linux-kernel - Re: [PATCH v6 04/14] x86: Secure Launch Resource Table header file

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Message-ID: <276bf3a2-2518-60cb-a745-5778aa5d66a5@apertussolutions.com>
Date:   Mon, 15 May 2023 16:58:50 -0400
From:   "Daniel P. Smith" <dpsmith@...rtussolutions.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>,
        Ross Philipson <ross.philipson@...cle.com>,
        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
Cc:     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 04/14] x86: Secure Launch Resource Table header file

On 5/10/23 19:04, Jarkko Sakkinen wrote:
> On Thu May 4, 2023 at 5:50 PM EEST, Ross Philipson wrote:
>> Introduce the Secure Launch Resource Table which forms the formal
>> interface between the pre and post launch code.
>>
>> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
>> ---
>>   include/linux/slr_table.h | 270 ++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 270 insertions(+)
>>   create mode 100644 include/linux/slr_table.h
>>
>> diff --git a/include/linux/slr_table.h b/include/linux/slr_table.h
>> new file mode 100644
>> index 0000000..d4b76e5
>> --- /dev/null
>> +++ b/include/linux/slr_table.h
>> @@ -0,0 +1,270 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Secure Launch Resource Table
>> + *
>> + * Copyright (c) 2023, Oracle and/or its affiliates.
>> + */
>> +
>> +#ifndef _LINUX_SLR_TABLE_H
>> +#define _LINUX_SLR_TABLE_H
>> +
>> +/* Put this in efi.h if it becomes a standard */
>> +#define SLR_TABLE_GUID				EFI_GUID(0x877a9b2a, 0x0385, 0x45d1, 0xa0, 0x34, 0x9d, 0xac, 0x9c, 0x9e, 0x56, 0x5f)
>> +
>> +/* SLR table header values */
>> +#define SLR_TABLE_MAGIC		0x4452544d
>> +#define SLR_TABLE_REVISION	1
>> +
>> +/* Current revisions for the policy and UEFI config */
>> +#define SLR_POLICY_REVISION		1
>> +#define SLR_UEFI_CONFIG_REVISION	1
>> +
>> +/* SLR defined architectures */
>> +#define SLR_INTEL_TXT		1
>> +#define SLR_AMD_SKINIT		2
>> +
>> +/* SLR defined bootloaders */
>> +#define SLR_BOOTLOADER_INVALID	0
>> +#define SLR_BOOTLOADER_GRUB	1
>> +
>> +/* Log formats */
>> +#define SLR_DRTM_TPM12_LOG	1
>> +#define SLR_DRTM_TPM20_LOG	2
>> +
>> +/* DRTM Policy Entry Flags */
>> +#define SLR_POLICY_FLAG_MEASURED	0x1
>> +#define SLR_POLICY_IMPLICIT_SIZE	0x2
>> +
>> +/* Array Lengths */
>> +#define TPM_EVENT_INFO_LENGTH		32
>> +#define TXT_VARIABLE_MTRRS_LENGTH	32
>> +
>> +/* Tags */
>> +#define SLR_ENTRY_INVALID	0x0000
>> +#define SLR_ENTRY_DL_INFO	0x0001
>> +#define SLR_ENTRY_LOG_INFO	0x0002
>> +#define SLR_ENTRY_ENTRY_POLICY	0x0003
>> +#define SLR_ENTRY_INTEL_INFO	0x0004
>> +#define SLR_ENTRY_AMD_INFO	0x0005
>> +#define SLR_ENTRY_ARM_INFO	0x0006
>> +#define SLR_ENTRY_UEFI_INFO	0x0007
>> +#define SLR_ENTRY_UEFI_CONFIG	0x0008
>> +#define SLR_ENTRY_END		0xffff
> 
> "Enums are preferred when defining several related constants."
> 
> See:
> 
> https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl

These values are only used for a u16 field in a packed structure. 
Correct me if I am mistaken, but if an enum is used this will result in 
type/casting handling to/from the u16 which would negate some of the 
main benefits of using an enum.

v/r,
dps