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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>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'