[Dwarf-Discuss] [Query] Address Space resolution in Dwarf

John DelSignore jdelsign at totalviewtech.com
Thu Jan 22 06:45:11 PST 2009

Just curious... What is "__user" and how is it implemented? Is it implemented as a type modifier/qualifier in the compiler? If we turn the argument declaration into English, what does it say?

I think "const char __user *filename" could be interpreted in one of two ways:

1) filename is a kernel-mode pointer to a user-mode const char.

2) filename is a user-mode pointer to a user-mode const char. But if that were true, then I'd expect the declaration to be "const char __user * __user filename".

Cheers, John D.

Roland McGrath wrote:
> There is no such information specified in DWARF.  DW_AT_address_class is
> similar, but not quite specified as the thing you want.  Moreover, no
> compiler produces such annotations.  Extending DWARF with an attribute
> clearly meaning what we want here is entirely straightforward.  Where work
> is required is in the compiler.  With existing binaries or ones produced
> today by existing compilers, the information you want is not available at all.
> Thanks,
> Roland
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