arm64: cpufeature: make cpus_have_cap() noinstr-safe

Currently it isn't safe to use cpus_have_cap() from noinstr code as
test_bit() is explicitly instrumented, and were cpus_have_cap() placed
out-of-line, cpus_have_cap() itself could be instrumented.

Make cpus_have_cap() noinstr safe by marking it __always_inline and
using arch_test_bit().

Aside from the prevention of instrumentation, there should be no
functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220912162210.3626215-2-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index fd7d75a..630c337 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -448,11 +448,11 @@ static __always_inline bool system_capabilities_finalized(void)
  *
  * Before the capability is detected, this returns false.
  */
-static inline bool cpus_have_cap(unsigned int num)
+static __always_inline bool cpus_have_cap(unsigned int num)
 {
        if (num >= ARM64_NCAPS)
                return false;
-       return test_bit(num, cpu_hwcaps);
+       return arch_test_bit(num, cpu_hwcaps);
 }
 
 /*