[PATCH] efi_loader: support EFI_OS_INDICATIONS_BOOT_TO_FW_UI

[Heinrich Schuchardt]

On 3/31/26 21:18, Gary Guo wrote:
> EFI variable OsIndications have a bit EFI_OS_INDICATIONS_BOOT_TO_FW_UI
> indicating that the OS (or next stage bootloader) requests booting into
> firmware UI instead of continuing autoboot process.
> 
> Support it by having autoboot.c asking EFI bootmgr if boot should continue,
> which checks and clear the bit (so the next boot continue as normal).
> 
> With this change, systemd-boot will show a "Reboot Into Firmware Interface"
> option which will be able to drop back to u-boot. This can be useful if
> bootdelay is configured to be -2.
> 
> Signed-off-by: Gary Guo <gary at garyguo.net>
> ---
>   common/autoboot.c            |  4 +++-
>   include/efi_loader.h         |  2 ++
>   lib/efi_loader/efi_bootmgr.c | 45 ++++++++++++++++++++++++++++++++++++
>   lib/efi_loader/efi_setup.c   |  4 ++++
>   4 files changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/common/autoboot.c b/common/autoboot.c
> index 1783ef92c94c..b889407612dc 100644
> --- a/common/autoboot.c
> +++ b/common/autoboot.c
> @@ -11,6 +11,7 @@
>   #include <cli.h>
>   #include <command.h>
>   #include <console.h>
> +#include <efi_loader.h>
>   #include <env.h>
>   #include <errno.h>
>   #include <fdtdec.h>
> @@ -503,7 +504,8 @@ void autoboot_command(const char *s)
>   {
>   	debug("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");
>   
> -	if (s && (stored_bootdelay == -2 ||
> +	if (s && !(IS_ENABLED(CONFIG_EFI_BOOTMGR) && efi_should_abort_autoboot()) &&

I do not understand why the logic should depend on CONFIG_EFI_BOOTMGR 
instead of CONFIG_EFI_LOADER. It seems applicable whenever we support UEFI.


> +	    (stored_bootdelay == -2 ||
>   		 (stored_bootdelay != -1 && !abortboot(stored_bootdelay)))) {
>   		bool lock;
>   		int prev;
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 3e70ac070550..449697ad13b3 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -583,6 +583,8 @@ efi_status_t efi_bootmgr_get_unused_bootoption(u16 *buf,
>   efi_status_t efi_bootmgr_update_media_device_boot_option(void);
>   /* Delete selected boot option */
>   efi_status_t efi_bootmgr_delete_boot_option(u16 boot_index);
> +/* Check if autoboot should be aborted based on EFI vars */
> +bool efi_should_abort_autoboot(void);
>   /* Invoke EFI boot manager */
>   efi_status_t efi_bootmgr_run(void *fdt);
>   /* search the boot option index in BootOrder */
> diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
> index a687f4d8e85c..39f255ac9de4 100644
> --- a/lib/efi_loader/efi_bootmgr.c
> +++ b/lib/efi_loader/efi_bootmgr.c
> @@ -1290,6 +1290,51 @@ out:
>   	return ret;
>   }
>   
> +/**
> + * efi_should_abort_autoboot() - check if autoboot should be aborted per EFI vars

Please, mention the relevant flag.

> + *
> + * Return:	true if autoboot should abort
> + */
> +bool efi_should_abort_autoboot(void)
> +{
> +	efi_status_t ret;
> +	u64 os_indications = 0x0;
> +	efi_uintn_t size;
> +	efi_status_t r;
> +
> +	/* Initialize EFI drivers */
> +	ret = efi_init_obj_list();

@Ilias:

Essentially this ends up in always running  efi_init_obj_list() if we 
have UEFI enabled.

Shouldn't we then replace all invocations of efi_init_obj_list() by a 
single call after preboot but before EVT_POST_PREBOOT?

Best regards

Heinrich

> +	if (ret != EFI_SUCCESS) {
> +		log_err("Error: Cannot initialize UEFI sub-system, r = %lu\n",
> +			ret & ~EFI_ERROR_MASK);
> +		return false;
> +	}
> +
> +	size = sizeof(os_indications);
> +	r = efi_get_variable_int(u"OsIndications", &efi_global_variable_guid,
> +				 NULL, &size, &os_indications, NULL);
> +	if (r != EFI_SUCCESS || size != sizeof(os_indications))
> +		return false;
> +
> +	if (!(os_indications & EFI_OS_INDICATIONS_BOOT_TO_FW_UI))
> +		return false;
> +
> +	/* Clear the BOOT_TO_FW_UI so next boot returns to normal */
> +	os_indications &= ~EFI_OS_INDICATIONS_BOOT_TO_FW_UI;
> +	r = efi_set_variable_int(u"OsIndications",
> +				 &efi_global_variable_guid,
> +				 EFI_VARIABLE_NON_VOLATILE |
> +				 EFI_VARIABLE_BOOTSERVICE_ACCESS |
> +				 EFI_VARIABLE_RUNTIME_ACCESS,
> +				 sizeof(os_indications),
> +				 &os_indications, false);
> +
> +	if (r != EFI_SUCCESS)
> +		log_err("Setting %ls failed\n", L"OsIndications");
> +
> +	return true;
> +}
> +
>   /**
>    * efi_bootmgr_run() - execute EFI boot manager
>    * @fdt:	Flat device tree
> diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> index f06cf49e4435..0ad02e9fe0dd 100644
> --- a/lib/efi_loader/efi_setup.c
> +++ b/lib/efi_loader/efi_setup.c
> @@ -156,6 +156,10 @@ static efi_status_t efi_init_os_indications(void)
>   {
>   	u64 os_indications_supported = 0;
>   
> +	if (IS_ENABLED(CONFIG_EFI_BOOTMGR))
> +		os_indications_supported |=
> +			EFI_OS_INDICATIONS_BOOT_TO_FW_UI;
> +
>   	if (IS_ENABLED(CONFIG_EFI_HAVE_CAPSULE_SUPPORT))
>   		os_indications_supported |=
>   			EFI_OS_INDICATIONS_CAPSULE_RESULT_VAR_SUPPORTED;