Re: [PATCH] tpm: Add a helper for checking hwrng enabled

["Jarkko Sakkinen" <jarkko@kernel.org>]

On Thu Aug 10, 2023 at 6:08 PM EEST, Limonciello, Mario wrote:
>
>
> On 8/10/2023 10:07 AM, Jarkko Sakkinen wrote:
> > On Tue Aug 8, 2023 at 7:12 AM EEST, Mario Limonciello wrote:
> >> The same checks are repeated in 3 places to decide whether to use
> >> hwrng.  Consolidate these into a helper.
> >>
> >> Also this fixes a case that one of them was missing a check in the
> >> cleanup path.
> >>
> >> Fixes: 554b841d4703 ("tpm: Disable RNG for all AMD fTPMs")
> >> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> >> ---
> >>   drivers/char/tpm/tpm-chip.c | 19 ++++++++++++++-----
> >>   1 file changed, 14 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> >> index e904aae9771be..ea6b4013bc38f 100644
> >> --- a/drivers/char/tpm/tpm-chip.c
> >> +++ b/drivers/char/tpm/tpm-chip.c
> >> @@ -521,10 +521,20 @@ static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
> >>   	return tpm_get_random(chip, data, max);
> >>   }
> >>   
> >> +static bool tpm_is_hwrng_enabled(struct tpm_chip *chip)
> >> +{
> >> +	if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> >> +		return false;
> >> +	if (tpm_is_firmware_upgrade(chip))
> >> +		return false;
> >> +	if (chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED)
> >> +		return false;
> >> +	return true;
> >> +}
> >> +
> >>   static int tpm_add_hwrng(struct tpm_chip *chip)
> >>   {
> >> -	if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM) || tpm_is_firmware_upgrade(chip) ||
> >> -	    chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED)
> >> +	if (!tpm_is_hwrng_enabled(chip))
> >>   		return 0;
> >>   
> >>   	snprintf(chip->hwrng_name, sizeof(chip->hwrng_name),
> >> @@ -629,7 +639,7 @@ int tpm_chip_register(struct tpm_chip *chip)
> >>   	return 0;
> >>   
> >>   out_hwrng:
> >> -	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
> >> +	if (tpm_is_hwrng_enabled(chip))
> >>   		hwrng_unregister(&chip->hwrng);
> >>   out_ppi:
> >>   	tpm_bios_log_teardown(chip);
> >> @@ -654,8 +664,7 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
> >>   void tpm_chip_unregister(struct tpm_chip *chip)
> >>   {
> >>   	tpm_del_legacy_sysfs(chip);
> >> -	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip) &&
> >> -	    !(chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED))
> >> +	if (tpm_is_hwrng_enabled(chip))
> >>   		hwrng_unregister(&chip->hwrng);
> >>   	tpm_bios_log_teardown(chip);
> >>   	if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
> > 
> > Given my previous queries: should I apply this or revert and apply v3?
> > 
> > BR, Jarkko
>
> Linus picked it up already directly.

I came two days behind, sorry.

BR, Jarkko