pushsection .discard.unreachable + .long \counter\()b -. + .popsection +.endm + +.macro ANNOTATE_REACHABLE counter:req +\counter: + .pushsection .discard.reachable + .long \counter\()b -. + .popsection +.endm + +.macro ASM_UNREACHABLE +999: + .pushsection .discard.unreachable + .long 999b - . + .popsection +.endm +#else /* CONFIG_STACK_VALIDATION */ +.macro ANNOTATE_UNREACHABLE counter:req +.endm + +.macro ANNOTATE_REACHABLE counter:req +.endm + +.macro ASM_UNREACHABLE +.endm +#endif /* CONFIG_STACK_VALIDATION */ + +#endif /* LINKER_SCRIPT */ +#endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ #ifndef __optimize -- 2.17.0 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nadav Amit Subject: [PATCH v4 2/9] x86: objtool: use asm macro for better compiler decisions Date: Tue, 12 Jun 2018 04:50:43 -0700 Message-ID: <20180612115050.185112-3-namit@vmware.com> References: <20180612115050.185112-1-namit@vmware.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20180612115050.185112-1-namit@vmware.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, x86@kernel.org Cc: Nadav Amit , Christopher Li , linux-sparse@vger.kernel.org List-Id: linux-sparse@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. In the case of objtool, this distortion is extreme, since anyhow the annotations of objtool are discarded during linkage. The solution is to set an assembly macro and call it from the inline assembly block. As a result GCC considers the inline assembly block as a single instruction. This patch slightly increases the kernel size. text data bss dec hex filename 18140829 10224724 2957312 31322865 1ddf2f1 ./vmlinux before 18140970 10225412 2957312 31323694 1ddf62e ./vmlinux after (+829) Static text symbols: Before: 40321 After: 40302 (-19) Cc: Christopher Li Cc: linux-sparse@vger.kernel.org Reviewed-by: Josh Poimboeuf Signed-off-by: Nadav Amit --- arch/x86/kernel/macros.S | 2 ++ include/linux/compiler.h | 56 ++++++++++++++++++++++++++++++---------- 2 files changed, 45 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S index cfc1c7d1a6eb..cee28c3246dc 100644 --- a/arch/x86/kernel/macros.S +++ b/arch/x86/kernel/macros.S @@ -5,3 +5,5 @@ * commonly used. The macros are precompiled into assmebly file which is later * assembled together with each compiled file. */ + +#include diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ab4711c63601..3efd85334774 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -99,22 +99,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, * unique, to convince GCC not to merge duplicate inline asm statements. */ #define annotate_reachable() ({ \ - asm volatile("%c0:\n\t" \ - ".pushsection .discard.reachable\n\t" \ - ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__COUNTER__)); \ + asm volatile("ANNOTATE_REACHABLE counter=%c0" \ + : : "i" (__COUNTER__)); \ }) #define annotate_unreachable() ({ \ - asm volatile("%c0:\n\t" \ - ".pushsection .discard.unreachable\n\t" \ - ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__COUNTER__)); \ + asm volatile("ANNOTATE_UNREACHABLE counter=%c0" \ + : : "i" (__COUNTER__)); \ }) -#define ASM_UNREACHABLE \ - "999:\n\t" \ - ".pushsection .discard.unreachable\n\t" \ - ".long 999b - .\n\t" \ - ".popsection\n\t" #else #define annotate_reachable() #define annotate_unreachable() @@ -280,6 +271,45 @@ unsigned long read_word_at_a_time(const void *addr) #endif /* __KERNEL__ */ +#else /* __ASSEMBLY__ */ + +#ifdef __KERNEL__ +#ifndef LINKER_SCRIPT + +#ifdef CONFIG_STACK_VALIDATION +.macro ANNOTATE_UNREACHABLE counter:req +\counter: + .pushsection .discard.unreachable + .long \counter\()b -. + .popsection +.endm + +.macro ANNOTATE_REACHABLE counter:req +\counter: + .pushsection .discard.reachable + .long \counter\()b -. + .popsection +.endm + +.macro ASM_UNREACHABLE +999: + .pushsection .discard.unreachable + .long 999b - . + .popsection +.endm +#else /* CONFIG_STACK_VALIDATION */ +.macro ANNOTATE_UNREACHABLE counter:req +.endm + +.macro ANNOTATE_REACHABLE counter:req +.endm + +.macro ASM_UNREACHABLE +.endm +#endif /* CONFIG_STACK_VALIDATION */ + +#endif /* LINKER_SCRIPT */ +#endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ #ifndef __optimize -- 2.17.0