[PATCH] doc: imx: habv4: Add Secure Boot guide for i.MX8M SPL targets
Marek Vasut
marex at denx.de
Tue Jul 12 17:04:52 CEST 2022
Add HABv4 documentation extension for SPL targets covering the
following topics:
- How to sign an securely boot an flash.bin container image.
- How to extend the root of trust for additional boot images.
- Add SPL and fitImage CSF examples.
- Add signature generation script example.
Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Breno Lima <breno.lima at nxp.com>
Cc: Fabio Estevam <festevam at denx.de>
Cc: Heiko Schocher <hs at denx.de>
Cc: Peng Fan <peng.fan at nxp.com>
Cc: Stefano Babic <sbabic at denx.de>
Cc: Utkarsh Gupta <utkarsh.gupta at nxp.com>
Cc: Ye Li <ye.li at nxp.com>
---
doc/imx/habv4/csf_examples/mx8m/csf.sh | 77 +++++
doc/imx/habv4/csf_examples/mx8m/csf_fit.txt | 36 +++
doc/imx/habv4/csf_examples/mx8m/csf_spl.txt | 33 +++
doc/imx/habv4/guides/mx8m_spl_secure_boot.txt | 265 ++++++++++++++++++
4 files changed, 411 insertions(+)
create mode 100644 doc/imx/habv4/csf_examples/mx8m/csf.sh
create mode 100644 doc/imx/habv4/csf_examples/mx8m/csf_fit.txt
create mode 100644 doc/imx/habv4/csf_examples/mx8m/csf_spl.txt
create mode 100644 doc/imx/habv4/guides/mx8m_spl_secure_boot.txt
diff --git a/doc/imx/habv4/csf_examples/mx8m/csf.sh b/doc/imx/habv4/csf_examples/mx8m/csf.sh
new file mode 100644
index 00000000000..6898513be51
--- /dev/null
+++ b/doc/imx/habv4/csf_examples/mx8m/csf.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+
+# 0) Generate keys
+#
+# WARNING: ECDSA keys are only supported by HAB 4.5 and newer (i.e. i.MX8M Plus)
+#
+# cd /path/to/cst-3.3.1/keys/
+# ./hab4_pki_tree.sh -existing-ca n -use-ecc n -kl 4096 -duration 10 -num-srk 4 -srk-ca y
+# cd /path/to/cst-3.3.1/crts/
+# ../linux64/bin/srktool -h 4 -t SRK_1_2_3_4_table.bin -e SRK_1_2_3_4_fuse.bin -d sha256 -c ./SRK1_sha256_4096_65537_v3_ca_crt.pem,./SRK2_sha256_4096_65537_v3_ca_crt.pem,./SRK3_sha256_4096_65537_v3_ca_crt.pem,./SRK4_sha256_4096_65537_v3_ca_crt.pem -f 1
+
+# 1) Build U-Boot (e.g. for i.MX8MM)
+#
+# export ATF_LOAD_ADDR=0x920000
+# cp -Lv /path/to/arm-trusted-firmware/build/imx8mm/release/bl31.bin .
+# cp -Lv /path/to/firmware-imx-8.14/firmware/ddr/synopsys/ddr3* .
