Re: [PATCH v5 08/23] FWU: Add boot time checks as highlighted by the FWU specification

Sughosh Ganu
2022-06-23T09:46:10Z

hi Etienne,

On Tue, 21 Jun 2022 at 16:26, Etienne Carriere
<etienne.carriere@linaro.org> wrote:
>
> Hi Sughosh,
>
> On Thu, 9 Jun 2022 at 14:31, 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.
> >
> > Add these checks in the board initialisation sequence, invoked after
> > relocation.
> >
> > Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
> > ---
> > common/board_r.c | 5 ++
> > include/fwu.h | 3 +
> > lib/fwu_updates/fwu.c | 170 ++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 178 insertions(+)
> > create mode 100644 lib/fwu_updates/fwu.c

<snip>

> > --- /dev/null
> > +++ b/lib/fwu_updates/fwu.c
> > @@ -0,0 +1,170 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (c) 2022, Linaro Limited
> > + */
> > +
> > +#include <dm.h>
> > +#include <efi.h>
> > +#include <efi_loader.h>
> > +#include <efi_variable.h>
> > +#include <fwu.h>
> > +#include <fwu_mdata.h>
> > +#include <malloc.h>
> > +
> > +#include <linux/errno.h>
> > +#include <linux/types.h>
> > +
> > +static u8 trial_state;
> > +static u8 boottime_check;
> > +
> > +static int fwu_trial_state_check(void)
> > +{
> > + int ret, i;
> > + efi_status_t status;
> > + efi_uintn_t var_size;
> > + u16 trial_state_ctr;
> > + u32 nimages, active_bank, var_attributes, active_idx;
> > + struct fwu_mdata *mdata = NULL;
> > + struct fwu_image_entry *img_entry;
> > + struct fwu_image_bank_info *img_bank_info;
> > +
> > + ret = fwu_get_mdata(&mdata);
> > + if (ret)
> > + return ret;
> > +
> > + ret = 0;
> > + nimages = CONFIG_FWU_NUM_IMAGES_PER_BANK;
> > + active_bank = mdata->active_index;
> > + img_entry = &mdata->img_entry[0];
> > + for (i = 0; i < nimages; i++) {
> > + img_bank_info = &img_entry[i].img_bank_info[active_bank];
> > + if (!img_bank_info->accepted) {
> > + trial_state = 1;
> > + break;
> > + }
> > + }
> > +
> > + 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(L"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;
> > + }
> > +
> > + trial_state_ctr = 0;
> > + status = efi_set_variable_int(L"TrialStateCtr",
> > + &efi_global_variable_guid,
> > + var_attributes,
> > + 0,
>
> s/0/var_size/ ?
> Ditto 24 lines below.

The variable size is 0 since the variable is being deleted here and
the other instance that you mention. Maybe I can put a comment in the
two places.

>
> > + &trial_state_ctr, false);
> > + if (status != EFI_SUCCESS) {
> > + log_err("Unable to clear TrialStateCtr variable\n");
> > + ret = -1;
> > + goto out;
> > + }
> > + } else {
> > + status = efi_set_variable_int(L"TrialStateCtr",
> > + &efi_global_variable_guid,
> > + var_attributes,
> > + var_size,
> > + &trial_state_ctr, false);
> > + if (status != EFI_SUCCESS) {
> > + log_err("Unable to increment TrialStateCtr variable\n");
> > + ret = -1;
> > + goto out;
> > + }
> > + }
> > + } else {
> > + trial_state_ctr = 0;
> > + status = efi_set_variable_int(L"TrialStateCtr",
> > + &efi_global_variable_guid,
> > + 0,
> > + 0, &trial_state_ctr,
> > + NULL);
>
> check status value.

Okay, I can put a log mentioning the error. There is not much use of
the status apart from this.

-sughosh

>
>
> > + }
> > +
> > +out:
> > + free(mdata);
> > + return ret;
> > +}
> > +
> > +u8 fwu_update_checks_pass(void)
> > +{
> > + return !trial_state && boottime_check;
> > +}
> > +
> > +int fwu_boottime_checks(void)
> > +{
> > + int ret;
> > + struct udevice *dev;
> > + u32 boot_idx, active_idx;
> > +
> > + if (uclass_get_device(UCLASS_FWU_MDATA, 0, &dev) || !dev) {
> > + log_err("FWU Metadata device not found\n");
> > + return 0;
> > + }
> > +
> > + ret = fwu_mdata_check();
> > + 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();
> > + if (!ret)
> > + boottime_check = 1;
> > +
> > + return 0;
> > +}
> > --
> > 2.25.1
> >