__CHECKER__, __user, and user-space pointers in the kernel

[Timur Tabi <timur.tabi@xxxxxxxxxxx>]

I recently discovered a problem in our driver where we're dereferencing 
user-space pointers.  Obviously, this is not allowed, but amazingly it 
seemd to work until we tried Fedora Core 2 (2.6.5 kernel).  Now I see 
that our driver may have this problem in more than one place.

Looking at compiler.h, I see that __user is defined if __CHECKER__ is 
defined:

# define __user	__attribute__((noderef, address_space(1)))

So I have some questions:

1. Where is __CHECKER__ defined?  I did a grep of an entire 2.6 kernel 
tree, and it's not defined in any source file, header file, or make 
file.  I see a few #ifdef's, but no #define __CHECKER__ or anything like 
that.

2. What does address_space(1) mean?

3. Is __CHECKER__ related to the 2.6 support for the "sparse" tool?  Is 
it related to the C=1 make command line parm?

--
Timur Tabi
Staff Software Engineer
timur.tabi@xxxxxxxxxxx

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature