Re: [PATCH v9 09/15] FWU: Add boot time checks as highlighted by the FWU specification

[Etienne Carriere <etienne.carriere@linaro.org>]

On Fri, 26 Aug 2022 at 11:58, Sughosh Ganu <sughosh.ganu@linaro.org> wrote:
>
> The FWU Multi Bank Update specification requires the Update Agent to
> carry out certain checks at the time of platform boot. The Update
> Agent is the component which is responsible for updating the firmware
> components and maintaining and keeping the metadata in sync.
>
> The spec requires that the Update Agent perform the following checks
> at the time of boot
> * Sanity check of both the metadata copies maintained by the platform.
> * Get the boot index passed to U-Boot by the prior stage bootloader
>   and use this value for metadata bookkeeping.
> * Check if the system is booting in Trial State. If the system boots
>   in the Trial State for more than a specified number of boot counts,
>   change the Active Bank to be booting the platform from.
>
> Call these checks through the main loop event at the time of platform
> boot.
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
> ---
> Changes since V8:
> * Call fwu_boottime_checks through the event interface
> * Add comments for API functions
>
>  include/fwu.h              |  13 +++
>  lib/efi_loader/efi_setup.c |   1 +
>  lib/fwu_updates/fwu.c      | 189 ++++++++++++++++++++++++++++++++++++-
>  3 files changed, 202 insertions(+), 1 deletion(-)
>
> diff --git a/include/fwu.h b/include/fwu.h
> index b8c207deaf..31c9923ff5 100644
> --- a/include/fwu.h
> +++ b/include/fwu.h
> @@ -252,4 +252,17 @@ int fwu_plat_get_update_index(uint *update_idx);
>   *
>   */
>  void fwu_plat_get_bootidx(void *boot_idx);
> +
> +/**
> + * fwu_update_checks_pass() - Check if FWU update can be done
> + *
> + * Check if the FWU update can be executed. The updates are
> + * allowed only when the platform is not in Trial State and
> + * the boot time checks have passed
> + *
> + * Return: 1 if OK, 0 on error
> + *
> + */
> +u8 fwu_update_checks_pass(void);
> +
>  #endif /* _FWU_H_ */
> diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> index 751beda590..23dc7a0710 100644
> --- a/lib/efi_loader/efi_setup.c
> +++ b/lib/efi_loader/efi_setup.c
> @@ -199,6 +199,7 @@ static efi_status_t __efi_init_early(void)
>                 goto out;
>
>         ret = efi_disk_init();
> +
>  out:
>         return ret;
>  }
> diff --git a/lib/fwu_updates/fwu.c b/lib/fwu_updates/fwu.c
> index 94b15859a5..27f48855af 100644
> --- a/lib/fwu_updates/fwu.c
> +++ b/lib/fwu_updates/fwu.c
> @@ -4,10 +4,19 @@
>   */
>
>  #include <dm.h>
> +#include <efi.h>
>  #include <efi_loader.h>
> +#include <efi_variable.h>
> +#include <event.h>
>  #include <fwu.h>
>  #include <fwu_mdata.h>
> -#include <log.h>
> +#include <malloc.h>
> +
> +#include <linux/errno.h>
> +#include <linux/types.h>
> +
> +static u8 trial_state;
> +static u8 boottime_check;
>
>  #include <linux/errno.h>
>  #include <linux/types.h>
> @@ -16,6 +25,112 @@
>  #define IMAGE_ACCEPT_SET       BIT(0)
>  #define IMAGE_ACCEPT_CLEAR     BIT(1)
>
> +static int trial_counter_update(u16 *trial_state_ctr)
> +{
> +       bool delete;
> +       u32 var_attr;
> +       efi_status_t status;
> +       efi_uintn_t var_size;
> +
> +       delete = !trial_state_ctr ? true : false;
> +       var_size = !trial_state_ctr ? 0 : (efi_uintn_t)sizeof(*trial_state_ctr);
> +       var_attr = !trial_state_ctr ? 0 : EFI_VARIABLE_NON_VOLATILE |
> +               EFI_VARIABLE_BOOTSERVICE_ACCESS;
> +       status = efi_set_variable_int(u"TrialStateCtr",
> +                                     &efi_global_variable_guid,
> +                                     var_attr,
> +                                     var_size, trial_state_ctr, false);
> +
> +       if ((delete && (status != EFI_NOT_FOUND &&
> +                       status != EFI_SUCCESS)) ||
> +           (!delete && status != EFI_SUCCESS))
> +               return -1;
> +
> +       return 0;
> +}
> +
> +static int in_trial_state(struct fwu_mdata *mdata)
> +{
> +       u32 i, active_bank;
> +       struct fwu_image_entry *img_entry;
> +       struct fwu_image_bank_info *img_bank_info;
> +
> +       active_bank = mdata->active_index;
> +       img_entry = &mdata->img_entry[0];
> +       for (i = 0; i < CONFIG_FWU_NUM_IMAGES_PER_BANK; i++) {
> +               img_bank_info = &img_entry[i].img_bank_info[active_bank];
> +               if (!img_bank_info->accepted) {
> +                       return 1;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +static int fwu_trial_state_check(struct udevice *dev)
> +{
> +       int ret;
> +       efi_status_t status;
> +       efi_uintn_t var_size;
> +       u16 trial_state_ctr;
> +       u32 var_attributes, active_idx;
> +       struct fwu_mdata mdata = { 0 };
> +
> +       ret = fwu_get_mdata(dev, &mdata);
> +       if (ret)
> +               return ret;
> +
> +       if ((trial_state = in_trial_state(&mdata))) {
> +               var_size = (efi_uintn_t)sizeof(trial_state_ctr);
> +               log_info("System booting in Trial State\n");
> +               var_attributes = EFI_VARIABLE_NON_VOLATILE |
> +                       EFI_VARIABLE_BOOTSERVICE_ACCESS;
> +               status = efi_get_variable_int(u"TrialStateCtr",
> +                                             &efi_global_variable_guid,
> +                                             &var_attributes,
> +                                             &var_size, &trial_state_ctr,
> +                                             NULL);
> +               if (status != EFI_SUCCESS) {
> +                       log_err("Unable to read TrialStateCtr variable\n");
> +                       ret = -1;
> +                       goto out;
> +               }
> +
> +               ++trial_state_ctr;
> +               if (trial_state_ctr > CONFIG_FWU_TRIAL_STATE_CNT) {
> +                       log_info("Trial State count exceeded. Revert back to previous_active_index\n");
> +                       active_idx = mdata.active_index;
> +                       ret = fwu_revert_boot_index();
> +                       if (ret) {
> +                               log_err("Unable to revert active_index\n");
> +                               goto out;
> +                       }
> +
> +                       /* Delete the TrialStateCtr variable */
> +                       ret = trial_counter_update(NULL);
> +                       if (ret) {
> +                               log_err("Unable to delete TrialStateCtr variable\n");
> +                               goto out;
> +                       }
> +               } else {
> +                       ret = trial_counter_update(&trial_state_ctr);
> +                       if (ret) {
> +                               log_err("Unable to increment TrialStateCtr variable\n");
> +                               goto out;
> +                       }
> +               }
> +       } else {
> +               /* Delete the variable */
> +               ret = trial_counter_update(NULL);
> +               if (ret) {
> +                       log_err("Unable to delete TrialStateCtr variable\n");
> +               }
> +       }
> +
> +out:
> +       return ret;
> +}
> +
>  static int fwu_get_dev(struct udevice **dev)
>
>  {
> @@ -382,3 +497,75 @@ __weak int fwu_plat_get_update_index(uint *update_idx)
>
>         return ret;
>  }
> +
> +/**
> + * fwu_update_checks_pass() - Check if FWU update can be done
> + *
> + * Check if the FWU update can be executed. The updates are
> + * allowed only when the platform is not in Trial State and
> + * the boot time checks have passed
> + *
> + * Return: 1 if OK, 0 on error
> + *
> + */
> +u8 fwu_update_checks_pass(void)
> +{
> +       return !trial_state && boottime_check;
> +}
> +
> +static int fwu_boottime_checks(void *ctx, struct event *event)
> +{
> +       int ret;
> +       struct udevice *dev;
> +       u32 boot_idx, active_idx;
> +
> +       ret = fwu_get_dev(&dev);
> +       if (ret)
> +               return ret;
> +
> +       ret = fwu_mdata_check(dev);
> +       if (ret) {
> +               return 0;
> +       }
> +
> +       /*
> +        * Get the Boot Index, i.e. the bank from
> +        * which the platform has booted. This value
> +        * gets passed from the ealier stage bootloader
> +        * which booted u-boot, e.g. tf-a. If the
> +        * boot index is not the same as the
> +        * active_index read from the FWU metadata,
> +        * update the active_index.
> +        */
> +       fwu_plat_get_bootidx(&boot_idx);
> +       if (boot_idx >= CONFIG_FWU_NUM_BANKS) {
> +               log_err("Received incorrect value of boot_index\n");
> +               return 0;
> +       }
> +
> +       ret = fwu_get_active_index(&active_idx);
> +       if (ret) {
> +               log_err("Unable to read active_index\n");
> +               return 0;
> +       }
> +
> +       if (boot_idx != active_idx) {
> +               log_info("Boot idx %u is not matching active idx %u, changing active_idx\n",
> +                        boot_idx, active_idx);
> +               ret = fwu_update_active_index(boot_idx);
> +               if (!ret)
> +                       boottime_check = 1;
> +
> +               return 0;
> +       }
> +
> +       if (efi_init_obj_list() != EFI_SUCCESS)
> +               return 0;
> +
> +       ret = fwu_trial_state_check(dev);
> +       if (!ret)
> +               boottime_check = 1;
> +
> +       return 0;
> +}
> +EVENT_SPY(EVT_MAIN_LOOP, fwu_boottime_checks);
> --
> 2.34.1
>