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[2620:137:e000::1:20]) by mx.google.com with ESMTP id y21-20020a170906471500b0093b06c911aasi824183ejq.463.2023.03.30.08.05.36; Thu, 30 Mar 2023 08:06:09 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232645AbjC3PDd (ORCPT + 99 others); Thu, 30 Mar 2023 11:03:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232602AbjC3PDc (ORCPT ); Thu, 30 Mar 2023 11:03:32 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4152983F3; Thu, 30 Mar 2023 08:03:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E5CFEB828F5; Thu, 30 Mar 2023 15:03:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE1CFC433EF; Thu, 30 Mar 2023 15:03:25 +0000 (UTC) Date: Thu, 30 Mar 2023 11:03:23 -0400 From: Steven Rostedt To: Ricardo Ribalda Cc: Eric Biederman , Baoquan He , Philipp Rudo , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Ross Zwisler , Simon Horman , stable@vger.kernel.org Subject: Re: [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections Message-ID: <20230330110323.7963e3c6@gandalf.local.home> In-Reply-To: <20230321-kexec_clang16-v5-1-5563bf7c4173@chromium.org> References: <20230321-kexec_clang16-v5-0-5563bf7c4173@chromium.org> <20230321-kexec_clang16-v5-1-5563bf7c4173@chromium.org> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 30 Mar 2023 11:44:47 +0200 Ricardo Ribalda wrote: > Clang16 links the purgatory text in two sections: > > [ 1] .text PROGBITS 0000000000000000 00000040 > 00000000000011a1 0000000000000000 AX 0 0 16 > [ 2] .rela.text RELA 0000000000000000 00003498 > 0000000000000648 0000000000000018 I 24 1 8 > ... > [17] .text.hot. PROGBITS 0000000000000000 00003220 > 000000000000020b 0000000000000000 AX 0 0 1 > [18] .rela.text.hot. RELA 0000000000000000 00004428 > 0000000000000078 0000000000000018 I 24 17 8 > > And both of them have their range [sh_addr ... sh_addr+sh_size] on the > area pointed by `e_entry`. > > This causes that image->start is calculated twice, once for .text and > another time for .text.hot. The second calculation leaves image->start > in a random location. > > Because of this, the system crashes immediately after: > > kexec_core: Starting new kernel > > Cc: stable@vger.kernel.org > Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory") > Reviewed-by: Ross Zwisler > Signed-off-by: Ricardo Ribalda > --- > kernel/kexec_file.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index f1a0e4e3fb5c..c7a0e51a6d87 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -901,10 +901,22 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, > } > > offset = ALIGN(offset, align); > + > + /* > + * Check if the segment contains the entry point, if so, > + * calculate the value of image->start based on it. > + * If the compiler has produced more than one .text section > + * (Eg: .text.hot), they are generally after the main .text > + * section, and they shall not be used to calculate > + * image->start. So do not re-calculate image->start if it > + * is not set to the initial value, and warn the user so they > + * have a chance to fix their purgatory's linker script. > + */ > if (sechdrs[i].sh_flags & SHF_EXECINSTR && > pi->ehdr->e_entry >= sechdrs[i].sh_addr && > pi->ehdr->e_entry < (sechdrs[i].sh_addr > - + sechdrs[i].sh_size)) { > + + sechdrs[i].sh_size) && > + !WARN_ON(kbuf->image->start != pi->ehdr->e_entry)) { > kbuf->image->start -= sechdrs[i].sh_addr; > kbuf->image->start += kbuf->mem + offset; > } > Reviewed-by: Steven Rostedt (Google) Thanks Ricardo! -- Steve