WhyCan Forum(哇酷开发者社区)

void mem_addr(unsigned long vaddr, unsigned long *paddr)
{
        int pageSize = getpagesize();//调用此函数获取系统设定的页面大小

        unsigned long v_pageIndex = vaddr / pageSize;//计算此虚拟地址相对于0x0的经过的页面数
        unsigned long v_offset = v_pageIndex * sizeof(uint64_t);//计算在/proc/pid/page_map文件中的偏移量
        unsigned long page_offset = vaddr % pageSize;//计算虚拟地址在页面中的偏移量
        uint64_t item = 0;//存储对应项的值

        int fd = open("/proc/self/pagemap", O_RDONLY);
        if(fd == -1)//判断是否打开失败
        {
                printf("open /proc/self/pagemap error\n");
                return;
        }

        if(lseek(fd, v_offset, SEEK_SET) == -1)//将游标移动到相应位置，即对应项的起始地址且判断是否移动失败
        {
                printf("sleek error\n");
                return;
        }

        if(read(fd, &item, sizeof(uint64_t)) != sizeof(uint64_t))//读取对应项的值，并存入item中，且判断读取数据位数是否正确
        {
                printf("read item error\n");
                return;
        }

        if((((uint64_t)1 << 63) & item) == 0)//判断present是否为0
        {
                printf("page present is 0\n");
                return ;
        }

        uint64_t phy_pageIndex = (((uint64_t)1 << 55) - 1) & item;//计算物理页号，即取item的bit0-54

        *paddr = (phy_pageIndex * pageSize) + page_offset;//再加上页内偏移量就得到了物理地址

        close(fd);
}