From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x226kHbtkHvIqJ5W+RW+jqSroBsPtK4Gztp4JsMWJRl/fZ+Vm+2na4mcruXKXYFGO8lCqFomp ARC-Seal: i=1; a=rsa-sha256; t=1519218548; cv=none; d=google.com; s=arc-20160816; b=Ncx6acEVK783Q8DDMc2KOsa7AolXv3m1o+6KKHyGBczZOXEZqjgyCJR4TNnvUoIi9r gONhosgGkJH3k+cJUs71M8lnOn83TvndLQUwvceKEI7aNJEfNMbxrwIvaH8eCffif0oD d6UamK3jHmncUGKkWGNl/pNv0WRU1WZjTz+17kPOmMeVd0BEapnpAKt6MBJYuW761upg olC1utWBSmNe4fwCh++uZXMqvif4+wXViIQiBVWo7+elrg7lJlIVVG74Ap2wsWsWfwYI aSBjVqdT0OQId7Ho3u836+rUPO72SEgq7ADPfTXEIOzLYql4ifgL0wgYyUrEbUbaqIad 4gBQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=rzbve1c0qRMiI9NjGtgqs8Q7AK5MKseQ5g675z48QNA=; b=NDDUEa+De6hWLzcL5Zrpb1FwhjzZIUPcS+iLYgDyqTfIWZrQHymO+ACBW5a3pxG3pQ cVrhmZlWllqoTDyqsXr56kVjBijJT8K+948/RKgfaAwL3poHg+bWaiAdd63OYpkGNbKD iyKMoD6+YIAXiSG+YWIdE1qaWcpg2z3chnMWCguIxmzmfM0t3yogrSCLwODbXeqFXHyC 7XScE1eaopk8enaBOzsxtMUwvMKmIrkXMc/DXwWD3YpeOeQ0ICBU45Bjfnf4XnBewpHe yJZrsQFcp2oworIZhh9pRgoDvMZ53DixagjOtHG8RGX/Pc8i6g3kAk/+v3JH6l3VQGgd k6SA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Linus Torvalds , "Peter Zijlstra (Intel)" , Andy Lutomirski , Arjan van de Ven , Borislav Petkov , Brian Gerst , Denys Vlasenko , "H. Peter Anvin" , Josh Poimboeuf , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.15 078/163] x86/debug: Use UD2 for WARN() Date: Wed, 21 Feb 2018 13:48:27 +0100 Message-Id: <20180221124534.760076350@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180221124529.931834518@linuxfoundation.org> References: <20180221124529.931834518@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1593015704879461165?= X-GMAIL-MSGID: =?utf-8?q?1593016108437819969?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit 3b3a371cc9bc980429baabe0a8e5f307f3d1f463 upstream. Since the Intel SDM added an ModR/M byte to UD0 and binutils followed that specification, we now cannot disassemble our kernel anymore. This now means Intel and AMD disagree on the encoding of UD0. And instead of playing games with additional bytes that are valid ModR/M and single byte instructions (0xd6 for instance), simply use UD2 for both WARN() and BUG(). Requested-by: Linus Torvalds Signed-off-by: Peter Zijlstra (Intel) Acked-by: Linus Torvalds Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20180208194406.GD25181@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/bug.h | 15 ++++++--------- arch/x86/kernel/traps.c | 2 +- 2 files changed, 7 insertions(+), 10 deletions(-) --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -5,23 +5,20 @@ #include /* - * Since some emulators terminate on UD2, we cannot use it for WARN. - * Since various instruction decoders disagree on the length of UD1, - * we cannot use it either. So use UD0 for WARN. + * Despite that some emulators terminate on UD2, we use it for WARN(). * - * (binutils knows about "ud1" but {en,de}codes it as 2 bytes, whereas - * our kernel decoder thinks it takes a ModRM byte, which seems consistent - * with various things like the Intel SDM instruction encoding rules) + * Since various instruction decoders/specs disagree on the encoding of + * UD0/UD1. */ -#define ASM_UD0 ".byte 0x0f, 0xff" +#define ASM_UD0 ".byte 0x0f, 0xff" /* + ModRM (for Intel) */ #define ASM_UD1 ".byte 0x0f, 0xb9" /* + ModRM */ #define ASM_UD2 ".byte 0x0f, 0x0b" #define INSN_UD0 0xff0f #define INSN_UD2 0x0b0f -#define LEN_UD0 2 +#define LEN_UD2 2 #ifdef CONFIG_GENERIC_BUG @@ -79,7 +76,7 @@ do { \ #define __WARN_FLAGS(flags) \ do { \ - _BUG_FLAGS(ASM_UD0, BUGFLAG_WARNING|(flags)); \ + _BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags)); \ annotate_reachable(); \ } while (0) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -181,7 +181,7 @@ int fixup_bug(struct pt_regs *regs, int break; case BUG_TRAP_TYPE_WARN: - regs->ip += LEN_UD0; + regs->ip += LEN_UD2; return 1; }