de18e892d3
While searching for some fs_config related symbols, I ran across this being out of date, so update it. The new documentation defers to the help section of the underlying script more to hopefully avoid this in the future. Test: n/a Change-Id: I94893cbb29b8d7e81963a12e3f8316ac3f41b7ae
137 lines
5.1 KiB
Text
137 lines
5.1 KiB
Text
_____ _____ _____ _____ __ __ _____
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/ _ \/ __\/ _ \| _ \/ \/ \/ __\
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| _ <| __|| _ || | || \/ || __|
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\__|\_/\_____/\__|__/|_____/\__ \__/\_____/
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The fs_config_generator.py tool uses the platform android_filesystem_config.h and the
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TARGET_FS_CONFIG_GEN files to generate the fs_config_dirs and fs_config_files files for each
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partition, as well as passwd and group files, and the generated_oem_aid.h header.
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The fs_config_dirs and fs_config_files binary files are interpreted by the libcutils fs_config()
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function, along with the built-in defaults, to serve as overrides to complete the results. The
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Target files are used by filesystem and adb tools to ensure that the file and directory properties
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are preserved during runtime operations. The host files in the ${OUT} directory are used in the
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final stages when building the filesystem images to set the file and directory properties.
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See ./fs_config_generator.py fsconfig --help for how these files are generated.
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The passwd and group files are formatted as documented in man pages passwd(5) and group(5) and used
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by bionic for implementing getpwnam() and related functions.
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See ./fs_config_generator.py passwd --help and ./fs_config_generator.py group --help for how these
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files are generated.
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The generated_oem_aid.h creates identifiers for non-platform AIDs for developers wishing to use them
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in their native code. To do so, include the oemaids_headers header library in the corresponding
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makefile and #include "generated_oem_aid.h" in the code wishing to use these identifiers.
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See ./fs_config_generator.py oemaid --help for how this file is generated.
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The parsing of the TARGET_FS_CONFIG_GEN files follows the Python ConfigParser specification, with
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the sections and fields as defined below. There are two types of sections, both sections require all
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options to be specified. The first section type is 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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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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