[PATCH] efi_loader: support EFI_OS_INDICATIONS_BOOT_TO_FW_UI
Ilias Apalodimas
ilias.apalodimas at linaro.org
Fri Apr 17 10:41:17 CEST 2026
Hi Heinrich
On Fri, 17 Apr 2026 at 08:59, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> 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.
That's a good point, but we install some protocols that are useful for
booting distros only when we boot via the bootmgr e.g the load_initrd
stuff. OTOH grub, systemd etc install their own version of the protocl
nowadays so I don't mind if we allow it in the generic case as well.
>
>
> > + (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?
I agree with you here and if we do that, your point above to depend on
EFI_LOADER instead of the bootmanager makes more sense.
Tom keeping in mind that more and more distros work out of the box
with U-Boot, can we bite the bullet and always init the subsystem
early now ?
If people don't plan to boot with EFI that can always disable the EFI_LOADER.
Thanks
/Ilias
>
> 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;
>
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