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

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Message-ID: <dad2d0b2-65d6-89bf-d2f0-7f420436e44c@apertussolutions.com>
Date:   Tue, 9 May 2023 12:09:14 -0400
From:   "Daniel P. Smith" <dpsmith@...rtussolutions.com>
To:     Simon Horman <horms@...nel.org>,
        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,
        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 5/5/23 12:34, Simon Horman wrote:
> 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?

Greetings Simon,

This was patterned after the move of sha256 to /lib. Upon re-inspection, 
it appears this has since been updated to use the __DISABLE_EXPORTS 
CFLAG mechanism of EXPORT_SYMBOL as a conditionally included rule in the 
Makefile where the desire to disable exporting is wanted. We will update 
this patch to follow the same pattern.

V/r,
Daniel P. Smith