[tpmdd-devel,v4,1/2] tpm: implement TPM 2.0 capability to get active PCR banks
diff mbox

Message ID 1484729090-16012-2-git-send-email-nayna@linux.vnet.ibm.com
State New
Headers show

Commit Message

Nayna Jan. 18, 2017, 8:44 a.m. UTC
This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
retrieve the active PCR banks from the TPM. This is needed
to enable extending all active banks as recommended by TPM 2.0
TCG Specification.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
---
 drivers/char/tpm/tpm.h      |  4 ++++
 drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

Comments

Jarkko Sakkinen Jan. 18, 2017, 1:45 p.m. UTC | #1
On Wed, Jan 18, 2017 at 03:44:49AM -0500, Nayna Jain wrote:
> This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
> retrieve the active PCR banks from the TPM. This is needed
> to enable extending all active banks as recommended by TPM 2.0
> TCG Specification.
> 
> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
> ---
>  drivers/char/tpm/tpm.h      |  4 ++++
>  drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 1ae9768..dddd573 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
>  };
>  
>  enum tpm2_capabilities {
> +	TPM2_CAP_PCRS		= 5,
>  	TPM2_CAP_TPM_PROPERTIES = 6,
>  };
>  
> @@ -187,6 +188,8 @@ struct tpm_chip {
>  
>  	const struct attribute_group *groups[3];
>  	unsigned int groups_cnt;
> +
> +	u16 active_banks[7];
>  #ifdef CONFIG_ACPI
>  	acpi_handle acpi_dev_handle;
>  	char ppi_version[TPM_PPI_VERSION_LEN + 1];
> @@ -545,4 +548,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
>  void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
>  unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
>  int tpm2_probe(struct tpm_chip *chip);
> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
>  #endif
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 6eda239..75a7546 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -998,3 +998,60 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>  		rc = -ENODEV;
>  	return rc;
>  }
> +
> +struct tpm2_pcr_selection {
> +	__be16  hash_alg;
> +	u8  size_of_select;
> +	u8  pcr_select[3];
> +} __packed;
> +
> +/**
> + * tpm2_get_pcr_allocation() - get TPM active PCR banks.
> + *
> + * @chip: TPM chip to use.
> + *
> + * Return: Same as with tpm_transmit_cmd.
> + */
> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
> +{
> +	struct tpm2_pcr_selection pcr_selection;
> +	struct tpm_buf buf;
> +	void *marker;
> +	unsigned int count = 0;

You shouldn't initialize 'count'.

> +	int rc;
> +	int i;
> +
> +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> +	if (rc)
> +		return rc;
> +
> +	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
> +	tpm_buf_append_u32(&buf, 0);
> +	tpm_buf_append_u32(&buf, 1);
> +
> +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
> +			      "get tpm pcr allocation");
> +	if (rc < 0)
> +		goto out;
> +
> +	count = be32_to_cpup(
> +		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
> +
> +	if (count > ARRAY_SIZE(chip->active_banks))
> +		return -ENODEV;
> +
> +	marker = &buf.data[TPM_HEADER_SIZE + 9];
> +	for (i = 0; i < count; i++) {
> +		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
> +		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
> +		marker = marker + sizeof(struct tpm2_pcr_selection);
> +	}
> +
> +out:
> +	if (count < ARRAY_SIZE(chip->active_banks))
> +		chip->active_banks[count] = 0;
> +
> +	tpm_buf_destroy(&buf);
> +
> +	return rc;
> +}
> -- 
> 2.5.0

