使用库函数API和C代码中嵌入汇编代码两种方式实现对sysinfo的系统调用

来源：互联网发布：字符串数组拷贝编辑：程序博客网时间：2024/06/05 15:45

本例对116号系统调用sysinfo，通过c语言和嵌入式汇编语言来实现。

1.C语言实现过程如下：

打开VIM编辑器边集sysinfo.c文件，如下

#include<stdio.h>#include<sys/sysinfo.h>int main(){    struct sysinfo info;    if(sysinfo(&info)<0)    {        perror("sysinfo failed!");        return -1;    }    printf("uptime  %ld\n",info.uptime);    printf("totalram    %ld\n",info.totalram);    printf("freeswap    %ld\n",info.freeswap);    return 0;}

编译：gcc sysinfo.c -o sysingfo

执行：./sysinfo得到如下结果

2.嵌入式汇编如下：

打开VIM编辑器边集sysinfo_asm.c文件，如下

#include <stdio.h>#include <sys/sysinfo.h>int main(){    struct sysinfo info;    asm volatile(        "mov $0,%%ebx\n\t"        "mov $0xd,%%eax\n\t"        "int $0x80\n\t"        "mov %%eax,%0\n\t"        :"=m"(info)            );    printf("uptime  %ld\n",info.uptime);    printf("totalram    %ld\n",info.totalram);    printf("freeswap    %ld\n",info.freeswap);    return 0;}

编译：gcc sysinfo_asm.c -o sysingfo_asm

执行：./sysinfo_asm得到如下结果

sysinfo系统调用的定义文件在sysinfo.h中，结构体如下，

struct sysinfo {    long uptime;             /* Seconds since boot */    unsigned long loads[3];  /* 1, 5, and 15 minute load averages */    unsigned long totalram;  /* Total usable main memory size */    unsigned long freeram;   /* Available memory size */    unsigned long sharedram; /* Amount of shared memory */    unsigned long bufferram; /* Memory used by buffers */    unsigned long totalswap; /* Total swap space size */    unsigned long freeswap;  /* swap space still available */    unsigned short procs;    /* Number of current processes */    unsigned long totalhigh; /* Total high memory size */    unsigned long freehigh;  /* Available high memory size */    unsigned int mem_unit;   /* Memory unit size in bytes */    char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding for libc5 */};

本文选择了其中的三个参数，uptime，totalram，freeswap，其他参数的使用方式类同。

0 0