From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754861AbbCQKKg (ORCPT ); Tue, 17 Mar 2015 06:10:36 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:42593 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753328AbbCQKKc (ORCPT ); Tue, 17 Mar 2015 06:10:32 -0400 Subject: [PATCH -tip ] kprobes/x86: Return correct length in __copy_instruction() From: Masami Hiramatsu To: Ingo Molnar Cc: Eugene Shatokhin , Ingo Molnar , Ingo Molnar , LKML Date: Tue, 17 Mar 2015 19:09:18 +0900 Message-ID: <20150317100918.28349.94654.stgit@localhost.localdomain> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eugene Shatokhin 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. This patch fixes the problem. Signed-off-by: Eugene Shatokhin Acked-by: Masami Hiramatsu Signed-off-by: Masami Hiramatsu --- 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)