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CMake: Support signing and merging TF-M binaries
This commit adds post binary hook support for TF-M targets. To apply this hook to a TF-M target, do the following in the target's `CMakeLists.txt`: * include `mbed_set_post_build_tfm.cmake` * call `mbed_post_build_tfm_sign_image()`, passing - Mbed OS target name - TF-M target name - path containing the target's bootloader, layout files and signing keys - path to the secure binary - path to the non-secure binary (i.e. the "raw" Mbed application)
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‎platform/FEATURE_EXPERIMENTAL_API/FEATURE_PSA/TARGET_TFM/TARGET_TFM_LATEST/scripts/generate_mbed_image.py

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#!/usr/bin/python
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# Copyright (c) 2017-2021 Arm Limited
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#
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# SPDX-License-Identifier: Apache-2.0
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import os
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from os.path import abspath, basename, dirname, splitext, isdir
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from os.path import join as path_join
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import re
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import subprocess
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import argparse
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SCRIPT_DIR = dirname(abspath(__file__))
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MBED_OS_ROOT = abspath(path_join(SCRIPT_DIR, os.pardir, os.pardir, os.pardir, os.pardir, os.pardir, os.pardir))
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def sign_and_merge_tfm_bin(target_name, target_path, non_secure_bin, secure_bin):
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assert os.path.isdir(target_path)
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assert os.path.isfile(secure_bin)
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assert os.path.isfile(non_secure_bin)
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build_dir = dirname(non_secure_bin)
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tempdir = path_join(build_dir, 'temp')
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if not isdir(tempdir):
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os.makedirs(tempdir)
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flash_layout = path_join(target_path, 'partition', 'flash_layout.h')
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mcuboot_bin = path_join(target_path, 'bl2.bin')
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image_macros_s = path_join(target_path, 'partition', 'signing_layout_s.c')
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image_macros_ns = path_join(target_path, 'partition', 'signing_layout_ns.c')
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s_bin_name, s_bin_ext = splitext(basename(secure_bin))
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s_signed_bin = abspath(path_join(tempdir, s_bin_name + '_signed' + s_bin_ext))
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ns_bin_name, ns_bin_ext = splitext(basename(non_secure_bin))
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ns_signed_bin = abspath(path_join(tempdir, 'tfm_' + ns_bin_name + '_signed' + ns_bin_ext))
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concatenated_bin = abspath(path_join(tempdir, s_bin_name + '_' + ns_bin_name + '_concat' + ns_bin_ext))
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assert os.path.isfile(image_macros_s)
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assert os.path.isfile(image_macros_ns)
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#1. Run wrapper to sign the TF-M secure binary
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cmd = [
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"python3",
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path_join(MBED_OS_ROOT, "tools", "psa","tfm", "bin_utils","wrapper.py"),
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"-v",
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'1.2.0',
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"-k",
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path_join(target_path, (target_name + '-root-rsa-3072.pem')),
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"--layout",
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image_macros_s,
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"--public-key-format",
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'full',
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"--align",
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'1',
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"--pad",
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"--pad-header",
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"-H",
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'0x400',
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"--overwrite-only",
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"-s",
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'auto',
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"-d",
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'(0,0.0.0+0)',
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abspath(secure_bin),
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s_signed_bin,
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]
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retcode = run_cmd(cmd, MBED_OS_ROOT)
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if retcode:
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raise Exception("Unable to sign " + target_name +
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" secure binary, Error code: " + str(retcode))
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#2. Run wrapper to sign the non-secure mbed binary
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cmd = [
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"python3",
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path_join(MBED_OS_ROOT, "tools", "psa","tfm", "bin_utils","wrapper.py"),
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"-v",
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'1.2.0',
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"-k",
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path_join(target_path, (target_name + '-root-rsa-3072_1.pem')),
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"--layout",
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image_macros_ns,
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"--public-key-format",
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'full',
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"--align",
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'1',
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"--pad",
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"--pad-header",
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"-H",
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'0x400',
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"--overwrite-only",
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"-s",
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'auto',
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"-d",
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'(1,0.0.0+0)',
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abspath(non_secure_bin),
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ns_signed_bin,
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]
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retcode = run_cmd(cmd, MBED_OS_ROOT)
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if retcode:
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raise Exception("Unable to sign " + target_name +
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" non-secure binary, Error code: " + str(retcode))
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#3. Concatenate signed secure TFM and non-secure mbed binaries
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cmd = [
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"python3",
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path_join(MBED_OS_ROOT, "tools", "psa","tfm", "bin_utils","assemble.py"),
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"--layout",
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image_macros_s,
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"-s",
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s_signed_bin,
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"-n",
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ns_signed_bin,
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"-o",
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concatenated_bin,
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]
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retcode = run_cmd(cmd, MBED_OS_ROOT)
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if retcode:
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raise Exception("Unable to concatenate " + target_name +
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" binaries, Error code: " + str(retcode))
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#4. Concatenate mcuboot and signed binary and overwrite mbed built binary file
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mcuboot_image_size = find_bl2_size(flash_layout)
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with open(mcuboot_bin, "rb") as mcuboot_fh, open(concatenated_bin, "rb") as concat_fh:
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with open(non_secure_bin, "w+b") as out_fh:
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out_fh.write(mcuboot_fh.read())
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out_fh.seek(mcuboot_image_size)
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out_fh.write(concat_fh.read())
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def find_bl2_size(configFile):
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bl2_size_re = re.compile(r"^#define\s+FLASH_AREA_BL2_SIZE\s+\({0,1}(0x[0-9a-fA-F]+)\){0,1}")
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bl2_size = None
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with open(configFile, 'r') as flash_layout_file:
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for line in flash_layout_file:
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m = bl2_size_re.match(line)
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if m is not None:
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bl2_size = int(m.group(1), 0)
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break
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return bl2_size
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def run_cmd(cmd, directory):
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popen_instance = subprocess.Popen(
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cmd,
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stdout=subprocess.PIPE,
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stderr=subprocess.STDOUT,
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cwd=directory,
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)
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popen_instance.communicate()
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return popen_instance.returncode
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def parse_args():
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parser = argparse.ArgumentParser()
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parser.add_argument(
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"--tfm-target",
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help="Name of the TF-M target",
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required=True
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)
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parser.add_argument(
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"--target-path",
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help="Path containing the target's bootloader, layouts and signing keys",
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required=True
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)
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parser.add_argument(
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"--non-secure-bin",
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help="Path to the non-secure binary",
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required=True
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)
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parser.add_argument(
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"--secure-bin",
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help="Path to the secure binary",
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required=True
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)
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return parser.parse_args()
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if __name__ == "__main__":
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args = parse_args()
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sign_and_merge_tfm_bin(args.tfm_target, args.target_path, args.non_secure_bin, args.secure_bin)

