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

Sughosh Ganu
2022-10-03T10:31:47Z

hi Ilias,

On Mon, 3 Oct 2022 at 15:26, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> 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?

The variable will be found the first time the platform transitions
from Trial State to regular state. However, on subsequent boots, the
variable would no longer be present, and the efi_set_variable_int()
would return EFI_NOT_FOUND. That would not be an error scenario and
hence the check.

>
> > + 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?

I thought of putting it along with a call to the fwu_get_dev_mdata()
function with mdata set to NULL.

>
> > 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

This being an event handler, is following the signature of event_handler_t.

>
> > +{
> > + 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 {}

Will remove

-sughosh

>
> > +
> > + /*
> > + * 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