qemu: arm64: Add documentation for capsule update
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>
This commit is contained in:
Sughosh Ganu
Heinrich Schuchardt
parent
7407595286
commit
c35df7c9e4
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@ -10,3 +10,4 @@ Emulation
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qemu-mips
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qemu-riscv
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qemu-x86
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qemu_capsule_update
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@ -0,0 +1,210 @@
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.. SPDX-License-Identifier: GPL-2.0+
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.. Copyright (C) 2020, Linaro Limited
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Enabling UEFI Capsule Update feature
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------------------------------------
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Support has been added for the UEFI capsule update feature which
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enables updating the U-Boot image using the UEFI firmware management
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protocol (fmp). The capsules are not passed to the firmware through
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the UpdateCapsule runtime service. Instead, capsule-on-disk
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functionality is used for fetching the capsule from the EFI System
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Partition (ESP) by placing the capsule file under the
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\EFI\UpdateCapsule directory.
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Currently, support has been added on the QEMU ARM64 virt platform for
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updating the U-Boot binary as a raw image when the platform is booted
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in non-secure mode, i.e. with CONFIG_TFABOOT disabled. For this
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configuration, the QEMU platform needs to be booted with
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'secure=off'. The U-Boot binary placed on the first bank of the NOR
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flash at offset 0x0. The U-Boot environment is placed on the second
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NOR flash bank at offset 0x4000000.
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The capsule update feature is enabled with the following configuration
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settings::
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CONFIG_MTD=y
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CONFIG_FLASH_CFI_MTD=y
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CONFIG_CMD_MTDPARTS=y
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CONFIG_CMD_DFU=y
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CONFIG_DFU_MTD=y
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CONFIG_PCI_INIT_R=y
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CONFIG_EFI_CAPSULE_ON_DISK=y
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CONFIG_EFI_CAPSULE_FIRMWARE_MANAGEMENT=y
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CONFIG_EFI_CAPSULE_FIRMWARE=y
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CONFIG_EFI_CAPSULE_FIRMWARE_RAW=y
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CONFIG_EFI_CAPSULE_FMP_HEADER=y
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In addition, the following config needs to be disabled(QEMU ARM specific)::
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CONFIG_TFABOOT
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The capsule file can be generated by using the GenerateCapsule.py
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script in EDKII::
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$ ./BaseTools/BinWrappers/PosixLike/GenerateCapsule -e -o \
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<capsule_file_name> --fw-version <val> --lsv <val> --guid \
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e2bb9c06-70e9-4b14-97a3-5a7913176e3f --verbose --update-image-index \
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<val> --verbose <u-boot.bin>
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The above is a wrapper script(GenerateCapsule) which eventually calls
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the actual GenerateCapsule.py script.
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As per the UEFI specification, the capsule file needs to be placed on
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the EFI System Partition, under the \EFI\UpdateCapsule directory. The
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EFI System Partition can be a virtio-blk-device.
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Before initiating the firmware update, the efi variables BootNext,
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BootXXXX and OsIndications need to be set. The BootXXXX variable needs
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to be pointing to the EFI System Partition which contains the capsule
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file. The BootNext, BootXXXX and OsIndications variables can be set
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using the following commands::
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=> efidebug boot add 0 Boot0000 virtio 0:1 <capsule_file_name>
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=> efidebug boot next 0
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=> setenv -e -nv -bs -rt -v OsIndications =0x04
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=> saveenv
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Finally, the capsule update can be initiated with the following
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command::
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=> efidebug capsule disk-update
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The updated U-Boot image will be booted on subsequent boot.
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Enabling Capsule Authentication
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The UEFI specification defines a way of authenticating the capsule to
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be updated by verifying the capsule signature. The capsule signature
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is computed and prepended to the capsule payload at the time of
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capsule generation. This signature is then verified by using the
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public key stored as part of the X509 certificate. This certificate is
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in the form of an efi signature list (esl) file, which is embedded as
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part of the platform's device tree blob using the mkeficapsule
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utility.
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On the QEMU virt platforms, the device-tree is generated on the fly
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based on the devices configured. This device tree is then passed on to
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the various software components booting on the platform, including
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U-Boot. Therefore, on the QEMU virt platform, the signatute is
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embedded on an overlay. This overlay is then applied at runtime to the
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base platform device-tree. Steps needed for embedding the esl file in
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the overlay are highlighted below.
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The capsule authentication feature can be enabled through the
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following config, in addition to the configs listed above for capsule
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update::
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CONFIG_EFI_CAPSULE_AUTHENTICATE=y
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The public and private keys used for the signing process are generated
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and used by the steps highlighted below::
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1. Install utility commands on your host
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* OPENSSL
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* efitools
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2. Create signing keys and certificate files on your host
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$ openssl req -x509 -sha256 -newkey rsa:2048 -subj /CN=CRT/ \
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-keyout CRT.key -out CRT.crt -nodes -days 365
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$ cert-to-efi-sig-list CRT.crt CRT.esl
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$ openssl x509 -in CRT.crt -out CRT.cer -outform DER
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$ openssl x509 -inform DER -in CRT.cer -outform PEM -out CRT.pub.pem
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$ openssl pkcs12 -export -out CRT.pfx -inkey CRT.key -in CRT.crt
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$ openssl pkcs12 -in CRT.pfx -nodes -out CRT.pem
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The capsule file can be generated by using the GenerateCapsule.py
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script in EDKII::
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$ ./BaseTools/BinWrappers/PosixLike/GenerateCapsule -e -o \
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<capsule_file_name> --monotonic-count <val> --fw-version \
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<val> --lsv <val> --guid \
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e2bb9c06-70e9-4b14-97a3-5a7913176e3f --verbose \
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--update-image-index <val> --signer-private-cert \
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/path/to/CRT.pem --trusted-public-cert \
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/path/to/CRT.pub.pem --other-public-cert /path/to/CRT.pub.pem \
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<u-boot.bin>
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Place the capsule generated in the above step on the EFI System
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Partition under the EFI/UpdateCapsule directory
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For embedding the public key certificate, the following steps need to
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be followed::
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1. Generate a skeleton overlay dts file, with a single fragment
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node and an empty __overlay__ node
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A typical skeleton overlay file will look like this
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/dts-v1/;
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/plugin/;
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/ {
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fragment@0 {
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target-path = "/";
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__overlay__ {
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};
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};
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};
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2. Convert the dts to a corresponding dtb with the following
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command
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./scripts/dtc/dtc -@ -I dts -O dtb -o <ov_dtb_file_name> \
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<dts_file>
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3. Run the dtb file generated above through the mkeficapsule tool
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in U-Boot
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./tools/mkeficapsule -O <pub_key.esl> -D <ov_dtb>
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Running the above command results in the creation of a 'signature'
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node in the dtb, under which the public key is stored as a
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'capsule-key' property. The '-O' option is to be used since the
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public key certificate(esl) file is being embedded in an overlay.
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The dtb file embedded with the certificate is now to be placed on an
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EFI System Partition. This would then be loaded and "merged" with the
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base platform flattened device-tree(dtb) at runtime.
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Build U-Boot with the following steps(QEMU ARM64)::
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$ make qemu_arm64_defconfig
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$ make menuconfig
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Disable CONFIG_TFABOOT
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Enable CONFIG_EFI_CAPSULE_AUTHENTICATE
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Enable all configs needed for capsule update(listed above)
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$ make all
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Boot the platform and perform the following steps on the U-Boot
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command line::
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1. Enable capsule authentication by setting the following env
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variable
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=> setenv capsule_authentication_enabled 1
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=> saveenv
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2. Load the overlay dtb to memory and merge it with the base fdt
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=> fatload virtio 0:1 <$fdtovaddr> EFI/<ov_dtb_file>
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=> fdt addr $fdtcontroladdr
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=> fdt resize <size_of_ov_dtb_file>
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=> fdt apply <$fdtovaddr>
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3. Set the following environment and UEFI boot variables
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=> setenv -e -nv -bs -rt -v OsIndications =0x04
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=> efidebug boot add 0 Boot0000 virtio 0:1 <capsule_file_name>
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=> efidebug boot next 0
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=> saveenv
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4. Finally, the capsule update can be initiated with the following
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command
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=> efidebug capsule disk-update
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On subsequent reboot, the platform should boot the updated U-Boot binary.
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