From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A0DDE34D926; Wed, 29 Apr 2026 14:30:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777473042; cv=none; b=Sb1N0SXeqSKFPhPIZWy8lgw/dIBGsm+xpfnWJ/DpkG3b6ENvykVw4wli4FBJu0/+uUbTrvPvdqSXCekHrSndNGT0WTAGTkyE5wbSGNmbZN4RbL5M3yqidDF1DgQaO65QsvmR2o1RWn7OIZFADEuC0PoleP0cLL0rCVXMe7Wbmoc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777473042; c=relaxed/simple; bh=yYUcrffafPaOm77R9dKuGdogYVbwK0I1WaJfySVSriM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LkA0PHCgLI72rYhpAOmlEiGrstWOuw34vxczp/aRPm1UGBCTuLsw+j62dltyfgca0/vbrOhcHqzQesjJRKUPdJcxtim7uJqyPC/R890jW2ay/nhD9vF1ZrB0gzwFzwUZtcieSNMVOxQKkDCQ8I9MTer/Rf9d6YPS1802ncjPFc8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=uyCgDRP/; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="uyCgDRP/" 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 82B5E1BCB; Wed, 29 Apr 2026 07:30:34 -0700 (PDT) Received: from [10.57.62.76] (unknown [10.57.62.76]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CE18C3F62B; Wed, 29 Apr 2026 07:30:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777473040; bh=yYUcrffafPaOm77R9dKuGdogYVbwK0I1WaJfySVSriM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=uyCgDRP/abTLDH1GF4bhkMX0G6Uck4hgIgyUBRuXB/drSr9g4g9bKGm5viIR9oygl cP56E8UqUoyxELCQIEk1OYF0wK9VrLrDWxYYc+nMmpWw8waMr9WI7BvBrp4N2WqRfM sg1QsRk3kKCYoyYwdAkATJHWTz8jmDVV0zK0xhLo= Message-ID: <2f5692d7-6589-4717-8258-f43d8227d74a@arm.com> Date: Wed, 29 Apr 2026 16:30:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 11/15] arm64: mm: Don't abuse memblock NOMAP to check for overlaps To: Ard Biesheuvel , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas , Mark Rutland , Ryan Roberts , Anshuman Khandual , Liz Prucka , Seth Jenkins , Kees Cook , Mike Rapoport , David Hildenbrand , Andrew Morton , linux-mm@kvack.org, linux-hardening@vger.kernel.org References: <20260427153416.2103979-17-ardb+git@google.com> <20260427153416.2103979-28-ardb+git@google.com> <8a315ca2-3754-4a66-990e-55b85191aa6e@arm.com> <1f9c1ca5-c15c-4a08-aa8c-cbe64f7f205b@app.fastmail.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: <1f9c1ca5-c15c-4a08-aa8c-cbe64f7f205b@app.fastmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/04/2026 16:23, Ard Biesheuvel wrote: > On Wed, 29 Apr 2026, at 12:54, Kevin Brodsky wrote: >> On 27/04/2026 17:34, Ard Biesheuvel wrote: >>> From: Ard Biesheuvel >>> >>> Now that the DRAM mapping routines respect existing table mappings and >>> contiguous block and page mappings, it is no longer needed to fiddle >>> with the memblock tables to set and clear the NOMAP attribute in order >>> to omit text and rodata when creating the linear map. >>> >>> Instead, map the kernel text and rodata alias first with the desired >>> attributes, so that they will not be remapped later with different >>> attributes when mapping the memblocks. >>> >>> Signed-off-by: Ard Biesheuvel >>> --- >>> arch/arm64/mm/mmu.c | 24 +++++++------------- >>> 1 file changed, 8 insertions(+), 16 deletions(-) >>> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>> index 5e2348b15783..1a4b4337d29a 100644 >>> --- a/arch/arm64/mm/mmu.c >>> +++ b/arch/arm64/mm/mmu.c >>> @@ -1148,12 +1148,15 @@ static void __init map_mem(void) >>> flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>> >>> /* >>> - * Take care not to create a writable alias for the >>> - * read-only text and rodata sections of the kernel image. >>> - * So temporarily mark them as NOMAP to skip mappings in >>> - * the following for-loop >>> + * Map the linear alias of the [_text, __init_begin) interval >>> + * as non-executable now, and remove the write permission in >>> + * mark_linear_text_alias_ro() above (which will be called after >>> + * alternative patching has completed). This makes the contents >>> + * of the region accessible to subsystems such as hibernate, >>> + * but protects it from inadvertent modification or execution. >>> */ >>> - memblock_mark_nomap(kernel_start, kernel_end - kernel_start); >>> + __map_memblock(kernel_start, kernel_end, pgprot_tagged(PAGE_KERNEL), >> Is it now necessary for that mapping to be tagged? If so, it should >> probably be called out in the commit message. >> > As you've pointed out, the initial r/w mapping of the linear alias of rodata > will need to be mapped tagged before moving the zero page there. So this patch > will just preserve that, rather than remapping the region tagged explicitly as > it does now. Right! I got lost in all the mappings :) - Kevin