Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751877AbaDYDXT (ORCPT ); Thu, 24 Apr 2014 23:23:19 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:37143 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750773AbaDYDXR (ORCPT ); Thu, 24 Apr 2014 23:23:17 -0400 Message-ID: <5359D51E.8080109@hitachi.com> Date: Fri, 25 Apr 2014 12:23:10 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Oleg Nesterov Cc: Denys Vlasenko , linux-kernel@vger.kernel.org, Jim Keniston , Ingo Molnar Subject: Re: Re: [PATCH] uprobes/x86: Refuse to attach uprobe to "word-sized" branch insns References: <1398359304-26472-1-git-send-email-dvlasenk@redhat.com> <20140424173333.GA416@redhat.com> In-Reply-To: <20140424173333.GA416@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/04/25 2:33), Oleg Nesterov wrote: > Thanks! > > Masami, Jim, any acks? > > On 04/24, Denys Vlasenko wrote: >> >> All branch insns on x86 can be prefixed with the operand-size >> override prefix, 0x66. It was only ever useful for performing >> jumps to 32-bit offsets in 16-bit code segments. >> >> In 32-bit code, such instructions are useless since >> they cause IP truncation to 16 bits, and in case of call insns, >> they save only 16 bits of return address and misalign >> the stack pointer as a "bonus". >> >> In 64-bit code, such instructions are treated differently by Intel >> and AMD CPUs: Intel ignores the prefix altogether, >> AMD treats them the same as in 32-bit mode. >> >> Before this patch, the emulation code would execute >> the instructions as if they have no 0x66 prefix. >> >> With this patch, we refuse to attach uprobes to such insns. >> >> Signed-off-by: Denys Vlasenko >> Cc: Oleg Nesterov Acked-by: Masami Hiramatsu Thank you :) >> --- >> arch/x86/kernel/uprobes.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c >> index ace2291..29b152d 100644 >> --- a/arch/x86/kernel/uprobes.c >> +++ b/arch/x86/kernel/uprobes.c >> @@ -582,6 +582,7 @@ static struct uprobe_xol_ops branch_xol_ops = { >> /* Returns -ENOSYS if branch_xol_ops doesn't handle this insn */ >> static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) >> { >> + int i; >> u8 opc1 = OPCODE1(insn); >> >> /* has the side-effect of processing the entire instruction */ >> @@ -612,6 +613,17 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) >> return -ENOSYS; >> } >> >> + /* >> + * 16-bit overrides such as CALLW (66 e8 nn nn) are not supported. >> + * Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix. >> + * No one uses these insns. >> + * Reject any branch insns with such prefix. >> + */ >> + for (i = 0; i < insn->prefixes.nbytes; i++) { >> + if (insn->prefixes.bytes[i] == 0x66) >> + return -ENOTSUPP; >> + } >> + >> auprobe->branch.opc1 = opc1; >> auprobe->branch.ilen = insn->length; >> auprobe->branch.offs = insn->immediate.value; >> -- >> 1.8.1.4 >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/