Add a new module named bli. It implements a small but quite useful part of the Boot Loader Interface [0]. This interface uses EFI variables for communication between the boot loader and the operating system.
When loaded, this module sets two EFI variables under the vendor GUID 4a67b082-0a4c-41cf-b6c7-440b29bb8c4f: - LoaderInfo: contains GRUB + <version number>. This allows the running operating system to identify the boot loader used during boot. - LoaderDevicePartUUID: contains the partition UUID of the EFI System Partition (ESP). This is used by systemd-gpt-auto-generator [1] to find the root partitions (and others too), via partition type IDs [2]. This module is available on EFI platforms only. bli relies on the part_gpt module which has to be loaded beforehand to make the GPT partitions discoverable. Update the documentation, add a new chapter "Modules" and describe the bli module there. [0] https://systemd.io/BOOT_LOADER_INTERFACE/ [1] https://www.freedesktop.org/software/systemd/man/systemd-gpt-auto-generator.html [2] https://uapi-group.org/specifications/specs/discoverable_partitions_specification/ Signed-off-by: Oliver Steffen <ostef...@redhat.com> --- docs/grub.texi | 23 +++++++ grub-core/Makefile.core.def | 6 ++ grub-core/commands/bli.c | 122 ++++++++++++++++++++++++++++++++++++ include/grub/efi/api.h | 5 ++ 4 files changed, 156 insertions(+) create mode 100644 grub-core/commands/bli.c diff --git a/docs/grub.texi b/docs/grub.texi index c49b2ed50..65e08f8d6 100644 --- a/docs/grub.texi +++ b/docs/grub.texi @@ -96,6 +96,7 @@ This edition documents version @value{VERSION}. * Filesystem:: Filesystem syntax and semantics * Interface:: The menu and the command-line * Environment:: GRUB environment variables +* Modules:: Available modules * Commands:: Available builtin commands * Internationalisation:: Topics relating to language support * Security:: Authentication, authorisation, and signatures @@ -3868,6 +3869,28 @@ using BIOS or EFI functions (no ATA, USB or IEEE1275). @command{grub-mkconfig} uses this facility to implement @samp{GRUB_SAVEDEFAULT} (@pxref{Simple configuration}). +@node Modules +@chapter Modules + +In this chapter, we list all modules that are available in GRUB (currently incomplete). + +Modules can be loaded via the @command{insmod} (@pxref{insmod}) command. + +@menu +* bli:: +@end menu + +@node bli +@section bli +This module provides basic support for the Boot Loader Interface. The Boot +Loader Interface specifies a set of EFI variables that are used to communicate +boot-time information between the boot loader and the operating system. + +When loaded, the bli module publishes the GPT partition UUID of the EFI System +Partition used during boot and a string identifying GRUB as the active boot +loader, including the version number. + +This module is only available on UEFI platforms. @node Commands @chapter Available commands diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def index c69c4a332..0c4fc0f5b 100644 --- a/grub-core/Makefile.core.def +++ b/grub-core/Makefile.core.def @@ -2578,3 +2578,9 @@ module = { common = commands/memtools.c; condition = COND_MM_DEBUG; }; + +module = { + name = bli; + efi = commands/bli.c; + enable = efi; +}; diff --git a/grub-core/commands/bli.c b/grub-core/commands/bli.c new file mode 100644 index 000000000..5c8cace54 --- /dev/null +++ b/grub-core/commands/bli.c @@ -0,0 +1,122 @@ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2023 Free Software Foundation, Inc. + * + * GRUB is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * GRUB is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GRUB. If not, see <http://www.gnu.org/licenses/>. + * + * Implementation of the Boot Loader Interface. + */ + +#include <grub/charset.h> +#include <grub/efi/api.h> +#include <grub/efi/disk.h> +#include <grub/efi/efi.h> +#include <grub/err.h> +#include <grub/extcmd.h> +#include <grub/gpt_partition.h> +#include <grub/misc.h> +#include <grub/mm.h> +#include <grub/partition.h> +#include <grub/types.h> + +GRUB_MOD_LICENSE ("GPLv3+"); + +#define MODNAME "bli" + +static const grub_guid_t bli_vendor_guid = GRUB_EFI_VENDOR_BOOT_LOADER_INTERFACE_GUID; + +static grub_err_t +get_part_uuid (const char *device_name, char **part_uuid) +{ + grub_device_t device; + grub_err_t status = GRUB_ERR_NONE; + grub_disk_t disk = NULL; + struct grub_gpt_partentry entry; + + device = grub_device_open (device_name); + if (device == NULL) + { + status = grub_error (grub_errno, N_("cannot open device: %s"), device_name); + goto fail; + } + + disk = grub_disk_open (device->disk->name); + if (disk == NULL) + { + status = grub_error (grub_errno, N_("cannot open disk: %s"), device_name); + return status; + } + + if (grub_strcmp (device->disk->partition->partmap->name, "gpt") != 0) + { + status = grub_error (GRUB_ERR_BAD_PART_TABLE, + N_("this is not a GPT partition table: %s"), device_name); + goto fail; + } + + if (grub_disk_read (disk, device->disk->partition->offset, + device->disk->partition->index, sizeof (entry), &entry) != GRUB_ERR_NONE) + { + status = grub_error (grub_errno, N_("read error: %s"), device_name); + goto fail; + } + + *part_uuid = grub_xasprintf ("%pG", &entry.guid); + if (*part_uuid == NULL) + status = grub_errno; + + fail: + grub_disk_close (disk); + grub_device_close (device); + + return status; +} + +static grub_err_t +set_loader_device_part_uuid (void) +{ + grub_efi_loaded_image_t *image; + char *device_name; + grub_err_t status = GRUB_ERR_NONE; + char *part_uuid = NULL; + + image = grub_efi_get_loaded_image (grub_efi_image_handle); + if (image == NULL) + return grub_error (GRUB_ERR_BAD_DEVICE, N_("unable to find boot device")); + + device_name = grub_efidisk_get_device_name (image->device_handle); + if (device_name == NULL) + return grub_error (GRUB_ERR_BAD_DEVICE, N_("unable to find boot device")); + + status = get_part_uuid (device_name, &part_uuid); + + if (status == GRUB_ERR_NONE) + status = grub_efi_set_variable_to_string ("LoaderDevicePartUUID", &bli_vendor_guid, part_uuid, + GRUB_EFI_VARIABLE_BOOTSERVICE_ACCESS + | GRUB_EFI_VARIABLE_RUNTIME_ACCESS); + else + grub_error (status, N_("unable to determine partition UUID of boot device")); + + grub_free (part_uuid); + grub_free (device_name); + return status; +} + +GRUB_MOD_INIT (bli) +{ + grub_efi_set_variable_to_string ("LoaderInfo", &bli_vendor_guid, PACKAGE_STRING, + GRUB_EFI_VARIABLE_BOOTSERVICE_ACCESS + | GRUB_EFI_VARIABLE_RUNTIME_ACCESS); + set_loader_device_part_uuid (); +} diff --git a/include/grub/efi/api.h b/include/grub/efi/api.h index 5609d7112..4550d2af5 100644 --- a/include/grub/efi/api.h +++ b/include/grub/efi/api.h @@ -374,6 +374,11 @@ { 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68 } \ } +#define GRUB_EFI_VENDOR_BOOT_LOADER_INTERFACE_GUID \ + { 0x4a67b082, 0x0a4c, 0x41cf, \ + {0xb6, 0xc7, 0x44, 0x0b, 0x29, 0xbb, 0x8c, 0x4f } \ + } + struct grub_efi_sal_system_table { grub_uint32_t signature; -- 2.40.1 _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
