Currently, efi-pstore, efivarfs and the efivars sysfs interface all share a common support layer which manages a linked list containing efivar_entry items describing each EFI variable that this support layer assumes to be present in the EFI variable store managed by the firmware. This shared layer also contains an efivars_operations pointer, which carries function pointers that refer to the underlying EFI get/set variable routines, but can be superseded by other implementations (currently, this is only implemented for Google x86 systems that implement the GSMI interface) Each user of this shared layer has its own linked list, which means they all have a different view of the underlying variable store, even though they might operate on the same variables. For EFI pstore related variables in particular, manipulating these behind the back of the other drivers is likely to result in fun. This shared layer as well as its 3 different users all use a single semaphore to mediate access to the individual linked lists and the ops pointer. The shared layer carries a substantial amount of 'business logic' related to which EFI variables are relevant to the firmware, to limit whether and how they may be manipulated. This aspect of the code is only relevant when such variables can be manipulated arbitrarily, e.g. by user space, but EFI pstore, for example, has no need for this, as it uses its own GUIDed namespace for EFI variables, and does not permit other variables to be manipulated. The two remaining users are efivars sysfs and efivarfs, both of which provide a cached view of these 'important' variables. Given that the former has been deprecated for a long time, and given the potential concerns around using both concurrently, let's get rid of the sysfs based one. Then, we can restructure the efivars API so that this business logic can be incorporated into the efivarfs driver, leaving only a minimal wrapper around the get/set variable calls, allowing the GSMI replacement to remain in use, as well as mediate access to the different services using the existing semaphore. This is mainly useful to ensure that set_variable() calls do no invalidate an enumeration of the EFI variables that is in progress using get_next_variable() by another task. Some of the prerequisites of this work have been posted separately and have been queued up in efi/next already, mainly to move other users away from the efivar API which they were using in the wrong way, or without a good reason. Changes since v2: - add a pstore_record::priv field and use it to record the EFI variable name exactly as it was used to retrieve the entry; - drop another pstore patch related to the ECC field that is no longer needed; - drop some remaining EXPORT_SYMBOL()s of the efivar API symbols that are now private to efivarfs Cc: Matthew Garrett <mjg59@xxxxxxxxxxxxx> Cc: Peter Jones <pjones@xxxxxxxxxx> Cc: Jeremy Kerr <jk@xxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Ard Biesheuvel (9): pstore: Add priv field to pstore_record for backend specific use efi: vars: Don't drop lock in the middle of efivar_init() efi: vars: Add thin wrapper around EFI get/set variable interface efi: pstore: Omit efivars caching EFI varstore access layer efi: vars: Use locking version to iterate over efivars linked lists efi: vars: Drop __efivar_entry_iter() helper which is no longer used efi: vars: Remove deprecated 'efivars' sysfs interface efi: vars: Switch to new wrapper layer efi: vars: Move efivar caching layer into efivarfs Documentation/x86/x86_64/uefi.rst | 2 +- arch/arm/configs/milbeaut_m10v_defconfig | 1 - arch/ia64/configs/bigsur_defconfig | 1 - arch/ia64/configs/generic_defconfig | 1 - arch/ia64/configs/gensparse_defconfig | 1 - arch/ia64/configs/tiger_defconfig | 1 - arch/ia64/configs/zx1_defconfig | 1 - arch/x86/configs/i386_defconfig | 1 - arch/x86/configs/x86_64_defconfig | 1 - drivers/firmware/efi/Kconfig | 13 +- drivers/firmware/efi/Makefile | 1 - drivers/firmware/efi/efi-pstore.c | 377 ++---- drivers/firmware/efi/efi.c | 1 + drivers/firmware/efi/efivars.c | 671 ----------- drivers/firmware/efi/vars.c | 1219 +++----------------- fs/efivarfs/Makefile | 2 +- fs/efivarfs/internal.h | 40 + fs/efivarfs/super.c | 15 +- fs/efivarfs/vars.c | 738 ++++++++++++ fs/pstore/inode.c | 1 + fs/pstore/platform.c | 1 + include/linux/efi.h | 80 +- include/linux/pstore.h | 4 + 23 files changed, 1031 insertions(+), 2142 deletions(-) delete mode 100644 drivers/firmware/efi/efivars.c create mode 100644 fs/efivarfs/vars.c -- 2.35.1