+# make -j imx8mm_board_defconfig
+# make -j`nproc` flash.bin
+
+# 2) Sign SPL and DRAM blobs
+
+cp doc/imx/habv4/csf_examples/mx8m/csf_spl.txt csf_spl.tmp
+cp doc/imx/habv4/csf_examples/mx8m/csf_fit.txt csf_fit.tmp
+
+spl_block_base=$(printf "0x%x" $(( $(sed -n "/CONFIG_SPL_TEXT_BASE=/ s at .*=@@p" .config) - 0x40)) )
+spl_block_size=$(printf "0x%x" $(stat -tc %s u-boot-spl-ddr.bin))
+sed -i "/Blocks = / s at .*@ Blocks = $spl_block_base 0x0 $spl_block_size \"flash.bin\"@" csf_spl.tmp
+
+# Generate CSF blob
+cst -i csf_spl.tmp -o csf_spl.bin
+
+# Patch CSF blob into flash.bin
+spl_csf_offset=$(xxd -s 24 -l 4 -e flash.bin | cut -d " " -f 2 | sed "s@^@0x@")
+spl_bin_offset=$(xxd -s 4 -l 4 -e flash.bin | cut -d " " -f 2 | sed "s@^@0x@")
+spl_dd_offset=$((${spl_csf_offset} - ${spl_bin_offset} + 0x40))
+dd if=csf_spl.bin of=flash.bin bs=1 seek=${spl_dd_offset} conv=notrunc
+
+# 3) Sign u-boot.itb
+
+# fitImage tree
+fit_block_base=$(printf "0x%x" $(( $(sed -n "/CONFIG_SYS_TEXT_BASE=/ s at .*=@@p" .config) - $(sed -n "/CONFIG_FIT_EXTERNAL_OFFSET=/ s at .*=@@p" .config) - 0x200 - 0x40)) )
+fit_block_offset=$(printf "0x%s" $(fdtget -t x u-boot.dtb /binman/imx-boot/uboot offset))
+fit_block_size=$(printf "0x%x" $(( ( $(fdtdump u-boot.itb 2>/dev/null | sed -n "/^...totalsize:/ s at .*\(0x[0-9a-f]\+\).*@\1 at p") + 0x1000 - 0x1 ) & ~(0x1000 - 0x1) + 0x20 )) )
+sed -i "/Blocks = / s at .*@ Blocks = $fit_block_base $fit_block_offset $fit_block_size \"flash.bin\", \\\\@" csf_fit.tmp
+
+# U-Boot
+uboot_block_base=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/uboot load))
+uboot_block_offset=$(printf "0x%x" $(( $(printf "0x%s" $(fdtget -t x u-boot.itb /images/uboot data-position)) + ${fit_block_offset} )))
+uboot_block_size=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/uboot data-size))
+sed -i "/0xuuuu/ s at .*@ $uboot_block_base $uboot_block_offset $uboot_block_size \"flash.bin\", \\\\@" csf_fit.tmp
+
+# ATF
+atf_block_base=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/atf load))
+atf_block_offset=$(printf "0x%x" $(( $(printf "0x%s" $(fdtget -t x u-boot.itb /images/atf data-position)) + ${fit_block_offset} )))
+atf_block_size=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/atf data-size))
+sed -i "/0xaaaa/ s at .*@ $atf_block_base $atf_block_offset $atf_block_size \"flash.bin\", \\\\@" csf_fit.tmp
+
+# DTB
+dtb_block_base=$(printf "0x%x" $(( ${uboot_block_base} + ${uboot_block_size} )))
+dtb_block_offset=$(printf "0x%x" $(( $(printf "0x%s" $(fdtget -t x u-boot.itb /images/fdt-1 data-position)) + ${fit_block_offset} )))
+dtb_block_size=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/fdt-1 data-size))
+sed -i "/0xdddd/ s at .*@ $dtb_block_base $dtb_block_offset $dtb_block_size \"flash.bin\"@" csf_fit.tmp
+
+# IVT
+ivt_ptr_base=$(printf "%08x" ${fit_block_base} | sed "s@\(..\)\(..\)\(..\)\(..\)@0x\4\3\2\1@")
+ivt_block_base=$(printf "%08x" $(( ${fit_block_base} + ${fit_block_size} - 0x20 )) | sed "s@\(..\)\(..\)\(..\)\(..\)@0x\4\3\2\1@")
+csf_block_base=$(printf "%08x" $(( ${fit_block_base} + ${fit_block_size} )) | sed "s@\(..\)\(..\)\(..\)\(..\)@0x\4\3\2\1@")
+ivt_block_offset=$((${fit_block_offset} + ${fit_block_size} - 0x20))
+csf_block_offset=$((${ivt_block_offset} + 0x20))
+
+echo "0xd1002041 ${ivt_ptr_base} 0x00000000 0x00000000 0x00000000 ${ivt_block_base} ${csf_block_base} 0x00000000" | xxd -r -p > ivt.bin
+dd if=ivt.bin of=flash.bin bs=1 seek=${ivt_block_offset} conv=notrunc
