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,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 D58D6C433DF for ; Fri, 12 Jun 2020 14:37:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ABCB0206A4 for ; Fri, 12 Jun 2020 14:37:56 +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="m7dUqlsL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726381AbgFLOhw (ORCPT ); Fri, 12 Jun 2020 10:37:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726257AbgFLOhv (ORCPT ); Fri, 12 Jun 2020 10:37:51 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25AF4C08C5C1 for ; Fri, 12 Jun 2020 07:37:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=tr0PHMWQDKASoKKJIXhHrp4k0+3m9wdOXqJFrwxEy6w=; b=m7dUqlsLdWPj6NFEZfD5d1/Rd3 Tlll3lUpiZGZxF8hgawXhytv2+kQjDA5UPIBpi1ouXmIjmRMskY+qsg7uLX7j8LSLMi2XaMFy+gwG a6bOoG7elz6CGMuRbRHrOhpgdJIJhrxTEsolDt34GmNXDBffN1A+ToB0GunvRz9GmQ3RpxhWNEyGX vsmqM4CFADfKccySgpmN8mMoMTkiDMksXLxS7T43d3AynTGZSkj4Zih6wkqvFZEHTmWLBWYjMJQ9/ dtPxahH/y75c5A1AmXsXIrAFiyQGRKSRUBeFP0V2JnQ2QGgP/xXfO9dxwd7g7QMgGSCslwO9mEIkc pUgPzoOw==; 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 1jjkoI-0006uc-6M; Fri, 12 Jun 2020 14:37:34 +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 EC7CD301AC6; Fri, 12 Jun 2020 16:37:31 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id CBA7C2389EBA3; Fri, 12 Jun 2020 16:37:31 +0200 (CEST) Message-ID: <20200612143554.071314718@infradead.org> User-Agent: quilt/0.66 Date: Fri, 12 Jun 2020 16:30:37 +0200 From: Peter Zijlstra To: Josh Poimboeuf Cc: linux-kernel@vger.kernel.org, x86@kernel.org, dvyukov@google.com, elver@google.com, andreyknvl@google.com, mark.rutland@arm.com, mhelsley@vmware.com, rostedt@goodmis.org, jthierry@redhat.com, mbenes@suse.cz, peterz@infradead.org Subject: [RFC][PATCH 3/3] objtool: Fix noinstr vs KCOV References: <20200612143034.933422660@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since many compilers cannot disable KCOV with a function attribute, help it to NOP out any __sanitizer_cov_*() calls injected in noinstr code. This turns: 12: e8 00 00 00 00 callq 17 13: R_X86_64_PLT32 __sanitizer_cov_trace_pc-0x4 into: 12: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 13: R_X86_64_NONE __sanitizer_cov_trace_pc-0x4 Just like recordmcount does. Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/arch.h | 2 ++ tools/objtool/arch/x86/decode.c | 18 ++++++++++++++++++ tools/objtool/arch/x86/include/arch_elf.h | 6 ++++++ tools/objtool/check.c | 19 +++++++++++++++++++ 4 files changed, 45 insertions(+) --- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -84,4 +84,6 @@ unsigned long arch_jump_destination(stru unsigned long arch_dest_reloc_offset(int addend); +const char *arch_nop_insn(int len); + #endif /* _ARCH_H */ --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -565,3 +565,21 @@ void arch_initial_func_cfi_state(struct state->regs[16].base = CFI_CFA; state->regs[16].offset = -8; } + +const char *arch_nop_insn(int len) +{ + static const char nops[5][5] = { + /* 1 */ { 0x90 }, + /* 2 */ { 0x66, 0x90 }, + /* 3 */ { 0x0f, 0x1f, 0x00 }, + /* 4 */ { 0x0f, 0x1f, 0x40, 0x00 }, + /* 5 */ { 0x0f, 0x1f, 0x44, 0x00, 0x00 }, + }; + + if (len < 1 || len > 5) { + WARN("invalid NOP size: %d\n", len); + return NULL; + } + + return nops[len-1]; +} --- /dev/null +++ b/tools/objtool/arch/x86/include/arch_elf.h @@ -0,0 +1,6 @@ +#ifndef _OBJTOOL_ARCH_ELF +#define _OBJTOOL_ARCH_ELF + +#define R_NONE R_X86_64_NONE + +#endif /* _OBJTOOL_ARCH_ELF */ --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -12,6 +12,7 @@ #include "check.h" #include "special.h" #include "warn.h" +#include "arch_elf.h" #include #include @@ -744,6 +745,24 @@ static int add_call_destinations(struct insn->call_dest = reloc->sym; /* + * Many compilers cannot disable KCOV with a function attribute + * so they need a little help, NOP out any KCOV calls from noinstr + * text. + */ + if (insn->sec->noinstr && + !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) { + if (reloc) { + reloc->type = R_NONE; + elf_write_reloc(file->elf, reloc); + } + + elf_write_insn(file->elf, insn->sec, + insn->offset, insn->len, + arch_nop_insn(insn->len)); + insn->type = INSN_NOP; + } + + /* * Whatever stack impact regular CALLs have, should be undone * by the RETURN of the called function. *