u-boot.git/include/efi_variable.h, branch v2026.01

efi_loader: correct efi_set_variable_int() description

2024-09-21T08:59:06+00:00

The name used in the function description must match the function.

Signed-off-by: Heinrich Schuchardt 
Reviewed-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: EFI_VARIABLE_READ_ONLY should be 32bit

2024-04-08T11:03:31+00:00

GetVariable() and SetVariable() only accept a 32bit value for attributes.
It makes not sense to define EFI_VARIABLE_READ_ONLY as unsigned long.

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

efi_loader: fix efi_get_next_variable_name_mem()

2022-12-20T15:06:48+00:00

The VariableNameSize parameter is in bytes but u16_strnlen() counts u16.

Fix the parameter check for null termination.

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

efi_loader: function to get GUID for variable name

2021-10-25T19:13:06+00:00

In multiple places we need the default GUID matching a variable name.
The patch provides a library function. For secure boot related variables
like 'PK', 'KEK', 'db' a lookup table is used. For all other variable
names EFI_GLOBAL_VARIABLE is returned.

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

efi_loader: treat UEFI variable name as const

2021-10-25T19:13:06+00:00

UEFI variable names are typically constants and hence should be defined as
const. Unfortunately some of our API functions do not define the parameters
for UEFI variable names as const. This requires unnecessary conversions.

Adjust parameters of several internal functions to tre UEFI variable names
as const.

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

efi_loader: efi_auth_var_type for AuditMode, DeployedMode

2021-09-04T10:03:57+00:00

Writing variables AuditMode and DeployedMode serves to switch between
Secure Boot modes. Provide a separate value for these in efi_auth_var_type.

With this patch the variables will not be read from from file even if they
are marked as non-volatile by mistake.

Signed-off-by: Heinrich Schuchardt

efi_loader: don't load signature database from file

2021-09-04T10:03:57+00:00

The UEFI specification requires that the signature database may only be
stored in tamper-resistant storage. So these variable may not be read
from an unsigned file.

Signed-off-by: Heinrich Schuchardt

efi_loader: Avoid emitting efi_var_buf to .GOT

2021-01-20T07:17:17+00:00

Atish reports that on RISC-V, accessing the EFI variables causes
a kernel panic. An objdump of the file verifies that, since the
global pointer for efi_var_buf ends up in .GOT section which is
not mapped in virtual address space for Linux.



0000000000000084 :
  84:   715d                    addi    sp,sp,-80

* objdump -dr
0000000000000086 <.LCFI2>:
  86:   e0a2                    sd  s0,64(sp)
  88:   fc26                    sd  s1,56(sp)
  8a:   e486                    sd  ra,72(sp)
  8c:   f84a                    sd  s2,48(sp)
  8e:   f44e                    sd  s3,40(sp)
  90:   f052                    sd  s4,32(sp)
  92:   ec56                    sd  s5,24(sp)
  94:   00000497            auipc   s1,0x0
            94: R_RISCV_GOT_HI20    efi_var_buf
  98:   0004b483            ld  s1,0(s1) # 94 <.LCFI2+0xe>
            98: R_RISCV_PCREL_LO12_I    .L0
            98: R_RISCV_RELAX   *ABS*

* objdump -t
0000000000000084 g     F .text.efi_runtime  00000000000000b8 efi_var_mem_find

With the patch applied:

* objdump -dr
0000000000000086 <.LCFI2>:
  86:   e0a2                    sd  s0,64(sp)
  88:   fc26                    sd  s1,56(sp)
  8a:   e486                    sd  ra,72(sp)
  8c:   f84a                    sd  s2,48(sp)
  8e:   f44e                    sd  s3,40(sp)
  90:   f052                    sd  s4,32(sp)
  92:   ec56                    sd  s5,24(sp)
  94:   00000497            auipc   s1,0x0
            94: R_RISCV_PCREL_HI20  .LANCHOR0
            94: R_RISCV_RELAX   *ABS*
  98:   00048493            mv  s1,s1
            98: R_RISCV_PCREL_LO12_I    .L0
            98: R_RISCV_RELAX   *ABS*

* objdump -t
0000000000000008 l     O .data.efi_runtime  0000000000000008 efi_var_buf

On arm64 this works, because there's no .GOT entries for this
and everything is converted to relative references.

* objdump -dr (identical pre-post patch, only the new function shows up)
00000000000000b4 :
  b4:   aa0003ee    mov x14, x0
  b8:   9000000a    adrp    x10, 0 
            b8: R_AARCH64_ADR_PREL_PG_HI21  .data.efi_runtime
  bc:   91000140    add x0, x10, #0x0
            bc: R_AARCH64_ADD_ABS_LO12_NC   .data.efi_runtime
  c0:   aa0103ed    mov x13, x1
  c4:   79400021    ldrh    w1, [x1]
  c8:   aa0203eb    mov x11, x2
  cc:   f9400400    ldr x0, [x0, #8]
  d0:   b940100c    ldr w12, [x0, #16]
  d4:   8b0c000c    add x12, x0, x12

So let's switch efi_var_buf to static and create a helper function for
anyone that needs to update it.

Fixes: e01aed47d6a0 ("efi_loader: Enable run-time variable support for tee based variables")
Reported-by: Atish Patra 
Tested-by: Atish Patra 
Signed-off-by: Ilias Apalodimas 
Reviewed-by: Heinrich Schuchardt

efi_loader: make variable store size customizable

2020-12-20T16:40:06+00:00

Currently the size of the buffer to keep UEFI variables in memory is fixed
at 16384 bytes. This size has proven to be too small for some use cases.

Make the size of the memory buffer for UEFI variables customizable.

Reported-by: Paulo Alcantara (SUSE) 
Signed-off-by: Heinrich Schuchardt 
Acked-by: Ilias Apalodimas