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=-3.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 628ADC28CC6 for ; Wed, 5 Jun 2019 13:23:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 366A52086A for ; Wed, 5 Jun 2019 13:23:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WaZgcoce" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728179AbfFENXb (ORCPT ); Wed, 5 Jun 2019 09:23:31 -0400 Received: from merlin.infradead.org ([205.233.59.134]:50914 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727966AbfFENX3 (ORCPT ); Wed, 5 Jun 2019 09:23:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=6vcpd/Yrl9598aZ1kT1YSLwwTRxt5Xg91scKOkavI0E=; b=WaZgcoceQDoG8x4MRnr/wmaQ4w YW0NogyHLAJbcu+UwLiuKz6BwIn+2m9ehMf9zvY2nCO5X+eE7r3MunHDyRXTUhnZy9zkT0bq/JEsO o2ZkRkEIIS1zFz610iab/DzB6IaI2COfZ1Ha2wznL550TEIl0ZbgnAj+2G4vnf7d/KsjvVX9epvPy qmERb9gJ8yCHWd5IgZTkx6c+xwnbvNpvTBLCes8JvJmKCJJ487N3BChp6aIUro9W6Xg5y0jf7NM9k EElzkgVMuj5PYyKop76NE+SkA0Aug7/gkeLRqWttNU1/vktv0v5yDBEemCfZaprAKRLxRpb7NykVV th1MaCfQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hYVsJ-0006rQ-2J; Wed, 05 Jun 2019 13:22:43 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 88F672073F418; Wed, 5 Jun 2019 15:22:39 +0200 (CEST) Message-Id: <20190605131944.946978563@infradead.org> User-Agent: quilt/0.65 Date: Wed, 05 Jun 2019 15:08:00 +0200 From: Peter Zijlstra To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel , Andy Lutomirski , Steven Rostedt , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Linus Torvalds , Masami Hiramatsu , Jason Baron , Jiri Kosina , David Laight , Borislav Petkov , Julia Cartwright , Jessica Yu , "H. Peter Anvin" , Nadav Amit , Rasmus Villemoes , Edward Cree , Daniel Bristot de Oliveira Subject: [PATCH 07/15] x86: Add int3_emulate_call() selftest References: <20190605130753.327195108@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Given that the entry_*.S changes for this functionality are somewhat tricky, make sure the paths are tested every boot, instead of on the rare occasion when we trip an INT3 while rewriting text. Requested-by: Andy Lutomirski Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/alternative.c | 81 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 77 insertions(+), 4 deletions(-) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -614,11 +614,83 @@ extern struct paravirt_patch_site __star __stop_parainstructions[]; #endif /* CONFIG_PARAVIRT */ +/* + * Self-test for the INT3 based CALL emulation code. + * + * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up + * properly and that there is a stack gap between the INT3 frame and the + * previous context. Without this gap doing a virtual PUSH on the interrupted + * stack would corrupt the INT3 IRET frame. + * + * See entry_{32,64}.S for more details. + */ +static void __init int3_magic(unsigned int *ptr) +{ + *ptr = 1; +} + +extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */ + +static int __init +int3_exception_notify(struct notifier_block *self, unsigned long val, void *data) +{ + struct die_args *args = data; + struct pt_regs *regs = args->regs; + + if (!regs || user_mode(regs)) + return NOTIFY_DONE; + + if (val != DIE_INT3) + return NOTIFY_DONE; + + if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip) + return NOTIFY_DONE; + + int3_emulate_call(regs, (unsigned long)&int3_magic); + return NOTIFY_STOP; +} + +static void __init int3_selftest(void) +{ + static __initdata struct notifier_block int3_exception_nb = { + .notifier_call = int3_exception_notify, + .priority = INT_MAX-1, /* last */ + }; + unsigned int val = 0; + + BUG_ON(register_die_notifier(&int3_exception_nb)); + + /* + * Basically: int3_magic(&val); but really complicated :-) + * + * Stick the address of the INT3 instruction into int3_selftest_ip, + * then trigger the INT3, padded with NOPs to match a CALL instruction + * length. + */ + asm volatile ("1: int3; nop; nop; nop; nop\n\t" + ".pushsection .init.data,\"aw\"\n\t" + ".align " __ASM_SEL(4, 8) "\n\t" + ".type int3_selftest_ip, @object\n\t" + ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t" + "int3_selftest_ip:\n\t" + __ASM_SEL(.long, .quad) " 1b\n\t" + ".popsection\n\t" + : : __ASM_SEL_RAW(a, D) (&val) : "memory"); + + BUG_ON(val != 1); + + unregister_die_notifier(&int3_exception_nb); +} + void __init alternative_instructions(void) { - /* The patching is not fully atomic, so try to avoid local interruptions - that might execute the to be patched code. - Other CPUs are not running. */ + int3_selftest(); + + /* + * The patching is not fully atomic, so try to avoid local + * interruptions that might execute the to be patched code. + * Other CPUs are not running. + */ stop_nmi(); /* @@ -643,10 +715,11 @@ void __init alternative_instructions(voi _text, _etext); } - if (!uniproc_patched || num_possible_cpus() == 1) + if (!uniproc_patched || num_possible_cpus() == 1) { free_init_pages("SMP alternatives", (unsigned long)__smp_locks, (unsigned long)__smp_locks_end); + } #endif apply_paravirt(__parainstructions, __parainstructions_end);