Re: X86: build failure

[Grygorii Strashko <grygorii_strashko@xxxxxxxx>]

Hi Andrew,

On 17.12.25 01:54, Andrew Cooper wrote:
> On 16/12/2025 11:35 pm, Grygorii Strashko wrote:
> > Hi All,
> >
> > I experience build failure with following Kconfig combination:
> >   CONFIG_DEBUG=n and CONFIG_XEN_IBT=n
> >
> > with gcc:
> >   gcc --version
> >   gcc (Ubuntu 11.4.0-1ubuntu1~22.04.2) 11.4.0
> >   Copyright (C) 2021 Free Software Foundation, Inc.
> >   This is free software; see the source for copying conditions.  There
> > is NO
> >   warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
> > PURPOSE.
> >
> > Is this known issue?
> >
> > ====== log ===============
> >    CC      arch/x86/x86_emulate.o
> > In file included from arch/x86/x86_emulate.c:27:
> > arch/x86/x86_emulate/x86_emulate.c: In function ‘x86_emulate’:
> > arch/x86/x86_emulate/x86_emulate.c:70:36: error: writing 1 byte into a
> > region of size 0 [-Werror=stringop-overflow=]
> >     70 |     gcc11_wrap(ptr)[0 - PFX_BYTES] = ext < ext_8f08 ? 0xc4 :
> > 0x8f; \
> > arch/x86/x86_emulate/x86_emulate.c:78:9: note: in expansion of macro
> > ‘copy_VEX’
> >     78 |         copy_VEX(ptr, vex); \
> >        |         ^~~~~~~~
> > arch/x86/x86_emulate/x86_emulate.c:8140:13: note: in expansion of
> > macro ‘copy_REX_VEX’
> >   8140 |             copy_REX_VEX(opc, rex_prefix, vex);
> >        |             ^~~~~~~~~~~~
> > In file included from arch/x86/x86_emulate/x86_emulate.c:11,
> >                   from arch/x86/x86_emulate.c:27:
> > arch/x86/x86_emulate/private.h:691:17: note: at offset [0, 4095] into
> > destination object of size [0, 9223372036854775807] allocated by
> > ‘map_domain_page’
> >    691 |     (stb).ptr = map_domain_page(_mfn(this_cpu(stubs.mfn))) + \
> >        |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > arch/x86/x86_emulate/x86_emulate.c:60:21: note: in expansion of macro
> > ‘get_stub’
> >     60 |     uint8_t *buf_ = get_stub(stub); \
> >        |                     ^~~~~~~~
> > arch/x86/x86_emulate/x86_emulate.c:3354:15: note: in expansion of
> > macro ‘init_prefixes’
> >   3354 |         opc = init_prefixes(stub);
> >        |               ^~~~~~~~~~~~~
> > arch/x86/x86_emulate/private.h:691:17: note: at offset [1, 4096] into
> > destination object of size [0, 9223372036854775807] allocated by
> > ‘map_domain_page’
> >    691 |     (stb).ptr = map_domain_page(_mfn(this_cpu(stubs.mfn))) + \
> >        |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > arch/x86/x86_emulate/x86_emulate.c:94:21: note: in expansion of macro
> > ‘get_stub’
> >     94 |     uint8_t *buf_ = get_stub(stub); \
> >        |                     ^~~~~~~~
> > arch/x86/x86_emulate/x86_emulate.c:3402:15: note: in expansion of
> > macro ‘init_evex’
> >   3402 |         opc = init_evex(stub);
> > [...]
> Hmm - that looks like more of the GCC 11 bounds bugs, but that's what
> the gcc11_wrap() visible at the top is supposed to be fixing.
>
> Neither of those CONFIG options ought to be relevant.
>
> Which Ubuntu is this?  Is it something local, or from one of our CI
> containers?  Is this on staging, or local?
Local. Nothing special - "Ubuntu 22.04.5 LTS"

======== apt show gcc
Package: gcc
Version: 4:11.2.0-1ubuntu1
Priority: optional
Build-Essential: yes
Section: devel
Source: gcc-defaults (1.193ubuntu1)
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@xxxxxxxxxxxxxxxx>
Original-Maintainer: Debian GCC Maintainers <debian-gcc@xxxxxxxxxxxxxxxx>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 51,2 kB
Provides: c-compiler, gcc-x86-64-linux-gnu (= 4:11.2.0-1ubuntu1)
Depends: cpp (= 4:11.2.0-1ubuntu1), gcc-11 (>= 11.2.0-1~)
Recommends: libc6-dev | libc-dev
Suggests: gcc-multilib, make, manpages-dev, autoconf, automake, libtool, flex, 
bison, gdb, gcc-doc
Conflicts: gcc-doc (<< 1:2.95.3)
Task: ubuntustudio-video, ubuntustudio-publishing, ubuntu-mate-core, 
ubuntu-mate-desktop
Download-Size: 5 112 B
APT-Manual-Installed: yes
APT-Sources: http://ua.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
Description: GNU C compiler
 This is the GNU C compiler, a fairly portable optimizing compiler for C.
 .
 This is a dependency package providing the default GNU C compiler.



--
Best regards,
-grygorii