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 41D06C4332F for ; Fri, 18 Nov 2022 00:04:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235184AbiKRAEg (ORCPT ); Thu, 17 Nov 2022 19:04:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240414AbiKRAEK (ORCPT ); Thu, 17 Nov 2022 19:04:10 -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 775023F051 for ; Thu, 17 Nov 2022 16:04:09 -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 E22F0622C6 for ; Fri, 18 Nov 2022 00:04:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5C89C433D6; Fri, 18 Nov 2022 00:04:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668729848; bh=mK0fXfcmMTUtxxGFZQCuyZs069DXktNhvNUJRupxs30=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=juXNzO82X3euW+WCpC/AAzcm6Z+0/8bDpiNs7f1fNI4RqG3gGpX87WAxGBmLicHoq mwqorWSamkKf8YJI4xh+DWN0yT1TC2r7Piy1lW/J4kxF5QTjxp684pgAnSBkZ18Bvd YiTZBygFAyEz4SewKQ2YLj+BaSKaHRHllPruU0RNhzZIhscDyYoLBq3By3s4u0SdUv IMFGxYA03geBYR1GrfyWAH63pKM49x/2YeoS8UOEElzPzYbAfYmmymu1LML8KyoFGo qsEs32ebovRYzqr2AwzIesUVRe2em6asFJKEqx1/2Ue0+zpyBLCqdwZlk7QatyZDRp 6X/fYCKTm18Yw== Date: Fri, 18 Nov 2022 09:04:05 +0900 From: Masami Hiramatsu (Google) To: Mark Rutland Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org, revest@chromium.org, rostedt@goodmis.org, will@kernel.org Subject: Re: [PATCH v2 0/4] arm64/ftrace: move to DYNAMIC_FTRACE_WITH_ARGS Message-Id: <20221118090405.5dc0c9f2caaec4e9720a47cd@kernel.org> In-Reply-To: <20221103170520.931305-1-mark.rutland@arm.com> References: <20221103170520.931305-1-mark.rutland@arm.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 Thu, 3 Nov 2022 17:05:16 +0000 Mark Rutland wrote: > This series replaces arm64's support for FTRACE_WITH_REGS with support > for FTRACE_WITH_ARGS. This removes some overhead and complexity, and > removes some latent issues with inconsistent presentation of struct > pt_regs (which can only be reliably saved/restored at exception > boundaries). > > The existing FTRACE_WITH_REGS support was added for two major reasons: > > (1) To make it possible to use the ftrace graph tracer with pointer > authentication, where it's necessary to snapshot/manipulate the LR > before it is signed by the instrumented function. > > (2) To make it possible to implement LIVEPATCH in future, where we need > to hook function entry before an instrumented function manipulates > the stack or argument registers. Practically speaking, we need to > preserve the argument/return registers, PC, LR, and SP. > > Neither of these requires the full set of pt_regs, and only requires us > to save/restore a subset of registers used for passing > arguments/return-values and context/return information (which is the > minimum set we always need to save/restore today). > > As there is no longer a need to save different sets of registers for > different features, we no longer need distinct `ftrace_caller` and > `ftrace_regs_caller` trampolines. This allows the trampoline assembly to > be simpler, and simplifies code which previously had to handle the two > trampolines. > > I've tested this with the ftrace selftests, where there are no > unexpected failures. > > I plan to build atop this with subsequent patches to add per-callsite > ftrace_ops, and I'm sending these patches on their own as I think they > make sense regardless. Thanks! this series looks good to me. Reviewed-by: Masami Hiramatsu (Google) So it is the good time to rewrite the new fprobe event handler based on these interfaces :) > > Since v1 [1]: > * Change ifdeferry per Steve's request > * Add ftrace_regs_query_register_offset() per Masami's request > * Fix a bunch of typos > > [1] https://lore.kernel.org/lkml/20221024140846.3555435-1-mark.rutland@arm.com > > This series can be found in my 'arm64/ftrace/minimal-regs' branch on > kernel.org: > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/ > git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git > > This version is tagged as: > > arm64-ftrace-minimal-regs-20221103 > > Thanks, > Mark. > > Mark Rutland (4): > ftrace: pass fregs to arch_ftrace_set_direct_caller() > ftrace: rename ftrace_instruction_pointer_set() -> > ftrace_regs_set_instruction_pointer() > ftrace: abstract DYNAMIC_FTRACE_WITH_ARGS accesses > ftrace: arm64: move from REGS to ARGS > > arch/arm64/Kconfig | 18 +++-- > arch/arm64/Makefile | 2 +- > arch/arm64/include/asm/ftrace.h | 72 ++++++++++++++++-- > arch/arm64/kernel/asm-offsets.c | 13 ++++ > arch/arm64/kernel/entry-ftrace.S | 117 ++++++++++++------------------ > arch/arm64/kernel/ftrace.c | 82 ++++++++++++--------- > arch/arm64/kernel/module.c | 3 - > arch/powerpc/include/asm/ftrace.h | 24 +++++- > arch/s390/include/asm/ftrace.h | 29 +++++++- > arch/x86/include/asm/ftrace.h | 49 +++++++++---- > include/linux/ftrace.h | 47 +++++++++--- > kernel/livepatch/patch.c | 2 +- > kernel/trace/Kconfig | 6 +- > kernel/trace/ftrace.c | 3 +- > 14 files changed, 309 insertions(+), 158 deletions(-) > > -- > 2.30.2 > -- Masami Hiramatsu (Google)