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Merge "Update fs_config documentation"

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Treehugger Robot 2019-06-18 22:08:46 +00:00 committed by Gerrit Code Review
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tools/fs_config/README
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@ -3,16 +3,33 @@
| _ <| __|| _ || | || \/ || __|
\__|\_/\_____/\__|__/|_____/\__ \__/\_____/
Generating the android_filesystem_config.h:
The fs_config_generator.py tool uses the platform android_filesystem_config.h and the
TARGET_FS_CONFIG_GEN files to generate the fs_config_dirs and fs_config_files files for each
partition, as well as passwd and group files, and the generated_oem_aid.h header.
To generate the android_filesystem_config.h file, one can set
TARGET_FS_CONFIG_GEN, which can be a list of intermediate fs configuration
files.
The fs_config_dirs and fs_config_files binary files are interpreted by the libcutils fs_config()
function, along with the built-in defaults, to serve as overrides to complete the results. The
Target files are used by filesystem and adb tools to ensure that the file and directory properties
are preserved during runtime operations. The host files in the ${OUT} directory are used in the
final stages when building the filesystem images to set the file and directory properties.
The parsing of the config file follows the Python ConfigParser specification,
with the sections and fields as defined below. There are two types of sections,
both sections require all options to be specified. The first section type is
the "caps" section.
See ./fs_config_generator.py fsconfig --help for how these files are generated.
The passwd and group files are formatted as documented in man pages passwd(5) and group(5) and used
by bionic for implementing getpwnam() and related functions.
See ./fs_config_generator.py passwd --help and ./fs_config_generator.py group --help for how these
files are generated.
The generated_oem_aid.h creates identifiers for non-platform AIDs for developers wishing to use them
in their native code. To do so, include the oemaids_headers header library in the corresponding
makefile and #include "generated_oem_aid.h" in the code wishing to use these identifiers.
See ./fs_config_generator.py oemaid --help for how this file is generated.
The parsing of the TARGET_FS_CONFIG_GEN files follows the Python ConfigParser specification, with
the sections and fields as defined below. There are two types of sections, both sections require all
options to be specified. The first section type is the "caps" section.
The "caps" section follows the following syntax:
@ -103,11 +120,6 @@ representation of value is preserved. Both choices were made for maximum readabi
file and to line up files. Sync lines are placed with the source file as comments in the generated
header file.
For OEMs wishing to use the define AIDs in their native code, one can access the generated header
file like so:
1. In your C code just #include "generated_oem_aid.h" and start using the declared identifiers.
2. In your Makefile add this static library like so: LOCAL_HEADER_LIBRARIES := oemaids_headers
Unit Tests:
From within the fs_config directory, unit tests can be executed like so:
@ -123,45 +135,3 @@ $ nose2
To add new tests, simply add a test_<xxx> method to the test class. It will automatically
get picked up and added to the test suite.
Using the android_filesystem_config.h:
The tool fs_config_generate is built as a dependency to fs_config_dirs and
fs_config_files host targets, and #includes the above supplied or generated
android_filesystem_config.h file, and can be instructed to generate the binary
data that lands in the device target locations /system/etc/fs_config_dirs and
/system/etc/fs_config_files and in the host's ${OUT} locations
${OUT}/target/product/<device>/system/etc/fs_config_dirs and
${OUT}/target/product/<device>/system/etc/fs_config_files. The binary files
are interpreted by the libcutils fs_conf() function, along with the built-in
defaults, to serve as overrides to complete the results. The Target files are
used by filesystem and adb tools to ensure that the file and directory
properties are preserved during runtime operations. The host files in the
${OUT} directory are used in the final stages when building the filesystem
images to set the file and directory properties.
For systems with separate partition images, such as vendor or oem,
fs_config_generate can be instructed to filter the specific file references
to land in each partition's etc/fs_config_dirs or etc/fs_config_files
locations. The filter can be instructed to blacklist a partition's data by
providing the comma separated minus sign prefixed partition names. The filter
can be instructed to whitelist partition data by providing the partition name.
For example:
- For system.img, but not vendor, oem or odm file references:
-P -vendor,-oem,-odm
This makes sure the results only contain content associated with the
system, and not vendor, oem or odm, blacklisting their content.
- For vendor.img file references: -P vendor
- For oem.img file references: -P oem
- For odm.img file references: -P odm
fs_config_generate --help reports:
Generate binary content for fs_config_dirs (-D) and fs_config_files (-F)
from device-specific android_filesystem_config.h override. Filter based
on a comma separated partition list (-P) whitelist or prefixed by a
minus blacklist. Partitions are identified as path references to
<partition>/ or system/<partition>
Usage: fs_config_generate -D|-F [-P list] [-o output-file]