x86/cpu: Elide KCSAN for cpu_has() and friends
authorPeter Zijlstra <peterz@infradead.org>
Mon, 2 May 2022 10:15:23 +0000 (12:15 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 14 Jun 2022 16:36:23 +0000 (18:36 +0200)
commit0853f905e48b92dcf27a8d931104c9aac10de191
tree2a192cfb77629e985459d4f235c401aefe31c1da
parent4adc7d7ee640b0dcfffa0ee6d2aa24c1ffd74ff4
x86/cpu: Elide KCSAN for cpu_has() and friends

[ Upstream commit a6a5eb269f6f3a2fe392f725a8d9052190c731e2 ]

As x86 uses the <asm-generic/bitops/instrumented-*.h> headers, the
regular forms of all bitops are instrumented with explicit calls to
KASAN and KCSAN checks. As these are explicit calls, these are not
suppressed by the noinstr function attribute.

This can result in calls to those check functions in noinstr code, which
objtool warns about:

vmlinux.o: warning: objtool: enter_from_user_mode+0x24: call to __kcsan_check_access() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0x28: call to __kcsan_check_access() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0x24: call to __kcsan_check_access() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0x24: call to __kcsan_check_access() leaves .noinstr.text section

Prevent this by using the arch_*() bitops, which are the underlying
bitops without explciit instrumentation.

[null: Changelog]
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220502111216.290518605@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
arch/x86/include/asm/cpufeature.h