add simg2dontcare.py (#169)

flash_system.sh

@@ -15,10 +15,9 @@ cd $DIR
 # Flash system
 fastboot --set-active=a
 
-# TODO: clean this up. move simg2dimg into a common repo?
 if [ -d $HOME/openpilot/provisioning ]; then
   DIMG=$(mktemp)
-  $HOME/openpilot/provisioning/scripts/simg2dontcare.py $OUTPUT_DIR/$ROOTFS_IMAGE $DIMG
+  $DIR/tools/simg2dontcare.py $OUTPUT_DIR/$ROOTFS_IMAGE $DIMG
   fastboot erase system_a
   fastboot flash system_a $DIMG
 else

tools/simg2dontcare.py

@@ -0,0 +1,76 @@
+#!/usr/bin/env python3
+import argparse
+import sys
+import struct
+from enum import IntEnum
+
+# https://android.googlesource.com/platform/system/core/+/master/libsparse/sparse_format.h
+class ChunkType(IntEnum):
+  RAW = 0xCAC1
+  FILL = 0xCAC2
+  DONT_CARE = 0xCAC3
+  CRC32 = 0xCAC4
+
+ChunkHeader = struct.Struct("<2H2I")
+
+
+def process_image(input_image: str, output_image: str) -> None:
+  with open(input_image, "rb") as inf, open(output_image, "wb") as outf:
+    dat = inf.read(28)
+    outf.write(dat)
+
+    header = struct.unpack("<I4H4I", dat)
+
+    magic = header[0]
+    major_version = header[1]
+    minor_version = header[2]
+    file_hdr_sz = header[3]
+    chunk_hdr_sz = header[4]
+    total_chunks = header[7]
+    image_checksum = header[8]
+
+    assert magic == 0xED26FF3A
+    assert major_version == 1 and minor_version == 0
+    assert file_hdr_sz == 28
+    assert chunk_hdr_sz == 12
+
+    for _ in range(1, total_chunks+1):
+      header_bin = inf.read(12)
+
+      header = ChunkHeader.unpack(header_bin)
+      chunk_type = ChunkType(header[0])
+      chunk_sz = header[2]
+      total_sz = header[3]
+      data_sz = total_sz - 12
+
+      # replace fill 0s with DONT_CARE chunks
+      if chunk_type == ChunkType.FILL:
+        assert data_sz == 4
+        fill_bin = inf.read(4)
+        fill = struct.unpack("<I", fill_bin)[0]
+        if fill == 0:
+          # https://coral.googlesource.com/img2simg/+/refs/heads/master/libsparse/output_file.c#351
+          dat = ChunkHeader.pack(ChunkType.DONT_CARE, 0, chunk_sz, ChunkHeader.size)
+          outf.write(dat)
+          continue
+        else:
+          inf.seek(inf.tell() - data_sz)
+
+      # pass through other chunk types
+      outf.write(header_bin)
+      dat = inf.read(data_sz)
+      outf.write(dat)
+
+
+if __name__ == "__main__":
+  parser = argparse.ArgumentParser(description="Replace FILL 0 chunks in a sparse image with DONT_CARE chunks",
+                                   formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+  parser.add_argument("input_image", nargs="?", help="Input sparse image")
+  parser.add_argument("output_image", nargs="?", help="Output sparse image")
+  args = parser.parse_args(sys.argv[1:])
+
+  if args.input_image is None or args.output_image is None:
+    parser.print_help()
+    exit(1)
+
+  process_image(args.input_image, args.output_image)