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

["luto at kernel dot org" <gcc-bugzilla at gcc dot gnu dot org>]

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

Andy Lutomirski <luto at kernel dot org> changed:

           What    |Removed                     |Added
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                 CC|                            |luto at kernel dot org

--- Comment #8 from Andy Lutomirski <luto at kernel dot org> ---
(In reply to H. Peter Anvin from comment #7)
> 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.

I would like to see something along these lines but even stronger: a way to
instruct GCC to use a particular type of access and relocation.  For example, I
think I should be able to ask GCC to reference symbol "foo" using a PC-relative
relocation or using an absolute relocation at my option.