lkml.org 
[lkml]   [2002]   [Dec]   [31]   [last100]   RSS Feed
Views: [more markup]   [less markup]   [headers]   [forward]  
 
Messages in this thread
/
Date31 Dec 2002 09:23:08 -0000
From"Vadlapudi Madhu" <>
SubjectRequire help in accessing file from kernel space
Hello Friends,

Please help me finding the bug in the following code. When i ran this code the system is
hanging (kernel panic). I am trying to open a file in kernel space and try to read, it is able open
the file but unable to read.

Code is :

##############################
  struct file     *filp;
  mm_segment_t    oldfs;
  char 		  *fname = "/etc/testfile";
  int 		  error = 0;
  char            *buf = NULL;
  int             bytesread = 0;
  oldfs = get_fs(); 
  set_fs(get_ds());
  buf = (char*)kmalloc(50, GFP_ATOMIC);
  if( buf == NULL ) {
    printk(KERN_DEBUG"[Unable to allocate buf memory]\n");
    error = -3;
    goto out2;
  }
  memset(buf,0,50);
  filp = filp_open(fname,O_RDONLY,0);

  if( IS_ERR(filp) || filp==NULL ) {
    printk(KERN_DEBUG"[opening file error:%s]\n",fname);
    error = -1;
    goto out;
  }
  if( !filp || !filp->f_op || !filp->f_op->read ) {
    printk(KERN_DEBUG"[filp does not have read function]\n");
    error = -2;
    goto out1;
  }
// I am getting error here
  bytesread = filp->f_op->read(filp, buf, 41, &filp->f_pos);
  buf[bytesread]='\0';
  printk(KERN_DEBUG"[buffer-%s]\n",buf);
 out1:
  if( filp!=NULL || !IS_ERR(filp) )
    filp_close(filp,NULL);
out:
  if( buf != NULL )
    kfree(buf);
out2:
  set_fs(oldfs); 
  return error;        
###################################
Thanks in advance.

Rgda,

Madhu V
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 11:32    [W:0.178 / U:1.530 seconds]
©2003-2008 Jasper Spaans