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

["Limonciello, Mario" <mario.limonciello@amd.com>]

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.