[v4] generate boot_aggregate log in IMA with TPM using CRB over FF-A

[PATCH v4 2/2] tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's built-in

Posted by Yeoreum Yun 3 months, 3 weeks ago

To generate the boot_aggregate log in the IMA subsystem using TPM PCR values,
the TPM driver must be built as built-in and must be probed before
the IMA subsystem is initialized.

However, when the TPM device operates over the FF-A protocol using the CRB interface,
probing fails and returns -EPROBE_DEFER
if the tpm_crb_ffa device — an FF-A device that provides
the communication interface to the tpm_crb driver — has not yet been probed.

This issue occurs because both crb_acpi_driver_init() and
tpm_crb_ffa_driver_init() are registered with device_initcall.
As a result, crb_acpi_driver_init() may be invoked before
tpm_crb_ffa_driver_init(), which is responsible for probing the tpm_crb_ffa device.

When this happens, IMA fails to detect the TPM device and
logs the following message:

  | ima: No TPM chip found, activating TPM-bypass!

Consequently, it cannot generate the boot_aggregate log with
the PCR values provided by the TPM.

To resolve this issue, the tpm_crb_ffa_init() function explicitly attempts to
probe the tpm_crb_ffa by register tpm_crb_ffa driver so that
when tpm_crb_ffa device is created before tpm_crb_ffa_init(),
probe the tpm_crb_ffa device in tpm_crb_ffa_init() to finish probe the
TPM device completely.

This ensures that the TPM device using CRB over FF-A
can be successfully probed, even if crb_acpi_driver_init() is called first.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 drivers/char/tpm/tpm_crb_ffa.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
index 4ead61f01299..462fcf610020 100644
--- a/drivers/char/tpm/tpm_crb_ffa.c
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -115,6 +115,7 @@ struct tpm_crb_ffa {
 };
 
 static struct tpm_crb_ffa *tpm_crb_ffa;
+static struct ffa_driver tpm_crb_ffa_driver;
 
 static int tpm_crb_ffa_to_linux_errno(int errno)
 {
@@ -168,13 +169,23 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
  */
 int tpm_crb_ffa_init(void)
 {
+	int ret = 0;
+
+	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
+		ret = ffa_register(&tpm_crb_ffa_driver);
+		if (ret) {
+			tpm_crb_ffa = ERR_PTR(-ENODEV);
+			return ret;
+		}
+	}
+
 	if (!tpm_crb_ffa)
-		return -ENOENT;
+		ret = -ENOENT;
 
 	if (IS_ERR_VALUE(tpm_crb_ffa))
-		return -ENODEV;
+		ret = -ENODEV;
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
 
@@ -369,7 +380,9 @@ static struct ffa_driver tpm_crb_ffa_driver = {
 	.id_table = tpm_crb_ffa_device_id,
 };
 
+#ifdef MODULE
 module_ffa_driver(tpm_crb_ffa_driver);
+#endif
 
 MODULE_AUTHOR("Arm");
 MODULE_DESCRIPTION("TPM CRB FFA driver");
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

Re: [PATCH v4 2/2] tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's built-in

Posted by Jarkko Sakkinen 3 months, 2 weeks ago

On Wed, Jun 18, 2025 at 11:23:02AM +0100, Yeoreum Yun wrote:
> To generate the boot_aggregate log in the IMA subsystem using TPM PCR values,
> the TPM driver must be built as built-in and must be probed before
> the IMA subsystem is initialized.
> 
> However, when the TPM device operates over the FF-A protocol using the CRB interface,
> probing fails and returns -EPROBE_DEFER
> if the tpm_crb_ffa device — an FF-A device that provides
> the communication interface to the tpm_crb driver — has not yet been probed.
> 
> This issue occurs because both crb_acpi_driver_init() and
> tpm_crb_ffa_driver_init() are registered with device_initcall.
> As a result, crb_acpi_driver_init() may be invoked before
> tpm_crb_ffa_driver_init(), which is responsible for probing the tpm_crb_ffa device.
> 
> When this happens, IMA fails to detect the TPM device and
> logs the following message:
> 
>   | ima: No TPM chip found, activating TPM-bypass!
> 
> Consequently, it cannot generate the boot_aggregate log with
> the PCR values provided by the TPM.
> 
> To resolve this issue, the tpm_crb_ffa_init() function explicitly attempts to
> probe the tpm_crb_ffa by register tpm_crb_ffa driver so that
> when tpm_crb_ffa device is created before tpm_crb_ffa_init(),
> probe the tpm_crb_ffa device in tpm_crb_ffa_init() to finish probe the
> TPM device completely.
> 
> This ensures that the TPM device using CRB over FF-A
> can be successfully probed, even if crb_acpi_driver_init() is called first.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---
>  drivers/char/tpm/tpm_crb_ffa.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
> index 4ead61f01299..462fcf610020 100644
> --- a/drivers/char/tpm/tpm_crb_ffa.c
> +++ b/drivers/char/tpm/tpm_crb_ffa.c
> @@ -115,6 +115,7 @@ struct tpm_crb_ffa {
>  };
>  
>  static struct tpm_crb_ffa *tpm_crb_ffa;
> +static struct ffa_driver tpm_crb_ffa_driver;
>  
>  static int tpm_crb_ffa_to_linux_errno(int errno)
>  {
> @@ -168,13 +169,23 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
>   */
>  int tpm_crb_ffa_init(void)
>  {
> +	int ret = 0;
> +
> +	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
> +		ret = ffa_register(&tpm_crb_ffa_driver);
> +		if (ret) {
> +			tpm_crb_ffa = ERR_PTR(-ENODEV);
> +			return ret;
> +		}
> +	}
> +
>  	if (!tpm_crb_ffa)
> -		return -ENOENT;
> +		ret = -ENOENT;
>  
>  	if (IS_ERR_VALUE(tpm_crb_ffa))
> -		return -ENODEV;
> +		ret = -ENODEV;
>  
> -	return 0;
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
>  
> @@ -369,7 +380,9 @@ static struct ffa_driver tpm_crb_ffa_driver = {
>  	.id_table = tpm_crb_ffa_device_id,
>  };
>  
> +#ifdef MODULE
>  module_ffa_driver(tpm_crb_ffa_driver);
> +#endif
>  
>  MODULE_AUTHOR("Arm");
>  MODULE_DESCRIPTION("TPM CRB FFA driver");
> -- 
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
> 

NAK

BR, Jarkko

Re: [PATCH v4 2/2] tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's built-in

Posted by Yeoreum Yun 3 months, 2 weeks ago

Hi Jarkkok,

> > --- a/drivers/char/tpm/tpm_crb_ffa.c
> > +++ b/drivers/char/tpm/tpm_crb_ffa.c
> > @@ -115,6 +115,7 @@ struct tpm_crb_ffa {
> >  };
> >
> >  static struct tpm_crb_ffa *tpm_crb_ffa;
> > +static struct ffa_driver tpm_crb_ffa_driver;
> >
> >  static int tpm_crb_ffa_to_linux_errno(int errno)
> >  {
> > @@ -168,13 +169,23 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
> >   */
> >  int tpm_crb_ffa_init(void)
> >  {
> > +	int ret = 0;
> > +
> > +	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
> > +		ret = ffa_register(&tpm_crb_ffa_driver);
> > +		if (ret) {
> > +			tpm_crb_ffa = ERR_PTR(-ENODEV);
> > +			return ret;
> > +		}
> > +	}
> > +
> >  	if (!tpm_crb_ffa)
> > -		return -ENOENT;
> > +		ret = -ENOENT;
> >
> >  	if (IS_ERR_VALUE(tpm_crb_ffa))
> > -		return -ENODEV;
> > +		ret = -ENODEV;
> >
> > -	return 0;
> > +	return ret;
> >  }
> >  EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
> >
> > @@ -369,7 +380,9 @@ static struct ffa_driver tpm_crb_ffa_driver = {
> >  	.id_table = tpm_crb_ffa_device_id,
> >  };
> >
> > +#ifdef MODULE
> >  module_ffa_driver(tpm_crb_ffa_driver);
> > +#endif
> >
> >  MODULE_AUTHOR("Arm");
> >  MODULE_DESCRIPTION("TPM CRB FFA driver");
> > --
> > LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
> >
>
> NAK

If you NACK with your comment on the cover letter,
Would you check the my comments please?

Actually, this wouldn't be fixed with the Kconfig.

Thanks

--
Sincerely,
Yeoreum Yun

Re: [PATCH v4 2/2] tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's built-in

