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_tee.c | 5 ----- 1 file changed, 5 deletions(-) (limited to 'lib/efi_loader/efi_variable_tee.c') diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c index dde135fd9f8..4f1aa298da1 100644 --- a/lib/efi_loader/efi_variable_tee.c +++ b/lib/efi_loader/efi_variable_tee.c @@ -959,11 +959,6 @@ void efi_variables_boot_exit_notify(void) log_err("Unable to notify the MM partition for ExitBootServices\n"); free(comm_buf); - /* - * Populate the list for runtime variables. - * asking EFI_VARIABLE_RUNTIME_ACCESS is redundant, since - * efi_var_mem_notify_exit_boot_services will clean those, but that's fine - */ ret = efi_var_collect(&var_buf, &len, EFI_VARIABLE_RUNTIME_ACCESS); if (ret != EFI_SUCCESS) log_err("Can't populate EFI variables. No runtime variables will be available\n"); -- cgit v1.2.3