[Linux] 添加系统调用

系统调用：

asmlinkage int sys_mysyscall(void){
    struct task_struct *p;
    printk("start mysystemcall\n");
    printk("总缺页数：%lu\n",pfcount);
    printk("当前进程缺页次数：%lu\n",current->pf);
        for_each_process(p){
        printk("进程%d的脏页数为%d\n",p->pid,p->nr_dirtied);
    }
    printk("end mysystemcall\n");
    return 0;
}

用户端：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<linux/unistd.h>
#include<sys/syscall.h>
#define __NR_mysyscall 223
#define MAX_LINE 1024
int substrcmp( char *s, char * tag){ // a simple function to match the tag
  char *sp;
  char *tp;
  int flag = 0;
  int equal = 1;
  int len = strlen(tag);
  while(*s){
    sp = s;
    tp = tag;
    equal = 1;
    for( int i = 0 ; i < len ; i ++ ){
      if(*(sp+i) != *(tp+i))
        equal = 0;
    }
    if( equal == 1 ){
      flag = 1;
      return flag;
    }
    s++;
  }
  return flag;
}
int main(){
  syscall(__NR_mysyscall);
  FILE *fp;
  char *start = "start mysystemcall"; //starttag
  char *end = "end mysystemcall"; //endtag
  char buf[MAX_LINE]; //buffer for the message
  int flag = 0; //the flag of printing
  if((fp=fopen("/var/log/kern.log","r"))==NULL){
    printf("cannot open the log!\n"); 	//for test
  }
  else{
    printf("file opened!\n"); 		//for test
    int count = 0;
    while(fgets(buf,MAX_LINE,fp)!=NULL){
      if( substrcmp(buf,start) == 1 )	//find the beginning
        count++;
    }
    rewind(fp);
    while(fgets(buf,MAX_LINE,fp)!=NULL){
      if( substrcmp(buf,end) == 1 )	//find the end
        flag = 0;
      if( flag == 1 && count == 0 ){
        char *pos = strchr(buf,']');// ']' is a signal tha between unnessary messsage
        printf("%s",pos+1);	    // and the important message	
      }
      if( substrcmp(buf,start) == 1 ){	//find the beginning
        flag = 1;
        count--;
      }
    }
  }
  if(fclose(fp)!=0){
    printf("the log cannot be closed!\n"); //for test
  }
  else{
    printf("close the log\n");		//for test
  }
  return 0;
}