doc/README.ti-secure

   1 README on how boot images are created for secure TI devices
   2
   3 CONFIG_TI_SECURE_DEVICE:
   4 Secure TI devices require a boot image that is authenticated by ROM
   5 code to function. Without this, even JTAG remains locked and the
   6 device is essentially useless. In order to create a valid boot image for
   7 a secure device from TI, the initial public software image must be signed
   8 and combined with various headers, certificates, and other binary images.
   9
  10 Information on the details on the complete boot image format can be obtained
  11 from Texas Instruments. The tools used to generate boot images for secure
  12 devices are part of a secure development package (SECDEV) that can be
  13 downloaded from:
  14
  15         http://www.ti.com/mysecuresoftware (login required)
  16
  17 The secure development package is access controlled due to NDA and export
  18 control restrictions. Access must be requested and granted by TI before the
  19 package is viewable and downloadable. Contact TI, either online or by way
  20 of a local TI representative, to request access.
  21
  22 Booting of U-Boot SPL
  23 =====================
  24
  25         When CONFIG_TI_SECURE_DEVICE is set, the U-Boot SPL build process
  26         requires the presence and use of these tools in order to create a
  27         viable boot image. The build process will look for the environment
  28         variable TI_SECURE_DEV_PKG, which should be the path of the installed
  29         SECDEV package. If the TI_SECURE_DEV_PKG variable is not defined or
  30         if it is defined but doesn't point to a valid SECDEV package, a
  31         warning is issued during the build to indicate that a final secure
  32         bootable image was not created.
  33
  34         Within the SECDEV package exists an image creation script:
  35
  36         ${TI_SECURE_DEV_PKG}/scripts/create-boot-image.sh
  37
  38         This is called as part of the SPL/u-boot build process. As the secure
  39         boot image formats and requirements differ between secure SOC from TI,
  40         the purpose of this script is to abstract these details as much as
  41         possible.
  42
  43         The script is basically the only required interface to the TI SECDEV
  44         package for creating a bootable SPL image for secure TI devices.
  45
  46         Invoking the script for AM43xx Secure Devices
  47         =============================================
  48
  49         create-boot-image.sh \
  50                 <IMAGE_FLAG> <INPUT_FILE> <OUTPUT_FILE> <SPL_LOAD_ADDR>
  51
  52         <IMAGE_FLAG> is a value that specifies the type of the image to
  53         generate OR the action the image generation tool will take. Valid
  54         values are:
  55                 SPI_X-LOADER - Generates an image for SPI flash (byte
  56                         swapped)
  57                 XIP_X-LOADER - Generates a single stage u-boot for
  58                         NOR/QSPI XiP
  59                 ISSW - Generates an image for all other boot modes
  60
  61         <INPUT_FILE> is the full path and filename of the public world boot
  62         loaderbinary file (depending on the boot media, this is usually
  63         either u-boot-spl.bin or u-boot.bin).
  64
  65         <OUTPUT_FILE> is the full path and filename of the final secure
  66         image. The output binary images should be used in place of the standard
  67         non-secure binary images (see the platform-specific user's guides and
  68         releases notes for how the non-secure images are typically used)
  69         u-boot-spl_HS_SPI_X-LOADER - byte swapped boot image for SPI flash
  70         u-boot_HS_XIP_X-LOADER - boot image for NOR or QSPI flash
  71         u-boot-spl_HS_ISSW - boot image for all other boot media
  72
  73         <SPL_LOAD_ADDR> is the address at which SOC ROM should load the
  74         <INPUT_FILE>
  75
  76         Invoking the script for DRA7xx/AM57xx Secure Devices
  77         ====================================================
  78
  79         create-boot-image.sh <IMAGE_TYPE> <INPUT_FILE> <OUTPUT_FILE>
  80
  81         <IMAGE_TYPE> is a value that specifies the type of the image to
  82         generate OR the action the image generation tool will take. Valid
  83         values are:
  84                 X-LOADER - Generates an image for NOR or QSPI boot modes
  85                 MLO - Generates an image for SD/MMC/eMMC boot modes
  86                 ULO - Generates an image for USB/UART peripheral boot modes
  87                 Note: ULO is not yet used by the u-boot build process
  88
  89         <INPUT_FILE> is the full path and filename of the public world boot
  90         loader binary file (for this platform, this is always u-boot-spl.bin).
