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 5C82D125A0; Mon, 5 Jun 2023 08:12:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD463C433D2; Mon, 5 Jun 2023 08:12:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685952732; bh=0a3Erj1+y05IXqjDMWsbKoIt+bMhOMaYKv6SbF8QYx8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Zu6xmXaSJOaYGEZ1M18sqNTyQoodb/FtprpnZS9jE7WS1RsqZh7vr80D82GP+H1i8 Qbu+kLGLXkmXcf2oXs54XG8W5AAc+Szj5iw7w1esJF0pl3B4pku9TUNP0nnZRtgroI L7ysBaeg9qWTT4omm1x3jmC2/a5iIXjq4VNltoSIXSnirdvBxVCgizUUrQFclxA9A9 JI6H8n/NsAtikP0Klus6G9HwEipbiVd/EmoeyXvbNSuuqp00lQftKP5siTorJJyFWk NlQqlLQB4dqezssu+rEQF7hm50+nogklsOxP5i6Esuay261E/tRiQMISJtPYoOP/Ua Cp41VdtuUrJ+Q== Date: Mon, 5 Jun 2023 11:11:43 +0300 From: Mike Rapoport To: Steven Rostedt Cc: Nadav Amit , "Edgecombe, Rick P" , "kent.overstreet@linux.dev" , Thomas Gleixner , "mcgrof@kernel.org" , "deller@gmx.de" , "netdev@vger.kernel.org" , "davem@davemloft.net" , "linux@armlinux.org.uk" , "linux-mips@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "hca@linux.ibm.com" , "catalin.marinas@arm.com" , "linux-kernel@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "palmer@dabbelt.com" , "chenhuacai@kernel.org" , "mpe@ellerman.id.au" , "x86@kernel.org" , "tsbogend@alpha.franken.de" , "linux-trace-kernel@vger.kernel.org" , "linux-parisc@vger.kernel.org" , "christophe.leroy@csgroup.eu" , Will Deacon , "dinguyen@kernel.org" , "naveen.n.rao@linux.ibm.com" , "sparclinux@vger.kernel.org" , "linux-modules@vger.kernel.org" , "bpf@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "song@kernel.org" , "linux-mm@kvack.org" , "loongarch@lists.linux.dev" , Andrew Morton Subject: Re: [PATCH 12/13] x86/jitalloc: prepare to allocate exectuatble memory as ROX Message-ID: <20230605081143.GA3460@kernel.org> References: <20230601101257.530867-1-rppt@kernel.org> <20230601101257.530867-13-rppt@kernel.org> <0f50ac52a5280d924beeb131e6e4717b6ad9fdf7.camel@intel.com> <68b8160454518387c53508717ba5ed5545ff0283.camel@intel.com> <50D768D7-15BF-43B8-A5FD-220B25595336@gmail.com> <20230604225244.65be9103@rorschach.local.home> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230604225244.65be9103@rorschach.local.home> On Sun, Jun 04, 2023 at 10:52:44PM -0400, Steven Rostedt wrote: > On Thu, 1 Jun 2023 16:54:36 -0700 > Nadav Amit wrote: > > > > The way text_poke() is used here, it is creating a new writable alias > > > and flushing it for *each* write to the module (like for each write of > > > an individual relocation, etc). I was just thinking it might warrant > > > some batching or something. > > I am not advocating to do so, but if you want to have many efficient > > writes, perhaps you can just disable CR0.WP. Just saying that if you > > are about to write all over the memory, text_poke() does not provide > > too much security for the poking thread. Heh, this is definitely and easier hack to implement :) > Batching does exist, which is what the text_poke_queue() thing does. For module loading text_poke_queue() will still be much slower than a bunch of memset()s for no good reason because we don't need all the complexity of text_poke_bp_batch() for module initialization because we are sure we are not patching live code. What we'd need here is a new batching mode that will create a writable alias mapping at the beginning of apply_relocate_*() and module_finalize(), then it will use memcpy() to that writable alias and will tear the mapping down in the end. Another option is to teach alternatives to update a writable copy rather than do in place changes like Song suggested. My feeling is that it will be more intrusive change though. > -- Steve > -- Sincerely yours, Mike.