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标题: 内存映射mmap [打印本页]

作者: zzappled 时间: 2011-03-29 16:49
标题: 内存映射mmap
本帖最后由 zzappled 于 2011-03-29 16:57 编辑

内核态程序创建1页面的缓存，同时用户程序进行mmap映射，并向其中写入数据，出现错误
segfault at ffffffffffffffff ip 00007ffc307d5782 sp 00007ffff299fb38 error 6 in libc-2.13.so[7ffc306ab000+191000]
不知道是怎么回事，请各位指教
内核态程序
#define PROC_PHYADDR "mem_addr"

unsigned long kernel_addr=0;
unsigned long kernel_start=0;

#define PAGES_ORDER 0
#define PAGES 1

static int proc_mem_addr(char *page, char **start, off_t off, int count,int* eof, void* data)
{
  return sprintf(page, "%lu\n", __pa(kernel_start));
}

static int init_sk_buff(void)
{
  unsigned long page=0;
  char *addr=NULL;
  create_proc_read_entry(PROC_PHYADDR, 0, NULL, proc_mem_addr,NULL);
  kernel_addr=__get_free_pages(GFP_ATOMIC,PAGES_ORDER);
  addr=(char*)kernel_addr;
  kernel_start=kernel_addr;
  memset(addr, 0, PAGE_SIZE << PAGES_ORDER);
  if(addr)
  {
while(page<=PAGES-1)
{
   SetPageReserved(virt_to_page(kernel_addr));
   kernel_addr+=PAGE_SIZE;
   page++;
}
return 1;
  }
  return 0;
}

static int __init ring_init(void)
{
  if(!init_sk_buff())
printk("init skb_buff error!");
  return 0;
}

static void __exit ring_exit(void)
{
  int page=0;
  char *addr=NULL;
  kernel_addr=kernel_start;
  addr=(char *)kernel_start;
  if(!addr)
return;
  printk("The content written by user is: %s\n", addr);
  while(page<=PAGES-1)
  {
ClearPageReserved(virt_to_page(kernel_addr));
kernel_addr+=PAGE_SIZE;
page++;
  }
  free_pages(kernel_start,PAGES_ORDER);
  remove_proc_entry(PROC_PHYADDR, NULL);
  return;
}

module_init(ring_init);
module_exit(ring_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("test");
MODULE_DESCRIPTION("Kernel memory share module.");

用户态程序：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mman.h>

#define PAGES 1

int main(int argc, char* argv[])
{
      if(argc != 2)
      {
            printf("Usage: %s string\n", argv[0]);
            return 0;
      }

      unsigned long phymem_addr;
      char *map_addr=NULL;
      char s[256];
      int fd;

      fd = open("/proc/mem_addr", O_RDONLY);
      if(fd < 0)
      {
            printf("cannot open file /proc/mem_addr\n");
            return 0;
      }
      read(fd, s, sizeof(s));
      sscanf(s, "%lu", &phymem_addr);
      close(fd);

      printf("phymem_addr=%lu\n", phymem_addr);
      /*memory map*/
      int map_fd = open("/dev/mem", O_RDWR);
      if(map_fd < 0)
      {
            printf("cannot open file /dev/mem\n");
            return 0;
      }

      map_addr = mmap(0, PAGES*4*1024, PROT_READ|PROT_WRITE, MAP_SHARED, map_fd, phymem_addr);
strcpy(map_addr, argv[1]);
      munmap(map_addr, PAGES*4*1024);
      close(map_fd);
      return 0;
}

作者: zzappled 时间: 2011-03-30 09:00
结贴，重新编译内核，去掉CONFIG_X86_PAT和CONFIG_STRICT_DEVMEM

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