linux-kernel - Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch early measurements

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Date:   Fri, 5 May 2023 18:34:54 +0200
From:   Simon Horman <horms@...nel.org>
To:     Ross Philipson <ross.philipson@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-crypto@...r.kernel.org, iommu@...ts.linux-foundation.org,
        kexec@...ts.infradead.org, linux-efi@...r.kernel.org,
        dpsmith@...rtussolutions.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, ardb@...nel.org, mjg59@...f.ucam.org,
        James.Bottomley@...senpartnership.com, luto@...capital.net,
        nivedita@...m.mit.edu, kanth.ghatraju@...cle.com,
        trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch
 early measurements

On Thu, May 04, 2023 at 02:50:15PM +0000, Ross Philipson wrote:
> From: "Daniel P. Smith" <dpsmith@...rtussolutions.com>
> 
> The SHA algorithms are necessary to measure configuration information into
> the TPM as early as possible before using the values. This implementation
> uses the established approach of #including the SHA libraries directly in
> the code since the compressed kernel is not uncompressed at this point.
> 
> The SHA code here has its origins in the code from the main kernel:
> 
> commit c4d5b9ffa31f ("crypto: sha1 - implement base layer for SHA-1")
> 
> That code could not be pulled directly into the setup portion of the
> compressed kernel because of other dependencies it pulls in. The result
> is this is a modified copy of that code that still leverages the core
> SHA algorithms.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@...rtussolutions.com>
> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
> ---
>  arch/x86/boot/compressed/Makefile       |  2 +
>  arch/x86/boot/compressed/early_sha1.c   | 97 +++++++++++++++++++++++++++++++++
>  arch/x86/boot/compressed/early_sha1.h   | 17 ++++++
>  arch/x86/boot/compressed/early_sha256.c |  7 +++
>  lib/crypto/sha1.c                       |  4 ++
>  lib/crypto/sha256.c                     |  8 +++
>  6 files changed, 135 insertions(+)
>  create mode 100644 arch/x86/boot/compressed/early_sha1.c
>  create mode 100644 arch/x86/boot/compressed/early_sha1.h
>  create mode 100644 arch/x86/boot/compressed/early_sha256.c
> 
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 6b6cfe6..1d327d4 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -112,6 +112,8 @@ vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
>  vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
>  vmlinux-objs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
>  
> +vmlinux-objs-$(CONFIG_SECURE_LAUNCH) += $(obj)/early_sha1.o $(obj)/early_sha256.o
> +
>  $(obj)/vmlinux: $(vmlinux-objs-y) FORCE
>  	$(call if_changed,ld)
>  
> diff --git a/arch/x86/boot/compressed/early_sha1.c b/arch/x86/boot/compressed/early_sha1.c
> new file mode 100644
> index 0000000..524ec23
> --- /dev/null
> +++ b/arch/x86/boot/compressed/early_sha1.c
> @@ -0,0 +1,97 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2022 Apertus Solutions, LLC.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/linkage.h>
> +#include <linux/string.h>
> +#include <asm/boot.h>
> +#include <asm/unaligned.h>
> +
> +#include "early_sha1.h"
> +
> +#define SHA1_DISABLE_EXPORT

Hi Ross,

I could be mistaken, but it seems to me that *_DISABLE_EXPORT
is a mechanism of this patch to disable exporting symbols
(use of EXPORT_SYMBOL), at compile time.

If so, this doesn't strike me as something that should be part of upstream
kernel code.  Could you consider dropping this part of the patch?

...