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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/115172] Invalid -fsanitize=bool sanitization of
 variable from named address space
Date: Tue, 21 May 2024 10:20:25 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115172

--- Comment #3 from Uro=C5=A1 Bizjak <ubizjak at gmail dot com> ---
(In reply to Jakub Jelinek from comment #1)

> What the kernel does is terrible, why they just don't declare the extern
> with __seg_gs attribute?

This is how kernel currently handles percpu variables. They are redefined t=
o a
named address space just before use, because the percpu infrastructure can't
handle AS qualified variables, mainly due to the extensive use of __typeof_=
_,
please see [1].

The solution is to use __typeof_unqual__ with gcc-14. The prototype patch at
[2] declares percpu variables as __seg_gs during decl time, as you proposed
above.

[1] https://lore.kernel.org/lkml/87bk7ux4e9.ffs@tglx/

[2]
https://lore.kernel.org/lkml/CAFULd4Z-stHtu2UWv02S+Nbx51QqytGUO8ZeW50Fc_Pbs=
fF8BA@mail.gmail.com/=