From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E0B7A5CAC; Fri, 24 May 2024 01:09:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716512964; cv=none; b=AmcqlJ3icAeKpSjLvXJ2i1AKhvp966PcxbuLKxa54Ku5TDlZfDxLf1gbRy0ZFCuaymlu0rvmhNBC80hHbm6cINgFsKM002bMaQA6BxXvwk4eRhAW3dXDPwVaOhj+zU7Ahq+pfagD1i7LI4VT7sXgc82w9ScyOkyEi/FXsSriBN8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716512964; c=relaxed/simple; bh=N5i8ODqIWK6xce8rPBypOBonIZKEmwJfgSq3wA+sDiM=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=nphwmOB4Raz3jdXhLYXDQcfA8GEpQ5So6bUtq3eIWZpQGQrcv10P0LMb7IJdw2iUhbbDtRq0AByo2CwG3tb3BS9VusiGX2EmKwWKE/WiA/4OSlJjC4asWcYnK1irtdKvuu8pmwnOPJl6M3Zo73fdvc0mqbg6MnDdKD6dmjo7Urk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nXhv6Pqn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nXhv6Pqn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D14EDC3277B; Fri, 24 May 2024 01:09:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716512963; bh=N5i8ODqIWK6xce8rPBypOBonIZKEmwJfgSq3wA+sDiM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nXhv6PqnFOr8LrGFjDqcJYW7eIwONusPVONYtH+Uxt0hcT+HI9cmsYnY1HkEZQqWN bqixDnXsLQRr0fJomyfPw5AepmT+Ls6sAnTU/qaYJ2ee9/6KN1fG5J+tEZB2E3EMgp THHdNP8nhRtqwPTHiNFhyeocUj+frWH/Dm3fw9Qziacqot2VXv8OBb3WfH3GtpHqST E7erDiXA3vnJhxnyH+mXsGkHqjp+UD+Oenn1HonCfuxfP49TV0RBY5lzQGIniZFRyE pr/niEFe+bRLtLnCSOtmPEL0DSU+EfnGxv/X5JfiDquxMFHjpIb4mo9+SDA3FyCx9a JwBOIxB+ogI+Q== Date: Fri, 24 May 2024 10:09:17 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: Alexei Starovoitov , Florent Revest , linux-trace-kernel@vger.kernel.org, LKML , Martin KaFai Lau , bpf , Sven Schnelle , Alexei Starovoitov , Jiri Olsa , Arnaldo Carvalho de Melo , Daniel Borkmann , Alan Maguire , Mark Rutland , Peter Zijlstra , Thomas Gleixner , Guo Ren Subject: Re: [PATCH v10 01/36] tracing: Add a comment about ftrace_regs definition Message-Id: <20240524100917.6983301f9df6da716591f136@kernel.org> In-Reply-To: <20240523191031.7574d944@gandalf.local.home> References: <171509088006.162236.7227326999861366050.stgit@devnote2> <171509089214.162236.6201493898649663823.stgit@devnote2> <20240523191031.7574d944@gandalf.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 23 May 2024 19:10:31 -0400 Steven Rostedt wrote: > On Tue, 7 May 2024 23:08:12 +0900 > "Masami Hiramatsu (Google)" wrote: > > > From: Masami Hiramatsu (Google) > > > > To clarify what will be expected on ftrace_regs, add a comment to the > > architecture independent definition of the ftrace_regs. > > > > Signed-off-by: Masami Hiramatsu (Google) > > Acked-by: Mark Rutland > > --- > > Changes in v8: > > - Update that the saved registers depends on the context. > > Changes in v3: > > - Add instruction pointer > > Changes in v2: > > - newly added. > > --- > > include/linux/ftrace.h | 26 ++++++++++++++++++++++++++ > > 1 file changed, 26 insertions(+) > > > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > > index 54d53f345d14..b81f1afa82a1 100644 > > --- a/include/linux/ftrace.h > > +++ b/include/linux/ftrace.h > > @@ -118,6 +118,32 @@ extern int ftrace_enabled; > > > > #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS > > > > +/** > > + * ftrace_regs - ftrace partial/optimal register set > > + * > > + * ftrace_regs represents a group of registers which is used at the > > + * function entry and exit. There are three types of registers. > > + * > > + * - Registers for passing the parameters to callee, including the stack > > + * pointer. (e.g. rcx, rdx, rdi, rsi, r8, r9 and rsp on x86_64) > > + * - Registers for passing the return values to caller. > > + * (e.g. rax and rdx on x86_64) > > + * - Registers for hooking the function call and return including the > > + * frame pointer (the frame pointer is architecture/config dependent) > > + * (e.g. rip, rbp and rsp for x86_64) > > + * > > + * Also, architecture dependent fields can be used for internal process. > > + * (e.g. orig_ax on x86_64) > > + * > > + * On the function entry, those registers will be restored except for > > + * the stack pointer, so that user can change the function parameters > > + * and instruction pointer (e.g. live patching.) > > + * On the function exit, only registers which is used for return values > > + * are restored. > > I wonder if we should also add a note about some architectures in some > circumstances may store all pt_regs in ftrace_regs. For example, if an > architecture supports FTRACE_WITH_REGS, it may pass the pt_regs within the > ftrace_regs. If that is the case, then ftrace_get_regs() called on it will > return a pointer to a valid pt_regs, or NULL if it is not supported or the > ftrace_regs does not have a all the registers. Agreed. That case also should be noted. Thanks for pointing! > > -- Steve > > > > + * > > + * NOTE: user *must not* access regs directly, only do it via APIs, because > > + * the member can be changed according to the architecture. > > + */ > > struct ftrace_regs { > > struct pt_regs regs; > > }; > -- Masami Hiramatsu (Google)