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 3B9B5C54E67 for ; Tue, 26 Mar 2024 17:10:00 +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:In-Reply-To:References:From:Subject:Cc: To:Message-Id:Date:Mime-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=W/CaUy3T6duhN8nfMT6GXs5anfJZ0gidpkhpea8nRkg=; b=Vzoa7pNU9vZNaB Pvni/VxzSfYdI3U3GzSTqCCtmhIJ/Z/n8R3kU/E8B3rVU0AgCsI7Z0B2lMTY3XxQeZ/lIMy9HEKRZ ghVwO6OqblMR4AZ57G4NNmzpZdx3Wr+h8zk8Iur8vh8oJwWwZ33r5eKV/+M1wqLeom9OsOTUmZf0f ZDTqcMqTnc8vZHdHsYpPKTQ9B2pOJYkcnvkDLWe7+LlTzgmybpyoSuah9ePB9F0BPWkVtb9yMdwsr XgGNpa2NP/vQmnVl33DSOzLn832J5qA6myoQ1JfihjyjXJpHIhUirwBRSoN+I++yjhVoHk2j7gjeG 15TjaDOoY8R6EhIC3jfQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rpAJ9-00000005ebp-0Y9H; Tue, 26 Mar 2024 17:09:55 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rpAJ5-00000005eYp-1BvR for linux-riscv@lists.infradead.org; Tue, 26 Mar 2024 17:09:53 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 6417961300; Tue, 26 Mar 2024 17:09:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B05F7C433C7; Tue, 26 Mar 2024 17:09:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711472990; bh=BY9c4E9vzDvOXrNiXYtkhJynRYSTojLgUhZvqEXN4A0=; h=Date:To:Cc:Subject:From:References:In-Reply-To:From; b=naXAvZRGyE6HDXlpW+PfEasgiZtDiIq7vGErdR+UkCVzNvE1u00wuDA2bJqsDtHP4 zjyneI29fkt+0PXJ3GgvesgC/O1vt6JkMZmd7uZsFG5NepewsbrCZVVSiUMZ4oCHRT +lZTDLV9CAyZBpx2LQozLSOth9ZL6B6fRMb/7nhnSSMfGQ9kbUXJoY+lYW05+H14lv pL8eNBMdLeEdOP/vHLNs8M65MNDcgLRmt4CuCk9jAwuc+4YbpZxaCBz+s+xzZzRDS8 aodzOvzeY5zlx80qHXVS0MeOmRBrUp9v0KiwUKM/Eii7Wv7VLEcUXMC5kG3wg5S9Ub KS1iHiIGRXF0Q== Mime-Version: 1.0 Date: Tue, 26 Mar 2024 19:09:46 +0200 Message-Id: To: "Calvin Owens" , "Masami Hiramatsu" Cc: "Mark Rutland" , , "Paul Walmsley" , "Palmer Dabbelt" , "Albert Ou" , , "Naveen N . Rao" , "Anil S Keshavamurthy" , "David S . Miller" , Subject: Re: [PATCH v2] arch/riscv: Enable kprobes when CONFIG_MODULES=n From: "Jarkko Sakkinen" X-Mailer: aerc 0.17.0 References: <20240323232908.13261-1-jarkko@kernel.org> <20240325115632.04e37297491cadfbbf382767@kernel.org> <20240327002403.62649aee45508b7a16caedba@kernel.org> In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240326_100951_456784_719BEF0D X-CRM114-Status: GOOD ( 33.99 ) X-BeenThere: linux-riscv@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-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Tue Mar 26, 2024 at 6:15 PM EET, Calvin Owens wrote: > On Wednesday 03/27 at 00:24 +0900, Masami Hiramatsu wrote: > > On Tue, 26 Mar 2024 14:46:10 +0000 > > Mark Rutland wrote: > > > > > Hi Masami, > > > > > > On Mon, Mar 25, 2024 at 11:56:32AM +0900, Masami Hiramatsu wrote: > > > > Hi Jarkko, > > > > > > > > On Sun, 24 Mar 2024 01:29:08 +0200 > > > > Jarkko Sakkinen wrote: > > > > > > > > > Tracing with kprobes while running a monolithic kernel is currently > > > > > impossible due the kernel module allocator dependency. > > > > > > > > > > Address the issue by allowing architectures to implement module_alloc() > > > > > and module_memfree() independent of the module subsystem. An arch tree > > > > > can signal this by setting HAVE_KPROBES_ALLOC in its Kconfig file. > > > > > > > > > > Realize the feature on RISC-V by separating allocator to module_alloc.c > > > > > and implementing module_memfree(). > > > > > > > > Even though, this involves changes in arch-independent part. So it should > > > > be solved by generic way. Did you checked Calvin's thread? > > > > > > > > https://lore.kernel.org/all/cover.1709676663.git.jcalvinowens@gmail.com/ > > > > > > > > I think, we'd better to introduce `alloc_execmem()`, > > > > CONFIG_HAVE_ALLOC_EXECMEM and CONFIG_ALLOC_EXECMEM at first > > > > > > > > config HAVE_ALLOC_EXECMEM > > > > bool > > > > > > > > config ALLOC_EXECMEM > > > > bool "Executable trampline memory allocation" > > > > depends on MODULES || HAVE_ALLOC_EXECMEM > > > > > > > > And define fallback macro to module_alloc() like this. > > > > > > > > #ifndef CONFIG_HAVE_ALLOC_EXECMEM > > > > #define alloc_execmem(size, gfp) module_alloc(size) > > > > #endif > > > > > > Please can we *not* do this? I think this is abstracting at the wrong level (as > > > I mentioned on the prior execmem proposals). > > > > > > Different exectuable allocations can have different requirements. For example, > > > on arm64 modules need to be within 2G of the kernel image, but the kprobes XOL > > > areas can be anywhere in the kernel VA space. > > > > > > Forcing those behind the same interface makes things *harder* for architectures > > > and/or makes the common code more complicated (if that ends up having to track > > > all those different requirements). From my PoV it'd be much better to have > > > separate kprobes_alloc_*() functions for kprobes which an architecture can then > > > choose to implement using a common library if it wants to. > > > > > > I took a look at doing that using the core ifdeffery fixups from Jarkko's v6, > > > and it looks pretty clean to me (and works in testing on arm64): > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=kprobes/without-modules > > > > > > Could we please start with that approach, with kprobe-specific alloc/free code > > > provided by the architecture? > > Heh, I also noticed that dead !RWX branch in arm64 patch_map(), I was > about to send a patch to remove it. > > > OK, as far as I can read the code, this method also works and neat! > > (and minimum intrusion). I actually found that exposing CONFIG_ALLOC_EXECMEM > > to user does not help, it should be an internal change. So hiding this change > > from user is better choice. Then there is no reason to introduce the new > > alloc_execmem, but just expand kprobe_alloc_insn_page() is reasonable. > > I'm happy with this, it solves the first half of my problem. But I want > eBPF to work in the !MODULES case too. > > I think Mark's approach can work for bpf as well, without needing to > touch module_alloc() at all? So I might be able to drop that first patch > entirely. Yeah, I think we're aligned. Later on, if/when you send the bpf series please also cc me and I might possibly test those patches too. BR, Jarkko _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv