Re: [PATCH v11 09/15] FWU: Add boot time checks as highlighted by the FWU specification

Ilias Apalodimas
2022-10-03T09:56:20Z

On Wed, Sep 28, 2022 at 02:59:50PM +0530, Sughosh Ganu 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>
> Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>
> ---
> Changes since V10:
> * Remove the spurious newline addition in efi_setup.c
> * Move the assignment of trial_state outside the if() as suggested by
> Jassi
>
> include/fwu.h | 13 +++
> lib/fwu_updates/fwu.c | 193 +++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 204 insertions(+), 2 deletions(-)
>
> diff --git a/include/fwu.h b/include/fwu.h
> index 71a03cf70b..2effa7da38 100644
> --- a/include/fwu.h
> +++ b/include/fwu.h
> @@ -253,4 +253,17 @@ int fwu_plat_get_update_index(uint *update_idx);
> *
> */
> void fwu_plat_get_bootidx(uint *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/fwu_updates/fwu.c b/lib/fwu_updates/fwu.c
> index 5cf6bec6a0..5cde5514d2 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>
> @@ -16,8 +25,113 @@
> #define IMAGE_ACCEPT_SET BIT(0)
> #define IMAGE_ACCEPT_CLEAR BIT(1)
>
> -static int fwu_get_dev_mdata(struct udevice **dev, struct fwu_mdata *mdata)
> +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 &&

Is there a legitimate case where we need to delete the variable while it's not there?
Wouldn't that be some kind of failure we shouldn't hide?

> + 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;
> + struct fwu_mdata mdata = { 0 };
> +
> + ret = fwu_get_mdata(dev, &mdata);
> + if (ret)
> + return ret;
> +
> + trial_state = in_trial_state(&mdata);
> + if (trial_state) {
> + 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");
> + 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_mdata(struct udevice **dev, struct fwu_mdata *mdata)
> {
> int ret;
>
> @@ -27,6 +141,9 @@ static int fwu_get_dev_mdata(struct udevice **dev, struct fwu_mdata *mdata)
> return ret;
> }
>
> + if (!mdata)
> + return 0;
> +

Doesn't this belong to the patch that introduced the function?

> ret = fwu_get_mdata(*dev, mdata);
> if (ret < 0)
> log_debug("Unable to get valid FWU metadata\n");
> @@ -388,3 +505,75 @@ __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)

I think this should be declared as bool

> +{
> + int ret;
> + struct udevice *dev;
> + u32 boot_idx, active_idx;
> +
> + ret = fwu_get_dev_mdata(&dev, NULL);
> + if (ret)
> + return ret;
> +
> + ret = fwu_mdata_check(dev);
> + if (ret) {
> + return 0;
> + }

You don't need {}

> +
> + /*
> + * 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_set_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
>

Cheers
/Ilias