Re: [PATCH v15 19/28] x86/tpm: Early TPM PCR extending driver

Dave Hansen
2025-12-16T21:53:48Z

I'm mostly spot-checking this to see what kind of shape it's in and how
much work and diligence has been applied in the last 8 months since v14.

On 12/15/25 15:33, Ross Philipson wrote:
...
> The driver could be extended for further operations if needed. This
> TPM dirver implementation relies as much as possible on existing mainline

<sigh>

v15 and no spell checking. :(

> --- /dev/null
> +++ b/arch/x86/boot/compressed/early_tpm_extend.c
> @@ -0,0 +1,601 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2010-2012 United States Government, as represented by
> + * the Secretary of Defense. All rights reserved.

IANAL, but this looks fishy.

It's theoretically fine to go grab random code off the Internet and
submit it to the kernel, given the correct license. But I do want to
know what its story is and where it came from.

I also seem to remember that there are special rules around the US
federal government's inability to hold copyrights. This seems worth at
least a mention ... somewhere.

This is helpful, for instance:

> + * based off of the original tools/vtpm_manager code base which is:
> + * Copyright (c) 2005, Intel Corp.
> + * All rights reserved.

so thanks for that one.

> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + *
> + * * Redistributions of source code must retain the above copyright
> + * notice, this list of conditions and the following disclaimer.
> + * * Redistributions in binary form must reproduce the above
> + * copyright notice, this list of conditions and the following
> + * disclaimer in the documentation and/or other materials provided
> + * with the distribution.
> + * * Neither the name of Intel Corporation nor the names of its
> + * contributors may be used to endorse or promote products derived
> + * from this software without specific prior written permission.
> + *
> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
> + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
> + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
> + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
> + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
> + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
> + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
> + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
> + * OF THE POSSIBILITY OF SUCH DAMAGE.
> + */

Also, IANAL, but this looks BSD-ish.

I would have kinda expected the SPDX header to say BSD-blah-blah and not
GPL-2.0-only.

I'd really appreciate if you could go have a huddle with your corporate
Open Source folks and make sure this is all proper. To me, it looks
fishy at _best_.

...
> +/*
> + * We're far too early to calibrate time. Assume a 5GHz processor (the upper
> + * end of the Fam19h range), which causes us to be wrong in the safe direction
> + * on slower systems.
> + */

https://docs.kernel.org/process/maintainer-tip.html#changelog

Imperative voice please.

...
> +static int __tis_recv_data(struct tpm_chip *chip, u8 *buf, int count)
> +{
> + int size = 0;
> + int burstcnt;
> +
> + while (size < count && __tis_wait_for_stat(chip, TPM_STS_DATA_AVAIL | TPM_STS_VALID, chip->timeout_c) == 0) {
> + burstcnt = __tis_get_burstcount(chip);
> +
> + for ( ; burstcnt > 0 && size < count; --burstcnt)
> + buf[size++] = tpm_read8(chip, TPM_DATA_FIFO(chip->locality));
> + }
> +
> + return size;
> +}
> +
> +/**
> + * tpm_tis_check_locality - Check if the given locality is the active one
> + * @chip: The TPM chip instance
> + * @loc: The locality to check
> + *
> + * Return: true - locality active, false - not active
> + */
> +bool tpm_tis_check_locality(struct tpm_chip *chip, int loc)
> +{
> + if ((tpm_read8(chip, TPM_ACCESS(loc)) & (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) == (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) {
> + chip->locality = loc;
> + return true;
> + }
> +
> + return false;
> +}
> +
> +/**
> + * tpm_tis_release_locality - Release the active locality
> + * @chip: The TPM chip instance
> + */
> +void tpm_tis_release_locality(struct tpm_chip *chip)
> +{
> + if ((tpm_read8(chip, TPM_ACCESS(chip->locality)) & (TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) == (TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID))
> + tpm_write8(chip, TPM_ACCESS(chip->locality), TPM_ACCESS_RELINQUISH_LOCALITY);
> +
> + chip->locality = 0;
> +}

I guess some folks aren't enforcing the 80-column limits. But this is
not even close. It's almost 80x2.

Has there even been an attempt to make this conform to kernel coding
style? What other checkpatch.pl warnings are being ignored?