How to write/edit/update the OsIndications efi variable from command line?

Question

In the need to enter the UEFI firmware setup utility while using ultra fast boot (keyboard drivers are not loaded during POST), I wish to write to the "Os Indications" efi variable. My OS is Ubuntu 14.04 kernel 3.13.0-35-generic.

OsIndications variable returns a UINT64 bitmask

OsIndicationsSupported variable returns a UINT64 bitmask

The EFI_OS_INDICATIONS_BOOT_TO_FW_UI bit can be set in the OsIndicationsSupported variable by the firmware, if the firmware supports OS requests to stop at a firmware user interface. The EFI_OS_INDICATIONS_BOOT_TO_FW_UI bit can be set by the OS in the OsIndications variable, if the OS desires for the firmware to stop at a firmware user interface on the next boot.

EFI_OS_INDICATIONS_BOOT_TO_FW_UI=0x0000000000000001 - Page 312 of UEFI spec 2.3.1C

My firmware has the ability to enter the firmware setup utility at next boot:

$ hexdump /sys/firmware/efi/vars/OsIndicationsSupported-8be4df61-93ca-11d2-aa0d-00e098032b8c/data
0000000 0001 0000 0000 0000
0000008

I can create a new variable on /sys/firmware/efi/efivars using

$ printf\x07\x00\x00\x00\x00" > myvar-12345678-1234-1234-1234-123456789abc

However writing to the efi variable OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c results in all sorts of write error: Invalid argument:

Using new efivarfs

# printf "x00\x00\x00\x01" > /sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c
-bash: printf: write error: Invalid argument

# printf "x00\x00\x00\x01" > /sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c
-bash: printf: write error: Invalid argument

# printf "\x01" > /sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c
-bash: printf: write error: Invalid argument

# cat enter-uefi-fw > /sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c
cat: write error: Invalid argument

Using old 1024 byte maximum sysfs-efivars

# cat enter-uefi-fw > /sys/firmware/efi/vars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c/raw_var
cat: write error: Input/output error

# cat enter-uefi-fw > /sys/firmware/efi/vars/new_var
cat: write error: Invalid argument

# echo 'enter-uefi-fw' > /sys/firmware/efi/vars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c/raw_var
-bash: echo: write error: Invalid argument

# printf "\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" > /sys/firmware/efi/vars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c/raw_var
-bash: printf: write error: Invalid argument

Checked the requirements for UEFI variables support to work properly

1. EFI Runtime Services support should be present in the kernel
   $ cat /boot/config-$(uname -r) | grep CONFIG_EFI=y returns CONFIG_EFI=y
2. Kernel processor bitness/arch and EFI processor bitness/arch should match
   ?
3. Kernel should be booted in EFI mode
   CSM is disabled in Firmware setup utility/BIOS
4. EFI runtime services in the kernel should not be disabled via kernel cmdline, i.e. noefi kernel parameter should not be used.
   cat /proc/cmdline | grep EFI returns nothing
5. efivarfs filesystem should be mounted at /sys/firmware/efi/efivars
   mount | grep efivars returns none on /sys/firmware/efi/efivars type efivarfs (rw)
6. efivar -l should list the EFI Variables without any error
   The command lists 82 lines and no errors.
7. Check for existence of /sys/firmware/efi/efivars/dump-* files.
   No dump- files exist there.

According to https://ask.fedoraproject.org/en/question/8264/after-installing-fedora-i-cant-open-biosefi-setup/?answer=16402#post-id-16402 the cat enter-uefi-fw > /sys/firmware/efi/vars/new_var command should work in Fedora 17.

First deleting OsIndications doesn't improve

# rm -rv /sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c
removed '/sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c'
# ls -l enter-uefi-fw
-rw-r--r-- 1 root root 2084 Aug 25 20:23 enter-uefi-fw
# cat enter-uefi-fw > /sys/firmware/efi/vars/new_var
cat: write error: Invalid argument

How can I update the already existing OsIndications efi variable in Ubuntu 14.04 (trusty) from the command-line?

Answer 1

The relevant 64-bit mask here is:

  #define EFI_OS_INDICATIONS_BOOT_TO_FW_UI 0x0000000000000001

This can be produced as a little-endian (Intel) format string using:

  str='\x01\x00\x00\x00\x00\x00\x00\x00'; printf "$str"

The output of printf "$str" above needs to go into the data contents of the efivarfs variable file $var, where

  var='/sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c'

However, each file in /sys/firmware/efi/efivars begins with a 4-byte header and is then followed by its data contents. Therefore, the output of printf "$str" needs to prefixed with the 4-byte header before we can write it onto the efivarfs variable file $var. With $str and $var as above, this can be done, e.g., using:

  { head -c 4 "$var"; printf "$str"; } > "$var"

Answer 2

Due to the presence of numerous firmware bugs where removing non-standard UEFI variables causes the system firmware to fail to POST, efivarfs files that are not well-known standardized variables are created as immutable files.

https://www.kernel.org/doc/Documentation/filesystems/efivarfs.txt

This can be verified and changed with the lsattr and chattr commands.

For example:

root@hi12:/tmp/test# hexdump -C out 
00000000  07 00 00 00 10 00 00 00                           |........|
00000008
root@hi12:/tmp/test# cp out /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
cp: cannot create regular file '/sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23': Operation not permitted
root@hi12:/tmp/test# lsattr  /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
----i-------------- /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23
root@hi12:/tmp/test# chattr -i /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
root@hi12:/tmp/test# lsattr  /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
------------------- /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23
root@hi12:/tmp/test# cp out /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
root@hi12:/tmp/test# chattr +i /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
root@hi12:/tmp/test# lsattr  /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23 
----i-------------- /sys/firmware/efi/efivars/BootSelectVariable-944fb13b-773f-4cbb-9c6f-326cebde4c23
root@hi12:/tmp/test# 

Answer 3

Try using echo instead of cat.

# echo 'enter-uefi-fw' > /sys/firmware/efi/vars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c/raw_var