From nobody Sun Feb 8 20:11:15 2026 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 B66F7C43334 for ; Wed, 22 Jun 2022 16:10:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358603AbiFVQK5 (ORCPT ); Wed, 22 Jun 2022 12:10:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359222AbiFVQKx (ORCPT ); Wed, 22 Jun 2022 12:10:53 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F27D3ED0B for ; Wed, 22 Jun 2022 09:10:53 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id C43681F8E0; Wed, 22 Jun 2022 16:10:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1655914251; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NZVsJ9w6p52CGnx+whse0Q5jtOMx+D4jAJ62tq6HNaI=; b=cd42wzcG9qaMXbWjJjPT6DeqeIeIraiBDdVXY8uFDunVR1bsFtlTkWabujY1sWEZYk3rPh g4T4IjxBOE8PIn0qEs6huxZI6p+qO7eNMCH7djqwSi30jRTgnY3Cy3I7CN1UN56ydHzj/A 48WC5iBIXNOX5SPuKT343/uLBidXZg0= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6E999134A9; Wed, 22 Jun 2022 16:10:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 8GO1GQs/s2JzCwAAMHmgww (envelope-from ); Wed, 22 Jun 2022 16:10:51 +0000 From: Juergen Gross To: xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Juergen Gross , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Boris Ostrovsky Subject: [PATCH 1/2] x86/xen: use clear_bss() for Xen PV guests Date: Wed, 22 Jun 2022 18:10:47 +0200 Message-Id: <20220622161048.4483-2-jgross@suse.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220622161048.4483-1-jgross@suse.com> References: <20220622161048.4483-1-jgross@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Instead of clearing the bss area in assembly code, use the clear_bss() function. This requires to pass the start_info address as parameter to xen_start_kernel() in order to avoid the xen_start_info being zeroed again. Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich --- arch/x86/include/asm/setup.h | 3 +++ arch/x86/kernel/head64.c | 2 +- arch/x86/xen/enlighten_pv.c | 8 ++++++-- arch/x86/xen/xen-head.S | 10 +--------- 4 files changed, 11 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index f8b9ee97a891..f37cbff7354c 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -120,6 +120,9 @@ void *extend_brk(size_t size, size_t align); static char __brk_##name[size] =20 extern void probe_roms(void); + +void clear_bss(void); + #ifdef __i386__ =20 asmlinkage void __init i386_start_kernel(void); diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index bd4a34100ed0..e7e233209a8c 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -426,7 +426,7 @@ void __init do_early_exception(struct pt_regs *regs, in= t trapnr) =20 /* Don't add a printk in there. printk relies on the PDA which is not init= ialized=20 yet. */ -static void __init clear_bss(void) +void __init clear_bss(void) { memset(__bss_start, 0, (unsigned long) __bss_stop - (unsigned long) __bss_start); diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index e3297b15701c..70fb2ea85e90 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1183,15 +1183,19 @@ static void __init xen_domu_set_legacy_features(voi= d) extern void early_xen_iret_patch(void); =20 /* First C function to be called on Xen boot */ -asmlinkage __visible void __init xen_start_kernel(void) +asmlinkage __visible void __init xen_start_kernel(struct start_info *si) { struct physdev_set_iopl set_iopl; unsigned long initrd_start =3D 0; int rc; =20 - if (!xen_start_info) + if (!si) return; =20 + clear_bss(); + + xen_start_info =3D si; + __text_gen_insn(&early_xen_iret_patch, JMP32_INSN_OPCODE, &early_xen_iret_patch, &xen_iret, JMP32_INSN_SIZE); diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 3a2cd93bf059..13af6fe453e3 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -48,15 +48,6 @@ SYM_CODE_START(startup_xen) ANNOTATE_NOENDBR cld =20 - /* Clear .bss */ - xor %eax,%eax - mov $__bss_start, %rdi - mov $__bss_stop, %rcx - sub %rdi, %rcx - shr $3, %rcx - rep stosq - - mov %rsi, xen_start_info mov initial_stack(%rip), %rsp =20 /* Set up %gs. @@ -71,6 +62,7 @@ SYM_CODE_START(startup_xen) cdq wrmsr =20 + mov %rsi, %rdi call xen_start_kernel SYM_CODE_END(startup_xen) __FINIT --=20 2.35.3 From nobody Sun Feb 8 20:11:15 2026 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 98651C43334 for ; Wed, 22 Jun 2022 16:11:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359403AbiFVQLC (ORCPT ); Wed, 22 Jun 2022 12:11:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359244AbiFVQKx (ORCPT ); Wed, 22 Jun 2022 12:10:53 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D36C3EF03 for ; Wed, 22 Jun 2022 09:10:53 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 0D4FE1F8E1; Wed, 22 Jun 2022 16:10:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1655914252; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3utwreIcXrsHaZ2aPHJW+ToYT/lkMci89t36LS1rRtk=; b=rX2V6UHCEbDokFsQZRoynOuusc4yhrQefn8Slx89yncv7CUS9rWToPJogg9VgkkRvxO5zF N7BA+/1Vos8rc9Z+chjfuoz3ATNTNR2xeetaKfYJXvrv6KH3E/uFe1jwy76fiUCBiELIRh sXBNDkiFiCrv7gLrbWjiPv+yKlln+t4= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id C084013AC7; Wed, 22 Jun 2022 16:10:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id +DmlLQs/s2JzCwAAMHmgww (envelope-from ); Wed, 22 Jun 2022 16:10:51 +0000 From: Juergen Gross To: xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Juergen Gross , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Subject: [PATCH 2/2] x86: fix setup of brk area Date: Wed, 22 Jun 2022 18:10:48 +0200 Message-Id: <20220622161048.4483-3-jgross@suse.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220622161048.4483-1-jgross@suse.com> References: <20220622161048.4483-1-jgross@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Commit e32683c6f7d2 ("x86/mm: Fix RESERVE_BRK() for older binutils") put the brk area into the .bss segment, causing it not to be cleared initially. As the brk area is used to allocate early page tables, these might contain garbage in not explicitly written entries. This is especially a problem for Xen PV guests, as the hypervisor will validate page tables (check for writable page tables and hypervisor private bits) before accepting them to be used. There have been reports of early crashes of PV guests due to illegal page table contents. Fix that by letting clear_bss() clear the brk area, too. Fixes: e32683c6f7d2 ("x86/mm: Fix RESERVE_BRK() for older binutils") Signed-off-by: Juergen Gross --- arch/x86/kernel/head64.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index e7e233209a8c..6a3cfaf6b72a 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -430,6 +430,8 @@ void __init clear_bss(void) { memset(__bss_start, 0, (unsigned long) __bss_stop - (unsigned long) __bss_start); + memset(__brk_base, 0, + (unsigned long) __brk_limit - (unsigned long) __brk_base); } =20 static unsigned long get_cmd_line_ptr(void) --=20 2.35.3