memory map io function

["Louis Lu" <netlu visto com>]

Hi:

   I just wondering whether or not anyone who has the experiences on memory map io function before? 

My code is as following:
  int *base;
  unsigned int fd;
  fd = open("dev/mem", O_RDWR);
  base = mmap(0, 0x80000, PROT_READ|PROT_WRITE,MAP_SHARED,   fd, 0xd800000);
  
(and I tried to write a value to a certian register of vga)

  *(int *)(base+0x60000/4) = 0x30f027f;
  munmap(base, 0x800000);
  close(fd);

The compile is ok, but when I runt it, I got segmentation fault (core dump).
I bassically need to write around 13 of them and I have even tried to change the size from 0x800000 to 0x8fffffff.  I still got core dump though.

So, I appreciate it if there is anyone who can teach me how to correct my problem here.  

Louis
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