linux-kernel - [PATCH 0/3] trivial: Fix several compilation errors/warnings with GCC12

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Date:   Thu, 14 Apr 2022 17:08:52 +0200
From:   Christophe de Dinechin <dinechin@...hat.com>
To:     trivial@...nel.org
Cc:     Ben Segall <bsegall@...gle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Mel Gorman <mgorman@...e.de>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Christophe de Dinechin <dinechin@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 0/3] trivial: Fix several compilation errors/warnings with GCC12

Compiling with GCC 12 using defconfig generates a number of build errors
due to new warnings, notably array-bounds checks. Some of these warnings appear
legitimate and relatively easy to fix.

Note that this series is not sufficient for a clean build yet. There are
in particular a number of warnings reported by the array-bounds check
that appear bogus, like:

| In function ‘__native_read_cr3’,
|     inlined from ‘__read_cr3’
|         at ./arch/x86/include/asm/special_insns.h:169:9,
|     inlined from ‘read_cr3_pa’
|         at ./arch/x86/include/asm/processor.h:252:9,
|     inlined from ‘relocate_restore_code’
|         at arch/x86/power/hibernate.c:165:17:
| ./arch/x86/include/asm/special_insns.h:48:9: error:
|    array subscript 0 is outside array bounds of ‘unsigned int[0]’
|    [-Werror=array-bounds]
|    48 | asm volatile("mov %%cr3,%0\n\t" : "=r" (val) : __FORCE_ORDER);
|       | ^~~
| cc1: all warnings being treated as errors

The error above is for an instruction that does not obviously address any
C array, in particular since the asm constraint is "=r" and not "=rm".

Consequently, the series here only addresses a few low hanging fruits that
appear legitimate and relatively easy to fix.

Christophe de Dinechin (3):
  sched/headers: Fix compilation error with GCC 12
  nodemask.h: Fix compilation error with GCC12
  virtio-pci: Use cpumask_available to fix compilation error

 drivers/virtio/virtio_pci_common.c |  2 +-
 include/linux/nodemask.h           | 13 ++++++-------
 kernel/sched/sched.h               | 11 +++++++++--
 3 files changed, 16 insertions(+), 10 deletions(-)

-- 
2.35.1