| commit | beba1df8ac1b10bdf12d7d4e7233f96eba4f7528 | [log] [tgz] |
|---|---|---|
| author | Jooyung Han <jooyung@google.com> | Thu Apr 15 03:12:07 2021 +0900 |
| committer | Jooyung Han <jooyung@google.com> | Thu Apr 15 10:18:58 2021 +0900 |
| tree | 46969567b1ff6e1d2fd83538a1041d9e50a4286e | |
| parent | fece76d589982967077f3a3e1c4d6dc903250b4b [diff] |
Add doc about linker.config.pb Since there's no mention about linker.config.pb, one may get confused they want to find the artifact from the device. Especially, /system/etc/linker.config.pb is not just compiled into .pb, but is amended during "make" to populated(or append) "provideLibs" key at make phase. Because /system/etc/linker.config.pb is a very crucial part of the system, it deserves more explanation. Bug: n/a Test: documentation Change-Id: Ib6db77a42ec842ab0ecea15a44f9557345b57a58
Linkerconfig is a program to generate linker configuration based on the runtime environment. Linkerconfig generates one or more ld.config.txt files and some other files under /linkerconfig during init. Linker will read this generated configuration file(s) to find out link relationship between libraries and executable.
TODO: explain inputs (e.g. /system/etc/public.libraries.txt, /apex/apex-info-list.xml, ..)
Linker configuration file can be used to add extra information while linkerconfig creates linker configuration with the module. This module can be defined as linker_config from Soong, and it will be translated as protobuf file at build time.
A linker configuration file(linker.config.json) is compiled into a protobuf at build time by conv_linker_config. You can find the compiled file under <base>/etc/linker.config.pb. For example, /apex/com.android.art/etc/linker.config.pb is a configuration for the com.android.art APEX.
/system/etc/linker.config.pb(or its source module system_linker_config) is special because its provideLibs key is generated at build time.
linker.config.json file is in json format which can contain properties as below.
| Property Name | Type | Description | Allowed module |
|---|---|---|---|
| permittedPaths | List | Additional permitted paths | APEX |
| visible | bool | Force APEX namespace to be visible from all sections if the value is true | APEX |
| provideLibs | List | Libraries providing from the module | System |
| requireLibs | List | Libraries required from the module | System |
{
"permittedPaths" : [ "/a", "/b/c", "/d/e/f"],
"visible": true
}
{
"provideLibs" : [ "a.so", "b.so", "c.so" ],
"requireLibs" : [ "foo.so", "bar.so", "baz.so" ]
}
TODO: a few words about the files
Check ld.config.format.md.
The file describes libraries exposed from APEXes. libnativeloader is the main consumer of this file.
# comment line jni com_android_foo libfoo_jni.so public com_android_bar libbar.so:libbaz.so
The file is line-based and each line consists of tag apex_namespace library_list.
tag explains what library_list is.apex_namespace is the namespace of the apex. Note that it is mangled like com_android_foo for the APEX(“com.android.foo”).library_list is colon-separated list of library names.tag is jni, library_list is the list of JNI libraries exposed by apex_namespace.tag is public, library_list is the list of public libraries exposed by apex_namespace. Here, public libraries are the libs listed in /system/etc/public.libraries.txt.