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=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable 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 CE154C433E5 for ; Fri, 17 Jul 2020 17:30:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B611B2076A for ; Fri, 17 Jul 2020 17:30:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727854AbgGQRaG (ORCPT ); Fri, 17 Jul 2020 13:30:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:51448 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726104AbgGQRaG (ORCPT ); Fri, 17 Jul 2020 13:30:06 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2914D2074B; Fri, 17 Jul 2020 17:30:05 +0000 (UTC) Date: Fri, 17 Jul 2020 13:30:03 -0400 From: Steven Rostedt To: gregory.herrero@oracle.com Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] recordmcount: only record relocation of type R_AARCH64_CALL26 on arm64. Message-ID: <20200717133003.025f2096@oasis.local.home> In-Reply-To: <20200717143338.19302-1-gregory.herrero@oracle.com> References: <20200717143338.19302-1-gregory.herrero@oracle.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 17 Jul 2020 16:33:38 +0200 gregory.herrero@oracle.com wrote: > From: Gregory Herrero > > Currently, if a section has a relocation to '_mcount' symbol, a new > __mcount_loc entry will be added whatever the relocation type is. > This is problematic when a relocation to '_mcount' is in the middle of a > section and is not a call for ftrace use. > > Such relocation could be generated with below code for example: > bool is_mcount(unsigned long addr) > { > return (target == (unsigned long) &_mcount); > } > > With this snippet of code, ftrace will try to patch the mcount location > generated by this code on module load and fail with: > > Call trace: > ftrace_bug+0xa0/0x28c > ftrace_process_locs+0x2f4/0x430 > ftrace_module_init+0x30/0x38 > load_module+0x14f0/0x1e78 > __do_sys_finit_module+0x100/0x11c > __arm64_sys_finit_module+0x28/0x34 > el0_svc_common+0x88/0x194 > el0_svc_handler+0x38/0x8c > el0_svc+0x8/0xc > ---[ end trace d828d06b36ad9d59 ]--- > ftrace failed to modify > [] 0xffffa2dbf3a3a41c > actual: 66:a9:3c:90 > Initializing ftrace call sites > ftrace record flags: 2000000 > (0) > expected tramp: ffffa2dc6cf66724 > > So Limit the relocation type to R_AARCH64_CALL26 as in perl version of > recordmcount. > I'd rather have this go through the arm64 tree, as they can test it better than I can. Acked-by: Steven Rostedt (VMware) -- Steve > Fixes: ed60453fa8f8 ("ARM: 6511/1: ftrace: add ARM support for C version of recordmcount") > Signed-off-by: Gregory Herrero > --- > scripts/recordmcount.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c > index 7225107a9aaf..e59022b3f125 100644 > --- a/scripts/recordmcount.c > +++ b/scripts/recordmcount.c > @@ -434,6 +434,11 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp) > return 1; > } > > +static int arm64_is_fake_mcount(Elf64_Rel const *rp) > +{ > + return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26; > +} > + > /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. > * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf > * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] > @@ -547,6 +552,7 @@ static int do_file(char const *const fname) > make_nop = make_nop_arm64; > rel_type_nop = R_AARCH64_NONE; > ideal_nop = ideal_nop4_arm64; > + is_fake_mcount64 = arm64_is_fake_mcount; > break; > case EM_IA_64: reltype = R_IA64_IMM64; break; > case EM_MIPS: /* reltype: e_class */ break;