When defining the contents of a SECTION block, specify the source files that are contributing to their sections.
In a large project, the list can become very long. For this reason, you have to use the asterisk (*) keyword. The * keyword represents the filenames of every file in your project. Note that since you have already added the .text sections from the main.c, file2.c, and file3.c files, the * keyword does not include the .text sections from those files again.