[Bug target/81490] x86: Handling of symbol ranges for __seg_fs/__seg_gs

["hpa at zytor dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81490

--- Comment #7 from H. Peter Anvin <hpa at zytor dot com> ---
Thinking about this some more, this is really not an aspect of __seg_* but
rather the section the symbol is placed in.  An embedded system kernel, for
example, could quite possibly want to access an absolute section while the
kernel itself is position-independent; maybe it is even running XIP.

As such perhaps a better solution would be to have attributes that control
these specific parameters.  A quick off-the-top-of-my-head proposal:

__attribute__((absolute))

... this symbol should be accessed using absolute address references.

__attribute__((range(from,to)))

... specifies the valid address range for this symbol.