[PATCH] efi_loader: support EFI_OS_INDICATIONS_BOOT_TO_FW_UI

[Ilias Apalodimas]

Hi Heinrich,

On Fri, 3 Apr 2026 at 13:30, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> Am 31. März 2026 21:18:51 MESZ schrieb Gary Guo <gary at garyguo.net>:
> >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>
>
> Thank you Gary for the patch. I am currently on travel and will have to look at it once I have returned.

On vacation here as well. I'll be off next week as well, nut I might
have time to take a closer look

>
> @Ilias
> Should we preferably integrate the detection of this bit into efi_init_early()?

Which part? This patch also touched EFI variables, which are not
initialized in the eraly code.

Thanks
/Ilias
>
> Best regards
>
> Heinrich
>
>
>
> >---
> > 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()) &&
> >+          (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
> >+ *
> >+ * 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();
> >+      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;
>