Otherwise,

Reviewed-by: Jarkko Sakkinen <jarkko.sakkien@linux.intel.com>

/Jarkko

------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, SlashDot.org! http://sdm.link/slashdot
Nayna Jan. 18, 2017, 1:49 p.m. UTC | #2
On 01/18/2017 07:15 PM, Jarkko Sakkinen wrote:
> On Wed, Jan 18, 2017 at 03:44:49AM -0500, Nayna Jain wrote:
>> This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
>> retrieve the active PCR banks from the TPM. This is needed
>> to enable extending all active banks as recommended by TPM 2.0
>> TCG Specification.
>>
>> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
>> ---
>>   drivers/char/tpm/tpm.h      |  4 ++++
>>   drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 61 insertions(+)
>>
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index 1ae9768..dddd573 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>> @@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
>>   };
>>
>>   enum tpm2_capabilities {
>> +	TPM2_CAP_PCRS		= 5,
>>   	TPM2_CAP_TPM_PROPERTIES = 6,
>>   };
>>
>> @@ -187,6 +188,8 @@ struct tpm_chip {
>>
>>   	const struct attribute_group *groups[3];
>>   	unsigned int groups_cnt;
>> +
>> +	u16 active_banks[7];
>>   #ifdef CONFIG_ACPI
>>   	acpi_handle acpi_dev_handle;
>>   	char ppi_version[TPM_PPI_VERSION_LEN + 1];
>> @@ -545,4 +548,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
>>   void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
>>   unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
>>   int tpm2_probe(struct tpm_chip *chip);
>> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
>>   #endif
>> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
>> index 6eda239..75a7546 100644
>> --- a/drivers/char/tpm/tpm2-cmd.c
>> +++ b/drivers/char/tpm/tpm2-cmd.c
>> @@ -998,3 +998,60 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>>   		rc = -ENODEV;
>>   	return rc;
>>   }
>> +
>> +struct tpm2_pcr_selection {
>> +	__be16  hash_alg;
>> +	u8  size_of_select;
>> +	u8  pcr_select[3];
>> +} __packed;
>> +
>> +/**
>> + * tpm2_get_pcr_allocation() - get TPM active PCR banks.
>> + *
>> + * @chip: TPM chip to use.
>> + *
>> + * Return: Same as with tpm_transmit_cmd.
>> + */
>> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>> +{
>> +	struct tpm2_pcr_selection pcr_selection;
>> +	struct tpm_buf buf;
>> +	void *marker;
>> +	unsigned int count = 0;
>
> You shouldn't initialize 'count'.

It is initialized for reason below:

>
>> +	int rc;
>> +	int i;
>> +
>> +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
>> +	if (rc)
>> +		return rc;
>> +
>> +	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
>> +	tpm_buf_append_u32(&buf, 0);
>> +	tpm_buf_append_u32(&buf, 1);
>> +
>> +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
>> +			      "get tpm pcr allocation");
>> +	if (rc < 0)
>> +		goto out;

if  tpm_transmit_cmd()fails, it jumps to out:
where count is used in if(..).

Thanks & Regards,
    - Nayna

>> +
>> +	count = be32_to_cpup(
>> +		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
>> +
>> +	if (count > ARRAY_SIZE(chip->active_banks))
>> +		return -ENODEV;
>> +
>> +	marker = &buf.data[TPM_HEADER_SIZE + 9];
>> +	for (i = 0; i < count; i++) {
>> +		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
>> +		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
>> +		marker = marker + sizeof(struct tpm2_pcr_selection);
>> +	}
>> +
>> +out:
>> +	if (count < ARRAY_SIZE(chip->active_banks))
>> +		chip->active_banks[count] = 0;
>> +
>> +	tpm_buf_destroy(&buf);
>> +
>> +	return rc;
>> +}
>> --
>> 2.5.0
>
> Otherwise,
>
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkien@linux.intel.com>
>
> /Jarkko
>


