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 BEFBD2FD1B3; Wed, 29 Apr 2026 13:51:46 +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=1777470710; cv=none; b=X8L+zPnZ3rIoTMO+mbhH5doowxTwHpY+3ofJO8dX1UTO8/KRsA0Fj7cDRs23kf072EKxU/FsuI526R2tbp1GWlaSVK1nhEOIAQjwCLK39kDcyaIfxQDugblgreFS41xqB3dJxsMG8cpuO4sAxbH2m66igXhdqRPS+usAl5GdKjw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777470710; c=relaxed/simple; bh=9ELD/DjcFqzDnlav/KpHjVLh1+VYuwo61V/4bESQjnU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EvHuT0NgxdSorzihTL4g8p3X0eU8rve44YL1IuZ5WshskPjN7c5mYjr/CkfJZL7iliOzlYq5P92BV+cQlTs6NS7tgmw+0Ft6eDIc1+S3TvO8CEVzljerTb+vt6husMH21tHTJp5tHbsvUoCwHv/kPobP1LlHW8U5Viej16XJEkA= 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=gX6jMWWv; 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="gX6jMWWv" 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 45D0E2574; Wed, 29 Apr 2026 06:51:39 -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 88EC53F62B; Wed, 29 Apr 2026 06:51:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777470704; bh=9ELD/DjcFqzDnlav/KpHjVLh1+VYuwo61V/4bESQjnU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gX6jMWWvzRfAvmOAyHfw3oN8bG5OkDuYdKN3FuWWM6nhaa2QUnNyeU/dyUa3NlDBi VXs6MpNaq7hopQBIK1wh64NZPzPhrdUFDqsIC1BKYJuqTwtkmHUbCfAApjLUnpBUHb gwlcI8mEEm00HYzB+UqwukBUQ6gsicOZH89qCdnE= Message-ID: <8a315ca2-3754-4a66-990e-55b85191aa6e@arm.com> Date: Wed, 29 Apr 2026 12:54:20 +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 , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , 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> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: <20260427153416.2103979-28-ardb+git@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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. - Kevin > + flags); > > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > @@ -1165,17 +1168,6 @@ static void __init map_mem(void) > __map_memblock(start, end, pgprot_tagged(PAGE_KERNEL), > flags); > } > - > - /* > - * 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() below (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. > - */ > - __map_memblock(kernel_start, kernel_end, PAGE_KERNEL, 0); > - memblock_clear_nomap(kernel_start, kernel_end - kernel_start); > } > > void mark_rodata_ro(void)