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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63C20C4332F for ; Wed, 30 Nov 2022 13:38:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230113AbiK3Nij (ORCPT ); Wed, 30 Nov 2022 08:38:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43590 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230393AbiK3Nia (ORCPT ); Wed, 30 Nov 2022 08:38:30 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 377222E6BF for ; Wed, 30 Nov 2022 05:38:20 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B595761BF2 for ; Wed, 30 Nov 2022 13:38:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9BF2C433D6; Wed, 30 Nov 2022 13:38:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669815499; bh=jw+awRGtgAZKGubWrz02rHawUZJ43c/ZqUDs43or8tI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fFkq7BVurt14DpUJg5zr+OW1tB7uUyAHvmDFfvbV5ken2SYrRNMBgu2K4znbWbwY2 eMBxxVXzSyZbLaE7AO8oq8/C2xIPwdeW2zmFZbmB6r5i5uAwm2b4TE43TXUEFUEKXg 6Y3MD6026UeiRb2D+iLZbvU5r2MrX1F+ueSeTIs/Ee13E0JOJMKuBPWAQ+vVpIByoS Dbb84OQw9nWcCRbW3umDu+MY0XMOWWSN182fChctJYSQ2cccl/UxcdGge9xO/cPQ7p xMXgx7hbotjZMuVUtiODrsRERUt9oGUr4idfjDaFtz3gy39frz2nxgHyBHXktZKy11 EtmpgACOHNKmA== Date: Wed, 30 Nov 2022 22:38:14 +0900 From: Masami Hiramatsu (Google) To: Chuang Wang Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Mark Brown , Rob Herring , Greg Kroah-Hartman , Alex Deucher , "Masami Hiramatsu (Google)" , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation Message-Id: <20221130223814.667999640ad298f843c2aaf2@kernel.org> In-Reply-To: <20221129084022.718355-1-nashuiliang@gmail.com> References: <20221129084022.718355-1-nashuiliang@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Nov 2022 16:39:51 +0800 Chuang Wang wrote: > For the `FF /digit` opcodes in prepare_emulation, use switch-case > instead of hand-written code to make the logic easier to understand. > > Signed-off-by: Chuang Wang This looks good to me. Acked-by: Masami Hiramatsu (Google) Thank you! > --- > arch/x86/kernel/kprobes/core.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index 66299682b6b7..66ec32b6cd0e 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -655,17 +655,19 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn) > * is determined by the MOD/RM byte. > */ > opcode = insn->modrm.bytes[0]; > - if ((opcode & 0x30) == 0x10) { > - if ((opcode & 0x8) == 0x8) > - return -EOPNOTSUPP; /* far call */ > - /* call absolute, indirect */ > + switch (X86_MODRM_REG(opcode)) { > + case 0b010: /* FF /2, call near, absolute indirect */ > p->ainsn.emulate_op = kprobe_emulate_call_indirect; > - } else if ((opcode & 0x30) == 0x20) { > - if ((opcode & 0x8) == 0x8) > - return -EOPNOTSUPP; /* far jmp */ > - /* jmp near absolute indirect */ > + break; > + case 0b100: /* FF /4, jmp near, absolute indirect */ > p->ainsn.emulate_op = kprobe_emulate_jmp_indirect; > - } else > + break; > + case 0b011: /* FF /3, call far, absolute indirect */ > + case 0b101: /* FF /5, jmp far, absolute indirect */ > + return -EOPNOTSUPP; > + } > + > + if (!p->ainsn.emulate_op) > break; > > if (insn->addr_bytes != sizeof(unsigned long)) > -- > 2.37.2 > -- Masami Hiramatsu (Google)