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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1os49d-00FlYc-Tq; Mon, 07 Nov 2022 15:35:18 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1os49b-00FlY0-33 for linux-arm-kernel@lists.infradead.org; Mon, 07 Nov 2022 15:35:16 +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 AE6216090B; Mon, 7 Nov 2022 15:35:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E27DC433C1; Mon, 7 Nov 2022 15:35:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667835314; bh=YgTjc9NWRa4hkCM5G3S0/8cBCSAgAXOlIov4LDNhgLA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=L0h0qU8/wbruaUY0+KTShGs7d4ZHYnVtjDKBT776gi82Vc5PUrq7aSP6OhXloFNRq QRL/JqICUb/pDv1M5V6P7oLyrzAWtqUhAs0D2y5lJ3H2ZBDxRAjT9S+0WRIfHzDsS4 lRSFqMUEBtpV3AxQWLIC+C8BTKeRybIogwS4G4/G4FkEMgmifzsK6z6bNWLmwPO8iq 47LT4LWt0q46ICgGe1m6HqZYOeRrqETvzZu9ZZAI1aYudHsLPeOCBNZKgm+VaxLRgK dxFJLSj3kjjlnwVi+/u+Le4bhJebjrb5rPRwWCY9AgGNBvbEFNHekNZd68S/j+vJ5O m4OWFNcGrpUQg== Date: Mon, 7 Nov 2022 15:35:07 +0000 From: Will Deacon To: Mark Rutland Cc: Jianlin Lv , corbet@lwn.net, catalin.marinas@arm.com, rostedt@goodmis.org, mingo@redhat.com, naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com, davem@davemloft.net, mhiramat@kernel.org, arnd@arndb.de, zhengzengkai@huawei.com, jianlv@ebay.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm64/kprobes: Add support for KPROBES_ON_FTRACE Message-ID: <20221107153506.GA21157@willie-the-truck> References: <20220728020250.1699-1-iecedge@gmail.com> <20221107144931.GA20793@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221107_073515_190537_FEF783C4 X-CRM114-Status: GOOD ( 24.12 ) 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 Mon, Nov 07, 2022 at 03:32:24PM +0000, Mark Rutland wrote: > On Mon, Nov 07, 2022 at 02:49:31PM +0000, Will Deacon wrote: > > [+Mark R] > > > > On Thu, Jul 28, 2022 at 02:02:50AM +0000, Jianlin Lv wrote: > > > This is the arm64 version of ftrace-based kprobes to avoid the overhead > > > with regular kprobes, by using the ftrace infrastructure. > > > > > > Signed-off-by: Jianlin Lv > > > --- > > > .../debug/kprobes-on-ftrace/arch-support.txt | 2 +- > > > arch/arm64/Kconfig | 1 + > > > arch/arm64/kernel/probes/Makefile | 1 + > > > arch/arm64/kernel/probes/kprobes-ftrace.c | 81 +++++++++++++++++++ > > > include/linux/kprobes.h | 2 + > > > kernel/kprobes.c | 4 +- > > > 6 files changed, 88 insertions(+), 3 deletions(-) > > > create mode 100644 arch/arm64/kernel/probes/kprobes-ftrace.c > > > > Sorry for the slow reply on this, but I think this deserved to be split > > into two patches: the first one reworking the core check_ftrace_location() > > logic to work properly with branch-and-link style architectures, and the > > second one adding support for arm64. > > I'd prefer we don't do this at all; there a bunch of issues with kprobes *not* > taking an exception, since we get a dodgy not-quite-real pt_regs, and to clean > up the existing issues the plan is: > > 1) Move ftrace over to ftrace_regs > 2) Implement fprobes using ftrace_regs > 3) Remove kretprobes > > ... and regular kprobes will need to take an exception (via BRK) to get a real > pt_regs, so that can't be optimized to use ftrace. OKey doke. Does that mean that other architectures will follow the same approach of taking an exception, or do they somehow work by magic? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel