u-boot.git/lib/efi_loader/efi_var_common.c, branch master

efi_loader: avoid superfluous variable store writes on unchanged data

2026-03-14T07:14:20+00:00

Every SetVariable() call triggers efi_var_mem_ins() followed by
efi_var_to_storage(), even when the variable value is not actually
changing. This is unfriendly to flash-backed stores that suffer
wear from unnecessary erase/write cycles.

Add a change-detection path to efi_var_mem_ins(): when size2 == 0
(i.e. not an append) and the caller passes a non-NULL changep flag,
look up the existing variable and compare attributes, length, time
and data byte-by-byte. If everything matches, set *changep = false
and return EFI_SUCCESS without touching the variable buffer.

Both efi_set_variable_int() and efi_set_variable_runtime() now
check the flag and skip efi_var_mem_del() / efi_var_to_storage()
when nothing changed.

Introduce efi_memcmp_runtime() - a runtime-safe byte-by-byte memory
comparison helper, following the same pattern as the existing
efi_memcpy_runtime(). The standard memcmp() is not available after
ExitBootServices() and calling it from Linux will crash.

Tested-by: Heinrich Schuchardt 
Reviewed-by: Heinrich Schuchardt 
Signed-off-by: Michal Simek 
Reviewed-by: Ilias Apalodimas

efi_loader: avoid buffer overrun in efi_var_restore()

2026-03-14T07:14:01+00:00

The value of buf->length comes from outside U-Boot and may be incorrect.
We must avoid to overrun our internal buffer for excessive values.

If buf->length is shorter than the variable file header, the variable
file is invalid.

Reviewed-by: Ilias Apalodimas 
Tested-by: Michal Simek 
Signed-off-by: Heinrich Schuchardt

efi_var_file: refactor to move buffer functions

2026-02-15T08:14:31+00:00

Currently efi_var_file.c has functions to store/read
EFI variables to/from memory buffer. These functions
can be used with other EFI variable stores so move
them out to efi_var_common.c

Signed-off-by: Shantur Rathore 
Signed-off-by: Michal Simek 
Tested-by: Neil Armstrong  # on AML-S905D3-CC
Reviewed-by: Ilias Apalodimas 
Reviewed-by: Heinrich Schuchardt

efi_loader: use LOGC_EFI consistently

2025-01-26T10:06:56+00:00

The log category should be LOGC_EFI all over the EFI sub-system.

Signed-off-by: Heinrich Schuchardt 
Reviewed-by: Ilias Apalodimas

efi_loader: enable QueryVariableInfo at runtime for file backed variables

2024-05-01T05:40:05+00:00

Since commit c28d32f946f0 ("efi_loader: conditionally enable SetvariableRT")
we are enabling the last bits of missing runtime services.
Add support for QueryVariableInfo which we already support at boottime
and we just need to mark some fucntions available at runtime and move
some checks around.

It's worth noting that pointer checks for maxmimum and remaining
variable storage aren't when we store variables on the RPMB, since the
Secure World backend is already performing them.

Signed-off-by: Ilias Apalodimas

efi_loader: add an EFI variable with the file contents

2024-04-20T06:22:24+00:00

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

efi_loader: typo mstching

2024-04-20T06:21:59+00:00

%s/mstching/matching/

Reported-by: E Shattow 
Signed-off-by: Heinrich Schuchardt 
Reviewed-by: Ilias Apalodimas

efi_loader: move efi_var_collect to common functions

2024-04-13T09:03:12+00:00

efi_var_collect() was initially placed in efi_var_file.c, since back
then we only supported efi variables stored in a file. Since then we
support variables stored in an RPMB as well and use that function to
collect variables that should be present at runtime.

So let's move it around in efi_var_common.c which makes more sense

Suggested-by: Heinrich Schuchardt 
Signed-off-by: Ilias Apalodimas 
Reviewed-by: Heinrich Schuchardt

efi_loader: all variable attributes are 32bit

2024-04-08T11:03:11+00:00

GetVariable() and SetVariable() use an uint32_t value for attributes.
The UEFI specification defines the related constants as 32bit.

Add the missing EFI_VARIABLE_ENHANCED_AUTHENTICATED_ACCESS constant.

Signed-off-by: Heinrich Schuchardt 
Reviewed-by: Ilias Apalodimas

efi_loader: Remove

2023-12-21T13:54:37+00:00

We largely do not need  in these files, so drop it. The only
exception here is that efi_freestanding.c needs  and had
been getting that via .

Reviewed-by: Simon Glass 
Signed-off-by: Tom Rini