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=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 8330AC432C0 for ; Mon, 18 Nov 2019 14:21:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4FE7020727 for ; Mon, 18 Nov 2019 14:21:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="PbmjpkhP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727264AbfKROVu (ORCPT ); Mon, 18 Nov 2019 09:21:50 -0500 Received: from mail.skyhub.de ([5.9.137.197]:60300 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726627AbfKROVt (ORCPT ); Mon, 18 Nov 2019 09:21:49 -0500 Received: from zn.tnic (p200300EC2F27B50084A11D83797EBEC7.dip0.t-ipconnect.de [IPv6:2003:ec:2f27:b500:84a1:1d83:797e:bec7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 637F91EC027B; Mon, 18 Nov 2019 15:21:48 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1574086908; 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:in-reply-to:in-reply-to: references:references; bh=Drk11FQiiBMEtrfW9/M48Q99qTus2Kx6p9Nmb9b9aEw=; b=PbmjpkhPOEFMbZr6Pzx3R4wyDJywmlAym8reaS86Kpx0UpuRIsg5vNjn7xYTJHbCJSpfnU h6En5/fAPDy4Rm9w+iPEInNkri8a1G11Fz+Abnyu8acE4JyTb+NRgScZqngxbyuxTb2CuT 3a/pX8XCszp1p12Et0oH3jM7PHDji40= Date: Mon, 18 Nov 2019 15:21:44 +0100 From: Borislav Petkov To: Jann Horn Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, Andrey Konovalov , Andy Lutomirski , Sean Christopherson Subject: Re: [PATCH v2 2/3] x86/traps: Print non-canonical address on #GP Message-ID: <20191118142144.GC6363@zn.tnic> References: <20191115191728.87338-1-jannh@google.com> <20191115191728.87338-2-jannh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191115191728.87338-2-jannh@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 15, 2019 at 08:17:27PM +0100, Jann Horn wrote: > dotraplinkage void > do_general_protection(struct pt_regs *regs, long error_code) > { > @@ -547,8 +581,15 @@ do_general_protection(struct pt_regs *regs, long error_code) > return; > > if (notify_die(DIE_GPF, desc, regs, error_code, > - X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP) > - die(desc, regs, error_code); > + X86_TRAP_GP, SIGSEGV) == NOTIFY_STOP) > + return; > + > + if (error_code) > + pr_alert("GPF is segment-related (see error code)\n"); > + else > + print_kernel_gp_address(regs); > + > + die(desc, regs, error_code); Right, this way, those messages appear before the main "general protection ..." message: [ 2.434372] traps: probably dereferencing non-canonical address 0xdfff000000000001 [ 2.442492] general protection fault: 0000 [#1] PREEMPT SMP Can we glue/merge them together? Or is this going to confuse tools too much: [ 2.542218] general protection fault while derefing a non-canonical address 0xdfff000000000001: 0000 [#1] PREEMPT SMP (and that sentence could be shorter too: "general protection fault for non-canonical address 0xdfff000000000001" looks ok to me too.) Here's a dirty diff together with a reproducer ontop of yours: --- diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index bf796f8c9998..dab702ba28a6 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -515,7 +515,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) * On 64-bit, if an uncaught #GP occurs while dereferencing a non-canonical * address, print that address. */ -static void print_kernel_gp_address(struct pt_regs *regs) +static unsigned long get_kernel_gp_address(struct pt_regs *regs) { #ifdef CONFIG_X86_64 u8 insn_bytes[MAX_INSN_SIZE]; @@ -523,7 +523,7 @@ static void print_kernel_gp_address(struct pt_regs *regs) unsigned long addr_ref; if (probe_kernel_read(insn_bytes, (void *)regs->ip, MAX_INSN_SIZE)) - return; + return 0; kernel_insn_init(&insn, insn_bytes, MAX_INSN_SIZE); insn_get_modrm(&insn); @@ -532,22 +532,22 @@ static void print_kernel_gp_address(struct pt_regs *regs) /* Bail out if insn_get_addr_ref() failed or we got a kernel address. */ if (addr_ref >= ~__VIRTUAL_MASK) - return; + return 0; /* Bail out if the entire operand is in the canonical user half. */ if (addr_ref + insn.opnd_bytes - 1 <= __VIRTUAL_MASK) - return; + return 0; - pr_alert("probably dereferencing non-canonical address 0x%016lx\n", - addr_ref); + return addr_ref; #endif } +#define GPFSTR "general protection fault" dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code) { - const char *desc = "general protection fault"; struct task_struct *tsk; + char desc[90]; RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); cond_local_irq_enable(regs); @@ -584,12 +584,18 @@ do_general_protection(struct pt_regs *regs, long error_code) X86_TRAP_GP, SIGSEGV) == NOTIFY_STOP) return; - if (error_code) - pr_alert("GPF is segment-related (see error code)\n"); - else - print_kernel_gp_address(regs); + if (error_code) { + snprintf(desc, 90, "segment-related " GPFSTR); + } else { + unsigned long addr_ref = get_kernel_gp_address(regs); + + if (addr_ref) + snprintf(desc, 90, GPFSTR " while derefing a non-canonical address 0x%lx", addr_ref); + else + snprintf(desc, 90, GPFSTR); + } - die(desc, regs, error_code); + die((const char *)desc, regs, error_code); return; } diff --git a/init/main.c b/init/main.c index 91f6ebb30ef0..7acc7e660be9 100644 --- a/init/main.c +++ b/init/main.c @@ -1124,6 +1124,9 @@ static int __ref kernel_init(void *unused) rcu_end_inkernel_boot(); + asm volatile("mov $0xdfff000000000001, %rax\n\t" + "jmpq *%rax\n\t"); + if (ramdisk_execute_command) { ret = run_init_process(ramdisk_execute_command); if (!ret) -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette