CODEWITHSUNDEEP
clinuxfwritekernel-module
Jake
Jake

Reputation: 16837

Read/Write to proc entry from user space

I have a LKM module which creates a proc entry using create_proc_entry(). I have to send some complex data (I am thinking of a structure) from user space program and store it in the /proc entry so that the LKM can receive it.

Right now, I am puzzled on how to convert structure data into buffered output using something like fwrite() because the callback for write from user space to /proc entry has the data argument in form of a buffer.

 // fwrite prototype
 size_t fwrite ( const void * ptr, size_t size, size_t count, FILE * stream );

 // user space write to /proc entry call back prototype
 int mod_write( struct file *filp, const char __user *buff,
  unsigned long len, void *data );

Any suggestions ?

Thanks.

Upvotes: 1

Views: 2298

Answers (1)

ugoren
ugoren

Reputation: 16441

You should be able to simply write the data. Something like this:

struct my_data s = { initialization... };
fwrite(&s, sizeof(s), 1, stream);
fflush(stream);

Then mod_write would get a pointer to s and would copy it into kernel space.
You may also use write, and then you won't need to flush it.

If your structure contains pointers, things get more complicated.

Upvotes: 1

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