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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61BA9C761A6 for ; Mon, 3 Apr 2023 14:43:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233849AbjDCOno (ORCPT ); Mon, 3 Apr 2023 10:43:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233908AbjDCOng (ORCPT ); Mon, 3 Apr 2023 10:43:36 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3328D280ED for ; Mon, 3 Apr 2023 07:42:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680532944; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=K+EPWgU2x5V4hfg46aLK3WZjBP8GTm1fIwNbw6N/r0w=; b=A+ls6enq87T/JavQCoKqnUn3U5dBSbmRHIm8tnbXpuWRr3AkctWrenQKYAP4hNuIu/DcNW AKnNavOFb1alIYOH7eEff0oNsLkes3GI+m4tpL5OXDU9MwKgYh9F1IylRkAHliBgINtbQm 3sNimNYAfcvsjrC5DDDLwCog3DMOcY4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-26-HcZVqk0iN06tvnzLG2XdLA-1; Mon, 03 Apr 2023 10:42:19 -0400 X-MC-Unique: HcZVqk0iN06tvnzLG2XdLA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7598E884EC5; Mon, 3 Apr 2023 14:42:18 +0000 (UTC) Received: from rotkaeppchen (unknown [10.39.192.158]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09E7C492C13; Mon, 3 Apr 2023 14:42:16 +0000 (UTC) Date: Mon, 3 Apr 2023 16:42:13 +0200 From: Philipp Rudo To: Ricardo Ribalda Cc: Eric Biederman , Baoquan He , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Ross Zwisler , Steven Rostedt , Simon Horman , stable@vger.kernel.org Subject: Re: [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections Message-ID: <20230403164213.108093ec@rotkaeppchen> 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> Organization: Red Hat inc. MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Hi Ricardo, 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)) { Looks good to me. I'm not sure if it is better to use WARN_ON_ONCE to avoid spamming the log when there are more than two .text sections or when you reload the kernel. But that's only a rare corner case. So no strong opinion from my side. Either way Reviewed-by: Philipp Rudo > kbuf->image->start -= sechdrs[i].sh_addr; > kbuf->image->start += kbuf->mem + offset; > } >