Linux – Find out which kernel source files were used when kernel was compiled

compilingkernellinux-kernelSecuritysource

I am compiling the Linux kernel for my specific hardware and I only select the drivers/options which I really need. This is in contrast to a typical distribution kernel, where they compile almost everything, to be compatible with as many hardware configurations as possible.

I imagine, for my kernel, I am only using 1% of the total kernel code (order of magnitude estimate).

Is there any way to find out which files from the kernel source I have actually used when I build my kernel?

This is not an academical question. Suppose I have compiled my kernel 3.18.1. Now a security update comes along, and 3.18.2 is released. I have learned in my other question how to find which files have change between releases. If I knew whether any of the files I am using have changed, I would recompile my kernel to the new version. If, on the other hand, the changes only affect files which I am not using anyway, I can keep my current kernel version.

Best Answer

Compiling my comment as answer:

  1. Run the following command on one shell. You can make a shell script of it or demonize with the -d option.

    inotifywait -m -r -e open --format '%f' /kernel_sources/directory/in_use/ -o /home/user/kernel_build.log

  2. On other shell, execute make

  3. The log file /home/user/kernel_build.log will have a list of the files that have been opened(read operation) during the build process.
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