------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, SlashDot.org! http://sdm.link/slashdot
Jarkko Sakkinen Jan. 19, 2017, 10:47 a.m. UTC | #3
On Wed, Jan 18, 2017 at 07:19:06PM +0530, Nayna wrote:
> 
> 
> On 01/18/2017 07:15 PM, Jarkko Sakkinen wrote:
> > On Wed, Jan 18, 2017 at 03:44:49AM -0500, Nayna Jain wrote:
> > > This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
> > > retrieve the active PCR banks from the TPM. This is needed
> > > to enable extending all active banks as recommended by TPM 2.0
> > > TCG Specification.
> > > 
> > > Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
> > > ---
> > >   drivers/char/tpm/tpm.h      |  4 ++++
> > >   drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
> > >   2 files changed, 61 insertions(+)
> > > 
> > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > > index 1ae9768..dddd573 100644
> > > --- a/drivers/char/tpm/tpm.h
> > > +++ b/drivers/char/tpm/tpm.h
> > > @@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
> > >   };
> > > 
> > >   enum tpm2_capabilities {
> > > +	TPM2_CAP_PCRS		= 5,
> > >   	TPM2_CAP_TPM_PROPERTIES = 6,
> > >   };
> > > 
> > > @@ -187,6 +188,8 @@ struct tpm_chip {
> > > 
> > >   	const struct attribute_group *groups[3];
> > >   	unsigned int groups_cnt;
> > > +
> > > +	u16 active_banks[7];
> > >   #ifdef CONFIG_ACPI
> > >   	acpi_handle acpi_dev_handle;
> > >   	char ppi_version[TPM_PPI_VERSION_LEN + 1];
> > > @@ -545,4 +548,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
> > >   void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
> > >   unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
> > >   int tpm2_probe(struct tpm_chip *chip);
> > > +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
> > >   #endif
> > > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> > > index 6eda239..75a7546 100644
> > > --- a/drivers/char/tpm/tpm2-cmd.c
> > > +++ b/drivers/char/tpm/tpm2-cmd.c
> > > @@ -998,3 +998,60 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> > >   		rc = -ENODEV;
> > >   	return rc;
> > >   }
> > > +
> > > +struct tpm2_pcr_selection {
> > > +	__be16  hash_alg;
> > > +	u8  size_of_select;
> > > +	u8  pcr_select[3];
> > > +} __packed;
> > > +
> > > +/**
> > > + * tpm2_get_pcr_allocation() - get TPM active PCR banks.
> > > + *
> > > + * @chip: TPM chip to use.
> > > + *
> > > + * Return: Same as with tpm_transmit_cmd.
> > > + */
> > > +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
> > > +{
> > > +	struct tpm2_pcr_selection pcr_selection;
> > > +	struct tpm_buf buf;
> > > +	void *marker;
> > > +	unsigned int count = 0;
> > 
> > You shouldn't initialize 'count'.
> 
> It is initialized for reason below:
> 
> > 
> > > +	int rc;
> > > +	int i;
> > > +
> > > +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> > > +	if (rc)
> > > +		return rc;
> > > +
> > > +	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
> > > +	tpm_buf_append_u32(&buf, 0);
> > > +	tpm_buf_append_u32(&buf, 1);
> > > +
> > > +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
> > > +			      "get tpm pcr allocation");
> > > +	if (rc < 0)
> > > +		goto out;
> 
> if  tpm_transmit_cmd()fails, it jumps to out:
> where count is used in if(..).

Why the out label is placed there and not after?

> 
> Thanks & Regards,
>    - Nayna
> 
> > > +
> > > +	count = be32_to_cpup(
> > > +		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
> > > +
> > > +	if (count > ARRAY_SIZE(chip->active_banks))
> > > +		return -ENODEV;

Hey, here's a regression (didn't notice it last time). You
nee to call tpm_buf_destroy().


> > > +
> > > +	marker = &buf.data[TPM_HEADER_SIZE + 9];
> > > +	for (i = 0; i < count; i++) {
> > > +		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
> > > +		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
> > > +		marker = marker + sizeof(struct tpm2_pcr_selection);
> > > +	}
> > > +
> > > +out:
> > > +	if (count < ARRAY_SIZE(chip->active_banks))
> > > +		chip->active_banks[count] = 0;
> > > +
> > > +	tpm_buf_destroy(&buf);
> > > +
> > > +	return rc;
> > > +}
> > > --
> > > 2.5.0
> > 
> > Otherwise,
> > 
> > Reviewed-by: Jarkko Sakkinen <jarkko.sakkien@linux.intel.com>
> > 
> > /Jarkko
> > 
> 

