syscall.c

#include <stdio.h>
#include <string.h>

#define SYSCALL_NUM	256

void *sys_call_table[SYSCALL_NUM] = { 0 };

int my_open(char *str) {
	printf("my_open() system call\n");
	printf("str = %s\n", str);
	return 0;
}

int my_read(int fd, char *buf, int size) {
	printf("my_read() system call\n");
	printf("fd = %d, buf = %s, size = %d\n", fd, buf, size);
	return 0;
}

int my_write(int fd, char *buf, int size) {
	printf("my_write() system call\n");
	printf("fd = %d, buf = %s, size = %d\n", fd, buf, size);
	return 0;
}

void my_close(int fd) {
	printf("my_close() system call\n");
}

void kill_proc(int signum) {
	printf("signum = %d\n", signum);
}

void (*my_signal(int signum, void(*handler)(int)))(int) {
	printf("my_signal() system call\n");
	printf("signum = %d\n", signum);
	handler(signum);

	return kill_proc;
}

void init_sys_call_table(void) {
	sys_call_table[0] = my_open;
	sys_call_table[1] = my_read;
	sys_call_table[2] = my_write;
	sys_call_table[3] = my_close;
	sys_call_table[4] = my_signal;
}

void syscall(int syscall_num) {
	int fd = 3;
	int kill_signal = 9;
	char filename[32] = "test.txt";
	char buf[32] = "contents";
	int len = strlen(buf);

	switch (syscall_num) {
	case 0:
		((int(*)(char *))sys_call_table[0])(filename);
		break;
	case 1:
		((int(*)(int, char *, int))sys_call_table[1])(fd, buf, len);
		break;
	case 2:
		((int(*)(int, char *, int))sys_call_table[2])(fd, buf, len);
		break;
	case 3:
		((void(*)(int))sys_call_table[3])(fd);
		break;
	case 4:
		((void(*)(int, void(*)(int)))(int)sys_call_table[4])(kill_signal, kill_proc);
		break;
	default:
		printf("There are no system call\n");
		break;
	}
}

int main(void) {
	int i;
	init_sys_call_table();

	for (i = 0; i < 5; i++) {
		syscall(i);
	}

	return 0;
}