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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 91743C2BB1D for ; Thu, 12 Mar 2020 13:51:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 651CB2073E for ; Thu, 12 Mar 2020 13:51:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="eiLA87mD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727427AbgCLNvk (ORCPT ); Thu, 12 Mar 2020 09:51:40 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:56978 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727315AbgCLNvj (ORCPT ); Thu, 12 Mar 2020 09:51:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Subject:Cc:To:From:Date:Message-Id: Sender:Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To:References; bh=6bbE2GpnlDAjnqkrXQiOeX0mGieefOOogMwttobSej8=; b=eiLA87mD5s9G7uaZekLuVfHqJK h0r9k8hIcycEBfzrqjWj1PFZ4MZcNJ3J8ZWg7EiPpxtpjzcGY70R+cYPL3DcgZJEtPkSeTlMjgKuh UlfZ1cNXf3plB1TwsIBWFniKsFojqo7b8AZdjU11Fr3TNK3glVrkb6ppPzmj1m8yibdKPSCFRZ6uM prk3WfCGBw3jld247jAIR+DDPjMBpROn9b97j1sh0XgyFkUoTTJYX/hn0Kc3oiBhlf5p9MaaR8Y0n XGdY+ax2oAZWxSb7p1r/5X/Dv7CrkPUqJDCKswtQ8Rp3anxiVM3/kQSop9z9uUTra9tTX8Cu0G+8f Sg7oxqRw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jCOFM-0006WU-4T; Thu, 12 Mar 2020 13:51:36 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 1240C300328; Thu, 12 Mar 2020 14:51:34 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 0585E2B7403AA; Thu, 12 Mar 2020 14:51:34 +0100 (CET) Message-Id: <20200312134107.700205216@infradead.org> User-Agent: quilt/0.65 Date: Thu, 12 Mar 2020 14:41:07 +0100 From: Peter Zijlstra To: tglx@linutronix.de, jpoimboe@redhat.com Cc: linux-kernel@vger.kernel.org, x86@kernel.org, peterz@infradead.org Subject: [RFC][PATCH 00/16] objtool: vmlinux.o and noinstr validation Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, These patches extend objtool to be able to run on vmlinux.o and validate Thomas's proposed noinstr annotation: https://lkml.kernel.org/r/20200310170951.87c29e9c1cfbddd93ccd92b3@kernel.org "That's why we want the sections and the annotation. If something calls out of a noinstr section into a regular text section and the call is not annotated at the call site, then objtool can complain and tell you. What Peter and I came up with looks like this: noinstr foo() do_protected(); <- Safe because in the noinstr section instr_begin(); <- Marks the begin of a safe region, ignored by objtool do_stuff(); <- All good instr_end(); <- End of the safe region. objtool starts looking again do_other_stuff(); <- Unsafe because do_other_stuff() is not protected and: noinstr do_protected() bar(); <- objtool will complain here " It should be accompanied by something like the below; which you'll find in a series by Thomas. --- --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -53,6 +53,9 @@ extern char __ctors_start[], __ctors_end /* Start and end of .opd section - used for function descriptors. */ extern char __start_opd[], __end_opd[]; +/* Start and end of instrumentation protected text section */ +extern char __noinstr_text_start[], __noinstr_text_end[]; + extern __visible const void __nosave_begin, __nosave_end; /* Function descriptor handling (if any). Override in asm/sections.h */ --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -550,6 +550,10 @@ #define TEXT_TEXT \ ALIGN_FUNCTION(); \ *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ + ALIGN_FUNCTION(); \ + __noinstr_text_start = .; \ + *(.noinstr.text) \ + __noinstr_text_end = .; \ *(.text..refcount) \ *(.ref.text) \ MEM_KEEP(init.text*) \ --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -120,12 +120,37 @@ void ftrace_likely_update(struct ftrace_ /* Annotate a C jump table to allow objtool to follow the code flow */ #define __annotate_jump_table __section(.rodata..c_jump_table) +/* Begin/end of an instrumentation safe region */ +#define instr_begin() ({ \ + asm volatile("%c0:\n\t" \ + ".pushsection .discard.instr_begin\n\t" \ + ".long %c0b - .\n\t" \ + ".popsection\n\t" : : "i" (__COUNTER__)); \ +}) + +#define instr_end() ({ \ + asm volatile("%c0:\n\t" \ + ".pushsection .discard.instr_end\n\t" \ + ".long %c0b - .\n\t" \ + ".popsection\n\t" : : "i" (__COUNTER__)); \ +}) + #else #define annotate_reachable() #define annotate_unreachable() #define __annotate_jump_table +#define instr_begin() do { } while(0) +#define instr_end() do { } while(0) #endif +#define INSTR(expr) ({ \ + typeof(({ expr; })) __ret; \ + instr_begin(); \ + __ret = ({ expr; }); \ + instr_end(); \ + __ret; \ +}) + #ifndef ASM_UNREACHABLE # define ASM_UNREACHABLE #endif --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -118,6 +118,11 @@ struct ftrace_likely_data { #define notrace __attribute__((__no_instrument_function__)) #endif +/* Section for code which can't be instrumented at all */ +#define noinstr \ + notrace __attribute((__section__(".noinstr.text"))) + + /* * it doesn't make sense on ARM (currently the only user of __naked) * to trace naked functions because then mcount is called without --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -953,7 +953,7 @@ static void check_section(const char *mo #define DATA_SECTIONS ".data", ".data.rel" #define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \ - ".kprobes.text", ".cpuidle.text" + ".kprobes.text", ".cpuidle.text", ".noinstr.text" #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \ ".fixup", ".entry.text", ".exception.text", ".text.*", \ ".coldtext"