/Jarkko

------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, SlashDot.org! http://sdm.link/slashdot
Nayna Jan. 19, 2017, 1:34 p.m. UTC | #4
On 01/19/2017 04:17 PM, Jarkko Sakkinen wrote:
> On Wed, Jan 18, 2017 at 07:19:06PM +0530, Nayna wrote:
>>
>>
>> On 01/18/2017 07:15 PM, Jarkko Sakkinen wrote:
>>> On Wed, Jan 18, 2017 at 03:44:49AM -0500, Nayna Jain wrote:
>>>> This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
>>>> retrieve the active PCR banks from the TPM. This is needed
>>>> to enable extending all active banks as recommended by TPM 2.0
>>>> TCG Specification.
>>>>
>>>> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
>>>> ---
>>>>    drivers/char/tpm/tpm.h      |  4 ++++
>>>>    drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
>>>>    2 files changed, 61 insertions(+)
>>>>
>>>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>>>> index 1ae9768..dddd573 100644
>>>> --- a/drivers/char/tpm/tpm.h
>>>> +++ b/drivers/char/tpm/tpm.h
>>>> @@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
>>>>    };
>>>>
>>>>    enum tpm2_capabilities {
>>>> +	TPM2_CAP_PCRS		= 5,
>>>>    	TPM2_CAP_TPM_PROPERTIES = 6,
>>>>    };
>>>>
>>>> @@ -187,6 +188,8 @@ struct tpm_chip {
>>>>
>>>>    	const struct attribute_group *groups[3];
>>>>    	unsigned int groups_cnt;
>>>> +
>>>> +	u16 active_banks[7];
>>>>    #ifdef CONFIG_ACPI
>>>>    	acpi_handle acpi_dev_handle;
>>>>    	char ppi_version[TPM_PPI_VERSION_LEN + 1];
>>>> @@ -545,4 +548,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
>>>>    void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
>>>>    unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
>>>>    int tpm2_probe(struct tpm_chip *chip);
>>>> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
>>>>    #endif
>>>> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
>>>> index 6eda239..75a7546 100644
>>>> --- a/drivers/char/tpm/tpm2-cmd.c
>>>> +++ b/drivers/char/tpm/tpm2-cmd.c
>>>> @@ -998,3 +998,60 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>>>>    		rc = -ENODEV;
>>>>    	return rc;
>>>>    }
>>>> +
>>>> +struct tpm2_pcr_selection {
>>>> +	__be16  hash_alg;
>>>> +	u8  size_of_select;
>>>> +	u8  pcr_select[3];
>>>> +} __packed;
>>>> +
>>>> +/**
>>>> + * tpm2_get_pcr_allocation() - get TPM active PCR banks.
>>>> + *
>>>> + * @chip: TPM chip to use.
>>>> + *
>>>> + * Return: Same as with tpm_transmit_cmd.
>>>> + */
>>>> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>>>> +{
>>>> +	struct tpm2_pcr_selection pcr_selection;
>>>> +	struct tpm_buf buf;
>>>> +	void *marker;
>>>> +	unsigned int count = 0;
>>>
>>> You shouldn't initialize 'count'.
>>
>> It is initialized for reason below:
>>
>>>
>>>> +	int rc;
>>>> +	int i;
>>>> +
>>>> +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
>>>> +	if (rc)
>>>> +		return rc;
>>>> +
>>>> +	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
>>>> +	tpm_buf_append_u32(&buf, 0);
>>>> +	tpm_buf_append_u32(&buf, 1);
>>>> +
>>>> +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
>>>> +			      "get tpm pcr allocation");
>>>> +	if (rc < 0)
>>>> +		goto out;
>>
>> if  tpm_transmit_cmd()fails, it jumps to out:
>> where count is used in if(..).
>
> Why the out label is placed there and not after?

Since tpm2_get_pcr_allocation() returns from here as failure,
chip->active_banks doesn't get anytime initialized.

By placing it there, for failure, chip->active_bank[0] is initialized to 0.
Then its later use like in tpm_pcr_extend(), it loops on this array till 
there is a value "0"(considered as invalid) or reaches max size of array.

>
>>
>> Thanks & Regards,
>>     - Nayna
>>
>>>> +
>>>> +	count = be32_to_cpup(
>>>> +		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
>>>> +
>>>> +	if (count > ARRAY_SIZE(chip->active_banks))
>>>> +		return -ENODEV;
>
> Hey, here's a regression (didn't notice it last time). You
> nee to call tpm_buf_destroy().

Oh!! Yes, Thanks !!. I will fix this with:
rc = -ENODEV;
goto out;

Thanks & Regards
    - Nayna

>
>
>>>> +
>>>> +	marker = &buf.data[TPM_HEADER_SIZE + 9];
>>>> +	for (i = 0; i < count; i++) {
>>>> +		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
>>>> +		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
>>>> +		marker = marker + sizeof(struct tpm2_pcr_selection);
>>>> +	}
>>>> +
>>>> +out:
>>>> +	if (count < ARRAY_SIZE(chip->active_banks))
>>>> +		chip->active_banks[count] = 0;
>>>> +
>>>> +	tpm_buf_destroy(&buf);
>>>> +
>>>> +	return rc;
>>>> +}
>>>> --
>>>> 2.5.0
>>>
>>> Otherwise,
>>>
>>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkien@linux.intel.com>
>>>
>>> /Jarkko
>>>
>>
>
> /Jarkko
>


------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, SlashDot.org! http://sdm.link/slashdot

Patch
diff mbox

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 1ae9768..dddd573 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -127,6 +127,7 @@  enum tpm2_permanent_handles {
 };
 
 enum tpm2_capabilities {
+	TPM2_CAP_PCRS		= 5,
 	TPM2_CAP_TPM_PROPERTIES = 6,
 };
 
@@ -187,6 +188,8 @@  struct tpm_chip {
 
 	const struct attribute_group *groups[3];
 	unsigned int groups_cnt;
+
+	u16 active_banks[7];
 #ifdef CONFIG_ACPI
 	acpi_handle acpi_dev_handle;
 	char ppi_version[TPM_PPI_VERSION_LEN + 1];
@@ -545,4 +548,5 @@  int tpm2_auto_startup(struct tpm_chip *chip);
 void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
 unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
 int tpm2_probe(struct tpm_chip *chip);
+ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
 #endif
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 6eda239..75a7546 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -998,3 +998,60 @@  int tpm2_auto_startup(struct tpm_chip *chip)
 		rc = -ENODEV;
 	return rc;
 }
+
+struct tpm2_pcr_selection {
+	__be16  hash_alg;
+	u8  size_of_select;
+	u8  pcr_select[3];
+} __packed;
+
+/**
+ * tpm2_get_pcr_allocation() - get TPM active PCR banks.
+ *
+ * @chip: TPM chip to use.
+ *
+ * Return: Same as with tpm_transmit_cmd.
+ */
+ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
+{
+	struct tpm2_pcr_selection pcr_selection;
+	struct tpm_buf buf;
+	void *marker;
+	unsigned int count = 0;
+	int rc;
+	int i;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	if (rc)
+		return rc;
+
+	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
+	tpm_buf_append_u32(&buf, 0);
+	tpm_buf_append_u32(&buf, 1);
+
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
+			      "get tpm pcr allocation");
+	if (rc < 0)
+		goto out;
+
+	count = be32_to_cpup(
+		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
+
+	if (count > ARRAY_SIZE(chip->active_banks))
+		return -ENODEV;
+
+	marker = &buf.data[TPM_HEADER_SIZE + 9];
+	for (i = 0; i < count; i++) {
+		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
+		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
+		marker = marker + sizeof(struct tpm2_pcr_selection);
+	}
+
+out:
+	if (count < ARRAY_SIZE(chip->active_banks))
+		chip->active_banks[count] = 0;
+
+	tpm_buf_destroy(&buf);
+
+	return rc;
+}