Adding a new Kernel Call in MINIX

(Working Draft)

This tutorial helps you to add a new kernel call in MINIX. Let's say your new kernel call is called sample.

• Add the prototype of your kernel function do_sample() in the file: /usr/src/minix/kernel/system.h

...
int do_sample(struct proc *caller, message *m_ptr);

#endif  /* SYSTEM_H */

• Write the implementation of do_sample() in its own source file: /usr/src/minix/kernel/system/do_sample.c

#include "kernel/system.h"
#include <minix/endpoint.h>

 /*===========================================================================*
  *                                do_sample                                  *
  *===========================================================================*/
int do_sample(struct proc *caller_ptr, message *m_ptr)
{
        return(OK);
}

• Add do_sample.c to the Makefile for compilation: /usr/src/minix/kernel/system/Makefile.inc

# Makefile for system library implementation
.include <bsd.own.mk>

.PATH:  ${.CURDIR}/system
SRCS+=  \
        do_fork.c \
        do_exec.c \
...

        do_statectl.c \
        do_sample.c

• Map SYS_SAMPLE to do_sample() in the system call table: /usr/src/minix/kernel/system.c

...
  map(SYS_STATECTL, do_statectl);       /* let a process control its state */
  map(SYS_SAMPLE, do_sample);           /* your kernel call */
...

• Add a prototype for the sys_sample function in the file: /usr/src/minix/include/minix/syslib.h

...
int sys_sample(unsigned flags, endpoint_t proc_ep);
...

• Add the call number for sys_sample to the call vector and increment its dimension: /usr/src/minix/include/minix/com.h

...
#  define SYS_PADCONF (KERNEL_CALL + 57)       /* sys_padconf() */
#  define SYS_SAMPLE    (KERNEL_CALL + 58)      /* sys_sample() */


/* Total */
#define NR_SYS_CALLS    59      /* number of kernel calls */
...

• Add the SAMPLE service to the system tab: /usr/src/minix/commands/service/parse.c; build the updated system tab and install it with make; make install from /usr/src/minix/commands/service/

...
struct
{
        char *label;
        int call_nr;
} system_tab[]=
{
...
        { "PADCONF",             SYS_PADCONF },
        { "SAMPLE",             SYS_SAMPLE },
        { NULL,         0 }
};
...

• Write your implementation of the function sys_sample in a new file: /usr/src/minix/lib/libsys/sys_sample.c

#include "syslib.h"

int sys_sample(unsigned flags, endpoint_t proc_ep)
{
        message m;

        return(_kernel_call(SYS_SAMPLE, &m));
}

• Add sys_sample.c to the /usr/src/minix/lib/libsys/Makefile, and install it in /usr/lib/${MACHINE_ARCH} with make install.

# Makefile for libsys

LIB=            sys

SRCS+=  \
...
        sys_sample.c \
...

1. Test the new kernel call with a hello driver in /usr/src/minix/drivers/sample_test.
2. Rebuild the kernel and install it with make; make install from /usr/src/releasetools.