184 lines
7.1 KiB
Plaintext
184 lines
7.1 KiB
Plaintext
_____ _____ _____ _____ __ __ _____
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/ _ \/ __\/ _ \| _ \/ \/ \/ __\
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| _ <| __|| _ || | || \/ || __|
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\__|\_/\_____/\__|__/|_____/\__ \__/\_____/
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Generating the android_filesystem_config.h:
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To generate the android_filesystem_config.h file, one can choose from
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one of two methods. The first method, is to declare
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TARGET_ANDROID_FILESYSTEM_CONFIG_H in the device BoardConfig.mk file. This
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variable can only have one item in it, and it is used directly as the
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android_filesystem_config.h header when building
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fs_config_generate_$(TARGET_DEVICE) which is used to generate fs_config_files
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and fs_config_dirs target executable.
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The limitation with this, is that it can only be set once, thus if the device
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has a make hierarchy, then each device needs its own file, and cannot share
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from a common source or that common source needs to include everything from
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both devices.
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The other way is to set TARGET_FS_CONFIG_GEN, which can be a list of
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intermediate fs configuration files. It is a build error on any one
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these conditions:
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* Specify TARGET_FS_CONFIG_GEN and TARGET_ANDROID_FILESYSTEM_CONFIG_H
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* Specify TARGET_FS_CONFIG_GEN and provide
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$(TARGET_DEVICE_DIR)/android_filesystem_config.h
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The parsing of the config file follows the Python ConfigParser specification,
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with the sections and fields as defined below. There are two types of sections,
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both sections require all options to be specified. The first section type is
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the "caps" section.
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The "caps" section follows the following syntax:
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[path]
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mode: Octal file mode
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user: AID_<user>
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group: AID_<group>
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caps: cap*
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Where:
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[path]
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The filesystem path to configure. A path ending in / is considered a dir,
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else its a file.
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mode:
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A valid octal file mode of at least 3 digits. If 3 is specified, it is
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prefixed with a 0, else mode is used as is.
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user:
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Either the C define for a valid AID or the friendly name. For instance both
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AID_RADIO and radio are acceptable. Note custom AIDs can be defined in the
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AID section documented below.
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group:
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Same as user.
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caps:
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The name as declared in
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system/core/include/private/android_filesystem_capability.h without the
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leading CAP_. Mixed case is allowed. Caps can also be the raw:
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* binary (0b0101)
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* octal (0455)
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* int (42)
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* hex (0xFF)
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For multiple caps, just separate by whitespace.
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It is an error to specify multiple sections with the same [path] in different
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files. Note that the same file may contain sections that override the previous
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section in Python versions <= 3.2. In Python 3.2 it's set to strict mode.
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The next section type is the "AID" section, for specifying OEM specific AIDS.
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The AID section follows the following syntax:
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[AID_<name>]
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value: <number>
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Where:
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[AID_<name>]
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The <name> can contain characters in the set uppercase, numbers
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and underscores.
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value:
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A valid C style number string. Hex, octal, binary and decimal are supported.
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See "caps" above for more details on number formatting.
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It is an error to specify multiple sections with the same [AID_<name>]. With
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the same constraints as [path] described above. It is also an error to specify
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multiple sections with the same value option. It is also an error to specify a
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value that is outside of the inclusive OEM ranges:
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* AID_OEM_RESERVED_START(2900) - AID_OEM_RESERVED_END(2999)
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* AID_OEM_RESERVED_2_START(5000) - AID_OEM_RESERVED_2_END(5999)
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as defined by system/core/include/private/android_filesystem_config.h.
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Ordering within the TARGET_FS_CONFIG_GEN files is not relevant. The paths for files are sorted
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like so within their respective array definition:
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* specified path before prefix match
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** ie foo before f*
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* lexicographical less than before other
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** ie boo before foo
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Given these paths:
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paths=['ac', 'a', 'acd', 'an', 'a*', 'aa', 'ac*']
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The sort order would be:
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paths=['a', 'aa', 'ac', 'acd', 'an', 'ac*', 'a*']
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Thus the fs_config tools will match on specified paths before attempting prefix, and match on the
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longest matching prefix.
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The declared AIDS are sorted in ascending numerical order based on the option "value". The string
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representation of value is preserved. Both choices were made for maximum readability of the generated
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file and to line up files. Sync lines are placed with the source file as comments in the generated
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header file.
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For OEMs wishing to use the define AIDs in their native code, one can access the generated header
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file like so:
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1. In your C code just #include "generated_oem_aid.h" and start using the declared identifiers.
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2. In your Makefile add this static library like so: LOCAL_HEADER_LIBRARIES := oemaids_headers
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Unit Tests:
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From within the fs_config directory, unit tests can be executed like so:
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$ python -m unittest test_fs_config_generator.Tests
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.............
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----------------------------------------------------------------------
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Ran 13 tests in 0.004s
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OK
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One could also use nose if they would like:
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$ nose2
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To add new tests, simply add a test_<xxx> method to the test class. It will automatically
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get picked up and added to the test suite.
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Using the android_filesystem_config.h:
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The tool fs_config_generate is built as a dependency to fs_config_dirs and
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fs_config_files host targets, and #includes the above supplied or generated
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android_filesystem_config.h file, and can be instructed to generate the binary
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data that lands in the device target locations /system/etc/fs_config_dirs and
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/system/etc/fs_config_files and in the host's ${OUT} locations
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${OUT}/target/product/<device>/system/etc/fs_config_dirs and
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${OUT}/target/product/<device>/system/etc/fs_config_files. The binary files
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are interpreted by the libcutils fs_conf() function, along with the built-in
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defaults, to serve as overrides to complete the results. The Target files are
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used by filesystem and adb tools to ensure that the file and directory
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properties are preserved during runtime operations. The host files in the
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${OUT} directory are used in the final stages when building the filesystem
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images to set the file and directory properties.
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For systems with separate partition images, such as vendor or oem,
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fs_config_generate can be instructed to filter the specific file references
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to land in each partition's etc/fs_config_dirs or etc/fs_config_files
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locations. The filter can be instructed to blacklist a partition's data by
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providing the comma separated minus sign prefixed partition names. The filter
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can be instructed to whitelist partition data by providing the partition name.
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For example:
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- For system.img, but not vendor, oem or odm file references:
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-P -vendor,-oem,-odm
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This makes sure the results only contain content associated with the
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system, and not vendor, oem or odm, blacklisting their content.
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- For vendor.img file references: -P vendor
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- For oem.img file references: -P oem
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- For odm.img file references: -P odm
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fs_config_generate --help reports:
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Generate binary content for fs_config_dirs (-D) and fs_config_files (-F)
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from device-specific android_filesystem_config.h override. Filter based
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on a comma separated partition list (-P) whitelist or prefixed by a
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minus blacklist. Partitions are identified as path references to
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<partition>/ or system/<partition>
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Usage: fs_config_generate -D|-F [-P list] [-o output-file]
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