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Daniel Allred98350f72016-05-19 19:10:41 -05001README on how boot images are created for secure TI devices
2
3CONFIG_TI_SECURE_DEVICE:
4Secure TI devices require a boot image that is authenticated by ROM
5code to function. Without this, even JTAG remains locked and the
6device is essentially useless. In order to create a valid boot image for
7a secure device from TI, the initial public software image must be signed
8and combined with various headers, certificates, and other binary images.
9
10Information on the details on the complete boot image format can be obtained
11from Texas Instruments. The tools used to generate boot images for secure
12devices are part of a secure development package (SECDEV) that can be
13downloaded from:
14
15 http://www.ti.com/mysecuresoftware (login required)
16
17The secure development package is access controlled due to NDA and export
18control restrictions. Access must be requested and granted by TI before the
19package is viewable and downloadable. Contact TI, either online or by way
20of a local TI representative, to request access.
21
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050022Booting of U-Boot SPL
23=====================
Daniel Allred98350f72016-05-19 19:10:41 -050024
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050025 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.
Daniel Allred98350f72016-05-19 19:10:41 -050033
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050034 Within the SECDEV package exists an image creation script:
Daniel Allred98350f72016-05-19 19:10:41 -050035
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050036 ${TI_SECURE_DEV_PKG}/scripts/create-boot-image.sh
Daniel Allred98350f72016-05-19 19:10:41 -050037
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050038 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.
Daniel Allred98350f72016-05-19 19:10:41 -050042
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050043 The script is basically the only required interface to the TI SECDEV
44 package for creating a bootable SPL image for secure TI devices.
Daniel Allred98350f72016-05-19 19:10:41 -050045
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050046 Invoking the script for AM43xx Secure Devices
47 =============================================
Daniel Allred98350f72016-05-19 19:10:41 -050048
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050049 create-boot-image.sh \
50 <IMAGE_FLAG> <INPUT_FILE> <OUTPUT_FILE> <SPL_LOAD_ADDR>
Daniel Allred98350f72016-05-19 19:10:41 -050051
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050052 <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
Daniel Allred98350f72016-05-19 19:10:41 -050060
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050061 <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)
Daniel Allred98350f72016-05-19 19:10:41 -050069 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
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050073 <SPL_LOAD_ADDR> is the address at which SOC ROM should load the
74 <INPUT_FILE>
Daniel Allred98350f72016-05-19 19:10:41 -050075
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050076 Invoking the script for DRA7xx/AM57xx Secure Devices
77 ====================================================
Daniel Allred98350f72016-05-19 19:10:41 -050078
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050079 create-boot-image.sh <IMAGE_TYPE> <INPUT_FILE> <OUTPUT_FILE>
Daniel Allred98350f72016-05-19 19:10:41 -050080
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050081 <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
Daniel Allred98350f72016-05-19 19:10:41 -050088
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050089 <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).
Daniel Allred98350f72016-05-19 19:10:41 -050091
Andreas Dannenberg8662bea2016-06-27 09:19:24 -050092 <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)
Daniel Allred98350f72016-05-19 19:10:41 -050096 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
Andreas Dannenberg8662bea2016-06-27 09:19:24 -0500103
104Booting 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.