Merge pull request #4 from Zubax/crc-script

pavel-kirienko · web-flow · commit fbde6913accd · 2019-05-04T17:45:23.000+03:00
A script for populating the CRC and size fields in the AppDescriptor structure
diff --git a/.travis.yml b/.travis.yml
@@ -15,6 +15,10 @@ before_script:
   - sudo apt-get install python3-pip
   - sudo pip3 install "uavcan>=1.0.0.dev30"
 
+after_script:
+  - cd test/make_boot_descriptor/
+  - ./test.sh
+
 matrix:
   include:
     #
diff --git a/README.md b/README.md
@@ -91,6 +91,16 @@ The parameters of the CRC-64 algorithm are the following:
 * Output xor: 0xFFFF'FFFF'FFFF'FFFF
 * Check: 0x62EC'59E3'F1A4'F00A
 
+The CRC and size fields cannot be populated until after the application binary is compiled and linked.
+A possible way to populate these fields is to initialize them with zeroes in the source code,
+and then use the script `populate_app_descriptor.py` after the binary is generated to update the fields
+with their actual values.
+The script can be invoked from the build system (e.g., from a Makefile rule) trivially as follows:
+
+```sh
+populate_app_descriptor.py firmware.bin
+```
+
 The following diagram documents the state machine implemented in the `BootloaderController` class:
 ![Kocherga State Machine Diagram](state_machine.svg "Kocherga State Machine Diagram")
 
