Re: [RFC PATCH 3/7] arm64: add check for comparison against tagged address

On Thu, Dec 05, 2019 at 05:28:42PM +0300, Dan Carpenter wrote:
> On Thu, Dec 05, 2019 at 04:27:03PM +0300, Dan Carpenter wrote:
> > > We hardcode symbols of interest that we consider to be untagged addresses. This
> > > provides good coverage but isn't very flexible. A better approach would be to
> > > annotate the kernel with address space tags, such as is the case for __user,
> > > __percpu, etc. Thus variables, struct members and function parameters could be
> > > annotated to indicate that they contain untagged addresses. Unfortunately:
> > > 
> > >  - At present it's not possible to determine a struct member's address space
> > >    from Smatch
> > 
> > I'm not sure how to get the address space for anything not just struct
> > members.  :(  I will investigate.
> 
> I was using the wrong attribute in my testing.  In the kernel __user is
> 
> #define __user         __attribute__((noderef, address_space(1)))
> 

My guess is that __untagged isn't something that Sparse knows about?
Sparse has "noderef" as a keyword in the parse.c and has a handler for
it.

regards,
dan carpenter