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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AB22CC6FD1C for ; Fri, 24 Mar 2023 16:00:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=IMgVk5zG01rHXSyLgHpnLu4apljkryXL6rRT/KyIuxw=; b=P4na0XLUi+nILY UuTL0vbnDjnhtGPdCDgF9hMgmAID51VN4rMOT3aYg7i2QlWZgtUXr98Vidl1Wq202X9MCaCgNBSx+ cd1F0lZ217oXb56i8zdo09RhbXg9+1SKUhU6pplfq8Zlx+YcsIwdWzBWkYytdYsLnGXeAB9qfw0I3 zfZOb/c/s2M10xb9UeKtvsgI0JUPLINajcBvqJWV/AZO5VnZX7omyvXzipS3RMorS/lLnMp9eP35N hgjXy77xagvQYf4vrFg+YhTb4lr9LLYt7+FoGUB9xJqJ+LORr8m56M+ieKQRwnQKBYh89alp9YMS9 7ul0ArO4wwkS3hLzt87Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pfjqP-004wG0-2V; Fri, 24 Mar 2023 16:00:45 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pfjqN-004wF7-0J for kexec@lists.infradead.org; Fri, 24 Mar 2023 16:00:44 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679673640; 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=07VOxlALNLKaWDkjoN/aehXC/dxN7MylPi136nBJvgk=; b=P6Upu06BWxCnsm7CkZGfXGy5T9M7B8FKgCJKAcRshGJnqysr7I4xsWc6cLHVDrlLkckZMf En9OOQfqHEs+T6wYqvgWyCwzEvlpFVTV7SvlCTWVps2WSun578v7r+oAKfY4PKzCu6EhFu c038ohvLE2rtvTXeoPyNc1TRUEG9I6o= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-640-f88pObpsOnOEHLOHZZAtqQ-1; Fri, 24 Mar 2023 12:00:34 -0400 X-MC-Unique: f88pObpsOnOEHLOHZZAtqQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6C75A1C09066; Fri, 24 Mar 2023 16:00:33 +0000 (UTC) Received: from rotkaeppchen (unknown [10.39.195.31]) by smtp.corp.redhat.com (Postfix) with ESMTP id 85690202701E; Fri, 24 Mar 2023 16:00:32 +0000 (UTC) Date: Fri, 24 Mar 2023 16:58:55 +0100 From: Philipp Rudo To: Ricardo Ribalda Cc: Eric Biederman , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Baoquan He Subject: Re: [PATCH v3] kexec: Support purgatories with .text.hot sections Message-ID: <20230324165855.23084947@rotkaeppchen> In-Reply-To: <20230321-kexec_clang16-v3-0-5f016c8d0e87@chromium.org> References: <20230321-kexec_clang16-v3-0-5f016c8d0e87@chromium.org> Organization: Red Hat inc. MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230324_090043_235156_CDDC9554 X-CRM114-Status: GOOD ( 34.97 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org Hi Ricardo, On Wed, 22 Mar 2023 20:09:21 +0100 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 inmediatly after: > > kexec_core: Starting new kernel Great analysis! > Signed-off-by: Ricardo Ribalda > --- > kexec: Fix kexec_file_load for llvm16 > > When upreving llvm I realised that kexec stopped working on my test > platform. This patch fixes it. > > To: Eric Biederman > Cc: Baoquan He > Cc: Philipp Rudo > Cc: kexec@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > --- > Changes in v3: > - Fix initial value. Thanks Ross! > - Link to v2: https://lore.kernel.org/r/20230321-kexec_clang16-v2-0-d10e5d517869@chromium.org > > Changes in v2: > - Fix if condition. Thanks Steven!. > - Update Philipp email. Thanks Baoquan. > - Link to v1: https://lore.kernel.org/r/20230321-kexec_clang16-v1-0-a768fc2c7c4d@chromium.org > --- > kernel/kexec_file.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index f1a0e4e3fb5c..25a37d8f113a 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -901,10 +901,21 @@ 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 sections > + * (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. > + */ > 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) && > + kbuf->image->start == pi->ehdr->e_entry) { I'm not entirely sure if this is the solution to go with. As you state in the comment above this solution assumes that the .text section comes before any other .text.