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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 91706C433F5 for ; Wed, 11 May 2022 14:36:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Mime-Version:References:In-Reply-To: Message-Id:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=TYiokL8R4MtMK09s0HKyZXuWPlCmiBDE3miaNpAm5bM=; b=O6FR7Kq+k1KxAe /8KEI+0trgL6UR+tXF3eSvGNbDKIohL4PWide7BA3Wx/26WEj3IvIdewc8WRG4P1wIMLdUFVHnJTt xLHvPWFVdAP/Hp3YCLKZOszcI1DHOosvJBQi/azId/8dDS6FG0in9pbkIDx3cHEgwcp5I6kCnI/xx 2fYs6rHvQxf0E3ls0PkQXPElB9HnhaXfTyKbKIj741kh/b78kih+03S9jA9Udl8mvMobeT+1iN0Gg 314S9QKPT+h8HqI9pkAQpKk1a5TJQkQMzWJVmq6djXAg/1KdmoxM8tTw1eL0ze2LiOnVRy+P+9dEy K3BSPClvoX/2RGtQcjhQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nonQc-007EtC-18; Wed, 11 May 2022 14:35:02 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nonQZ-007Eqz-Kw for linux-arm-kernel@lists.infradead.org; Wed, 11 May 2022 14:35:01 +0000 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 E00766119A; Wed, 11 May 2022 14:34:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D091C34113; Wed, 11 May 2022 14:34:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652279696; bh=t7NtYe4g+ZzXlwVJbcVCuf8BrT1ifHZjftu0dkcPeDU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=To96SnoomjvJcuaMcVymixOJKBqwvB0ITJ+cp+vmiv8nwaFwLDwKSKJ/Sr+oLcrR5 TyQh9/nvJJtSIxdnQPCdaQkXOAxZGiMSemQmOsGMGmspApEEZuYY8eAnpZHNiEOJh2 bpiKc+VpbVcbtRQravcMqQ5F7cgSyzOiRHSxmdTqw60/TuZmyFIZBBWuWltVhIg/wk DWH8JzHRc0JiNYk0Ox5rmApFMwqjD6cTikfNyrQ6dFkNv1TD3RrveXHQtpdMY7apuK beMKIK9UmoQYfJqU/T3YtjEQTPCtKKJJ5fFRo6WpIPsD7RtQngDab7O2rctMyb20+M ti4O54qXJ/VNg== Date: Wed, 11 May 2022 23:34:50 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Mark Rutland , Wang ShaoBo , cj.chengjian@huawei.com, huawei.libin@huawei.com, xiexiuqi@huawei.com, liwei391@huawei.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, zengshun.wu@outlook.com, Jiri Olsa Subject: Re: [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically allocated trampolines Message-Id: <20220511233450.40136cdf6a53eb32cd825be8@kernel.org> In-Reply-To: <20220510104446.6d23b596@gandalf.local.home> References: <20220421100639.03c0d123@gandalf.local.home> <20220421114201.21228eeb@gandalf.local.home> <20220421130648.56b21951@gandalf.local.home> <20220422114541.34d71ad9@gandalf.local.home> <20220426174749.b5372c5769af7bf901649a05@kernel.org> <20220505121538.04773ac98e2a8ba17f675d39@kernel.org> <20220509142203.6c4f2913@gandalf.local.home> <20220510181012.d5cba23a2547f14d14f016b9@kernel.org> <20220510104446.6d23b596@gandalf.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220511_073459_816942_0AAAE4CC X-CRM114-Status: GOOD ( 33.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 10 May 2022 10:44:46 -0400 Steven Rostedt wrote: > On Tue, 10 May 2022 18:10:12 +0900 > Masami Hiramatsu wrote: > > > > > > > This was suggested by both Peter Zijlstra and Thomas Gleixner when I > > > introduced FTRACE_WITH_ARGS, where all functions can now get the arguments > > > from fregs, but not the full pt_regs. > > > > Hmm, I thought the ftrace_get_regs() is the all-or-nothing interface, or > > is there any way to get the arguments from fregs? > > Not yet generically. But that can easily be added. If you look at x86 live > patching, since it is arch specific, it just took the regs parameter > directly, knowing that the args were already set up. That is, ftrace_regs is > just a wrapper around pt_regs with just the regs for the arguments and stack > initialized. If you get regs from ftrace_get_regs(fregs) it will return > NULL if it wasn't full set of regs. But we can add generic functions to get > the parameters. > > That is, we can create a ftrace_get_kernel_argument() function that takes > fregs instead of pt_regs, and produce the same thing as > regs_get_kernel_argument(). > > x86 live kernel patching has this: > > arch/x86/include/asm/ftrace.h: > > #define ftrace_instruction_pointer_set(fregs, _ip) \ > do { (fregs)->regs.ip = (_ip); } while (0) > > > arch/x86/include/asm/livepatch.h: > > static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip) > { > ftrace_instruction_pointer_set(fregs, ip); > } > > Where fregs is not a full set of regs. OK, so fregs::regs will have a subset of pt_regs, and accessibility of the registers depends on the architecture. If we can have a checker like ftrace_regs_exist(fregs, reg_offset) kprobe on ftrace or fprobe user (BPF) can filter user's requests. I think I can introduce a flag for kprobes so that user can make a kprobe handler only using a subset of registers. Maybe similar filter code is also needed for BPF 'user space' library because this check must be done when compiling BPF. Thank you, > > > > > If a ftrace_ops has the REGS flag set > > > (using ftrace_regs_caller), the ftrace_get_regs(fregs) will return the > > > pt_regs, or it will return NULL if ftrace_regs_caller was not used. > > > > > > This way the same parameter can provide full pt_regs or a subset, and have > > > an generic interface to tell the difference. > > > > If it can provide a partial (subset of) pt_regs, that could be good for me > > too, since at least kprobe-events on ftrace can check the traced register > > is in the subset or not and reject it if it doesn't saved. > > That's exactly the use case for ftrace_regs. > > -- Steve -- Masami Hiramatsu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel