diff mbox series

efi_loader: check tcg2 protocol installation outside the TCG protocol

Message ID 20211125060727.26093-1-masahisa.kojima@linaro.org
State Superseded
Headers show
Series efi_loader: check tcg2 protocol installation outside the TCG protocol | expand

Commit Message

Masahisa Kojima Nov. 25, 2021, 6:07 a.m. UTC
There are functions that calls tcg2_agile_log_append() outside
of the TCG protocol invocation (e.g tcg2_measure_pe_image).
These functions must to check that tcg2 protocol is installed.
If not, measurement shall be skipped.

Together with above change, this commit also removes the
unnecessary tcg2_uninit() call in efi_tcg2_register(),
refactors efi_tcg2_register() not to include the process
that is not related to the tcg2 protocol registration.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
---
 include/efi_loader.h       |  4 ++
 lib/efi_loader/efi_setup.c |  3 ++
 lib/efi_loader/efi_tcg2.c  | 89 +++++++++++++++++++++++++++++++-------
 3 files changed, 81 insertions(+), 15 deletions(-)

Comments

Ilias Apalodimas Nov. 25, 2021, 8:24 a.m. UTC | #1
Hello Kojima-san

On Thu, 25 Nov 2021 at 08:04, Masahisa Kojima
<masahisa.kojima@linaro.org> wrote:
>
> There are functions that calls tcg2_agile_log_append() outside
> of the TCG protocol invocation (e.g tcg2_measure_pe_image).
> These functions must to check that tcg2 protocol is installed.
> If not, measurement shall be skipped.
>
> Together with above change, this commit also removes the
> unnecessary tcg2_uninit() call in efi_tcg2_register(),
> refactors efi_tcg2_register() not to include the process
> that is not related to the tcg2 protocol registration.
>
> Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
> ---
>  include/efi_loader.h       |  4 ++
>  lib/efi_loader/efi_setup.c |  3 ++
>  lib/efi_loader/efi_tcg2.c  | 89 +++++++++++++++++++++++++++++++-------
>  3 files changed, 81 insertions(+), 15 deletions(-)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index d52e399841..fe29c10906 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -525,6 +525,10 @@ efi_status_t efi_disk_register(void);
>  efi_status_t efi_rng_register(void);
>  /* Called by efi_init_obj_list() to install EFI_TCG2_PROTOCOL */
>  efi_status_t efi_tcg2_register(void);
> +/* Called by efi_init_obj_list() to do the required setup for the measurement */
> +efi_status_t efi_tcg2_setup_measurement(void);
> +/* Called by efi_init_obj_list() to do initial measurement */
> +efi_status_t efi_tcg2_do_initial_measurement(void);
>  /* measure the pe-coff image, extend PCR and add Event Log */
>  efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
>                                    struct efi_loaded_image_obj *handle,
> diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> index a2338d74af..781d10590d 100644
> --- a/lib/efi_loader/efi_setup.c
> +++ b/lib/efi_loader/efi_setup.c
> @@ -271,6 +271,9 @@ efi_status_t efi_init_obj_list(void)
>                 ret = efi_tcg2_register();
>                 if (ret != EFI_SUCCESS)
>                         goto out;
> +
> +               efi_tcg2_setup_measurement();
> +               efi_tcg2_do_initial_measurement();
>         }
>
>         /* Secure boot */
> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> index 8c1f22e337..46300cae79 100644
> --- a/lib/efi_loader/efi_tcg2.c
> +++ b/lib/efi_loader/efi_tcg2.c
> @@ -153,6 +153,20 @@ static u16 alg_to_len(u16 hash_alg)
>         return 0;
>  }
>
> +/**
> + * is_tcg2_protocol_installed - chech whether tcg2 protocol is installed
> + *
> + * @Return: true if tcg2 protocol is installed, false if not
> + */
> +bool is_tcg2_protocol_installed(void)
> +{
> +       struct efi_handler *handler;
> +       efi_status_t ret;
> +
> +       ret = efi_search_protocol(efi_root, &efi_guid_tcg2_protocol, &handler);
> +       return ((ret == EFI_SUCCESS) ? true : false);
> +}
> +
>  static u32 tcg_event_final_size(struct tpml_digest_values *digest_list)
>  {
>         u32 len;
> @@ -886,6 +900,9 @@ efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
>         IMAGE_NT_HEADERS32 *nt;
>         struct efi_handler *handler;
>
> +       if (!is_tcg2_protocol_installed())
> +               return EFI_NOT_READY;
> +
>         ret = platform_get_tpm2_device(&dev);
>         if (ret != EFI_SUCCESS)
>                 return ret;
> @@ -1759,6 +1776,9 @@ efi_status_t efi_tcg2_measure_efi_app_invocation(struct efi_loaded_image_obj *ha
>         u32 event = 0;
>         struct smbios_entry *entry;
>
> +       if (!is_tcg2_protocol_installed())
> +               return EFI_NOT_READY;
> +
>         if (tcg2_efi_app_invoked)
>                 return EFI_SUCCESS;
>
> @@ -1809,6 +1829,9 @@ efi_status_t efi_tcg2_measure_efi_app_exit(void)
>         efi_status_t ret;
>         struct udevice *dev;
>
> +       if (!is_tcg2_protocol_installed())
> +               return EFI_NOT_READY;
> +
>         ret = platform_get_tpm2_device(&dev);
>         if (ret != EFI_SUCCESS)
>                 return ret;
> @@ -1833,6 +1856,11 @@ efi_tcg2_notify_exit_boot_services(struct efi_event *event, void *context)
>
>         EFI_ENTRY("%p, %p", event, context);
>
> +       if (!is_tcg2_protocol_installed()) {
> +               ret =  EFI_NOT_READY;
> +               goto out;
> +       }
> +
>         event_log.ebs_called = true;
>         ret = platform_get_tpm2_device(&dev);
>         if (ret != EFI_SUCCESS)
> @@ -1863,6 +1891,9 @@ efi_status_t efi_tcg2_notify_exit_boot_services_failed(void)
>         struct udevice *dev;
>         efi_status_t ret;
>
> +       if (!is_tcg2_protocol_installed())
> +               return EFI_NOT_READY;
> +
>         ret = platform_get_tpm2_device(&dev);
>         if (ret != EFI_SUCCESS)
>                 goto out;
> @@ -1932,6 +1963,45 @@ error:
>         return ret;
>  }
>
> +/**
> + * efi_tcg2_setup_measurement() - setup for the measurement
> + *
> + * Return:     status code
> + */
> +efi_status_t efi_tcg2_setup_measurement(void)
> +{
> +       efi_status_t ret;
> +       struct efi_event *event;
> +
> +       ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
> +                              efi_tcg2_notify_exit_boot_services, NULL,
> +                              NULL, &event);
> +
> +       return ret;
> +}
> +
> +/**
> + * efi_tcg2_do_initial_measurement() - do initial measurement
> + *
> + * Return:     status code
> + */
> +efi_status_t efi_tcg2_do_initial_measurement(void)
> +{
> +       efi_status_t ret;
> +       struct udevice *dev;
> +
> +       ret = platform_get_tpm2_device(&dev);
> +       if (ret != EFI_SUCCESS)
> +               goto out;
> +
> +       ret = tcg2_measure_secure_boot_variable(dev);
> +       if (ret != EFI_SUCCESS)
> +               goto out;
> +
> +out:
> +       return ret;
> +}
> +
>  /**
>   * efi_tcg2_register() - register EFI_TCG2_PROTOCOL
>   *
> @@ -1943,7 +2013,6 @@ efi_status_t efi_tcg2_register(void)
>  {
>         efi_status_t ret = EFI_SUCCESS;
>         struct udevice *dev;
> -       struct efi_event *event;
>         u32 err;
>
>         ret = platform_get_tpm2_device(&dev);
> @@ -1969,6 +2038,10 @@ efi_status_t efi_tcg2_register(void)
>                 goto fail;
>         }
>
> +       /*
> +        * efi_add_protocol() is called at last on purpose.
> +        * tcg2_uninit() does not uninstall the tcg2 protocol, but it is intended.
> +        */
>         ret = efi_add_protocol(efi_root, &efi_guid_tcg2_protocol,
>                                (void *)&efi_tcg2_protocol);
>         if (ret != EFI_SUCCESS) {
> @@ -1976,20 +2049,6 @@ efi_status_t efi_tcg2_register(void)
>                 goto fail;
>         }
>
> -       ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
> -                              efi_tcg2_notify_exit_boot_services, NULL,
> -                              NULL, &event);
> -       if (ret != EFI_SUCCESS) {
> -               tcg2_uninit();
> -               goto fail;
> -       }
> -
> -       ret = tcg2_measure_secure_boot_variable(dev);
> -       if (ret != EFI_SUCCESS) {
> -               tcg2_uninit();
> -               goto fail;
> -       }
> -
>         return ret;
>
>  fail:
> --
> 2.17.1
>

This looks reasonable.  I've just finished reviewing Ruchika's
patchset adding TF-A eventlog support though [1]. Can you please
rebase this on top of that series?


[1] https://lore.kernel.org/u-boot/CAC_iWjLPfwos2_x9e536jxwufQ3g7JhuzyEBf8s70MBEqfOadA@mail.gmail.com/

Thanks
/Ilias
Masahisa Kojima Nov. 25, 2021, 11:34 a.m. UTC | #2
Hi Ilias,

On Thu, 25 Nov 2021 at 17:25, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> Hello Kojima-san
>
> On Thu, 25 Nov 2021 at 08:04, Masahisa Kojima
> <masahisa.kojima@linaro.org> wrote:
> >
> > There are functions that calls tcg2_agile_log_append() outside
> > of the TCG protocol invocation (e.g tcg2_measure_pe_image).
> > These functions must to check that tcg2 protocol is installed.
> > If not, measurement shall be skipped.
> >
> > Together with above change, this commit also removes the
> > unnecessary tcg2_uninit() call in efi_tcg2_register(),
> > refactors efi_tcg2_register() not to include the process
> > that is not related to the tcg2 protocol registration.
> >
> > Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
> > ---
> >  include/efi_loader.h       |  4 ++
> >  lib/efi_loader/efi_setup.c |  3 ++
> >  lib/efi_loader/efi_tcg2.c  | 89 +++++++++++++++++++++++++++++++-------
> >  3 files changed, 81 insertions(+), 15 deletions(-)
> >
> > diff --git a/include/efi_loader.h b/include/efi_loader.h
> > index d52e399841..fe29c10906 100644
> > --- a/include/efi_loader.h
> > +++ b/include/efi_loader.h
> > @@ -525,6 +525,10 @@ efi_status_t efi_disk_register(void);
> >  efi_status_t efi_rng_register(void);
> >  /* Called by efi_init_obj_list() to install EFI_TCG2_PROTOCOL */
> >  efi_status_t efi_tcg2_register(void);
> > +/* Called by efi_init_obj_list() to do the required setup for the measurement */
> > +efi_status_t efi_tcg2_setup_measurement(void);
> > +/* Called by efi_init_obj_list() to do initial measurement */
> > +efi_status_t efi_tcg2_do_initial_measurement(void);
> >  /* measure the pe-coff image, extend PCR and add Event Log */
> >  efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
> >                                    struct efi_loaded_image_obj *handle,
> > diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> > index a2338d74af..781d10590d 100644
> > --- a/lib/efi_loader/efi_setup.c
> > +++ b/lib/efi_loader/efi_setup.c
> > @@ -271,6 +271,9 @@ efi_status_t efi_init_obj_list(void)
> >                 ret = efi_tcg2_register();
> >                 if (ret != EFI_SUCCESS)
> >                         goto out;
> > +
> > +               efi_tcg2_setup_measurement();
> > +               efi_tcg2_do_initial_measurement();
> >         }
> >
> >         /* Secure boot */
> > diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> > index 8c1f22e337..46300cae79 100644
> > --- a/lib/efi_loader/efi_tcg2.c
> > +++ b/lib/efi_loader/efi_tcg2.c
> > @@ -153,6 +153,20 @@ static u16 alg_to_len(u16 hash_alg)
> >         return 0;
> >  }
> >
> > +/**
> > + * is_tcg2_protocol_installed - chech whether tcg2 protocol is installed
> > + *
> > + * @Return: true if tcg2 protocol is installed, false if not
> > + */
> > +bool is_tcg2_protocol_installed(void)
> > +{
> > +       struct efi_handler *handler;
> > +       efi_status_t ret;
> > +
> > +       ret = efi_search_protocol(efi_root, &efi_guid_tcg2_protocol, &handler);
> > +       return ((ret == EFI_SUCCESS) ? true : false);
> > +}
> > +
> >  static u32 tcg_event_final_size(struct tpml_digest_values *digest_list)
> >  {
> >         u32 len;
> > @@ -886,6 +900,9 @@ efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
> >         IMAGE_NT_HEADERS32 *nt;
> >         struct efi_handler *handler;
> >
> > +       if (!is_tcg2_protocol_installed())
> > +               return EFI_NOT_READY;
> > +
> >         ret = platform_get_tpm2_device(&dev);
> >         if (ret != EFI_SUCCESS)
> >                 return ret;
> > @@ -1759,6 +1776,9 @@ efi_status_t efi_tcg2_measure_efi_app_invocation(struct efi_loaded_image_obj *ha
> >         u32 event = 0;
> >         struct smbios_entry *entry;
> >
> > +       if (!is_tcg2_protocol_installed())
> > +               return EFI_NOT_READY;
> > +
> >         if (tcg2_efi_app_invoked)
> >                 return EFI_SUCCESS;
> >
> > @@ -1809,6 +1829,9 @@ efi_status_t efi_tcg2_measure_efi_app_exit(void)
> >         efi_status_t ret;
> >         struct udevice *dev;
> >
> > +       if (!is_tcg2_protocol_installed())
> > +               return EFI_NOT_READY;
> > +
> >         ret = platform_get_tpm2_device(&dev);
> >         if (ret != EFI_SUCCESS)
> >                 return ret;
> > @@ -1833,6 +1856,11 @@ efi_tcg2_notify_exit_boot_services(struct efi_event *event, void *context)
> >
> >         EFI_ENTRY("%p, %p", event, context);
> >
> > +       if (!is_tcg2_protocol_installed()) {
> > +               ret =  EFI_NOT_READY;
> > +               goto out;
> > +       }
> > +
> >         event_log.ebs_called = true;
> >         ret = platform_get_tpm2_device(&dev);
> >         if (ret != EFI_SUCCESS)
> > @@ -1863,6 +1891,9 @@ efi_status_t efi_tcg2_notify_exit_boot_services_failed(void)
> >         struct udevice *dev;
> >         efi_status_t ret;
> >
> > +       if (!is_tcg2_protocol_installed())
> > +               return EFI_NOT_READY;
> > +
> >         ret = platform_get_tpm2_device(&dev);
> >         if (ret != EFI_SUCCESS)
> >                 goto out;
> > @@ -1932,6 +1963,45 @@ error:
> >         return ret;
> >  }
> >
> > +/**
> > + * efi_tcg2_setup_measurement() - setup for the measurement
> > + *
> > + * Return:     status code
> > + */
> > +efi_status_t efi_tcg2_setup_measurement(void)
> > +{
> > +       efi_status_t ret;
> > +       struct efi_event *event;
> > +
> > +       ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
> > +                              efi_tcg2_notify_exit_boot_services, NULL,
> > +                              NULL, &event);
> > +
> > +       return ret;
> > +}
> > +
> > +/**
> > + * efi_tcg2_do_initial_measurement() - do initial measurement
> > + *
> > + * Return:     status code
> > + */
> > +efi_status_t efi_tcg2_do_initial_measurement(void)
> > +{
> > +       efi_status_t ret;
> > +       struct udevice *dev;
> > +
> > +       ret = platform_get_tpm2_device(&dev);
> > +       if (ret != EFI_SUCCESS)
> > +               goto out;
> > +
> > +       ret = tcg2_measure_secure_boot_variable(dev);
> > +       if (ret != EFI_SUCCESS)
> > +               goto out;
> > +
> > +out:
> > +       return ret;
> > +}
> > +
> >  /**
> >   * efi_tcg2_register() - register EFI_TCG2_PROTOCOL
> >   *
> > @@ -1943,7 +2013,6 @@ efi_status_t efi_tcg2_register(void)
> >  {
> >         efi_status_t ret = EFI_SUCCESS;
> >         struct udevice *dev;
> > -       struct efi_event *event;
> >         u32 err;
> >
> >         ret = platform_get_tpm2_device(&dev);
> > @@ -1969,6 +2038,10 @@ efi_status_t efi_tcg2_register(void)
> >                 goto fail;
> >         }
> >
> > +       /*
> > +        * efi_add_protocol() is called at last on purpose.
> > +        * tcg2_uninit() does not uninstall the tcg2 protocol, but it is intended.
> > +        */
> >         ret = efi_add_protocol(efi_root, &efi_guid_tcg2_protocol,
> >                                (void *)&efi_tcg2_protocol);
> >         if (ret != EFI_SUCCESS) {
> > @@ -1976,20 +2049,6 @@ efi_status_t efi_tcg2_register(void)
> >                 goto fail;
> >         }
> >
> > -       ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
> > -                              efi_tcg2_notify_exit_boot_services, NULL,
> > -                              NULL, &event);
> > -       if (ret != EFI_SUCCESS) {
> > -               tcg2_uninit();
> > -               goto fail;
> > -       }
> > -
> > -       ret = tcg2_measure_secure_boot_variable(dev);
> > -       if (ret != EFI_SUCCESS) {
> > -               tcg2_uninit();
> > -               goto fail;
> > -       }
> > -
> >         return ret;
> >
> >  fail:
> > --
> > 2.17.1
> >
>
> This looks reasonable.  I've just finished reviewing Ruchika's
> patchset adding TF-A eventlog support though [1]. Can you please
> rebase this on top of that series?

I have sent the rebased v2 patch.

Thanks,
Masahisa Kojima

>
>
> [1] https://lore.kernel.org/u-boot/CAC_iWjLPfwos2_x9e536jxwufQ3g7JhuzyEBf8s70MBEqfOadA@mail.gmail.com/
>
> Thanks
> /Ilias
diff mbox series

Patch

diff --git a/include/efi_loader.h b/include/efi_loader.h
index d52e399841..fe29c10906 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -525,6 +525,10 @@  efi_status_t efi_disk_register(void);
 efi_status_t efi_rng_register(void);
 /* Called by efi_init_obj_list() to install EFI_TCG2_PROTOCOL */
 efi_status_t efi_tcg2_register(void);
+/* Called by efi_init_obj_list() to do the required setup for the measurement */
+efi_status_t efi_tcg2_setup_measurement(void);
+/* Called by efi_init_obj_list() to do initial measurement */
+efi_status_t efi_tcg2_do_initial_measurement(void);
 /* measure the pe-coff image, extend PCR and add Event Log */
 efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
 				   struct efi_loaded_image_obj *handle,
diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
index a2338d74af..781d10590d 100644
--- a/lib/efi_loader/efi_setup.c
+++ b/lib/efi_loader/efi_setup.c
@@ -271,6 +271,9 @@  efi_status_t efi_init_obj_list(void)
 		ret = efi_tcg2_register();
 		if (ret != EFI_SUCCESS)
 			goto out;
+
+		efi_tcg2_setup_measurement();
+		efi_tcg2_do_initial_measurement();
 	}
 
 	/* Secure boot */
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index 8c1f22e337..46300cae79 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -153,6 +153,20 @@  static u16 alg_to_len(u16 hash_alg)
 	return 0;
 }
 
+/**
+ * is_tcg2_protocol_installed - chech whether tcg2 protocol is installed
+ *
+ * @Return: true if tcg2 protocol is installed, false if not
+ */
+bool is_tcg2_protocol_installed(void)
+{
+	struct efi_handler *handler;
+	efi_status_t ret;
+
+	ret = efi_search_protocol(efi_root, &efi_guid_tcg2_protocol, &handler);
+	return ((ret == EFI_SUCCESS) ? true : false);
+}
+
 static u32 tcg_event_final_size(struct tpml_digest_values *digest_list)
 {
 	u32 len;
@@ -886,6 +900,9 @@  efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
 	IMAGE_NT_HEADERS32 *nt;
 	struct efi_handler *handler;
 
+	if (!is_tcg2_protocol_installed())
+		return EFI_NOT_READY;
+
 	ret = platform_get_tpm2_device(&dev);
 	if (ret != EFI_SUCCESS)
 		return ret;
@@ -1759,6 +1776,9 @@  efi_status_t efi_tcg2_measure_efi_app_invocation(struct efi_loaded_image_obj *ha
 	u32 event = 0;
 	struct smbios_entry *entry;
 
+	if (!is_tcg2_protocol_installed())
+		return EFI_NOT_READY;
+
 	if (tcg2_efi_app_invoked)
 		return EFI_SUCCESS;
 
@@ -1809,6 +1829,9 @@  efi_status_t efi_tcg2_measure_efi_app_exit(void)
 	efi_status_t ret;
 	struct udevice *dev;
 
+	if (!is_tcg2_protocol_installed())
+		return EFI_NOT_READY;
+
 	ret = platform_get_tpm2_device(&dev);
 	if (ret != EFI_SUCCESS)
 		return ret;
@@ -1833,6 +1856,11 @@  efi_tcg2_notify_exit_boot_services(struct efi_event *event, void *context)
 
 	EFI_ENTRY("%p, %p", event, context);
 
+	if (!is_tcg2_protocol_installed()) {
+		ret =  EFI_NOT_READY;
+		goto out;
+	}
+
 	event_log.ebs_called = true;
 	ret = platform_get_tpm2_device(&dev);
 	if (ret != EFI_SUCCESS)
@@ -1863,6 +1891,9 @@  efi_status_t efi_tcg2_notify_exit_boot_services_failed(void)
 	struct udevice *dev;
 	efi_status_t ret;
 
+	if (!is_tcg2_protocol_installed())
+		return EFI_NOT_READY;
+
 	ret = platform_get_tpm2_device(&dev);
 	if (ret != EFI_SUCCESS)
 		goto out;
@@ -1932,6 +1963,45 @@  error:
 	return ret;
 }
 
+/**
+ * efi_tcg2_setup_measurement() - setup for the measurement
+ *
+ * Return:	status code
+ */
+efi_status_t efi_tcg2_setup_measurement(void)
+{
+	efi_status_t ret;
+	struct efi_event *event;
+
+	ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
+			       efi_tcg2_notify_exit_boot_services, NULL,
+			       NULL, &event);
+
+	return ret;
+}
+
+/**
+ * efi_tcg2_do_initial_measurement() - do initial measurement
+ *
+ * Return:	status code
+ */
+efi_status_t efi_tcg2_do_initial_measurement(void)
+{
+	efi_status_t ret;
+	struct udevice *dev;
+
+	ret = platform_get_tpm2_device(&dev);
+	if (ret != EFI_SUCCESS)
+		goto out;
+
+	ret = tcg2_measure_secure_boot_variable(dev);
+	if (ret != EFI_SUCCESS)
+		goto out;
+
+out:
+	return ret;
+}
+
 /**
  * efi_tcg2_register() - register EFI_TCG2_PROTOCOL
  *
@@ -1943,7 +2013,6 @@  efi_status_t efi_tcg2_register(void)
 {
 	efi_status_t ret = EFI_SUCCESS;
 	struct udevice *dev;
-	struct efi_event *event;
 	u32 err;
 
 	ret = platform_get_tpm2_device(&dev);
@@ -1969,6 +2038,10 @@  efi_status_t efi_tcg2_register(void)
 		goto fail;
 	}
 
+	/*
+	 * efi_add_protocol() is called at last on purpose.
+	 * tcg2_uninit() does not uninstall the tcg2 protocol, but it is intended.
+	 */
 	ret = efi_add_protocol(efi_root, &efi_guid_tcg2_protocol,
 			       (void *)&efi_tcg2_protocol);
 	if (ret != EFI_SUCCESS) {
@@ -1976,20 +2049,6 @@  efi_status_t efi_tcg2_register(void)
 		goto fail;
 	}
 
-	ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
-			       efi_tcg2_notify_exit_boot_services, NULL,
-			       NULL, &event);
-	if (ret != EFI_SUCCESS) {
-		tcg2_uninit();
-		goto fail;
-	}
-
-	ret = tcg2_measure_secure_boot_variable(dev);
-	if (ret != EFI_SUCCESS) {
-		tcg2_uninit();
-		goto fail;
-	}
-
 	return ret;
 
 fail: