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Signed-off-by: Andrew F. Davis <afd@ti.com> Reviewed-by: Tom Rini <trini@konsulko.com> Reviewed-by: Andreas Dannenberg <dannenberg@ti.com>
227 lines
10 KiB
Plaintext
227 lines
10 KiB
Plaintext
README on how boot images are created for secure TI devices
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CONFIG_TI_SECURE_DEVICE:
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Secure TI devices require a boot image that is authenticated by ROM
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code to function. Without this, even JTAG remains locked and the
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device is essentially useless. In order to create a valid boot image for
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a secure device from TI, the initial public software image must be signed
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and combined with various headers, certificates, and other binary images.
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Information on the details on the complete boot image format can be obtained
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from Texas Instruments. The tools used to generate boot images for secure
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devices are part of a secure development package (SECDEV) that can be
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downloaded from:
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http://www.ti.com/mysecuresoftware (login required)
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The secure development package is access controlled due to NDA and export
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control restrictions. Access must be requested and granted by TI before the
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package is viewable and downloadable. Contact TI, either online or by way
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of a local TI representative, to request access.
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Booting of U-Boot SPL
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=====================
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When CONFIG_TI_SECURE_DEVICE is set, the U-Boot SPL build process
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requires the presence and use of these tools in order to create a
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viable boot image. The build process will look for the environment
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variable TI_SECURE_DEV_PKG, which should be the path of the installed
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SECDEV package. If the TI_SECURE_DEV_PKG variable is not defined or
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if it is defined but doesn't point to a valid SECDEV package, a
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warning is issued during the build to indicate that a final secure
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bootable image was not created.
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Within the SECDEV package exists an image creation script:
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${TI_SECURE_DEV_PKG}/scripts/create-boot-image.sh
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This is called as part of the SPL/u-boot build process. As the secure
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boot image formats and requirements differ between secure SOC from TI,
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the purpose of this script is to abstract these details as much as
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possible.
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The script is basically the only required interface to the TI SECDEV
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package for creating a bootable SPL image for secure TI devices.
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Invoking the script for AM33xx Secure Devices
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=============================================
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create-boot-image.sh \
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<IMAGE_FLAG> <INPUT_FILE> <OUTPUT_FILE> <SPL_LOAD_ADDR>
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<IMAGE_FLAG> is a value that specifies the type of the image to
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generate OR the action the image generation tool will take. Valid
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values are:
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SPI_X-LOADER - Generates an image for SPI flash (byte swapped)
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X-LOADER - Generates an image for non-XIP flash
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MLO - Generates an image for SD/MMC/eMMC media
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2ND - Generates an image for USB, UART and Ethernet
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XIP_X-LOADER - Generates a single stage u-boot for NOR/QSPI XiP
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<INPUT_FILE> is the full path and filename of the public world boot
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loaderbinary file (depending on the boot media, this is usually
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either u-boot-spl.bin or u-boot.bin).
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<OUTPUT_FILE> is the full path and filename of the final secure
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image. The output binary images should be used in place of the standard
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non-secure binary images (see the platform-specific user's guides and
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releases notes for how the non-secure images are typically used)
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u-boot-spl_HS_SPI_X-LOADER - byte swapped boot image for SPI flash
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u-boot-spl_HS_X-LOADER - boot image for NAND or SD/MMC/eMMC rawmode
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u-boot-spl_HS_MLO - boot image for SD/MMC/eMMC media
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u-boot-spl_HS_2ND - boot image for USB, UART and Ethernet
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u-boot_HS_XIP_X-LOADER - boot image for NOR or QSPI Xip flash
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<SPL_LOAD_ADDR> is the address at which SOC ROM should load the
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<INPUT_FILE>
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Invoking the script for AM43xx Secure Devices
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=============================================
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create-boot-image.sh \
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<IMAGE_FLAG> <INPUT_FILE> <OUTPUT_FILE> <SPL_LOAD_ADDR>
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<IMAGE_FLAG> is a value that specifies the type of the image to
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generate OR the action the image generation tool will take. Valid
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values are:
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SPI_X-LOADER - Generates an image for SPI flash (byte
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swapped)
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XIP_X-LOADER - Generates a single stage u-boot for
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NOR/QSPI XiP
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ISSW - Generates an image for all other boot modes
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<INPUT_FILE> is the full path and filename of the public world boot
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loaderbinary file (depending on the boot media, this is usually
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either u-boot-spl.bin or u-boot.bin).
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<OUTPUT_FILE> is the full path and filename of the final secure
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image. The output binary images should be used in place of the standard
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non-secure binary images (see the platform-specific user's guides and
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releases notes for how the non-secure images are typically used)
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u-boot-spl_HS_SPI_X-LOADER - byte swapped boot image for SPI flash
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u-boot_HS_XIP_X-LOADER - boot image for NOR or QSPI flash
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u-boot-spl_HS_ISSW - boot image for all other boot media
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<SPL_LOAD_ADDR> is the address at which SOC ROM should load the
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<INPUT_FILE>
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Invoking the script for DRA7xx/AM57xx Secure Devices
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====================================================
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create-boot-image.sh \
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<IMAGE_TYPE> <INPUT_FILE> <OUTPUT_FILE> <SPL_LOAD_ADDR>
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<IMAGE_TYPE> is a value that specifies the type of the image to
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generate OR the action the image generation tool will take. Valid
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values are:
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X-LOADER - Generates an image for NOR or QSPI boot modes
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MLO - Generates an image for SD/MMC/eMMC boot modes
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ULO - Generates an image for USB/UART peripheral boot modes
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<INPUT_FILE> is the full path and filename of the public world boot
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loader binary file (for this platform, this is always u-boot-spl.bin).