  91
  92         <OUTPUT_FILE> is the full path and filename of the final secure image.
  93         The output binary images should be used in place of the standard
  94         non-secure binary images (see the platform-specific user's guides
  95         and releases notes for how the non-secure images are typically used)
  96         u-boot-spl_HS_MLO - boot image for SD/MMC/eMMC. This image is
  97                 copied to a file named MLO, which is the name that
  98                 the device ROM bootloader requires for loading from
  99                 the FAT partition of an SD card (same as on
 100                 non-secure devices)
 101         u-boot-spl_HS_X-LOADER - boot image for all other flash memories
 102                 including QSPI and NOR flash
 103
 104 Booting of Primary U-Boot (u-boot.img)
 105 ======================================
 106
 107         The SPL image is responsible for loading the next stage boot loader,
 108         which is the main u-boot image. For secure TI devices, the SPL will
 109         be authenticated, as described above, as part of the particular
 110         device's ROM boot process. In order to continue the secure boot
 111         process, the authenticated SPL must authenticate the main u-boot
 112         image that it loads.
 113
 114         The configurations for secure TI platforms are written to make the boot
 115         process use the FIT image format for the u-boot.img (CONFIG_SPL_FRAMEWORK
 116         and CONFIG_SPL_LOAD_FIT). With these configurations the binary
 117         components that the SPL loads include a specific DTB image and u-boot
 118         image. These DTB image may be one of many available to the boot
 119         process. In order to secure these components so that they can be
 120         authenticated by the SPL as they are loaded from the FIT image, the
 121         build procedure for secure TI devices will secure these images before
 122         they are integrated into the FIT image. When those images are extracted
 123         from the FIT image at boot time, they are post-processed to verify that
 124         they are still secure. The outlined security-related SPL post-processing
 125         is enabled through the CONFIG_SPL_FIT_IMAGE_POST_PROCESS option which
 126         must be enabled for the secure boot scheme to work. In order to allow
 127         verifying proper operation of the secure boot chain in case of successful
 128         authentication messages like "Authentication passed: CERT_U-BOOT-NOD" are
 129         output by the SPL to the console for each blob that got extracted from the
 130         FIT image. Note that the last part of this log message is the (truncated)
 131         name of the signing certificate embedded into the blob that got processed.
 132
 133         The exact details of the how the images are secured is handled by the
 134         SECDEV package. Within the SECDEV package exists a script to process
 135         an input binary image:
 136
 137         ${TI_SECURE_DEV_PKG}/scripts/secure-binary-image.sh
 138
 139         This is called as part of the u-boot build process. As the secure
 140         image formats and requirements can differ between the various secure
 141         SOCs from TI, this script in the SECDEV package abstracts these
 142         details. This script is essentially the only required interface to the
 143         TI SECDEV package for creating a u-boot.img image for secure TI
 144         devices.
 145
 146         The SPL/u-boot code contains calls to dedicated secure ROM functions
 147         to perform the validation on the secured images. The details of the
 148         interface to those functions is shown in the code. The summary
 149         is that they are accessed by invoking an ARM secure monitor call to
 150         the device's secure ROM (fixed read-only-memory that is secure and
 151         only accessible when the ARM core is operating in the secure mode).
 152
 153         Invoking the secure-binary-image script for Secure Devices
 154         ==========================================================
 155
 156         secure-binary-image.sh <INPUT_FILE> <OUTPUT_FILE>
 157
 158         <INPUT_FILE> is the full path and filename of the input binary image
 159
 160         <OUTPUT_FILE> is the full path and filename of the output secure image.