+
+# Generate CSF blob
+cst -i csf_fit.tmp -o csf_fit.bin
+# Patch CSF blob into flash.bin
+dd if=csf_fit.bin of=flash.bin bs=1 seek=${csf_block_offset} conv=notrunc
diff --git a/doc/imx/habv4/csf_examples/mx8m/csf_fit.txt b/doc/imx/habv4/csf_examples/mx8m/csf_fit.txt
new file mode 100644
index 00000000000..cd1d4070a5e
--- /dev/null
+++ b/doc/imx/habv4/csf_examples/mx8m/csf_fit.txt
@@ -0,0 +1,36 @@
+[Header]
+ Version = 4.3
+ Hash Algorithm = sha256
+ Engine = CAAM
+ Engine Configuration = 0
+ Certificate Format = X509
+ Signature Format = CMS
+
+[Install SRK]
+ # FIXME: Adjust path here
+ File = "/path/to/cst-3.3.1/crts/SRK_1_2_3_4_table.bin"
+ Source index = 0
+
+[Install CSFK]
+ # FIXME: Adjust path here
+ File = "/path/to/cst-3.3.1/crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"
+
+[Authenticate CSF]
+
+[Install Key]
+ Verification index = 0
+ Target Index = 2
+ # FIXME: Adjust path here
+ File = "/path/to/cst-3.3.1/crts/IMG1_1_sha256_4096_65537_v3_usr_crt.pem"
+
+[Authenticate Data]
+ Verification index = 2
+ # FIXME:
+ # Line 1 -- fitImage tree
+ # Line 2 -- U-Boot u-boot-nodtb.bin blob
+ # Line 3 -- ATF BL31 blob
+ # Line 4 -- DT blob
+ Blocks = 0x401fcdc0 0x57c00 0xffff "flash.bin", \
+ 0x40200000 0x62c00 0xuuuu "flash.bin", \
+ 0x920000 0x00000 0xaaaa "flash.bin", \
+ 0x40200000 0x00000 0xdddd "flash.bin"
diff --git a/doc/imx/habv4/csf_examples/mx8m/csf_spl.txt b/doc/imx/habv4/csf_examples/mx8m/csf_spl.txt
new file mode 100644
index 00000000000..00e34f6b1b9
--- /dev/null
+++ b/doc/imx/habv4/csf_examples/mx8m/csf_spl.txt
@@ -0,0 +1,33 @@
+[Header]
+ Version = 4.3
+ Hash Algorithm = sha256
+ Engine = CAAM
+ Engine Configuration = 0
+ Certificate Format = X509
+ Signature Format = CMS
+
+[Install SRK]
+ # FIXME: Adjust path here
+ File = "/path/to/cst-3.3.1/crts/SRK_1_2_3_4_table.bin"
+ Source index = 0
+
+[Install CSFK]
+ # FIXME: Adjust path here
+ File = "/path/to/cst-3.3.1/crts/CSF1_1_sha256_4096_65537_v3_usr_crt.pem"
+
+[Authenticate CSF]
+
+[Unlock]
+ Engine = CAAM
+ Features = MID
+
+[Install Key]
+ Verification index = 0
+ Target Index = 2
+ # FIXME: Adjust path here
+ File = "/path/to/cst-3.3.1/crts/IMG1_1_sha256_4096_65537_v3_usr_crt.pem"
+
+[Authenticate Data]
+ Verification index = 2
+ # FIXME: Adjust start (first column) and size (third column) here
+ Blocks = 0x7e0fc0 0x0 0x306f0 "flash.bin"
diff --git a/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt b/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt
new file mode 100644
index 00000000000..747f7cd260f
--- /dev/null
+++ b/doc/imx/habv4/guides/mx8m_spl_secure_boot.txt
@@ -0,0 +1,265 @@
+ +=========================================================+
+ + i.MX8M U-Boot HABv4 Secure Boot guide for SPL targets +
+ +=========================================================+
+
+1. HABv4 secure boot process
+-----------------------------
+
+This document is an addendum of mx6_mx7_spl_secure_boot.txt guide describing
+a step-by-step procedure on how to sign and securely boot an U-Boot image for
+SPL targets on i.MX8M, i.MX8M Mini, i.MX8M Nano, i.MX8M Plus.
+
+Details about HAB can be found in the application note AN4581[1] and in the
+introduction_habv4.txt document.
+
+1.1 Building a SPL target supporting secure boot
+-------------------------------------------------
+
+The U-Boot build for i.MX8M SoC makes use of Second Program Loader (SPL)
+support, fitImage support and custom i.MX8M specific flash.bin container.
