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a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1598638430; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=/jYI5IHuv43D+ZADrXsFhwBXIJnV8i1FIyxJtyua/Yg=; b=KXRzfulyqoFzRZ+dj+HluE21PJnj0cjQ69UGDcWcPA264jRdoC9l65vRds3AZNoIGQLiw/ etQ7GAfkKPIWNnJokkDlepYsvcxMPquvY19el5NfnOAs2br3nC3Vjryk/KQaFohIqhnVUW NNFAZll3B7FQ4406XApoT0w5nSGLFcY= Date: Fri, 28 Aug 2020 20:13:46 +0200 From: Borislav Petkov To: Joerg Roedel Subject: Re: [PATCH v6 31/76] x86/head/64: Setup MSR_GS_BASE before calling into C code Message-ID: <20200828181346.GB19342@zn.tnic> References: <20200824085511.7553-1-joro@8bytes.org> <20200824085511.7553-32-joro@8bytes.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200824085511.7553-32-joro@8bytes.org> Cc: Juergen Gross , Tom Lendacky , x86@kernel.org, Mike Stunes , Kees Cook , kvm@vger.kernel.org, Peter Zijlstra , Cfir Cohen , Dave Hansen , linux-kernel@vger.kernel.org, Sean Christopherson , virtualization@lists.linux-foundation.org, Martin Radev , Joerg Roedel , Masami Hiramatsu , Andy Lutomirski , hpa@zytor.com, Erdem Aktas , David Rientjes , Dan Williams , Jiri Slaby X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Mon, Aug 24, 2020 at 10:54:26AM +0200, Joerg Roedel wrote: > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 2b2e91627221..800053219054 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -78,6 +78,14 @@ SYM_CODE_START_NOALIGN(startup_64) > call startup_64_setup_env > popq %rsi > > + /* > + * Setup %gs here already to make stack-protector work - it needs to be > + * setup again after the switch to kernel addresses. The address read > + * from initial_gs is a kernel address, so it needs to be adjusted first > + * for the identity mapping. > + */ > + movl $MSR_GS_BASE,%ecx I'm confused: is this missing those three lines: movl initial_gs(%rip),%eax movl initial_gs+4(%rip),%edx wrmsr as it is done in secondary_startup_64 ? Or why would you otherwise put 0xc0000101 in %ecx and not do anything with it... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization