Hello All,
Suppose I want to implement read/write file operations
of a simple file system. Consider the read system
call. The file system's struct file_operations
function that will be called is this
ssize_t (*read) (struct file *, char *, size_t, loff_t
*);
The char * in the arguments of read is a user-space
buffer pointer. Suppose I don't want to send this
buffer that we have got to the generic_file_read
function or some other function and instead want to
create a new buffer and send it to the
generic_file_read (or other) function. Then copy this
buffer that we have sent to the generic_file_read to
the actual buffer that we had received so that the
call can be completed and the buffer received is
filled.
Consider what I am doing now is
static ssize_t
foo_read(file_t *file, char *buf, size_t count, loff_t
*ppos)
{
...
char __user local_buffer[10]; //TODO
count = 10; // setting a new count
// read_XXX below is to be taken as a function that
// will do read for us e.g. generic_file_read can be
// such a function
err = read_XXX( file, local_buffer, count, ppos);
// now copy local_buffer into buf
...
// the err is -14 or BAD ADDRESS
return err;
}
Any help regrading this is welcome.
Thanks,
Uzair Lakhani,
Karachi, Pakistan.
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