From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Lendacky Subject: Re: [PATCH v5 32/32] x86/mm: Add support to make use of Secure Memory Encryption Date: Tue, 30 May 2017 10:37:03 -0500 Message-ID: <115ca39d-6ae7-f603-a415-ead7c4e8193d@amd.com> References: <20170418211612.10190.82788.stgit@tlendack-t1.amdoffice.net> <20170418212223.10190.85121.stgit@tlendack-t1.amdoffice.net> <20170519112703.voajtn4t7uy6nwa3@pd.tnic> <7c522f65-c5c8-9362-e1eb-d0765e3ea6c9@amd.com> <20170530145459.tyuy6veqxnrqkhgw@pd.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170530145459.tyuy6veqxnrqkhgw@pd.tnic> Content-Language: en-US Sender: owner-linux-mm@kvack.org To: Borislav Petkov Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Rik van Riel , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Toshimitsu Kani , Arnd Bergmann , Jonathan Corbet , Matt Fleming , "Michael S. Tsirkin" , Joerg Roedel , Konrad Rzeszutek Wilk , Paolo Bonzini , Larry Woodman , Brijesh Singh , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Andrey Ryabinin List-Id: linux-efi@vger.kernel.org On 5/30/2017 9:55 AM, Borislav Petkov wrote: > On Tue, May 30, 2017 at 09:38:36AM -0500, Tom Lendacky wrote: >> In this case we're running identity mapped and the "on" constant ends up >> as kernel address (0xffffffff81...) which results in a segfault. > > Would > > static const char *__on_str = "on"; > > ... > > if (!strncmp(buffer, __pa_nodebug(__on_str), 2)) > ... > > work? > > __phys_addr_nodebug() seems to pay attention to phys_base and > PAGE_OFFSET and so on... Except that phys_base hasn't been adjusted yet so that doesn't work either. > > I'd like to avoid that rip-relative address finding in inline asm which > looks fragile to me. I can define the command line option and the "on" and "off" values as character buffers in the function and initialize them on a per character basis (using a static string causes the same issues as referencing a string constant), i.e.: char cmdline_arg[] = {'m', 'e', 'm', '_', 'e', 'n', 'c', 'r', 'y', 'p', 't', '\0'}; char cmdline_off[] = {'o', 'f', 'f', '\0'}; char cmdline_on[] = {'o', 'n', '\0'}; It doesn't look the greatest, but it works and removes the need for the rip-relative addressing. Thanks, Tom > > Thanks. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org