diff --git a/populate_app_descriptor.py b/populate_app_descriptor.py
@@ -0,0 +1,293 @@
+#!/usr/bin/env python3
+#
+#   Copyright (c) 2012-2015 PX4 Development Team. All rights reserved.
+#   Copyright (c) 2018-2019 Zubax Robotics <info@zubax.com>. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# Based on make_can_boot_descriptor.py originally created by Ben Dyer, David Sidrane and Pavel Kirienko for PX4.
+# See https://github.com/PX4/Firmware/blob/nuttx_next/Tools/make_can_boot_descriptor.py
+#
+
+import os
+import sys
+import struct
+import optparse
+import binascii
+from io import BytesIO
+
+
+class AppDescriptor(object):
+    """
+    Kocherga application image descriptor format:
+        uint64_t signature (bytes [7:0] set to 'APDesc00' in source)
+        uint64_t image_crc (set to 0 in source, updated by this script)
+        uint32_t image_size (set to 0 in source, updated by this script)
+        uint32_t vcs_commit (set in source)
+        uint8_t version_major (set in source)
+        uint8_t version_minor (set in source)
+        uint8_t flags (1 - release build, 2 - dirty build) (set in source)
+        (uint8_t reserved)
+        uint32_t build_timestamp_utc (set in source)
+    """
+
+    LENGTH = 32
+    SIGNATURE = b'APDesc00'
+    FORMAT = '<8sQLLBBBxL'
+
+    def __init__(self, bytes=None):
+        self.signature = AppDescriptor.SIGNATURE
+        self.image_crc = 0
+        self.image_size = 0
+        self.vcs_commit = 0
+        self.version_major = 0
+        self.version_minor = 0
+        self.release_build = False
+        self.dirty_build = False
+        self.build_timestamp_utc = 0
+
+        if bytes:
+            try:
+                self.unpack(bytes)
+            except Exception:
+                raise ValueError("Invalid AppDescriptor: {0}".format(binascii.b2a_hex(bytes)))
+
+    def pack(self):
+        flags = 0
+        if self.release_build:
+            flags |= 1
+
+        if self.dirty_build:
+            flags |= 2
+
+        return struct.pack(self.FORMAT, self.signature, self.image_crc, self.image_size, self.vcs_commit,
+                           self.version_major, self.version_minor, flags, self.build_timestamp_utc)
+
+    def unpack(self, bytes):
+        (self.signature,
+         self.image_crc,
+         self.image_size,
+         self.vcs_commit,
+         self.version_major,
+         self.version_minor,
+         flags,
+         self.build_timestamp_utc) = struct.unpack(self.FORMAT, bytes)
+
+        self.release_build = bool(flags & 1)
+        self.dirty_build   = bool(flags & 2)
+
+        if not self.empty and not self.valid:
+            raise ValueError()
+
+    @property
+    def empty(self):
+        return (self.signature == AppDescriptor.SIGNATURE and
+                self.image_crc == 0 and self.image_size == 0)
+
+    @property
+    def valid(self):
+        return (self.signature == AppDescriptor.SIGNATURE and
+                self.image_crc != 0 and self.image_size > 0 and
+                self.build_timestamp_utc > 0)
+
+
+class FirmwareImage(object):
+    # Padding to 8 bytes is required by Kocherga
+    PADDING = 8
+
+    def __init__(self, path, mode="r"):
+        self._file = open(path, (mode + "b").replace("bb", "b"))
+        self._padding = self.PADDING
+
+        if "r" in mode:
+            self._contents = BytesIO(self._file.read())
+        else:
+            self._contents = BytesIO()
+        self._do_write = False
+
+        self._length = None
+        self._descriptor_offset = None
+        self._descriptor_bytes = None
+        self._descriptor = None
+
+    def __enter__(self):
+        return self
+
+    def __getattr__(self, attr):
+        if attr == "write":
+            self._do_write = True
+        return getattr(self._contents, attr)
+
+    def __iter__(self):
+        return iter(self._contents)
+
+    def __exit__(self, *args):
+        if self._do_write:
+            if getattr(self._file, "seek", None):
+                self._file.seek(0)
+            self._file.write(self._contents.getvalue())
+            if self._padding:
+                self._file.write(b'\xff' * self._padding)
+
+        self._file.close()
+
+    def _write_descriptor_raw(self):
+        # Seek to the appropriate location, write the serialized descriptor, and seek back.
+        prev_offset = self._contents.tell()
+        self._contents.seek(self._descriptor_offset)
+        self._contents.write(self._descriptor.pack())
+        self._contents.seek(prev_offset)
+
+    def write_descriptor(self):
+        # Set the descriptor's length and CRC to the values required for CRC computation
+        self.app_descriptor.image_size = self.length
+        self.app_descriptor.image_crc = 0
+
+        self._write_descriptor_raw()
+
+        # Update the descriptor's CRC based on the computed value and write it out again
+        self.app_descriptor.image_crc = self.crc
+
+        self._write_descriptor_raw()
+
+    @property
+    def crc(self):
+        MASK = 0xFFFFFFFFFFFFFFFF
+        POLY = 0x42F0E1EBA9EA3693
+
+        # Calculate the image CRC with the image_crc field in the app descriptor zeroed out.
+        crc_offset = self.app_descriptor_offset + len(AppDescriptor.SIGNATURE)
+        content = bytearray(self._contents.getvalue())
+        content[crc_offset:crc_offset + 8] = bytearray(b"\x00" * 8)
+        if self._padding:
+            content += bytearray(b"\xff" * self._padding)
+        val = MASK
+        for byte in content:
+            val ^= (byte << 56) & MASK
+            for bit in range(8):
+                if val & (1 << 63):
+                    val = ((val << 1) & MASK) ^ POLY
+                else:
+                    val <<= 1
+
+        return (val & MASK) ^ MASK
+
+    @property
+    def length(self):
+        if not self._length:
+            # Find the length of the file by seeking to the end and getting the offset
+            prev_offset = self._contents.tell()
+            self._contents.seek(0, os.SEEK_END)
+            self._length = self._contents.tell()
+            if self._padding:
+                mod = self._length % self._padding
+                self._padding = self._padding - mod if mod else 0
+                self._length += self._padding
+            self._contents.seek(prev_offset)
+
+        return self._length
+
+    @property
+    def app_descriptor_offset(self):
+        if not self._descriptor_offset:
+            # Save the current position
+            prev_offset = self._contents.tell()
+            # Check each byte in the file to see if a valid descriptor starts at that location.
+            # Slow, but not slow enough to matter.
+            offset = 0
+            while offset < self.length - AppDescriptor.LENGTH:
+                self._contents.seek(offset)
+                try:
+                    # If this throws an exception, there isn't a valid descriptor at this offset
+                    AppDescriptor(self._contents.read(AppDescriptor.LENGTH))
+                except Exception:
+                    offset += 1
+                else:
+                    self._descriptor_offset = offset
+                    break
+            # Go back to the previous position
+            self._contents.seek(prev_offset)
+
+        return self._descriptor_offset
+
+    @property
+    def app_descriptor(self):
+        if not self._descriptor:
+            # Save the current position
+            prev_offset = self._contents.tell()
+            # Jump to the descriptor and parse it
+            self._contents.seek(self.app_descriptor_offset)
+            self._descriptor_bytes = self._contents.read(AppDescriptor.LENGTH)
+            self._descriptor = AppDescriptor(self._descriptor_bytes)
+            # Go back to the previous offset
+            self._contents.seek(prev_offset)
+
+        return self._descriptor
+
+    @app_descriptor.setter
+    def app_descriptor(self, value):
+        self._descriptor = value
+
+
+if __name__ == "__main__":
+    parser = optparse.OptionParser(usage=
+                                   "Usage:   %prog [options] <input binary>\n"
+                                   "Example: %prog firmware.bin")
+    parser.add_option("--also-patch-descriptor-in",
+                      dest="also_patch_descriptor_in",
+                      default=[],
+                      action='append',
+                      help="file(s) where the descriptor will be updated too (e.g., an ELF executable for debugging)",
+                      metavar="PATH")
+
+    options, args = parser.parse_args()
+    if len(args) != 1:
+        parser.error("Invalid usage")
+
+    input_binary = args[0]
+    base_name_without_extension = os.path.basename(input_binary).rsplit('.', 1)[0]
+
+    with FirmwareImage(input_binary, "rb") as in_image:
+        # Firmware version format adopted by this script (feel free to change):
+        # <base name>-<major>.<minor>.<VCS commit>.<CRC>.application.bin
+        out_file = '%s-%s.%s.%08x.%016x.application.bin' % (base_name_without_extension,
+                                                            in_image.app_descriptor.version_major,
+                                                            in_image.app_descriptor.version_minor,
+                                                            in_image.app_descriptor.vcs_commit,
+                                                            in_image.crc)
+        with FirmwareImage(out_file, "wb") as out_image:
+            image = in_image.read()
+            out_image.write(image)
+            out_image.write_descriptor()
+
+            for patchee in options.also_patch_descriptor_in:
+                with open(patchee, "rb") as im:
+                    also_image = im.read()
+                also_image = also_image.replace(in_image.app_descriptor.pack(), out_image.app_descriptor.pack())
+                with open(patchee, "wb") as im:
+                    im.write(also_image)
diff --git a/test/populate_app_descriptor/test.image-1.0.bin b/test/populate_app_descriptor/test.image-1.0.bin
diff --git a/test/populate_app_descriptor/test.sh b/test/populate_app_descriptor/test.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+set -e
+
+../../populate_app_descriptor.py test.image-1.0.bin
+
+# Padded correctly? File created?
+size=$(stat --printf="%s" *.application.bin)
+[ $(($size % 8)) -eq 0 ]