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<OUTPUT_FILE> is the full path and filename of the final secure image.
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The output binary images should be used in place of the standard
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non-secure binary images (see the platform-specific user's guides
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and releases notes for how the non-secure images are typically used)
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u-boot-spl_HS_MLO - boot image for SD/MMC/eMMC. This image is
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copied to a file named MLO, which is the name that
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the device ROM bootloader requires for loading from
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the FAT partition of an SD card (same as on
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non-secure devices)
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u-boot-spl_HS_ULO - boot image for USB/UART peripheral boot modes
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u-boot-spl_HS_X-LOADER - boot image for all other flash memories
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including QSPI and NOR flash
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<SPL_LOAD_ADDR> is the address at which SOC ROM should load the
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<INPUT_FILE>
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Invoking the script for Keystone2 Secure Devices
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================================================
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create-boot-image.sh \
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<UNUSED> <INPUT_FILE> <OUTPUT_FILE> <UNUSED>
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<UNUSED> is currently ignored and reserved for future use.
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<INPUT_FILE> is the full path and filename of the public world boot
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loader binary file (only u-boot.bin is currently supported on
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Keystone2 devices, u-boot-spl.bin is not currently supported).
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<OUTPUT_FILE> is the full path and filename of the final secure image.
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The output binary images should be used in place of the standard
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non-secure binary images (see the platform-specific user's guides
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and releases notes for how the non-secure images are typically used)
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u-boot_HS_MLO - signed and encrypted boot image that can be used to
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boot from all media. Secure boot from SPI NOR flash is not
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currently supported.
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Invoking the script for K3 Secure Devices
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=========================================
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The signing steps required to produce a bootable SPL image on secure
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K3 TI devices are the same as those performed on non-secure devices.
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The only difference is the key is not checked on non-secure devices so
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a dummy key is used when building U-Boot for those devices. For secure
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K3 TI devices simply use the real hardware key for your device. This
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real key can be set with the Kconfig option "K3_KEY". The environment
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variable TI_SECURE_DEV_PKG is also searched for real keys when the
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build targets secure devices.
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Booting of Primary U-Boot (u-boot.img)
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======================================
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The SPL image is responsible for loading the next stage boot loader,
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which is the main u-boot image. For secure TI devices, the SPL will
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be authenticated, as described above, as part of the particular
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device's ROM boot process. In order to continue the secure boot
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process, the authenticated SPL must authenticate the main u-boot
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image that it loads.
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The configurations for secure TI platforms are written to make the boot
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process use the FIT image format for the u-boot.img (CONFIG_SPL_FRAMEWORK
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and CONFIG_SPL_LOAD_FIT). With these configurations the binary
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components that the SPL loads include a specific DTB image and u-boot
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image. These DTB image may be one of many available to the boot
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process. In order to secure these components so that they can be
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authenticated by the SPL as they are loaded from the FIT image, the
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build procedure for secure TI devices will secure these images before
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they are integrated into the FIT image. When those images are extracted
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from the FIT image at boot time, they are post-processed to verify that
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they are still secure. The outlined security-related SPL post-processing
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is enabled through the CONFIG_SPL_FIT_IMAGE_POST_PROCESS option which
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must be enabled for the secure boot scheme to work. In order to allow
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verifying proper operation of the secure boot chain in case of successful
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authentication messages like "Authentication passed" are output by the
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SPL to the console for each blob that got extracted from the FIT image.
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The exact details of the how the images are secured is handled by the
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SECDEV package. Within the SECDEV package exists a script to process
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an input binary image:
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${TI_SECURE_DEV_PKG}/scripts/secure-binary-image.sh
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This is called as part of the u-boot build process. As the secure
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image formats and requirements can differ between the various secure
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SOCs from TI, this script in the SECDEV package abstracts these
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details. This script is essentially the only required interface to the
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TI SECDEV package for creating a u-boot.img image for secure TI
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devices.
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The SPL/u-boot code contains calls to dedicated secure ROM functions
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to perform the validation on the secured images. The details of the
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interface to those functions is shown in the code. The summary
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is that they are accessed by invoking an ARM secure monitor call to
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the device's secure ROM (fixed read-only-memory that is secure and
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only accessible when the ARM core is operating in the secure mode).
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Invoking the secure-binary-image script for Secure Devices
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==========================================================
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secure-binary-image.sh <INPUT_FILE> <OUTPUT_FILE>
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<INPUT_FILE> is the full path and filename of the input binary image
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<OUTPUT_FILE> is the full path and filename of the output secure image.
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