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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 2D289C433DF for ; Fri, 12 Jun 2020 16:06:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01D0E20801 for ; Fri, 12 Jun 2020 16:06:07 +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="TWFYJhy9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726340AbgFLQGG (ORCPT ); Fri, 12 Jun 2020 12:06:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42622 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726053AbgFLQGF (ORCPT ); Fri, 12 Jun 2020 12:06:05 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CACEC03E96F for ; Fri, 12 Jun 2020 09:06:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=N1uaLpyQMdwVjun7pUEBDc50plR3DjmpgwYvI+V9ogo=; b=TWFYJhy9OxMpaFG1lwTqeVGxib 75Y2VwSLQUxKx92r9Vh0nNiA/53AXfMu//G9WrL7mjR13Pc5GK3U4LkD9U2HJEWQ6SvlbYX44WJHl dmdIg/4IqctMS6qbRJ1Fv1UD0gVskFs30vZUBiSmR8FP6C+V7dRrkpuVgqY+VbReBHNsM4rAp/QwQ AqkHMqpDxYB/9fV4BSFv+W7o0E9WQGfQIQ1Hbd1WQHVqtRvw5YQTFZkbhcj3s9Pw2aJasM3rzi8Hn MjQR5x6pNBCMz4q49yPdAvPR2EMuWuU16XkKnykpSA5W2d2yVwKfB1NAfB4Fq0Y2e8Lp2p+cAlKV/ BVk+6cSw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jjmBV-00075H-QS; Fri, 12 Jun 2020 16:05:38 +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 79106301AC6; Fri, 12 Jun 2020 18:05:34 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 322E32146F532; Fri, 12 Jun 2020 18:05:34 +0200 (CEST) Date: Fri, 12 Jun 2020 18:05:34 +0200 From: Peter Zijlstra To: Matt Helsley Cc: linux-kernel@vger.kernel.org, Josh Poimboeuf , Steven Rostedt , Sami Tolvanen , Julien Thierry , Kamalesh Babulal Subject: Re: [RFC][PATCH v4 18/32] objtool: mcount: Move nop_mcount() Message-ID: <20200612160534.GD2554@hirez.programming.kicks-ass.net> References: <7109ceb239a88c2901eeb7f52c29f69cdb413cd3.1591125127.git.mhelsley@vmware.com> <20200612132656.GQ2531@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200612132656.GQ2531@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 12, 2020 at 03:26:57PM +0200, Peter Zijlstra wrote: > On Tue, Jun 02, 2020 at 12:50:11PM -0700, Matt Helsley wrote: > > +static int nop_mcount(struct section * const rels, > > + const char *const txtname) > > +{ > > + struct reloc *reloc; > > + struct section *txts = find_section_by_index(lf, rels->sh.sh_info); > > + unsigned mcountsym = 0; > > + int once = 0; > > + > > + list_for_each_entry(reloc, &rels->reloc_list, list) { > > + int ret = -1; > > + > > + if (!mcountsym) > > + mcountsym = get_mcountsym(reloc); > > + > > + if (mcountsym == GELF_R_INFO(reloc->sym->idx, reloc->type) && !is_fake_mcount(reloc)) { > > This makes no sense to me; why not have mcountsym be a 'struct symbol > *' and have get_mcountsym() return one of those. > > if (reloc->sym == mcountsym && ... ) > > is much nicer, no? On top of that, I suppose we can do something like the below. Then you can simply write: if (reloc->sym->class == SYM_MCOUNT && ..) --- diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile index 45452facff3b..94e4b8fcf9c1 100644 --- a/kernel/locking/Makefile +++ b/kernel/locking/Makefile @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 # Any varying coverage in these files is non-deterministic # and is generally not a function of system call inputs. -KCOV_INSTRUMENT := n +# KCOV_INSTRUMENT := n obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 432417a83902..133c0c285be6 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -341,6 +341,24 @@ static int read_sections(struct elf *elf) return 0; } +static bool is_mcount_symbol(const char *name) +{ + if (name[0] == '.') + name++; + + if (name[0] == '_') + name++; + + return !strcmp(name, "mcount", 6) || + !strcmp(name, "_fentry__") || + !strcmp(name, "_gnu_mcount_nc"); +} + +static bool is_kcov_symbol(const char *name) +{ + return !strncmp(name, "__sanitizer_cov_", 16); +} + static int read_symbols(struct elf *elf) { struct section *symtab, *symtab_shndx, *sec; @@ -410,6 +428,12 @@ static int read_symbols(struct elf *elf) } else sym->sec = find_section_by_index(elf, 0); + + if (is_mcount_symbol(sym->name)) + sym->class = SYM_MCOUNT; + else if (is_kcov_symbol(sym->name)) + sym->class = SYM_KCOV; + sym->offset = sym->sym.st_value; sym->len = sym->sym.st_size; diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index 78a2db23b8b6..3c1cccb7b5ff 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -42,6 +42,12 @@ struct section { bool changed, text, rodata, noinstr; }; +enum symbol_class { + SYM_REGULAR = 0, + SYM_MCOUNT, + SYM_KCOV, +}; + struct symbol { struct list_head list; struct rb_node node; @@ -55,6 +61,7 @@ struct symbol { unsigned long offset; unsigned int len; struct symbol *pfunc, *cfunc, *alias; + enum symbol_class class; bool uaccess_safe; };