android related image generation

android related image generation

调用build_image.py的cmd如下，system.img、userdata.img、cache.img、vendor.img都是调用这个cmd去生成image的

./build/tools/releasetools/build_image.py $TARGET_OUT $IMAGE_INFO $PRODUCT_OUT/$PARTITION_NAME.img $PRODUCT_OUT/system

比如为system.img时，$IMAGE_INFO为$PRODUCT_OUT/obj/PACKAGING/systemimage_intermediates/system_image_info.txt，这个文件里的内容如下：

system_reserved_size=52428800
system_selinux_fc=out/target/product/device/obj/ETC/file_contexts.bin_intermediates/file_contexts.bin
ext_mkuserimg=mkuserimg_mke2fs
fs_type=ext4
extfs_sparse_flag=-s
squashfs_sparse_flag=-s
f2fs_sparse_flag=-S
avb_avbtool=avbtool
avb_system_hashtree_enable=true
avb_system_add_hashtree_footer_args=--prop com.android.build.system.fingerprint:customer/device_an64/device:11/RP1A.200720.011/$date:userdebug/test-keys --prop com.android.build.system.os_version:11 --prop com.android.build.system.security_patch:2022-04-05
root_dir=out/target/product/device/root
use_dynamic_partition_size=true
skip_fsck=true

对于userdata.img，userdata_image_info.txt里的内容如下：

userdata_fs_type=f2fs
userdata_size=1073741824
needs_casefold=1
needs_projid=1
userdata_selinux_fc=out/target/product/device/obj/ETC/file_contexts.bin_intermediates/file_contexts.bin
ext_mkuserimg=mkuserimg_mke2fs
fs_type=ext4
extfs_sparse_flag=-s
squashfs_sparse_flag=-s
f2fs_sparse_flag=-S
avb_avbtool=avbtool
avb_system_hashtree_enable=true
avb_system_add_hashtree_footer_args=--prop com.android.build.system.fingerprint:customer/device_an64/device:11/RP1A.200720.011/$date:userdebug/test-keys --prop com.android.build.system.os_version:11 --prop com.android.build.system.security_patch:2022-04-05
root_dir=out/target/product/device/root
use_dynamic_partition_size=true
skip_fsck=true

build/make/tools/releasetools/build_image.py

def main(argv):
763   if len(argv) != 4:
764     print(__doc__)
765     sys.exit(1)
766 
767   common.InitLogging()
768 
769   in_dir = argv[0]
770   glob_dict_file = argv[1]
771   out_file = argv[2]
772   target_out = argv[3]
773 
774   glob_dict = LoadGlobalDict(glob_dict_file)
775   if "mount_point" in glob_dict:
776     # The caller knows the mount point and provides a dictionary needed by
777     # BuildImage().
778     image_properties = glob_dict
779   else:
780     image_filename = os.path.basename(out_file)
781     mount_point = ""
782     if image_filename == "system.img":
783       mount_point = "system"
784     elif image_filename == "system_other.img":
785       mount_point = "system_other"
786     elif image_filename == "userdata.img":
787       mount_point = "data"
788     elif image_filename == "cache.img":
789       mount_point = "cache"
790     elif image_filename == "vendor.img":
791       mount_point = "vendor"
792     elif image_filename == "odm.img":
793       mount_point = "odm"
794     elif image_filename == "oem.img":
795       mount_point = "oem"
796     elif image_filename == "product.img":
797       mount_point = "product"
798     elif image_filename == "system_ext.img":
799       mount_point = "system_ext"
800     else:
801       logger.error("Unknown image file name %s", image_filename)
802       sys.exit(1)
803 
804     image_properties = ImagePropFromGlobalDict(glob_dict, mount_point)
805 
806   try:
807     BuildImage(in_dir, image_properties, out_file, target_out)

上面BuildImage函数将解析image_properties prop_dict（由$IMAGE_INFO文件而来）去调用生成对应文件系统的cmd去生成image，如果这个image是有开AVB的，比如hashtree，则会调用avbtool add_hashtree_footer去生成hashtree、vbmeta、footer并依次将它们append到out_file（$PRODUCT_OUT/$PARTITION_NAME.img）

注：ImagePropFromGlobalDict(glob_dict, mount_point)里会设置image_properties里的partition_name为mount_point，比如设置为"system"