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

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)))

Just get_type() should work:

        arg = get_argument_from_call_expr(expr->args, 0);
        if (!arg)
                return;
        type = get_type(arg);
        if (!type || !type->ctype.as)
                return;
        sm_msg("%s: expr = '%s' address space = %s", __func__, expr_to_str(expr), type->ctype.as->name);

The output looks like:

test.c:23 main() check_namespace: expr = 'frob(f->p)' address space = <asn:1>

regards,
dan carpenter