* section. But this assumption isn't much stronger than the assumption that there is only a single .text section, which is used nowadays. The best solution I can come up with right now is to introduce a linker script for the purgatory that simply merges the .text sections into one. Similar to what I did for s390 in arch/s390/purgatory/purgatory.lds.S (although for a different reason). But that would require every architecture to get one. An alternative would be to find a way to get rid of the -r option on the LD_FLAGS, which IIRC is the reason why both section overlap in the first place. Thanks Philipp > kbuf->image->start -= sechdrs[i].sh_addr; > kbuf->image->start += kbuf->mem + offset; > } > > --- > base-commit: 17214b70a159c6547df9ae204a6275d983146f6b > change-id: 20230321-kexec_clang16-4510c23d129c > > Best regards, _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec 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 46919C6FD20 for ; Fri, 24 Mar 2023 16:01:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231499AbjCXQBX (ORCPT ); Fri, 24 Mar 2023 12:01:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229441AbjCXQBV (ORCPT ); Fri, 24 Mar 2023 12:01:21 -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 A947A222C1 for ; Fri, 24 Mar 2023 09:00:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679673635; 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=07VOxlALNLKaWDkjoN/aehXC/dxN7MylPi136nBJvgk=; b=QdJVX/vF8QjusTX/X19wiOQI9pAtJ5Qe089bDBMMzaZJf3DxIq1rrMg4c2mum7c7Lh/wz6 gRbTCA9dMjIh1c4gIN9thDC9fXmUltnWwuiQ/DUyXuo9HO3fmGzLy5VFv2lY7Rj1b1BIXi 4JJZndB70B3J8gEI/IQGPdopjHZHz2c= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-640-f88pObpsOnOEHLOHZZAtqQ-1; Fri, 24 Mar 2023 12:00:34 -0400 X-MC-Unique: f88pObpsOnOEHLOHZZAtqQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6C75A1C09066; Fri, 24 Mar 2023 16:00:33 +0000 (UTC) Received: from rotkaeppchen (unknown [10.39.195.31]) by smtp.corp.redhat.com (Postfix) with ESMTP id 85690202701E; Fri, 24 Mar 2023 16:00:32 +0000 (UTC) Date: Fri, 24 Mar 2023 16:58:55 +0100 From: Philipp Rudo To: Ricardo Ribalda Cc: Eric Biederman , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Baoquan He Subject: Re: [PATCH v3] kexec: Support purgatories with .text.hot sections Message-ID: <20230324165855.23084947@rotkaeppchen> In-Reply-To: <20230321-kexec_clang16-v3-0-5f016c8d0e87@chromium.org> References: <20230321-kexec_clang16-v3-0-5f016c8d0e87@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 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ricardo, On Wed, 22 Mar 2023 20:09:21 +0100 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 inmediatly after: > > kexec_core: Starting new kernel Great analysis! > Signed-off-by: Ricardo Ribalda > --- > kexec: Fix kexec_file_load for llvm16 > > When upreving llvm I realised that kexec stopped working on my test > platform. This patch fixes it. > > To: Eric Biederman > Cc: Baoquan He > Cc: Philipp Rudo > Cc: kexec@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > --- > Changes in v3: > - Fix initial value. Thanks Ross! > - Link to v2: https://lore.kernel.org/r/20230321-kexec_clang16-v2-0-d10e5d517869@chromium.org > > Changes in v2: > - Fix if condition. Thanks Steven!. > - Update Philipp email. Thanks Baoquan. > - Link to v1: https://lore.kernel.org/r/20230321-kexec_clang16-v1-0-a768fc2c7c4d@chromium.org > --- > kernel/kexec_file.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index f1a0e4e3fb5c..25a37d8f113a 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -901,10 +901,21 @@ 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 sections > + * (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. > + */ > 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) && > + kbuf->image->start == pi->ehdr->e_entry) { I'm not entirely sure if this is the solution to go with. As you state in the comment above this solution assumes that the .text section comes before any other .text.* section. But this assumption isn't much stronger than the assumption that there is only a single .text section, which is used nowadays. The best solution I can come up with right now is to introduce a linker script for the purgatory that simply merges the .text sections into one. Similar to what I did for s390 in arch/s390/purgatory/purgatory.lds.S (although for a different reason). But that would require every architecture to get one. An alternative would be to find a way to get rid of the -r option on the LD_FLAGS, which IIRC is the reason why both section overlap in the first place. Thanks Philipp > kbuf->image->start -= sechdrs[i].sh_addr; > kbuf->image->start += kbuf->mem + offset; > } > > --- > base-commit: 17214b70a159c6547df9ae204a6275d983146f6b > change-id: 20230321-kexec_clang16-4510c23d129c > > Best regards,