‎platform/FEATURE_EXPERIMENTAL_API/FEATURE_PSA/TARGET_TFM/TARGET_TFM_LATEST/scripts/mbed_set_post_build_tfm.cmake

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# Copyright (c) 2021 ARM Limited. All rights reserved.
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# SPDX-License-Identifier: Apache-2.0
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include(${MBED_PATH}/tools/cmake/mbed_set_post_build.cmake)
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#
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# Sign TF-M secure and non-secure images and combine them with the bootloader
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#
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function(mbed_post_build_tfm_sign_image
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mbed_target
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tfm_target
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target_path
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secure_bin
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)
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find_package(Python3)
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set(mbed_target_name ${mbed_target})
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set(post_build_command
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COMMAND ${Python3_EXECUTABLE}
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${MBED_PATH}/platform/FEATURE_EXPERIMENTAL_API/FEATURE_PSA/TARGET_TFM/TARGET_TFM_LATEST/scripts/generate_mbed_image.py
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--tfm-target ${tfm_target}
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--target-path ${target_path}
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--secure-bin ${secure_bin}
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--non-secure-bin ${CMAKE_BINARY_DIR}/$<TARGET_PROPERTY:mbed-post-build-bin-${mbed_target_name},application>.bin
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)
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mbed_set_post_build_operation()
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endfunction()

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