Linux Kernel system call implementation with struct parameter

Question

I just know how to add system calls to kernel of Linux. My system call (like lots of other system calls) takes a pointer to a struct created by me. If I want to add the struct to kernel source how and where should I add it?

Answer 1

Place a header containing the new struct in include/uapi/linux. Avoid namespace pollution by using the appropriate types e.g. __u16 instead of unsigned short/uint16_t, __kernel_time_t instead of time_t ...etc. Check out struct mii_ioctl_data for an example.

By adding a header-y += new_header.h entry to include/uapi/linux/Kbuild, you can then export the header with make headers_install.

By default, it installs the headers in ./usr. If you want it to install them as system headers, use make headers_install INSTALL_HDR_PATH=/usr instead. This results in the contents of the uapi directory being merged into /usr/include. You may then #include <linux/new_header.h> in your userspace program.