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List: grub-devel
Subject: [PATCH v8 09/10] Add a module for the Boot Loader Interface
From: Oliver Steffen <osteffen () redhat ! com>
Date: 2023-05-24 14:55:57
Message-ID: 20230524145558.2219878-10-osteffen () redhat ! com
[Download RAW message or body]
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 <osteffen@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
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