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1 Chapter 5 Chapter 6 Chapter 7 chapter 6 Part Part 2 Part 3 145

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3 Chapter 5 Chapter 6 Chapter 7 Part 1 Part 2 Part 3 147

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5 Chapter 5 Chapter 6 Chapter 7 Part 1 Part 2 Part 3 149

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7 Chapter 5 Chapter 6 Chapter Part 3 Part 2 Part 1 151

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9 Chapter 5 Chapter 6 Chapter 7 Part 3 Part 2 Part 1 153

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11 Chapter 5 Chapter 6 Chapter Part 1 Part 2 Part 3 155

12 #ifndef _ASM_I386_UNISTD_H_ #define _ASM_I386_UNISTD_H_ /* * This file contains the system call numbers. */ #define NR_exit 1 #define NR_fork 2 #define NR_read 3... #define NR_getdents #define NR_fcntl #ifndef _ASM_I386_UNISTD_H_ #define _ASM_I386_UNISTD_H_ /* 156

13 Chapter 5 Chapter 6 Chapter 7 * This file contains the system call numbers. */ #define NR_exit 1 #define NR_fork 2 #define NR_read 3... #define NR_getdents #define NR_fcntl #define NR_mysyscall 222 //... Part 1... #include <linux/config.h> #include <linux/sys.h> #include <linux/linkage.h> #include <asm/segment.h> #define ASSEMBLY #include <asm/smp.h> EBX ECX... = 0x00 = 0x04 Part 2 Part 3 157

.. #define NR_getdents64 220 #define NR_fcntl64 221 #define NR_mysyscall 222 //... Part 1.

14 ... ENTRY(sys_call_table).long SYMBOL_NAME(sys_ni_syscall) /* 0. old "setup()" system call*/.long SYMBOL_NAME(sys_exit).long SYMBOL_NAME(sys_fork)....long SYMBOL_NAME(sys_getdents64) /* 220 */.long SYMBOL_NAME(sys_fcntl64).long SYMBOL_NAME(sys_mysyscall) /* 222 */.long SYMBOL_NAME(sys_ni_syscall) /* reserved for TUX */... /* Sys_mysyscall() */ #include <linux/unistd.h> #include <linux/errno.h> #include <linux/kernel.h> #include <linux/sched.h> asmlinkage int sys_mysyscall() { printk("hello Linux Kernel Programming!\n"); return 0; } 158

long SYMBOL_NAME(sys_mysyscall) /* 222 */.long SYMBOL_NAME(sys_ni_syscall) /* reserved for TUX */.

15 Chapter 5 Chapter 6 Chapter 7... O_TARGET := kernel.o export-objs = signal.o sys.o kmod.o context.o ksyms.o pm.o exec_domain.o printk.o Part 1 Part 2 Part 3 obj-y = sched.o dma.o fork.o exec_domain.o panic.o printk.o \ module.o exit.o itimer.o info.o time.o softirq.o resource.o \ sysctl.o acct.o capability.o ptrace.o timer.o user.o \ signal.o sys.o kmod.o context.o

$o fork.o exec_domain.o panic.o printk.o \ module.o exit.o itimer.o info.o time.o softirq.$

16 ... O_TARGET := kernel.o export-objs = signal.o sys.o kmod.o context.o ksyms.o pm.o exec_domain.o printk.o obj-y = sched.o dma.o fork.o exec_domain.o panic.o printk.o \ module.o exit.o itimer.o info.o time.o softirq.o resource.o \ sysctl.o acct.o capability.o ptrace.o timer.o user.o \ signal.o sys.o kmod.o context.o mysyscall.o... /* */ mysyscall.c #include <linux/unistd.h> _syscall0(int, mysyscall); 160

$o info.o time.o softirq.o resource.o \ sysctl.o acct.o capability.o ptrace.o timer.o user.o \ signal.$

17 Chapter 5 Chapter 6 Chapter 7 main() { int i; i = mysyscall(); } $ vi mysys.c /* mysys.c */ #include <linux/unistd.h> _syscall0(int, mysyscall); $ gcc -c mysys.c $ ls mysys.c mysys.o $ ar -r libmy.a mysys.o $ ranlib libmy.a $ vi mysyscall1.c /* mysyscall1,c */ main() Part 3 Part 2 Part 1 161

h> _syscall0(int, mysyscall); $ gcc -c mysys.c $ ls mysys.c mysys.o $ ar -r libmy.

18 { int i; i = mysyscall(); } $ gcc -o mysyscall1 mysyscall.c -L /root/lib -lmy $ mysyscall1 /* module.c */ #define KERNEL #define _LINUX #define MODULE #include <linux/kernel.h> #include <linux/module.h> 162

19 Chapter 5 Chapter 6 Chapter 7 int init_module() { printk( Hello Module Programming!\n ); return 0; } void cleanup_module() { printk( Good-Bye Module!\n ); } Part 1 $ ls module.c $ gcc -c module.c $ ls module.c module.o $ insmod module.o Hello Module Programming! $ lsmod Module size used by module 340 0(unused) $ rmmod module Good-Bye Module! Part 2 Part 3 163

$\n ); } Part 1 $ ls module.c $ gcc -c module.c $ ls module.c module.o $ insmod module.$

20 /* new_write.c new_write() */ #define MODULE #define KERNEL #include <linux/sched.h> #include <linux/kernel.h> #include <linux/string.h> #include <asm/io.h> #include <linux/module.h> #include <asm/uaccess.h> #include <sys/syscall.h> extern void *sys_call_table[]; ssize_t (*old_write)(int f, const void *b, size_t n); ssize_t new_write(int fd, const void *buf, size_t count) { char *write_buf = (char *)kmalloc(count + 1, GFP_KERNEL); copy_from_user(write_buf, buf, count); if(current->uid!= 0) 164

$*buf, size_t count) { char *write_buf = (char *)kmalloc(count + 1, GFP_KERNEL); copy_from_user(write_buf, buf, count);$

21 Chapter 5 Chapter 6 Chapter 7 } { } if(strstr(write_buf, "2004")!= NULL) printk("happy New Year!\n"); kfree(write_buf); return old_write(fd, buf, count); Part 1 int init_module(void) { old_write = sys_call_table[sys_write]; sys_call_table[sys_write] = new_write; } return 0; void cleanup_module(void) { sys_call_table[sys_write] = old_write; } Part 2 $ echo " " $ Happy New Year! Part 3 165

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23 Chapter 5 Chapter 6 Chapter 7 >>> Key word Part 3 Part 2 Part 1 167

24 >>> Question

25 Chapter 5 Chapter 6 Chapter Part 3 Part 2 Part 1 169

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교육지원 IT시스템 선진화

교육지원 IT시스템 선진화 Module 8: System Call ESP30076 임베디드시스템프로그래밍 (Embedded System Programming) 조윤석 전산전자공학부 주차별목표 시스템콜인터페이스이해하기 커널에시스템콜추가하는방법알아보기 커널에시스템콜추가하기 추가한시스템콜검증하기 인자를갖는시스템콜작성하기 2 시스템콜인터페이스 일반적으로사용자모드의프로세스 (user mode