Re: [PATCH] tpm: require to compile as part of the kernel

From: Jason Gunthorpe
Date: Fri Jun 29 2018 - 11:31:50 EST


On Fri, Jun 29, 2018 at 06:10:02PM +0300, Jarkko Sakkinen wrote:
> Do not allow to compile TPM core as a module. TPM defines a root of
> trust for integrity and keyring subsystems and should be always
> available and not be loaded from the user space. There is no a
> reasonable use case for a loadable module existing.
>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
> drivers/char/tpm/Kconfig | 2 +-
> include/linux/tpm.h | 3 +--
> 2 files changed, 2 insertions(+), 3 deletions(-)

This doesn't really make sense..

The kconfig method is that if IMA requires TPM it should declare so
and TPM will become non-modular because IMA is non-modular.

There are lots of legitimate use cases for TPM that don't involve IMA
or keyring.

> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 18c81cbe4704..9728771aecbd 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -3,7 +3,7 @@
> #
>
> menuconfig TCG_TPM
> - tristate "TPM Hardware Support"
> + bool "TPM Hardware Support"
> depends on HAS_IOMEM
> select SECURITYFS
> select CRYPTO
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 4609b94142d4..cefa61b12891 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -50,8 +50,7 @@ struct tpm_class_ops {
> void (*clk_enable)(struct tpm_chip *chip, bool value);
> };
>
> -#if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
> -
> +#if defined(CONFIG_TCG_TPM)

Huh. This new version is certainly right

Jason