From 00da8d65a3baea8c3745367bea99b1d76f8f129c Mon Sep 17 00:00:00 2001 From: Ilias Apalodimas Date: Thu, 18 Apr 2024 15:54:52 +0300 Subject: efi_loader: add an EFI variable with the file contents Previous patches enabled SetVariableRT using a RAM backend. Although EBBR [0] defines a variable format we can teach userspace tools and write the altered variables, it's better if we skip the ABI requirements completely. So let's add a new variable, in its own namespace called "VarToFile" which contains a binary dump of the updated RT, BS and, NV variables and will be updated when GetVariable is called. Some adjustments are needed to do that. Currently we discard BS-only variables in EBS(). We need to preserve those on the RAM backend that exposes the variables. Since BS-only variables can't appear at runtime we need to move the memory masking checks from efi_var_collect() to efi_get_next_variable_name_mem()/ efi_get_variable_mem() and do the filtering at runtime. We also need an efi_var_collect() variant available at runtime, in order to construct the "VarToFile" buffer on the fly. All users and applications (for linux) have to do when updating a variable is dd that variable in the file described by "RTStorageVolatile". Linux efivarfs uses a first 4 bytes of the output to represent attributes in little-endian format. So, storing variables works like this: $~ efibootmgr -n 0001 $~ dd if=/sys/firmware/efi/efivars/VarToFile-b2ac5fc9-92b7-4acd-aeac-11e818c3130c of=/boot/efi/ubootefi.var skip=4 bs=1 [0] https://arm-software.github.io/ebbr/index.html#document-chapter5-variable-storage Suggested-by: Ard Biesheuvel # dumping all variables to a variable Co-developed-by: Heinrich Schuchardt # contributed on efi_var_collect_mem() Signed-off-by: Heinrich Schuchardt Signed-off-by: Ilias Apalodimas --- lib/efi_loader/efi_variable.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'lib/efi_loader/efi_variable.c') diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c index 47bb7992057..0cbed53d1db 100644 --- a/lib/efi_loader/efi_variable.c +++ b/lib/efi_loader/efi_variable.c @@ -209,14 +209,16 @@ efi_get_variable_int(const u16 *variable_name, const efi_guid_t *vendor, u32 *attributes, efi_uintn_t *data_size, void *data, u64 *timep) { - return efi_get_variable_mem(variable_name, vendor, attributes, data_size, data, timep); + return efi_get_variable_mem(variable_name, vendor, attributes, data_size, + data, timep, 0); } efi_status_t __efi_runtime efi_get_next_variable_name_int(efi_uintn_t *variable_name_size, u16 *variable_name, efi_guid_t *vendor) { - return efi_get_next_variable_name_mem(variable_name_size, variable_name, vendor); + return efi_get_next_variable_name_mem(variable_name_size, variable_name, + vendor, 0); } /** -- cgit v1.2.3