Re: [PATCH v13 09/15] FWU: Add boot time checks as highlighted by the FWU specification

Sughosh Ganu
2022-10-14T07:04:37Z

On Fri, 14 Oct 2022 at 12:04, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> On Thu, Oct 06, 2022 at 02:36:23PM +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 V12: None
> >
> > include/fwu.h | 13 +++
> > lib/fwu_updates/fwu.c | 191 +++++++++++++++++++++++++++++++++++++++++-
> > 2 files changed, 203 insertions(+), 1 deletion(-)
> >
> > 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 70482d14a0..b14c0dfadd 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>
> > @@ -18,6 +27,112 @@ enum {
> > IMAGE_ACCEPT_CLEAR,
> > };
> >
> > +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;
> > + 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;
>
> Why are we setting those before a get_variable?

Will remove

>
> > + 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;
> > @@ -28,6 +143,9 @@ static int fwu_get_dev_mdata(struct udevice **dev, struct fwu_mdata *mdata)
> > return ret;
> > }
> >
> > + if (!mdata)
> > + return 0;
> > +
> > ret = fwu_get_mdata(*dev, mdata);
> > if (ret < 0)
> > log_debug("Unable to get valid FWU metadata\n");
> > @@ -389,3 +507,74 @@ __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_mdata(&dev, NULL);
> > + 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_set_active_index(boot_idx);
> > + if (!ret)
> > + boottime_check = 1;
> > +
> > + return 0;
>
> Why are we returning 0 here? If fwu_set_active_index() failed, shouldn't
> we report that to upper layers?

This is declared as an event handler called before the call to
main_loop() which expects an integer return value. The decision to
proceed with an update is taken based on the values of the
bootime_check and trial_state variables.

-sughosh

>
> > + }
> > +
> > + if (efi_init_obj_list() != EFI_SUCCESS)
> > + return 0;
> > +
> > + ret = fwu_trial_state_check(dev);
> > + if (!ret)
> > + boottime_check = 1;
>
> ditto
>
> > +
> > + return 0;
> > +}
> > +EVENT_SPY(EVT_MAIN_LOOP, fwu_boottime_checks);
> > --
> > 2.34.1
> >