Question

For a college assignment we have to add a system call to the Linux kernel. I have “Hello, World” done no problem. In terms of adding a more complicated call, I know (or at least think) I can’t use C functions like malloc, but I’m wondering can I use syscall() to use other system calls?

Answer 1

The kernel has its own specific calls for pretty much everything. You don’t have access to system calls or <sys/xxxx.h> header files.

For your exmaple, yes, you can’t use malloc() but you can use kmalloc()

In older versions of the kernel (2.4) you could use syscall() via: syscallN() macros. I’m pretty sure that’s been removed.

In general syscalls() from the kernel is not a good idea. Really system calls are just a way of user space going into the kernel to do something, so if you’re already in the kernel there should be a better way to do what you’re trying to do.