Add canned_fs_config to apex module type

The property is used to customize uid/gid/mode/capabilities of files in
an APEX.

Bug: 209971551
Test: m
Change-Id: I484e46ff819a5266c1e8046dae337e18ef3fefea

apex/apex.go

@@ -98,6 +98,14 @@ type apexBundleProperties struct {
 	// /system/sepolicy/apex/<module_name>_file_contexts.
 	File_contexts *string `android:"path"`
 
+	// Path to the canned fs config file for customizing file's uid/gid/mod/capabilities. The
+	// format is /<path_or_glob> <uid> <gid> <mode> [capabilities=0x<cap>], where path_or_glob is a
+	// path or glob pattern for a file or set of files, uid/gid are numerial values of user ID
+	// and group ID, mode is octal value for the file mode, and cap is hexadecimal value for the
+	// capability. If this property is not set, or a file is missing in the file, default config
+	// is used.
+	Canned_fs_config *string `android:"path"`
+
 	ApexNativeDependencies
 
 	Multilib apexMultilibProperties

apex/builder.go

@@ -1067,6 +1067,11 @@ func (a *apexBundle) buildCannedFsConfig(ctx android.ModuleContext) android.Outp
 		file := appSetFiles[dir]
 		cmd.Text("zipinfo -1").Input(file).Textf(`| sed "s:\(.*\):/%s/\1 1000 1000 0644:";`, dir)
 	}
+	// Custom fs_config is "appended" to the last so that entries from the file are preferred
+	// over default ones set above.
+	if a.properties.Canned_fs_config != nil {
+		cmd.Text("cat").Input(android.PathForModuleSrc(ctx, *a.properties.Canned_fs_config))
+	}
 	cmd.Text(")").FlagWithOutput("> ", cannedFsConfig)
 	builder.Build("generateFsConfig", fmt.Sprintf("Generating canned fs config for %s", a.BaseModuleName()))