+This leads to a generation of multiple intermediate build artifacts, the
+U-Boot SPL, U-Boot binary, DT blob. These later two artifacts are bundled
+with external ATF BL31 blob to form a fitImage. The fitImage is bundled
+with SPL and external DDR and optional HDMI PHY initialization blobs to
+form the final flash.bin container. The HABv4 can be used to authenticate
+all of the input binaries separately.
+
+Out of reset the ROM code authenticates the SPL and PHY initialization
+blobs, combination of which is responsible for initializing essential
+features such as DDR, UART, PMIC and clock enablement. Once the DDR is
+available, the SPL code loads the secondary fitImage to its specific
+address and call the HAB APIs to extend the root of trust on its
+components.
+
+The U-Boot SPL provides support to secure boot configuration and also
+provide access to the HAB APIs exposed by the ROM vector table, the
+U-Boot provides access to HAB APIs via SMC calls to ATF. The support
+is enabled by selecting the CONFIG_IMX_HAB option.
+
+When built with this configuration the U-Boot correctly pads combined
+SPL and PHY initialization blob image, called u-boot-spl-ddr.bin, by
+aligning to the next 0xC00 address, so the CSF signature data generated
+by CST can be concatenated to the image.
+
+The U-Boot also reserves space in the fitImage binary (u-boot.itb) between
+the fitImage tree and external blobs included in it, so it can be used to
+inject IVT and CST signatures used by SPL HAB calls to authenticate the
+fitImage components.
+
+The diagram below illustrate a signed SPL combined with DDR PHY
+initialization firmware blobs part of flash.bin container layout.
+This part is loaded to memory address ( CONFIG_SPL_TEXT_BASE - 0x40 ) and
+authenticated the BootROM. The reason for the offset is so that the *entry
+would be at memory address CONFIG_SPL_TEXT_BASE when BootROM executes the
+code within it:
+
+ ------- +-----------------------------+ <-- *start
+ ^ | Image Vector Table |
+ | | (0x20 bytes) |
+ | +-----------------------------+ <-- *boot_data
+ | | Boot Data |
+ | +-----------------------------+
+ | | Padding |
+ Signed | | to 0x40 bytes from *start |
+ Data | +-----------------------------+ <-- *entry
+ | | |
+ | | SPL combined with DDR PHY |
+ | | initialization blobs |
+ | | (u-boot-spl-ddr.bin) |
+ | | |
+ | +-----------------------------+
+ v | Padding |
+ ------- +-----------------------------+ <-- *csf
+ | |
+ | Command Sequence File (CSF) |
+ | |
+ +-----------------------------+
+ | Padding (optional) |
+ +-----------------------------+
+
+The diagram below illustrate a signed U-Boot binary, DT blob and external
+ATF BL31 blob combined to form fitImage part of flash.bin container layout.
+The *load_address is derived from CONFIG_SYS_TEXT_BASE such that the U-Boot
+binary *start is placed exactly at CONFIG_SPL_TEXT_BASE in DRAM, however the
+SPL moves the fitImage tree further to location:
+ *load_address = CONFIG_SPL_TEXT_BASE - CONFIG_FIT_EXTERNAL_OFFSET (=12kiB) -
+ 512 Byte sector - sizeof(mkimage header)
+
+ ------- +-----------------------------+ <-- *load_address
+ ^ | |
+ | | fitImage tree |
+ | | with external data at |
+ | | offset 12 kiB from tree |
+ | | (cca. 1 kiB) |
+ Signed | | |
+ .----- Tree | +-----------------------------+
+ | Data | | Padding to next 4k aligned |
+ | | | from *load_address |
+ | | +-----------------------------+ <-- *ivt
+ | | | Image Vector Table |
+ | v | (0x20 bytes) |
