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

Heinrich Schuchardt
2022-06-15T06:34:29Z

On 6/9/22 14:29, 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.
>
> 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
>
> diff --git a/common/board_r.c b/common/board_r.c
> index 6f4aca2077..33a600715d 100644
> --- a/common/board_r.c
> +++ b/common/board_r.c
> @@ -15,6 +15,7 @@
> #include <cpu_func.h>
> #include <exports.h>
> #include <flash.h>
> +#include <fwu.h>
> #include <hang.h>
> #include <image.h>
> #include <irq_func.h>
> @@ -797,6 +798,10 @@ static init_fnc_t init_sequence_r[] = {
> #if defined(CONFIG_PRAM)
> initr_mem,
> #endif
> +
> +#ifdef CONFIG_FWU_MULTI_BANK_UPDATE
> + fwu_boottime_checks,
> +#endif
> run_main_loop,
> };
>
> diff --git a/include/fwu.h b/include/fwu.h
> index 41774ff9e2..8fbd91b463 100644
> --- a/include/fwu.h
> +++ b/include/fwu.h
> @@ -33,6 +33,9 @@ struct fwu_mdata_ops {
> EFI_GUID(0x8a7a84a0, 0x8387, 0x40f6, 0xab, 0x41, \
> 0xa8, 0xb9, 0xa5, 0xa6, 0x0d, 0x23)
>
> +int fwu_boottime_checks(void);
> +u8 fwu_update_checks_pass(void);
> +
> int fwu_get_mdata(struct fwu_mdata **mdata);
> int fwu_update_mdata(struct fwu_mdata *mdata);
> int fwu_get_active_index(u32 *active_idx);
> diff --git a/lib/fwu_updates/fwu.c b/lib/fwu_updates/fwu.c
> new file mode 100644
> index 0000000000..af884439fb
> --- /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,
> + &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);
> + }
> +
> +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)

efi_init_obj_list() slows down the boot process. Why do want to invoke
it if no EFI binary is launched?

See also Takahiro's hint in
https://lore.kernel.org/all/20220615061616.GD58082@laputa/

Best regards

Heinrich

> + return 0;
> +
> + ret = fwu_trial_state_check();
> + if (!ret)
> + boottime_check = 1;
> +
> + return 0;
> +}