It turns out checking from userspace is not 100% reliable to figure out
whether the firmware had TPM2 support enabled or not. For example with
EDK2 arm64, the default upstream build config bundles TPM2 support with
SecureBoot support, so if the latter is disabled, TPM2 is also unavailable.
But still, the ACPI TPM2 table is created just as if it was enabled. So,
/sys/firmware/acpi/tables/TPM2 exists and looks correct but there are no
measurements, neither the firmware nor the loader/stub can do them, and
/sys/kernel/security/tpm0/binary_bios_measurements does not exist.
So, userspace cannot really tell what was going on in UEFI mode.
The loader can use the apposite UEFI protocol to check, which is a more
definitive answer. Export the bitmask with the list of active banks as-is.
If it's not 0, then in userspace we can be sure a working TPM2 was available
in UEFI mode.
systemd-boot and systemd-stub v258 (current main) set this variable and
userspace portion consumes it to be able to tell what was available in
the firmware context.
Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The get_part_uuid() function made an assumption that the target GRUB
device is a partition device and accessed device->disk->partition
without checking for NULL. There are four situations where this
assumption is problematic:
1. The device is a net device instead of a disk.
2. The device is an abstraction device, like LVM, RAID, or CRYPTO, which
is mostly logical "disk" ((lvmid/<UUID>) and so on).
3. Firmware RAID may present the ESP to GRUB as an EFI disk (hd0) device
if it is contained within a Linux software RAID.
4. When booting from a CD-ROM, the ESP is a VFAT image indexed by the El
Torito boot catalog. The boot device is set to (cd0), corresponding
to the CD-ROM image mounted as an ISO 9660 filesystem.
As a result, get_part_uuid() could lead to a NULL pointer dereference
and trigger a synchronous exception during boot if the ESP falls into
one of these categories. This patch fixes the problem by adding the
necessary checks to handle cases where the ESP is not a partition device.
Additionally, to avoid disrupting the boot process, this patch relaxes
the severity of the errors in this context to non-critical. Errors will
be logged, but they will not prevent the boot process from continuing.
Fixes: e0fa7dc84 (bli: Add a module for the Boot Loader Interface)
Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-By: Oliver Steffen <osteffen@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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. The bli module 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>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
