From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752115AbbCJC7l (ORCPT ); Mon, 9 Mar 2015 22:59:41 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:46453 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750933AbbCJC7j (ORCPT ); Mon, 9 Mar 2015 22:59:39 -0400 Message-ID: <54FE5E14.8090303@hitachi.com> Date: Tue, 10 Mar 2015 11:59:32 +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: Eugene Shatokhin , Ingo Molnar CC: LKML , Ingo Molnar Subject: Re: [PATCH] kprobes/x86: Return correct length in __copy_instruction() References: <1425899954-24380-1-git-send-email-eugene.shatokhin@rosalab.ru> In-Reply-To: <1425899954-24380-1-git-send-email-eugene.shatokhin@rosalab.ru> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2015/03/09 20:19), Eugene Shatokhin wrote: > On x86-64, __copy_instruction() always returns 0 (error) if the > instruction uses %rip-relative addressing. This is because > kernel_insn_init() is called the second time for 'insn' instance > in such cases and sets all its fields to 0. > > Because of this, trying to place a Kprobe on such instruction will > fail, register_kprobe() will return -EINVAL. Oops, good catch! Acked-by: Masami Hiramatsu Thank you! > > This patch fixes the problem. > > Signed-off-by: Eugene Shatokhin > --- > arch/x86/kernel/kprobes/core.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index 4e3d5a9..03189d8 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -354,6 +354,7 @@ int __copy_instruction(u8 *dest, u8 *src) > { > struct insn insn; > kprobe_opcode_t buf[MAX_INSN_SIZE]; > + int length; > unsigned long recovered_insn = > recover_probed_instruction(buf, (unsigned long)src); > > @@ -361,16 +362,18 @@ int __copy_instruction(u8 *dest, u8 *src) > return 0; > kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE); > insn_get_length(&insn); > + length = insn.length; > + > /* Another subsystem puts a breakpoint, failed to recover */ > if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) > return 0; > - memcpy(dest, insn.kaddr, insn.length); > + memcpy(dest, insn.kaddr, length); > > #ifdef CONFIG_X86_64 > if (insn_rip_relative(&insn)) { > s64 newdisp; > u8 *disp; > - kernel_insn_init(&insn, dest, insn.length); > + kernel_insn_init(&insn, dest, length); > insn_get_displacement(&insn); > /* > * The copied instruction uses the %rip-relative addressing > @@ -394,7 +397,7 @@ int __copy_instruction(u8 *dest, u8 *src) > *(s32 *) disp = (s32) newdisp; > } > #endif > - return insn.length; > + return length; > } > > static int arch_copy_kprobe(struct kprobe *p) > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com