+ | ------- +-----------------------------+ <-- *csf
+ | | Command Sequence File (CSF) |
+ | | for all signed entries in |
+ >--------------->| the fitImage, tree and data |
+ | | (cca 6-7 kiB) |
+ | +-----------------------------+
+ | | Padding to 12 kiB offset |
+ | | from *load_address |
+ | ------- +-----------------------------+ <-- *start
+ | ^ | |
+ | Signed | | |
+ |---- Payload | | U-Boot external data blob |
+ | Data | | |
+ | v | |
+ | ------- +-----------------------------+
+ | | Padding to 4 Bytes |
+ | ------- +-----------------------------+
+ | ^ | |
+ | Signed | | |
+ |---- Payload | | ATF external data blob |
+ | Data | | |
+ | v | |
+ | ------- +-----------------------------+
+ | | Padding to 4 Bytes |
+ | ------- +-----------------------------+
+ | ^ | |
+ | Signed | | |
+ '---- Payload | | DTB external data blob |
+ Data | | |
+ v | |
+ ------- +-----------------------------+
+
+The diagram below illustrate a combined flash.bin container layout:
+
+ +-----------------------------+
+ | Signed SPL part |
+ +-----------------------------+
+ | Signed fitImage part |
+ +-----------------------------+
+
+1.2 Enabling the secure boot support
+-------------------------------------
+
+The first step is to generate an U-Boot image supporting the HAB features
+mentioned above, this can be achieved by adding CONFIG_IMX_HAB to the
+build configuration:
+
+- Defconfig:
+
+ CONFIG_IMX_HAB=y
+
+- Kconfig:
+
+ ARM architecture -> Support i.MX HAB features
+
+1.3 Signing the images
+-----------------------
+
+The CSF contains all the commands that the HAB executes during the secure
+boot. These commands instruct the HAB code on which memory areas of the image
+to authenticate, which keys to install, use and etc.
+
+CSF examples are available under doc/imx/habv4/csf_examples/ directory.
+
+CSF "Blocks" line for csf_spl.txt can be generated as follows:
+
+```
+spl_block_base=$(printf "0x%x" $(( $(sed -n "/CONFIG_SPL_TEXT_BASE=/ s at .*=@@p" .config) - 0x40)) )
+spl_block_size=$(printf "0x%x" $(stat -tc %s u-boot-spl-ddr.bin))
+sed -i "/Blocks = / s at .*@ Blocks = $spl_block_base 0x0 $spl_block_size \"flash.bin\"@" csf_spl.txt
+```
+
+The resulting line looks as follows:
+```
+ Blocks = 0x7e0fc0 0x0 0x306f0 "flash.bin"
+```
+
+The columns mean:
+ - CONFIG_SPL_TEXT_BASE - 0x40 -- Start address of signed data, in DRAM
+ - 0x0 -- Start address of signed data, in "flash.bin"
+ - 0x306f0 -- Length of signed data, in "flash.bin"
+ - Filename -- "flash.bin"
+
+To generate signature for the SPL part of flash.bin container, use CST:
+```
+cst -i csf_spl.tmp -o csf_spl.bin
+```
+
+The newly generated CST blob has to be patched into existing flash.bin
+container. Conveniently, flash.bin IVT contains physical address of the
+CSF blob. Remember, the SPL part of flash.bin container is loaded by the
+BootROM at CONFIG_SPL_TEXT_BASE - 0x40 , so the offset of CSF blob in
+the fitImage can be calculated and inserted into the flash.bin in the
+correct location as follows:
+```
+# offset = IVT_HEADER[6 = CSF address] - CONFIG_SPL_TEXT_BASE - 0x40
+spl_csf_offset=$(xxd -s 24 -l 4 -e flash.bin | cut -d " " -f 2 | sed "s@^@0x@")
+spl_bin_offset=$(xxd -s 4 -l 4 -e flash.bin | cut -d " " -f 2 | sed "s@^@0x@")
+spl_dd_offset=$((${spl_csf_offset} - ${spl_bin_offset} + 0x40))
+dd if=csf_spl.bin of=flash.bin bs=1 seek=${spl_dd_offset} conv=notrunc
+```
+
+CSF "Blocks" line for csf_fit.txt can be generated as follows:
+```
+# fitImage tree
