Add documentation highlighting the steps for using the uefi capsule update feature for updating the u-boot firmware image.
Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org ---
Changes since V1: * Change the documentation to reflect the usage of overlays for embedding the public key certs at runtime * Fix the build for 'make htmldocs'
doc/board/emulation/qemu-arm.rst | 188 +++++++++++++++++++++++++++++++ 1 file changed, 188 insertions(+)
diff --git a/doc/board/emulation/qemu-arm.rst b/doc/board/emulation/qemu-arm.rst index 8d7fda10f1..11d91811b3 100644 --- a/doc/board/emulation/qemu-arm.rst +++ b/doc/board/emulation/qemu-arm.rst @@ -90,3 +90,191 @@ The debug UART on the ARM virt board uses these settings:: CONFIG_DEBUG_UART_PL010=y CONFIG_DEBUG_UART_BASE=0x9000000 CONFIG_DEBUG_UART_CLOCK=0 + +Enabling Uefi Capsule Update feature +------------------------------------ + +Support has been added for the uefi capsule update feature which +enables updating the u-boot image using the uefi firmware management +protocol (fmp). The capsules are not passed to the firmware through +the UpdateCapsule runtime service. Instead, capsule-on-disk +functionality is used for fetching the capsule from the EFI System +Partition (ESP). + +Currently, support has been added for updating the u-boot binary as a +raw image when the platform is booted in non-secure mode, i.e with +CONFIG_TFABOOT disabled. For this configuration, the qemu platform +needs to be booted with 'secure=off'. The u-boot binary placed on the +first bank of the Nor Flash at offset 0x0. The u-boot environment is +placed on the second Nor Flash bank at offset 0x4000000. + +The capsule update feature is enabled with the following configs:: + + CONFIG_MTD=y + CONFIG_FLASH_CFI_MTD=y + CONFIG_CMD_MTDPARTS=y + CONFIG_CMD_DFU=y + CONFIG_DFU_MTD=y + CONFIG_PCI_INIT_R=y + CONFIG_EFI_CAPSULE_ON_DISK=y + CONFIG_EFI_CAPSULE_FIRMWARE_MANAGEMENT=y + CONFIG_EFI_CAPSULE_FIRMWARE=y + CONFIG_EFI_CAPSULE_FIRMWARE_RAW=y + CONFIG_EFI_CAPSULE_FMP_HEADER=y + +In addition, the following config needs to be disabled:: + + CONFIG_TFABOOT + +The capsule file can be generated by using the GenerateCapsule.py +script in edk2:: + + $ ./BaseTools/BinWrappers/PosixLike/GenerateCapsule -e -o \ + <capsule_file_name> --fw-version <val> --lsv <val> --guid \ + e2bb9c06-70e9-4b14-97a3-5a7913176e3f --verbose --update-image-index \ + <val> --verbose <u-boot.bin> + +As per the uefi specification, the capsule file needs to be placed on +the EFI System Partition, under the EFI/UpdateCapsule/ directory. The +EFI System Partition can be a virtio-blk-device. + +Before initiating the firmware update, the efi variables BootNext, +BootXXXX and OsIndications need to be set. The BootXXXX variable needs +to be pointing to the EFI System Partition which contains the capsule +file. The BootNext, BootXXXX and OsIndications variables can be set +using the following commands:: + + => efidebug boot add 0 Boot0000 virtio 0:1 <capsule_file_name> + => efidebug boot next 0 + => setenv -e -nv -bs -rt -v OsIndications =0x04 + => saveenv + +Finally, the capsule update can be initiated with the following +command:: + + => efidebug capsule disk-update + +The updated u-boot image will be booted on subsequent boot. + +Enabling Capsule Authentication +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The uefi specification defines a way of authenticating the capsule to +be updated by verifying the capsule signature. The capsule signature +is computed and prepended to the capsule payload at the time of +capsule generation. This signature is then verified by using the +public key stored as part of the X509 certificate. This certificate is +in the form of an efi signature list (esl) file, which is embedded as +part of the platform's device tree blob using the mkeficapsule +utility. + +On the qemu virt platforms, the device-tree is generated on the fly +based on the devices configured. This device tree is then passed on to +the various software components booting on the platform, including +u-boot. Therefore, on the qemu virt platform, the signatute is +embedded on an overlay. This overlay is then applied at runtime to the +base platform device-tree. Steps needed for embedding the esl file in +the overlay are highlighted below. + +The capsule authentication feature can be enabled through the +following config, in addition to the configs listed above for capsule +update:: + + CONFIG_EFI_CAPSULE_AUTHENTICATE=y + +The public and private keys used for the signing process are generated +and used by the steps highlighted below:: + + 1. Install utility commands on your host + * openssl + * efitools + + 2. Create signing keys and certificate files on your host + + $ openssl req -x509 -sha256 -newkey rsa:2048 -subj /CN=CRT/ \ + -keyout CRT.key -out CRT.crt -nodes -days 365 + $ cert-to-efi-sig-list CRT.crt CRT.esl + + $ openssl x509 -in CRT.crt -out CRT.cer -outform DER + $ openssl x509 -inform DER -in CRT.cer -outform PEM -out CRT.pub.pem + + $ openssl pkcs12 -export -out CRT.pfx -inkey CRT.key -in CRT.crt + $ openssl pkcs12 -in CRT.pfx -nodes -out CRT.pem + +The capsule file can be generated by using the GenerateCapsule.py +script in edk2:: + + $ ./BaseTools/BinWrappers/PosixLike/GenerateCapsule -e -o \ + <capsule_file_name> --monotonic-count <val> --fw-version \ + <val> --lsv <val> --guid \ + e2bb9c06-70e9-4b14-97a3-5a7913176e3f --verbose \ + --update-image-index <val> --signer-private-cert \ + /path/to/CRT.pem --trusted-public-cert \ + /path/to/CRT.pub.pem --other-public-cert /path/to/CRT.pub.pem \ + <u-boot.bin> + +Place the capsule generated in the above step on the EFI System +Partition under the EFI/UpdateCapsule directory + +For embedding the public key certificate, the following steps need to +be followed:: + + 1. Generate a skeleton overlay dts file, with a single fragment + node and an empty __overlay__ node + + 2. Convert the dts to a corresponding dtb with the following + command + ./scripts/dtc/dtc -@ -I dts -O dtb -o <ov_dtb_file_name> \ + <dts_file> + + 3. Run the dtb file generated above through the mkeficapsule tool + in u-boot + ./tools/mkeficapsule -O <pub_key.esl> -D <ov_dtb> + +Running the above command results in the creation of a 'signature' +node in the dtb, under which the public key is stored as a +'capsule-key' property. The '-O' option is to be used since the +public key certificate(esl) file is being embedded in an overlay. + +The dtb file embedded with the certificate is now to be placed on an +EFI System Partition. This would then be loaded and "merged" with the +base platform fdt at runtime. + +Build u-boot with the following steps:: + + $ make qemu_arm64_defconfig + $ make menuconfig + Disable CONFIG_TFABOOT + Enable CONFIG_EFI_CAPSULE_AUTHENTICATE + Enable all configs needed for capsule update(listed above) + $ make all + +Boot the platform and perform the following steps on the u-boot +command line:: + + 1. Enable capsule authentication by setting the following env + variable + + => setenv capsule_authentication_enabled 1 + => saveenv + + 2. Load the overlay dtb to memory and merge it with the base fdt + + => fatload virtio 0:1 <$fdtovaddr> EFI/<ov_dtb_file> + => fdt addr $fdtcontroladdr + => fdt resize <size_of_ov_dtb_file> + => fdt apply <$fdtovaddr> + + 3. Set the following env and efi Boot variables + + => setenv -e -nv -bs -rt -v OsIndications =0x04 + => efidebug boot add 0 Boot0000 virtio 0:1 <capsule_file_name> + => efidebug boot next 0 + => saveenv + + 4. Finally, the capsule update can be initiated with the following + command + + => efidebug capsule disk-update + +On subsequent reboot, the platform should boot the updated u-boot binary.