linux-kernel - Re: [PATCH v5 29/32] x86/mm: Add support to encrypt the kernel in-place

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Date:   Wed, 31 May 2017 08:12:56 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <kexec@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <iommu@...ts.linux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 29/32] x86/mm: Add support to encrypt the kernel
 in-place

On 5/31/2017 4:51 AM, Borislav Petkov wrote:
> On Tue, May 30, 2017 at 11:39:07AM -0500, Tom Lendacky wrote:
>> Yes, it's from objtool:
>>
>> arch/x86/mm/mem_encrypt_boot.o: warning: objtool: .text+0xd2: return
>> instruction outside of a callable function
> 
> Oh, well, let's make it a global symbol then. Who knows, we might have
> to live-patch it someday :-)

Can do.

Thanks,
Tom

> 
> ---
> diff --git a/arch/x86/mm/mem_encrypt_boot.S b/arch/x86/mm/mem_encrypt_boot.S
> index fb58f9f953e3..7720b0050840 100644
> --- a/arch/x86/mm/mem_encrypt_boot.S
> +++ b/arch/x86/mm/mem_encrypt_boot.S
> @@ -47,9 +47,9 @@ ENTRY(sme_encrypt_execute)
>   	movq	%rdx, %r12		/* Kernel length */
>   
>   	/* Copy encryption routine into the workarea */
> -	movq	%rax, %rdi		/* Workarea encryption routine */
> -	leaq	.Lenc_start(%rip), %rsi	/* Encryption routine */
> -	movq	$(.Lenc_stop - .Lenc_start), %rcx	/* Encryption routine length */
> +	movq	%rax, %rdi				/* Workarea encryption routine */
> +	leaq	__enc_copy(%rip), %rsi			/* Encryption routine */
> +	movq	$(.L__enc_copy_end - __enc_copy), %rcx	/* Encryption routine length */
>   	rep	movsb
>   
>   	/* Setup registers for call */
> @@ -70,8 +70,7 @@ ENTRY(sme_encrypt_execute)
>   	ret
>   ENDPROC(sme_encrypt_execute)
>   
> -.Lenc_start:
> -ENTRY(sme_enc_routine)
> +ENTRY(__enc_copy)
>   /*
>    * Routine used to encrypt kernel.
>    *   This routine must be run outside of the kernel proper since
> @@ -147,5 +146,5 @@ ENTRY(sme_enc_routine)
>   	wrmsr
>   
>   	ret
> -ENDPROC(sme_enc_routine)
> -.Lenc_stop:
> +.L__enc_copy_end:
> +ENDPROC(__enc_copy)
>