+fit_block_base=$(printf "0x%x" $(( $(sed -n "/CONFIG_SYS_TEXT_BASE=/ s at .*=@@p" .config) - $(sed -n "/CONFIG_FIT_EXTERNAL_OFFSET=/ s at .*=@@p" .config) - 0x200 - 0x40)) )
+fit_block_offset=$(printf "0x%s" $(fdtget -t x u-boot.dtb /binman/imx-boot/uboot offset))
+fit_block_size=$(printf "0x%x" $(( ( $(fdtdump u-boot.itb 2>/dev/null | sed -n "/^...totalsize:/ s at .*\(0x[0-9a-f]\+\).*@\1 at p") + 0x1000 - 0x1 ) & ~(0x1000 - 0x1) + 0x20 )) )
+sed -i "/Blocks = / s at .*@ Blocks = $fit_block_base $fit_block_offset $fit_block_size \"flash.bin\", \\\\@" csf_fit.tmp
+
+# U-Boot
+uboot_block_base=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/uboot load))
+uboot_block_offset=$(printf "0x%x" $(( $(printf "0x%s" $(fdtget -t x u-boot.itb /images/uboot data-position)) + ${fit_block_offset} )))
+uboot_block_size=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/uboot data-size))
+sed -i "/0xuuuu/ s at .*@ $uboot_block_base $uboot_block_offset $uboot_block_size \"flash.bin\", \\\\@" csf_fit.tmp
+
+# ATF
+atf_block_base=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/atf load))
+atf_block_offset=$(printf "0x%x" $(( $(printf "0x%s" $(fdtget -t x u-boot.itb /images/atf data-position)) + ${fit_block_offset} )))
+atf_block_size=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/atf data-size))
+sed -i "/0xaaaa/ s at .*@ $atf_block_base $atf_block_offset $atf_block_size \"flash.bin\", \\\\@" csf_fit.tmp
+
+# DTB
+dtb_block_base=$(printf "0x%x" $(( ${uboot_block_base} + ${uboot_block_size} )))
+dtb_block_offset=$(printf "0x%x" $(( $(printf "0x%s" $(fdtget -t x u-boot.itb /images/fdt-1 data-position)) + ${fit_block_offset} )))
+dtb_block_size=$(printf "0x%s" $(fdtget -t x u-boot.itb /images/fdt-1 data-size))
+sed -i "/0xdddd/ s at .*@ $dtb_block_base $dtb_block_offset $dtb_block_size \"flash.bin\"@" csf_fit.tmp
+```
+
+The fitImage part of flash.bin requires separate IVT. Generate the IVT and
+patch it into the correct aligned location of flash.bin as follows:
+```
+# IVT
+ivt_ptr_base=$(printf "%08x" ${fit_block_base} | sed "s@\(..\)\(..\)\(..\)\(..\)@0x\4\3\2\1@")
+ivt_block_base=$(printf "%08x" $(( ${fit_block_base} + ${fit_block_size} - 0x20 )) | sed "s@\(..\)\(..\)\(..\)\(..\)@0x\4\3\2\1@")
+csf_block_base=$(printf "%08x" $(( ${fit_block_base} + ${fit_block_size} )) | sed "s@\(..\)\(..\)\(..\)\(..\)@0x\4\3\2\1@")
+ivt_block_offset=$((${fit_block_offset} + ${fit_block_size} - 0x20))
+csf_block_offset=$((${ivt_block_offset} + 0x20))
+
+echo "0xd1002041 ${ivt_ptr_base} 0x00000000 0x00000000 0x00000000 ${ivt_block_base} ${csf_block_base} 0x00000000" | xxd -r -p > ivt.bin
+dd if=ivt.bin of=flash.bin bs=1 seek=${ivt_block_offset} conv=notrunc
+
+To generate CSF signature for the fitImage part of flash.bin container, use CST:
+```
+cst -i csf_fit.tmp -o csf_fit.bin
+```
+
+Finally, patch the CSF signature into the fitImage right past the IVT:
+```
+dd if=csf_fit.bin of=flash.bin bs=1 seek=${csf_block_offset} conv=notrunc
+```
+
+The entire script is available in doc/imx/habv4/csf_examples/mx8m/csf.sh
+
+1.4 Closing the device
+-----------------------
+
+The procedure for closing the device is similar as in Non-SPL targets, for a
+complete procedure please refer to section "1.5 Programming SRK Hash" in
+mx6_mx7_secure_boot.txt document available under doc/imx/habv4/guides/
+directory.
+
+References:
+[1] AN4581: "Secure Boot on i.MX 50, i.MX 53, i.MX 6 and i.MX 7 Series using
+ HABv4" - Rev 2.
--
2.35.1
More information about the U-Boot
mailing list