System Call Source Code Pointers

These are some of the files essential to system calls on the ARM architecture. System calls are very dependent on architecture, both in how they are invoked as well as what calls are available to be made.

The include/linux/syscalls.h file provides architecture independent forward declarations of all kernel system calls. This is the kernel's internal interface to system call functions.

The arch/arm/include/uapi/asm/unistd.h file provides ARM architecture specific definitions of system call numbers.

The arch/arm/kernel/entry-common.S file provides the ARM architecture specific entry point for system calls.

The arch/arm/tools/syscall.tbl file installs system call numbers and associated function addresses into the ARM hardware's system call table.

The following files don't actually pertain to system calls, but to system boot - one of the few other ways that the kernel can execute.

The init directory contains kernel intialization code.

The init/main.c file provides start_kernel, which is the first C function that is executed by the Linux kernel, and once invoked it never returns. Prior to this, the kernel only runs via architecture specific assembly code and firmware. Chapter 16 of Linux Device Drivers has a great introduction to main.c and start_kernel.