Posted by Jarkko Sakkinen 3 months, 2 weeks ago

On Wed, Jun 25, 2025 at 11:37:44AM +0100, Yeoreum Yun wrote:
> Hi Jarkkok,
> 
> > > --- a/drivers/char/tpm/tpm_crb_ffa.c
> > > +++ b/drivers/char/tpm/tpm_crb_ffa.c
> > > @@ -115,6 +115,7 @@ struct tpm_crb_ffa {
> > >  };
> > >
> > >  static struct tpm_crb_ffa *tpm_crb_ffa;
> > > +static struct ffa_driver tpm_crb_ffa_driver;
> > >
> > >  static int tpm_crb_ffa_to_linux_errno(int errno)
> > >  {
> > > @@ -168,13 +169,23 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
> > >   */
> > >  int tpm_crb_ffa_init(void)
> > >  {
> > > +	int ret = 0;
> > > +
> > > +	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
> > > +		ret = ffa_register(&tpm_crb_ffa_driver);
> > > +		if (ret) {
> > > +			tpm_crb_ffa = ERR_PTR(-ENODEV);
> > > +			return ret;
> > > +		}
> > > +	}
> > > +
> > >  	if (!tpm_crb_ffa)
> > > -		return -ENOENT;
> > > +		ret = -ENOENT;
> > >
> > >  	if (IS_ERR_VALUE(tpm_crb_ffa))
> > > -		return -ENODEV;
> > > +		ret = -ENODEV;
> > >
> > > -	return 0;
> > > +	return ret;
> > >  }
> > >  EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
> > >
> > > @@ -369,7 +380,9 @@ static struct ffa_driver tpm_crb_ffa_driver = {
> > >  	.id_table = tpm_crb_ffa_device_id,
> > >  };
> > >
> > > +#ifdef MODULE
> > >  module_ffa_driver(tpm_crb_ffa_driver);
> > > +#endif
> > >
> > >  MODULE_AUTHOR("Arm");
> > >  MODULE_DESCRIPTION("TPM CRB FFA driver");
> > > --
> > > LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
> > >
> >
> > NAK
> 
> If you NACK with your comment on the cover letter,
> Would you check the my comments please?
> 
> Actually, this wouldn't be fixed with the Kconfig.

I got into the same page (see my response to your response at 0/2) :-)

Thanks for the patience.

> 
> Thanks
> 
> --
> Sincerely,
> Yeoreum Yun

BR, Jarkko

Re: [PATCH v4 2/2] tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's built-in

Posted by Mimi Zohar 3 months, 2 weeks ago

On Wed, 2025-06-18 at 11:23 +0100, Yeoreum Yun wrote:
> To generate the boot_aggregate log in the IMA subsystem using TPM PCR values,
> the TPM driver must be built as built-in and must be probed before
> the IMA subsystem is initialized.
> 
> However, when the TPM device operates over the FF-A protocol using the CRB interface,
> probing fails and returns -EPROBE_DEFER
> if the tpm_crb_ffa device — an FF-A device that provides
> the communication interface to the tpm_crb driver — has not yet been probed.
> 
> This issue occurs because both crb_acpi_driver_init() and
> tpm_crb_ffa_driver_init() are registered with device_initcall.
> As a result, crb_acpi_driver_init() may be invoked before
> tpm_crb_ffa_driver_init(), which is responsible for probing the tpm_crb_ffa device.
> 
> When this happens, IMA fails to detect the TPM device and
> logs the following message:
> 
>   | ima: No TPM chip found, activating TPM-bypass!
> 
> Consequently, it cannot generate the boot_aggregate log with
> the PCR values provided by the TPM.
> 
> To resolve this issue, the tpm_crb_ffa_init() function explicitly attempts to
> probe the tpm_crb_ffa by register tpm_crb_ffa driver so that
> when tpm_crb_ffa device is created before tpm_crb_ffa_init(),
> probe the tpm_crb_ffa device in tpm_crb_ffa_init() to finish probe the
> TPM device completely.
> 
> This ensures that the TPM device using CRB over FF-A
> can be successfully probed, even if crb_acpi_driver_init() is called first.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---
>  drivers/char/tpm/tpm_crb_ffa.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
> index 4ead61f01299..462fcf610020 100644
> --- a/drivers/char/tpm/tpm_crb_ffa.c
> +++ b/drivers/char/tpm/tpm_crb_ffa.c
> @@ -115,6 +115,7 @@ struct tpm_crb_ffa {
>  };
>  
>  static struct tpm_crb_ffa *tpm_crb_ffa;
> +static struct ffa_driver tpm_crb_ffa_driver;
>  
>  static int tpm_crb_ffa_to_linux_errno(int errno)
>  {
> @@ -168,13 +169,23 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
>   */
>  int tpm_crb_ffa_init(void)
>  {
> +	int ret = 0;
> +
> +	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
> +		ret = ffa_register(&tpm_crb_ffa_driver);
> +		if (ret) {
> +			tpm_crb_ffa = ERR_PTR(-ENODEV);
> +			return ret;
> +		}
> +	}
> +
>  	if (!tpm_crb_ffa)
> -		return -ENOENT;
> +		ret = -ENOENT;
>  
>  	if (IS_ERR_VALUE(tpm_crb_ffa))
> -		return -ENODEV;
> +		ret = -ENODEV;
>  
> -	return 0;
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
>  
> @@ -369,7 +380,9 @@ static struct ffa_driver tpm_crb_ffa_driver = {
>  	.id_table = tpm_crb_ffa_device_id,
>  };
>  
> +#ifdef MODULE
>  module_ffa_driver(tpm_crb_ffa_driver);
> +#endif
>  
>  MODULE_AUTHOR("Arm");
>  MODULE_DESCRIPTION("TPM CRB FFA driver");

LGTM.  Using ifndef/ifdef MODULE is similar to how module_init() works for both
builtin and loadable kernel modules. Except module_init() is on the
device_initcall().

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>