kernel/drivers/firmware/efi/vars.c, branch linux-6.9.y

efivarfs: automatically update super block flag

2023-12-11T10:19:18Z

efivar operation is updated when the tee_stmm_efi module is probed. tee_stmm_efi module supports SetVariable runtime service, but user needs to manually remount the efivarfs as RW to enable the write access if the previous efivar operation does not support SetVariable and efivarfs is mounted as read-only. This commit notifies the update of efivar operation to efivarfs subsystem, then drops SB_RDONLY flag if the efivar operation supports SetVariable. Signed-off-by: Masahisa Kojima [ardb: use per-superblock instance of the notifier block] Signed-off-by: Ard Biesheuvel

efivarfs: expose used and total size

2023-05-17T16:21:34Z

When writing EFI variables, one might get errors with no other message on why it fails. Being able to see how much is used by EFI variables helps analyzing such issues. Since this is not a conventional filesystem, block size is intentionally set to 1 instead of PAGE_SIZE. x86 quirks of reserved size are taken into account; so that available and free size can be different, further helping debugging space issues. With this patch, one can see the remaining space in EFI variable storage via efivarfs, like this: $ df -h /sys/firmware/efi/efivars/ Filesystem Size Used Avail Use% Mounted on efivarfs 176K 106K 66K 62% /sys/firmware/efi/efivars Signed-off-by: Anisse Astier [ardb: - rename efi_reserved_space() to efivar_reserved_space() - whitespace/coding style tweaks] Signed-off-by: Ard Biesheuvel

Change DEFINE_SEMAPHORE() to take a number argument

2023-04-18T18:15:24Z

Fundamentally semaphores are a counted primitive, but DEFINE_SEMAPHORE() does not expose this and explicitly creates a binary semaphore. Change DEFINE_SEMAPHORE() to take a number argument and use that in the few places that open-coded it using __SEMAPHORE_INITIALIZER(). Signed-off-by: Peter Zijlstra (Intel) [mcgrof: add some tribal knowledge about why some folks prefer binary sempahores over mutexes] Reviewed-by: Sergey Senozhatsky Reviewed-by: Davidlohr Bueso Signed-off-by: Luis Chamberlain

efi: efivars: prevent double registration

2023-01-26T20:32:01Z

Add the missing sanity check to efivars_register() so that it is no longer possible to override an already registered set of efivar ops (without first deregistering them). This can help debug initialisation ordering issues where drivers have so far unknowingly been relying on overriding the generic ops. Signed-off-by: Johan Hovold Signed-off-by: Ard Biesheuvel

efi: efivars: add efivars printk prefix

2023-01-23T11:32:21Z

Add an 'efivars: ' printk prefix to make the log entries stand out more, for example: efivars: Registered efivars operations While at it, change the sole remaining direct printk() call to pr_err(). Signed-off-by: Johan Hovold Signed-off-by: Ard Biesheuvel

efi: efivars: make efivar_supports_writes() return bool

2023-01-17T15:21:45Z

For consistency with the new efivar_is_available() function, change the return type of efivar_supports_writes() to bool. Signed-off-by: Johan Hovold Signed-off-by: Ard Biesheuvel

efi: efivars: drop kobject from efivars_register()

2023-01-17T15:14:36Z

Since commit 0f5b2c69a4cb ("efi: vars: Remove deprecated 'efivars' sysfs interface") and the removal of the sysfs interface there are no users of the efivars kobject. Drop the kobject argument from efivars_register() and add a new efivar_is_available() helper in favour of the old efivars_kobject(). Note that the new helper uses the prefix 'efivar' (i.e. without an 's') for consistency with efivar_supports_writes() and the rest of the interface (except the registration functions). For the benefit of drivers with optional EFI support, also provide a dummy implementation of efivar_is_available(). Signed-off-by: Johan Hovold Signed-off-by: Ard Biesheuvel

efi: efivars: Fix variable writes with unsupported query_variable_store()

2022-10-28T16:26:30Z

Commit 8a254d90a775 ("efi: efivars: Fix variable writes without query_variable_store()") addressed an issue that was introduced during the EFI variable store refactor, where alternative implementations of the efivars layer that lacked query_variable_store() would no longer work. Unfortunately, there is another case to consider here, which was missed: if the efivars layer is backed by the EFI runtime services as usual, but the EFI implementation predates the introduction of QueryVariableInfo(), we will return EFI_UNSUPPORTED, and this is no longer being dealt with correctly. So let's fix this, and while at it, clean up the code a bit, by merging the check_var_size() routines as well as their callers. Cc: # v6.0 Fixes: bbc6d2c6ef22 ("efi: vars: Switch to new wrapper layer") Signed-off-by: Ard Biesheuvel Tested-by: Aditya Garg

efi: efivars: Fix variable writes without query_variable_store()

2022-10-21T09:09:40Z

Commit bbc6d2c6ef22 ("efi: vars: Switch to new wrapper layer") refactored the efivars layer so that the 'business logic' related to which UEFI variables affect the boot flow in which way could be moved out of it, and into the efivarfs driver. This inadvertently broke setting variables on firmware implementations that lack the QueryVariableInfo() boot service, because we no longer tolerate a EFI_UNSUPPORTED result from check_var_size() when calling efivar_entry_set_get_size(), which now ends up calling check_var_size() a second time inadvertently. If QueryVariableInfo() is missing, we support writes of up to 64k - let's move that logic into check_var_size(), and drop the redundant call. Cc: # v6.0 Fixes: bbc6d2c6ef22 ("efi: vars: Switch to new wrapper layer") Signed-off-by: Ard Biesheuvel

efi: vars: Move efivar caching layer into efivarfs

2022-06-24T18:40:19Z

Move the fiddly bits of the efivar layer into its only remaining user, efivarfs, and confine its use to that particular module. All other uses of the EFI variable store have no need for this additional layer of complexity, given that they either only read variables, or read and write variables into a separate GUIDed namespace, and cannot be used to manipulate EFI variables that are covered by the EFI spec and/or affect the boot flow. Signed-off-by: Ard Biesheuvel