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 BCB05CD1288 for ; Wed, 3 Apr 2024 16:52:07 +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:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=VXpbpu6dVmwmUx2w++hmeN2KFYJNOxCZ6ZF9grxPG60=; b=dZH2FQQJfTqPVw JfvAx/ErKZgIlbm619rmYUiqn0iopQqsjPNlAfLUua8j3yUonksOCoNBGw+PDDe4v2AArqjhAM8+q 9o4YsqpWuVaQEUa6jtoZeNIszdJ/urjdXxdzXY+F/LqSi62fAq8s9Gb9MWb54AmGNyDFNYI8HeuPI FHCEM8hZkSzy9UTEgd95/JaqM+QDjeO40poCRSnq7Id4W5YyFoIrH1UOF0XzpObOdTQpkeFXHHeH5 nZgnfqGdEJjOb+wwhLt1aIfBB4kVo90tvejVNWX1N/buxalLaipzULpxNd4KWA/pNLaetbDp5vP5p feSLTxcTwlzssvchonCg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rs3q8-0000000H2rP-0oa0; Wed, 03 Apr 2024 16:51:56 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rs3q5-0000000H2qG-0wDB for linux-arm-kernel@lists.infradead.org; Wed, 03 Apr 2024 16:51:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3F23F1007; Wed, 3 Apr 2024 09:52:21 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 263C83F64C; Wed, 3 Apr 2024 09:51:48 -0700 (PDT) Date: Wed, 3 Apr 2024 17:51:44 +0100 From: Mark Rutland To: Jarkko Sakkinen Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , anil.s.keshavamurthy@intel.com, aou@eecs.berkeley.edu, davem@davemloft.net, linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org, naveen.n.rao@linux.ibm.com, palmer@dabbelt.com, paul.walmsley@sifive.com Subject: Re: [PATCH v2 1/4] arm64: patching: always use fixmap Message-ID: References: <20240403150154.667649-1-mark.rutland@arm.com> <20240403150154.667649-2-mark.rutland@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240403_095153_373102_25E6D85C X-CRM114-Status: GOOD ( 36.06 ) 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 Wed, Apr 03, 2024 at 07:20:31PM +0300, Jarkko Sakkinen wrote: > On Wed Apr 3, 2024 at 6:01 PM EEST, Mark Rutland wrote: > > For historical reasons, patch_map() won't bother to fixmap non-image > > addresses when CONFIG_STRICT_MODULE_RWX=n, matching the behaviour prior > > to the introduction of CONFIG_STRICT_MODULE_RWX. However, as arm64 > > doesn't select CONFIG_ARCH_OPTIONAL_KERNEL_RWX, CONFIG_MODULES implies > > CONFIG_STRICT_MODULE_RWX, so any kernel built with module support will > > use the fixmap for any non-image address. > > Not familiar with the config flag but I'd guess it is essentially > w^x enforcement right for the sections? Essentially, yes. > > Historically we only used patch_map() for the kernel image and modules, > > but these days its also used by BPF and KPROBES to write to read-only > > pages of executable text. Currently these both depend on CONFIG_MODULES, > > but we'd like to change that in subsequent patches, which will require > > using the fixmap regardless of CONFIG_STRICT_MODULE_RWX. > > > > This patch changes patch_map() to always use the fixmap, and simplifies > > the logic: > > > > * Use is_image_text() directly in the if-else, rather than using a > > temporary boolean variable. > > > > * Use offset_in_page() to get the offset within the mapping. > > > > * Remove uintaddr and cast the address directly when using > > is_image_text(). > > > > For kernels built with CONFIG_MODULES=y, there should be no functional > > change as a result of this patch. > > > > For kernels built with CONFIG_MODULES=n, patch_map() will use the fixmap > > for non-image addresses, but there are no extant users with non-image > > addresses when CONFIG_MODULES=n, and hence there should be no functional > > change as a result of this patch alone. > > > > Signed-off-by: Mark Rutland > > Cc: Catalin Marinas > > Cc: Will Deacon > > --- > > arch/arm64/kernel/patching.c | 10 +++------- > > 1 file changed, 3 insertions(+), 7 deletions(-) > > > > Catalin, Will, this is a prerequisite for the final two patches in the > > series. Are you happy for this go via the tracing tree? > > > > Mark. > > > > diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c > > index 2555349303684..f0f3a2a82ca5a 100644 > > --- a/arch/arm64/kernel/patching.c > > +++ b/arch/arm64/kernel/patching.c > > @@ -30,20 +30,16 @@ static bool is_image_text(unsigned long addr) > > > > static void __kprobes *patch_map(void *addr, int fixmap) > > { > > - unsigned long uintaddr = (uintptr_t) addr; > > - bool image = is_image_text(uintaddr); > > struct page *page; > > > > - if (image) > > + if (is_image_text((unsigned long)addr)) > > page = phys_to_page(__pa_symbol(addr)); > > - else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) > > - page = vmalloc_to_page(addr); > > else > > - return addr; > > + page = vmalloc_to_page(addr); > > > > BUG_ON(!page); > > return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + > > - (uintaddr & ~PAGE_MASK)); > > + offset_in_page(addr)); > > nit: could be a single line but i guess it is up to the taste (and > subsystem maintainer). I.e. checkpatch will allow it at least. > > I don't mind it too much just mentioning for completeness. At that point it goes to 93 chars long, and I stuck with the existing line wrapping at 80 chars. I'd rather have a temporary 'phys_addr_t phys' variable and do: phys = page_to_phys(page) + offset_in_page(addr); return (void *)set_fixmap(fixmap, phys); ... but I'll leave this as-is for now. > > } > > > > static void __kprobes patch_unmap(int fixmap) > > If my assumption about the config flag holds this makes sense: > > Reviewed-by: Jarkko Sakkinen Thanks! I assume that should be "kernel.org", with an 'o' ;) Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel