linux内核模块编译先决条件

Question

I've just started to learn about linux kernel modules and the book I'm referring to says:

"For this [compilation] to work, the kernel source has to be suitably prepared; in particular it has to have a configuration file (.config in the main kernel source directory) and proper dependencies setup"

However, as far as I know (and have tried), the .config file is generated by the make menuconfig (or any of the equivalent make config commands) - and that doesn't seem to be enough for my module files to compile. What's the bare minimum I need to do in the kernel source directory?

make modules ?

Answer 1

Yes, the .config file is generated using make *config .

Here are some of them:

make defconfig creates the default configuration for your architecture.

make config is the most primitive method, it prompts on every configuration.

make menuconfig is ncurses config menu. That's the one I prefer if I'm not editing .config file directly.

make gconfig is like menuconfig, but using gtk+.

Don't forget that make oldconfig should be called after modifying the .config file yourself.

Your current config might also be stored somewhere on your disk. For many linux versions, it's location is /boot/config-$(uname -r) If it exists, you can start with it. If not, your best bet is make defconfig , then editing the config file to suit your needs.

After configuration:

Before building modules, you might want to compile the kernel since your modules will not be used by the current kernel and even if you make your current kernel use those modules, it'll most probably cause a panic since symbol tables will not be in the order that your compiled modules assumes. make -jN is the most used method for compiling, N being twice your CPU core count. This also compiles modules, but creates .ko files for them, instead of embedding into the vmlinuz file.

After that, you can sudo make install to install your kernel. This usually wraps the kernel object you've just compiled into a suitable format and puts under /boot (it doesn't have to be /boot, actually).

Then you sudo make modules_install to copy the created .ko files into /lib/modules/$(uname -r) . This builds all modules.

After doing that, you might prefer only building your own module, instead of all of them. When on the kernel tree root, you may make M=your_modules_relative_path to only build your module.

I don't know which book you're reading, but if you're building a module externally, you still have to perform the work above. After that, you may use LDD examples as a starting point for your makefiles.

See https://github.com/duxing2007/ldd3-examples-3.x