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November 19, 2010

kernel code not working

I wrote small code in read_write.c in linux- I am trying to retrieve entire path of some file where read operation is being performed. I changed 'SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)' to call my function 'getEntirePath(file->f_dentry, path, &length)'.
The definition of getEntirePath is as follows:

void getEntirePath(struct dentry *self, char *filePath, int *length)
int i=0;
//int offset;
char stack[MAX_PATH_DEPTH][40];

strcpy(stack[i], self->d_name.name);
printk("swapnil: Dir::%s",stack[i]);
if(i!=0 && stack[i][0]!='/')
}while(stack[i++][0]!='/' && i<MAX_PATH_DEPTH);


This code takes the dentry *self as input parameter and should trace back the path up to '/'.
This code hangs as soon as I enable it through a driver. Also I want to know from which function I should call this code for getting the entire path of file being read/written? I called it from vfs_write/vfs_read, do_sync_write/do_sync_read, but the function is not getting called each time some file is read/wrote.
dentry structure reference: http://www.freeweb.hu/linuxkernel2/ch12lev1sec7.html
qstr structure reference: http://www.win.tue.nl/~aeb/linux/lk/lk-8.html

Thanks for help.

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