• Peter Zijlstra's avatar
    x86/cpu: Elide KCSAN for cpu_has() and friends · a6a5eb26
    Peter Zijlstra authored
    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: default avatarkernel test robot <lkp@intel.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lkml.kernel.org/r/20220502111216.290518605@infradead.org
    a6a5eb26
cpufeature.h 8.28 KB