c – mmap：不允许操作

我试图在用户空间中使用mmap来读取’mem_map’开始的物理内存.它是一个包含所有物理页面的数组.这是运行3.0内核的i386机器.

代码是这样的：

....

//define page size
//
#define PAGE_SIZE 0x1000 //4096 bytes
#define PAGE_MASK (PAGE_SIZE - 1)

....

  /* open /dev/mem file*/
  if((fd = open("/dev/mem",O_RDWR | O_SYNC)) == -1) {
        printf("/dev/mem could not be opened.n");
    perror("open");
        exit(1);
  } else {
    printf("/dev/mem opened.n");
  }

  /* Map one page */
  printf(" mem_map is at physical addr: 0x%xn",mem_map_phy_addr);

  map_base = mmap(0,PAGE_SIZE,PROT_READ,MAP_SHARED,fd,(mem_map_phy_addr & ~PAGE_MASK)); //mem_map_phy_addr is at 0x356f2000

  if(map_base == (void *) -1) {
    printf("Memory map failed. err num = %dn",errno);
    perror("mmap"); //failed here
  } else {
    printf("Memory mapped at address %p.n",map_base);
  }

我把它作为根运行.输出是：

/dev/mem opened.
 mem_map is at physical addr: 0x356f2000
Memory map failed. err num = 1
mmap: Operation not permitted

可以肯定的是,我搜索了问题并将以下行添加到我的/etc/sysctl.conf文件中：

vm.mmap_min_addr = 0

但这也不起作用.

任何人都知道为什么不允许这样的mem_map操作以及我如何绕过它？

谢谢.