From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [PATCH v3 35/75] x86/head/64: Build k/head64.c with -fno-stack-protector Date: Tue, 19 May 2020 11:15:26 +0200 Message-ID: <20200519091526.GB444@zn.tnic> References: <20200428151725.31091-1-joro@8bytes.org> <20200428151725.31091-36-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20200428151725.31091-36-joro@8bytes.org> Sender: linux-kernel-owner@vger.kernel.org To: Joerg Roedel Cc: x86@kernel.org, hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Thomas Hellstrom , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Joerg Roedel , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Tue, Apr 28, 2020 at 05:16:45PM +0200, Joerg Roedel wrote: > From: Joerg Roedel > > The code inserted by the stack protector does not work in the early > boot environment because it uses the GS segment, at least with memory > encryption enabled. Can you elaborate on why is that a problem? The stack cookie is not generated that early yet so it should be comparing %gs:40 to 0. Also, it generates the checking code here only with CONFIG_STACKPROTECTOR_STRONG=y > Make sure the early code is compiled without this feature enabled. If so, then this should be with CONFIG_AMD_MEM_ENCRYPT ifdeffery around it. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette