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 5FAA43998BA; Mon, 1 Jun 2026 10:43:20 +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=1780310606; cv=none; b=rFrap4Oj5Q30O/TJM3WzJtIr8QPKOdDfsWM2mZcvRRB7GVOeRPAKrAiHl+a01AZldZzL2X/2ex6w+YyWm2N0SUdsRr881DeUiAMSxM6xPfxia2KPWnTDlGfXqP5d3RTvgleZnDIc4yuh63Ow2ebVJI620cCob4NCGkrT3raPZEE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780310606; c=relaxed/simple; bh=M9JAdG5DV/7YdqUDPO7phO8QpaY+0Cm/rOxjWCg5rg4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=n93qFIjtmjFukeiK1IJh/sIxKboiX4Jz75WefXYLBUoN8jLJQk+c35QddpbrJuJiVaJRffO/zCQQhS/lksEto2YKll8OezYqBq0fe8gP50+4XMy936vXxKwMDqFQqC0c1+TtZuVjJrwRDUwjv+Sndl3EzzbEGcBQppt9JjT3UB8= 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=F8Byp1c2; 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="F8Byp1c2" 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 8FA3F2696; Mon, 1 Jun 2026 03:43:14 -0700 (PDT) Received: from [10.57.94.8] (unknown [10.57.94.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A5FEA3F905; Mon, 1 Jun 2026 03:43:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1780310599; bh=M9JAdG5DV/7YdqUDPO7phO8QpaY+0Cm/rOxjWCg5rg4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=F8Byp1c2fESYbQpuqvr4AlWD6wXTjIviMOELOHMH97zUW2cYZrKpsdEn1LfcD6kXz UJIy+EgpBQi+xkE4miNGCmjzdHMfaUipsb7TkmxOblXjY1f60mslkBJ2kiKuhbuSA2 1yYR+XdZ5mwIByNNWcqVdJfgqcvs2DD6HSpBSnVM= Message-ID: Date: Mon, 1 Jun 2026 12:43:12 +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 v7 10/15] 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 , Jann Horn , linux-mm@kvack.org, linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org References: <20260529150150.1670604-17-ardb+git@google.com> <20260529150150.1670604-27-ardb+git@google.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: <20260529150150.1670604-27-ardb+git@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/05/2026 17:02, Ard Biesheuvel wrote: > From: Ard Biesheuvel > > Now that the linear region 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 > initial attributes and granularity, so that the loop iterating over the > memblocks will not remap it in a manner that prevents it from being > remapped with updated attributes later. > > Signed-off-by: Ard Biesheuvel Reviewed-by: Kevin Brodsky > --- > arch/arm64/mm/mmu.c | 26 ++++++++------------ > 1 file changed, 10 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 971996e46fd1..dcfca5667e5c 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1164,12 +1164,17 @@ 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 first > + * so that its write permissions can be removed later without the need > + * to split any block mappings created by the loop below. > + * > + * Write permissions are needed for alternatives patching, and will be > + * removed later by mark_linear_text_alias_ro() above. 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), > + flags); > > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > @@ -1181,17 +1186,6 @@ 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)