From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7EE882DC33D; Fri, 7 Nov 2025 10:10:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762510226; cv=none; b=POVjR/+y3zhY6KBo3mSgcR3CKmG112wUzLnGKv6hujORQkKiIdHz7AJaJfm88qL50NMGEw5g1WDrDRrpITeIf2vajsKavqKLunohiWftDS3/NNU43cHzuUg5maV/FucOVOKdLxh7KNgtsiDOwCyB8qK1mwHDgbi1W8HJ1bucsAc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762510226; c=relaxed/simple; bh=fOgQDtqlVQWIBqxX53OOUmVK1mIb6jmBaOa0euHWYBw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=D8U+TBR5mu1PeT252+/iT9v3jxijF5ITK1tr1izOTU+7Zn4gWj1BKu1eU7zJorGn5LYqK4Oz8NgK0Eu6ah9eF3ONdOBbPRC1q8aTCxiERAm8yOQAHO3pVXxf/yKltiDuVrqtXF2kcOkuNha8wXqeJznlZa1sH1+CzOADEuPnhWc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=IBrvoXGc; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IBrvoXGc" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=PqT8GpjqV7V4Ir3awIVbzA8+VPhRFtrr00TKXqiZ7lA=; b=IBrvoXGcOJHDdCOMIpE8Xp0W6y ob3QvgnIrMYOanEwNsFEryZLmJUJCnJaQCT0zV+awTzc/g1ZpVSaAlWcxrrVRwjJjeUQZBfajSO9e z+CZlzahTnLXT0gSDFJ1HvRnxneBRvnadqMnXFSnXwVIvkyMahHu3Br5+Me4O5gCT1IAYoa/hOrvU P/2VT13RpIMprSKtXQCdToYXGzjpkRphQORm2RQ3k1kJJq7R8p/QS5oTkrVWQcYMW6oiZajktCJjk hqBuJX14y91pI2wcl/EdPQUN12fxh8ueOTlF7kam+mi9zkkS9XYWRj5CfSAvmv/0fgW7GlKA8rEX3 ZYh3kSgA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vHJPv-00000006Ygd-3M4o; Fri, 07 Nov 2025 10:10:05 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id B737B300325; Fri, 07 Nov 2025 11:10:03 +0100 (CET) Date: Fri, 7 Nov 2025 11:10:03 +0100 From: Peter Zijlstra To: Ard Biesheuvel Cc: Dave Hansen , Sohil Mehta , Andy Lutomirski , the arch/x86 maintainers , Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Jonathan Corbet , "H. Peter Anvin" , Josh Poimboeuf , "Kirill A . Shutemov" , Xin Li , David Woodhouse , Sean Christopherson , Rick P Edgecombe , Vegard Nossum , Andrew Cooper , Randy Dunlap , Geert Uytterhoeven , Kees Cook , Tony Luck , Alexander Shishkin , linux-doc@vger.kernel.org, Linux Kernel Mailing List , linux-efi@vger.kernel.org Subject: Re: [PATCH v11 5/9] x86/efi: Disable LASS while mapping the EFI runtime services Message-ID: <20251107101003.GB1618871@noisy.programming.kicks-ass.net> References: <20251029210310.1155449-1-sohil.mehta@intel.com> <20251029210310.1155449-6-sohil.mehta@intel.com> <3e9c4fdd-88a8-4597-9405-d865fb837d95@intel.com> <6dec8398-3f7c-44db-a30d-33593af0217f@intel.com> <20251107090406.GU3245006@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Nov 07, 2025 at 10:22:30AM +0100, Ard Biesheuvel wrote: > There is also PRM, which is much worse, as it permits devices in the > ACPI namespace to call firmware routines that are mapped privileged in > the OS address space in the same way. I objected to this at the time, > and asked for a facility where we could at least mark such code as > unprivileged (and run it as such) but this was ignored, as Intel and > MS had already sealed the deal and put this into production. This is > much worse than typical EFI routines, as the PRM code is ODM/OEM code > rather than something that comes from the upstream EFI implementation. > It is basically a dumping ground for code that used to run in SMM > because it was too ugly to run anywhere else. 'https://uefi.org/sites/default/files/resources/Platform Runtime Mechanism - with legal notice.pdf' Has on page 16, section 3.1: 8. PRM handlers must not contain any privileged instructions. So we should be able to actually run this crap in ring3, right?